SAUNDERS
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FERRETS, RABBITS, AND RODENTS: CLINICAL MEDICINE AND SURGERY

ISBN 0-7216-9377-6

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Notice
Veterinary medicine is an ever-changing field. Standard safety precautions must be followed, but as
new research and clinical experience broaden our knowledge, changes in treatment and drug
therapy may become necessary or appropriate. Readers are advised to check the most current
product information provided by the manufacturer of each drug to be administered to verify the
recommended dose, the method and duration of administration, and contraindications. It is the
responsibility of the licensed prescriber, relying on experience and knowledge of the patient, to
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I dedicate this book with love to my husband, Robert, for his patience and support, and to
my wonderful children, Zachary and Chelsea, who are the center of my world. I extend
special and heartfelt thanks to my friend and colleague, Dr. Elizabeth Hillyer, who
envisioned this project with me and was my co-editor on the first edition. I give a special
dedication to the late Dr. Si-Kwang Liu, who was a pioneer in the field of exotic animal
pathology. He never stopped teaching or learning, and he was a constant source of
encouragement and inspiration during the 20 years that I was privileged to work
with him at the Animal Medical Center.
KEQ

I dedicate this book to my associates in the Zoological Medicine Service at the College
of Veterinary Medicine, Kansas State University, and to the 22 interns and 4 residents
we have trained since 1990. Their understanding, support, and encouragement, which
have allowed me to undertake projects such as this book, are greatly appreciated.
In addition, I wish to thank veterinary students Gretchen Cole and Christopher J.
Marion for assisting us in the preparation of this book.
Special thanks to my wife, Terry, and children, Erin and Michael, for their
support during this 21/2-year project.
JWC


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CONTRIBUTORS
Sean Aiken, DVM, MS, Diplomate ACVS

Barbara J. Deeb, DVM, MS

The Animal Medical Center
New York, New York

All Pet Veterinary Clinic
Shoreline, Washington
Affiliate Clinical Assistant Professor
Department of Comparative Medicine
University of Washington
Seattle, Washington

Natalie Antinoff, DVM, Diplomate ABVP
Gulf Coast Avian and Exotics
Gulf Coast Veterinary Specialists
Houston, Texas

Louise Bauck, DVM, MVSc
Alexandria Veterinary Clinic
Alexandria, Ontario, Canada

Judith A. Bell, DVM, MSc, PhD

Department of Population Medicine
Ontario Veterinary College
University of Guelph
Guelph, Ontario, Ontario

R. Avery Bennett, DVM, MS, Diplomate ACVS
Associate Professor of Surgery
Department of Small Animal Clinical Studies
School of Veterinary Medicine
University of Pennsylvania
Philadelphia, Pennsylvania

Craig Bihun, DVM, DVSc
NRC Senior Veterinarian
National Research Council
Ottawa, Ontario, Canada

Rosie Booth, BVSc
Brisbane
Queensland, Australia

Dale L. Brooks, DVM, PhD
School of Veterinary Medicine
University of California
Davis, California

Thomas M. Donnelly, BVSc, Diplomate ACLAM
Member, Warren Institute
Ossining, New York
Consultant in Laboratory Animal Medicine and Exotic Pets

New York, New York

Richard S. Funk, MA, DVM
Department of Exotic Pets
Mesa Veterinary Hospital
Mesa, Arizona

Darryl J. Heard, BVMS, PhD, Diplomate ACZM
Associate Professor of Zoological Medicine
Department of Small Animal Clinical Sciences
College of Veterinary Medicine
University of Florida
Gainesville, Florida

Stephen J. Hernandez-Divers, BVetMed, CBiol MIBiol,
DZooMed, MRCVS, Diplomate RCVS Zoological
Medicine, RCVS Recognised Specialist in Zoo and
Wildlife Medicine
Assistant Professor of Exotic Animal, Wildlife and Zoological
Medicine
Department of Small Animal Medicine and Surgery
College of Veterinary Medicine
University of Georgia
Athens, Georgia

Laurie Hess, DVM, Diplomate ABVP

Susan A. Brown, DVM

The Animal Medical Center

New York, New York

Midwest Bird & Exotic Animal Hospital
Westchester, Illinois

Elizabeth V. Hillyer, DVM
Oldwick, New Jersey

David A. Crossley, BVetMed, MRCVS, FAVD,
Diplomate EVDC
Unit of Oral Pathology
University Dental Hospital of Manchester
Manchester, United Kingdom
Department of Surgery
Rutland House Referrals
St. Helens, United Kingdom
Department of Surgery
Animal Medical Centre Referral Services
Manchester, United Kingdom

Heidi L. Hoefer, DVM, Diplomate ABVP
West Hills Animal Hospital
Huntington, West Virginia

Sharon M. Huston, DVM, Diplomate ACVIM
(Cardiology)
Staff Cardiologist
Veterinary Internal Medicine and Allergy Specialists
New York, New York


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vi

CONTRIBUTORS

Evelyn Ivey, DVM, Diplomate ABVP

Dorcas P. O’Rourke, DVM, MS, Diplomate ACLAM

Department of Clinical Studies
University of Pennsylvania
School of Veterinary Medicine
Philadelphia, Pennsylvania

Associate Professor
Department of Comparative Medicine
College of Veterinary Medicine
University of Tennessee
Knoxville, Tennessee

Jeffrey R. Jenkins, DVM, Diplomate ABVP
Jean A. Paré, DMV, DVSc, Diplomate ACZM

Avian and Exotic Animal Hospital
San Diego, California


Assistant Professor
Special Species Health
Department of Surgical Sciences
School of Veterinary Medicine
University of Wisconsin
Madison, Wisconsin

Amy Kapatkin, DVM, Diplomate ACVS
Assistant Professor of Orthopaedic Surgery
Department of Clinical Studies
School of Veterinary Medicine
University of Pennsylvania
Philadelphia, Pennsylvania

Joanne Paul-Murphy, DVM, Diplomate ACZM
Assistant Professor
Department of Surgical Sciences
School of Veterinary Medicine
University of Wisconsin
Madison, Wisconsin

Andrew S. Loar, DVM, Diplomate ACVIM
Consultant, Department of Pathology
The Animal Medical Center
New York, New York

Lori Ludwig, VMD, MS, Diplomate ACVS

Jean-Paul Petrie, DVM, Diplomate ACVIM

(Cardiology)

The Animal Medical Center
New York, New York

Big Pine Key, Florida

Staff Cardiologist
Department of Medicine
Bobst Hospital of the Animal Medical Center
New York, New York

Mark A. Mitchell, DVM, MS, PhD

Christal G. Pollock, DVM, Diplomate ABVP

Assistant Professor
Department of Veterinary Clinical Sciences
School of Veterinary Medicine
Louisiana State University
Baton Rouge, Louisiana

Clinical Assistant Professor
Zoological Medicine
Department of Clinical Sciences
College of Veterinary Medicine
Kansas State University
Manhattan, Kansas

Douglas R. Mader, MS, DVM, Diplomate ABVP


James K. Morrisey, DVM, Diplomate ABVP
Karen L. Rosenthal, DVM, MS, Diplomate ABVP

Chief of Companion Exotic Animal Medicine Service
Department of Clinical Sciences
College of Veterinary Medicine
Cornell University
Ithaca, New York

Clinical Assistant Professor
Director of Special Species Medicine
Matthew J. Ryan Veterinary Hospital
University of Pennsylvania
Philadelphia, Pennsylvania

Holly S. Mullen, DVM, Diplomate ACVS
Chief of Surgery, California Veterinary Surgical Practice
Emergency Animal Hospital and Referral Center of San Diego
San Diego, California

Joseph D. Stefanacci, VMD, Diplomate ACVR
Radiology Department
Long Island Veterinary Specialists
Plainview, New York

Michael J. Murray, DVM
Monterey, California

Robert D. Ness, DVM

Ness Exotic Wellness Center
Lisle, Illinois

Thomas N. Tully, Jr., DVM, MS, Diplomate ABVP
Professor
Department of Veterinary Clinical Sciences
School of Veterinary Medicine
Louisiana State University
Baton Rouge, Louisiana

Connie Orcutt, DVM, Diplomate ABVP
Angell Memorial Animal Hospital
Boston, Massachusetts

James Walberg, DVM, Diplomate ACVP
Consultant, Department of Pathology
The Animal Medical Center
New York, New York

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CONTRIBUTORS

Charles A. Weiss, DVM
Bradley Hills Animal Hospital
Bethesda, Maryland


Bruce H. Williams, DVM, Diplomate ACVP
Department of Telemedicine
Armed Forces Institute of Pathology
Washington, District of Columbia

Alexandra van der Woerdt, DVM, MS, Diplomate
ACVO, ECVO
Staff Ophthalmologist
Associate Director, Bobst Hospital of the Animal Medical
Center
New York, New York

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PREFACE
Since the first edition of this book was published, the specialty area of veterinary exotic pet practice has undergone
tremendous growth. Whereas small mammal species were once
considered novelty pets, many veterinarians have now incorporated these species into their general small animal practices.
Increasing numbers of veterinarians now practice exclusively
with exotic pets, including small mammals, birds, and reptiles.
Many books, periodicals, and on-line sources pertaining to the
veterinary care of these animals have become available. The
information in many of these sources is excellent, whereas in
others, it is anecdotal at best.
Parallel to this growth and perhaps a driving force in this

change, the owners of these types of pets are no longer satisfied
with simply finding a veterinarian who is willing to examine
their pet. Because of the wealth of information now available at
the touch of a computer keyboard, owners are much more
informed and demand a higher level of care. Many will go to
great lengths and travel long distances for access to the best that
veterinary medicine has to offer their animals.
Just as advances in medicine and surgery have increased our
capacity to help individual animals, recent outbreaks of infectious diseases such as monkeypox and SARS have re-emphasized
the link between these types of animals and the broader concerns of public health. The potential of exotic and novelty pets
to serve as carriers of diseases infectious to humans must be an
ongoing concern to veterinarians on both an individual and a
public health level.
In this second edition, we have again tried to provide a
concise, reader-friendly source of information about small
mammal species commonly kept as pets. In addition to ferrets,
rabbits, and the more common small rodents, we have expanded
the species list to include prairie dogs, sugar gliders, and African

hedgehogs. Along with the more traditional small mammals
kept as pets, these species are now commonly presented for veterinary care.
We have included chapters on cutting-edge topics that were
just developing when the first edition was prepared. New chapters on small mammal dentistry, cardiovascular and lymphoproliferative diseases of rabbits, zoonotic diseases, endoscopy,
and cytology and hematology provide much-needed information in one source that is difficult to find elsewhere. The chapters on cytology and hematology and on endoscopy include
full-color plates with detailed descriptions, clearly illustrating
important topics. Other chapters in the first edition have been
completely updated, many written by new authors and including new and updated information.
As in the first edition, the authors reflect a broad background
of expertise and interests. Included in the contributor list are
practitioners, university faculty members, laboratory animal veterinarians, and board-certified specialists in such diverse fields

as surgery, cardiology, ophthalmology, pathology, and zoo
animal medicine. This varied group provides a wealth of information and perspectives, all tremendously instructive and
helpful. We hope that you will find their viewpoints and experiences valuable.
In bringing this project together into its final form, we
thank the authors for their hard work, the editors at Elsevier
for their willingness and patience in working with us, and especially, Ray Kersey for supporting us so completely and in spearheading this second edition. It could not have happened without
him.
KATHERINE E. QUESENBERRY
JAMES W. CARPENTER

xi
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Plate I Endoscopic view of the horizontal ear canal and the normal
tympanum (T) of a rabbit. (Courtesy Stephen Hernandez-Divers, Ithaca, New
York, and Michael Murray, Monterey, California.)

Plate 2 Endoscopic view of the ventral nasal concha (V) and the nasal
septum (N) as seen from the common nasal meatus of a rabbit. (Courtesy
Stephen Hernandez-Divers, Ithaca, New York, and Michael Murray, Monterey,
California. )

Plate 3 Typical wide-angle view into the oral cavity as provided by the

Plate 4 Nasal breathing in rabbits is facilitated by the entrapment of
the epiglottis dorsal to the soft palate. The butterfly-shaped epiglottis
(black arrows) is clearly visible through the relatively transparent caudal
soft palate (white arrows). The vascular pattern depicted here is typical for
a rabbit. (Courtesy Stephen Hernandez-Divers, Ithaca, New York, and Michael

Murray, Monterey, California.)

rigid endoscope. Rotating the scope 180 degrees downward provides a
view of the lower arcade. Closer, magnified view of individual teeth is
made possible by advancing the telescope toward the tooth. (Courtesy
Stephen Hernandez-Divers, Ithaca, New York, and Michael MUlTaY, Monterey,
California. )

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Plate 9 (see also Figure 38-4) Fecal smear (acid-fast stain, X40). Numerous Cryptosporidium oocysts are present. When Cryptosporidium cause diarrhea, the organisms are numerous and easily identified. These protozoal cysts, 4 to 7 urn in diameter, are approximately the size of a red
blood cell and are weakly acid-fast positive. The acid-fast stain used here
(TBQuick Stain, Becton Dickinson Microbiology Systems, Sparks, MD) is
a "cold" acid-fast stain and in our experience is easy to use and works
well. An acid-fast stain specifically designed for Cryptosporidium species is
not necessary (I. W., personal observation).

Plate 10 Mycobacteria: lymph node aspirate from a cat (Wright's stain
counterstained with acid-fast stain, X 100). Numerous negative-staining
bacilli are observed both within macrophages and free in the background.
Counterstaining with a cold acid-fast stain (TBQuick Stain, Becton Dickinson Microbiology Systems) shows distinct, acid-fast-positive organisms.
(Although not a recognized technique, counterstaining a Wright's-stained
smear will stain some of the organisms and was used here because no
unstained specimens were available for staining.) The morphologic features are similar in all species of animals. Mycobacteria are either weakly
gram positive or are not readily stained by Gram stain because of waxy
material in the cell wall. Typically, when acid-fast organisms are so numerous, they are often Mycobacterium avium.

Plate II Aspirate of a cutaneous neoplasm in a ferret (Wright's stain, x 100). This round cell tumor
contains characteristic purple or metachromatic granules in the cytoplasm characteristic of a mast cell tumor. The granules are purplish and not as distinct as those in other mammals. Mast cell tumors are described in the skin of ferrets and typically do not metastasize. The characteristic granules can be leached out

in Diff-Quik stains. Without the granules, a diagnosis cannot be made with certainty. Granules from basophils can leach out as well; for this reason, we do not routinely use Diff-Quik stain.

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Plate 12 Rabbit peripheral blood (Wright's stain, X 100). This field
shows the three common types of white blood cells in peripheral blood
(monocyte, lymphocyte, and heterophil). The rabbit heterophil is analogous to the neutrophil in other species and is frequently mistaken for an
eosinophil. Monocytes have a light blue cytoplasm and are occasionally
vacuolated. Platelets in rabbits are small. Note a platelet adherent to a
red blood cell adjacent to the monocyte.

Plate 13 Rabbit peripheral blood (Wright's stain, X 100). This is a rabbit eosinophil. These cells are rare but distinct from heterophils in that
they are larger, have larger granules that are more tightly packed, and have
subtly different tinctorial properties. Note the crenation of most of the
red blood cells. Crenated erythrocytes (echinocytes) have spicules that are
evenly spaced and about the same size. Echinocytes are usually an artifact
that can be associated with excess ethylenediamine tetraacetic acid
(EDTA) anticoagulant or prolonged storage of blood, or they are a nonspecific finding in a variety of pathologic conditions.

Plate 14 Rabbit peripheral blood (Wright's stain, X 100). This is a rabbit basophil. Basophils are distinctive cells with purplish granules stippling the cytoplasm. They are more frequently observed than
eosinophils and occur with approximately the same frequency in rabbits as eosinophils do in other species
(l.w., personal observation).

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Plate 15 Rabbit peripheral blood (Wright's stain, X 100). This is a
platelet and fibrin clot with two trapped white blood cells (monocyte and
lymphocyte). Microscopic clots are more frequently observed at the trailing edge of a blood smear and are frequently seen in peripheral blood

from rabbits (J.W., personal observation). This area should be scanned
for clots and platelet clumps, which should be noted on the differential
count. Platelets and white blood cells are not evenly dispersed in clotted
blood, which compromises the accuracy of the automated or estimated
counts.

Plate 16 Guinea pig peripheral blood (Wright's stain, X 100). This field
shows a monocyte and a neutrophil. Neutrophils are sometimes referred
to pseudoeosinophils because of the distinct small eosinophilic granules.

Plate 17 Guinea pig peripheral blood (Wright's stain, X 100). This is an eosinophil and is easily recognized by its distinctive large granules (compare with the granules in the nearby degenerating neutrophil).

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Plate 18 Guinea pig peripheral blood (Wright's stain, x 100). This is a
basophil and is easily recognized, although granules may leach out with
Diff-Quik stains.

Plate 19 Lymphocytes are the predominant type of white blood cell in
guinea pigs. This lymphocyte contains a Kurloffs body (K), which is typically solitary, reddish in Wright's stain, and large (up to 8 urn in diameter). Sometimes it is difficult to distinguish the nucleus from a Kurloff's
body. Lymphocytes containing Kurloffs bodies, also known as PoaKurloff cells, account for 3% to 4% of peripheral leukocytes. They are
unique to the guinea pig. and are generally regarded as the equivalent of
large granular lymphocytes (natural killer cells) in other mammals'-"

Plate 20 Guinea pig peripheral blood (Wright's stain, x 100). A rounded, large Kurloffs body is present
within the lymphocyte.

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Plate 5 Gentle pressure on the soft palate (black arrow) frees the epiglottis (E) and allows the endotracheal tube (T) to be advanced and inserted
between the arytenoid cartilages (white arrows). (Courtesy Stephen Hernandez-Divers, Ithaca, New York, and MichaelMurray, Monterey, California.)

Plate 6 Cystoscopic view of the mucosal surface of the rabbit urinary
bladder. Note the air bubble (B). This rabbit had hematuria; a spaceoccupying mass (arrow) was outlined by the positive contrast of the urine
within the bladder. Histologic diagnosis of epithelial hyperplasia was
made from a biopsy sample. (Courtesy Stephen Hernandez-Divers, ithaca,
New York, and Michael Murray, Monterey, California.)

Plate 7 Laparoscopic (left cranial flank) view of the duodenum (D),
pancreas (P), and cecum (C) of a rabbit. (Courtesy Stephen HernandezDivers, Ithaca, New York, and Michael Murray, Monterey, California.)

Plate 8 Endoscopic biopsy of the liver of a rabbit. The biopsy forceps
(B) are used to take a tissue sample from the caudal edge of the liver (L).
(Courtesy Stephen Hernandez-Divers, Ithaca, New York, and MichaelMurray,
Monterey, California.)

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1
Basic Anatomy, Physiology, and
Husbandry
Susan A. Brown, DVM

HISTORY
USES

ANATOMY AND PHYSIOLOGY
Body Morphology
Hair Coat and Skin
Special Senses
Skeletal System
Thoracic Cavity and Pharyngeal Anatomy
Abdominal Viscera
Urogenital Tract
Physiologic Values

HUSBANDRY
Behavior
Reproduction
Housing
Nutrition
“There is something about ferrets. Some people find them good
working partners for a frosty morning’s rabbiting. Some enjoy
their individuality and admire their courage, or appreciate their
affable companionship. Some react with a knowing laugh or
shudder. The majority, perhaps, dismiss ferrets as smelly
animals that bite and that spend much of their time down the
trousers of foolhardy men. The majority are very wrong
indeed.”19

HISTORY
Ferrets belong to the family Mustelidae and are related to
weasels, mink, otters, badgers, stoats, martens, and skunks. There
are three species of ferrets (also known as polecats in Europe and
Asia): the European polecat (Mustela putorius), the Steppe or
Siberian polecat (Mustela eversmanni), and the black-footed ferret

(Mustela nigripes). The European polecat is found in various areas
from the Atlantic to the Ural mountains and dwells along the
edges of woodlands and wetlands.8 The Siberian polecat is found
in Eurasia from the thirtieth to the sixtieth degree of latitude,
may be larger than the European polecat, and lives primarily in
open areas such as steppes, slopes of ravines, and semi-deserts.8
The black-footed ferret is native to the prairies of North America.
It almost became extinct in the wild because of habitat destruction and the decimation of its main food source, the prairie dog,

from poisoning and hunting.8 Currently, captive breeding and
reintroduction programs are under way in an attempt to reestablish the black-footed ferret into its native range. It is illegal to
own this endangered species.
The origin of the domestic ferret (Mustela putorius furo) is
shrouded in mystery. The Latin name translates loosely as
“mouse-eating (mustela) smelly (putorius) thief ( furo).” This
species may have originated from either the Siberian or the
European polecat.5,23 It is difficult to find archaelogic evidence
of domestication, possibly because of the ferret’s small skeleton,
which may have deteriorated rapidly, or the lack of paraphernalia associated with the ferret. We know that European ferret kits,
if taken into captivity before their eyes open, can imprint readily
on human beings and become tame.16 The first recorded reference that can be reasonably assumed to refer to a ferret is around
350 BC by Aristotole.5,23 Ferrets were introduced into Europe possibly by the Romans or the Normans during their invasions.10
Over the centuries, numerous references have been made to the
use of ferrets in Europe, including for rodent control in homes,
farms, and ships, and for hunting rabbits both for damage
control and for human food.
The domestic ferret was introduced into Australia from
Europe in the 1800s to control the populations of European
rabbits that had been previously released.10 Fortunately, enough
other predators, such as foxes, dingoes, and hawks, preyed on

the ferret so that feral populations never developed.10 However,
when they were introduced into New Zealand for the same
reason in the late 1800s along with stoats and weasels, there were
no predators to control their numbers.10 Feral populations of
domestic ferrets therefore developed and are still present
today.5,10 The impact of feral ferrets on native wildlife has been
controversial.
The domestic ferret was probably introduced into the United
States from Europe by the shipping industry in the 1700s. They
may have come as pets or as hunting companions.5,10,19

USES
Early references to ferrets record their use for rodent or rabbit
control.5,10,19 Ferrets are efficient little predators that can bring
down prey quite a bit larger than themselves and can maneuver
in small spaces more effectively than cats. Ferrets were used on

2

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Basic Anatomy, Physiology, and Husbandry
ships in colonial days to control the rat populations.5 In the early
1900s, the U.S. Department of Agriculture encouraged the use
of ferrets as a means of controlling rabbits, raccoons, gophers,
mice, and rats around granaries and farms.5,19 One needed only
to call the local “ferret master” to bring out his ferrets, which

were set loose to do their work and then recaptured to work
another day. Large facilities kept their own ferrets on site. Ferrets
are still used for rodent and rabbit control in some areas of
Europe and Australia today. However, hunting with ferrets is
prohibited in the United States.
Ferrets have long been used to hunt rabbits—not only for
control, but as a food source for human beings (Fig. 1-1). “Ferreting” was a common sport in the United Kingdom and many
other areas of Europe. It is still practiced today but to a much
lesser degree. Ferrets are released in a rabbit warren area, where
they investigate burrows and flush out rabbits. The rabbits are
then caught in nets or by dogs or shot by the waiting hunter.
Domestic ferrets have been bred for their pelts. A coat made
of ferret fur is referred to as fitch. Ferret fur never really took hold
in the United States, but it still exists in a few areas of Northern
Europe.
An entertainment peculiar to English pubs and still found
in a few isolated areas of the United Kingdom is called ferretlegging. This is a sport in which a man securely ties his trouser
legs closed at the ankles and then places two ferrets, each with
a full set of teeth, into his trousers. He then securely ties the
trousers closed at the waist. The contest is to see how long he
can stand having the ferrets in his trousers. If a ferret bites, it
can only be dislodged from the outside of the trousers. The
record of 5 hours and 26 minutes was set by a 72-year-old Yorkshire man.5
Domestic ferrets have also been used to transport cables
through long stretches of conduit. They have been used to string
cable for oilmen of the North Sea, for camera crews, in jets, and
for the telephone company.5
Ferrets have been used in biomedical research since the early
1900s, when they were used to study human influenza and other
viral diseases.5 Today ferrets are used in the fields of virology,


3

reproductive physiology, anatomy, endocrinology, and toxicology.5 Although the use of ferrets in research is very distasteful to
some, much of the information gained has directly benefited the
pet ferret as well.
The main use for ferrets today, however, particularly in the
United States, is as a companion animal. Their popularity has
increased dramatically over the past few decades. There has been
a proliferation of ferret organizations dedicated to the well-being
of this pet. It is difficult to say when the first ferret was kept
strictly as a pet, but it is hard to imagine people in the distant
past not feeling some attraction to the engaging personalities of
this animal.
Ferrets make suitable pets for many people. They are small,
clean, and very interactive with human beings and each other.
However, as with all companion animals, the prospective owner
should be educated on their husbandry requirements and behavior. For instance, ferrets (as with most pets) are not suitable for
children younger than 6 years. Another consideration is that the
majority of ferrets in the United States will likely be afflicted by
one or more neoplastic diseases as they age. In addition, certain
legal restrictions relate to the ownership of ferrets. Ferrets are still
not considered domestic animals in most areas of the United
States despite their long history. In some areas owning a ferret
as a pet is illegal, and in other areas permits must be obtained
for ownership.
With the advent of an approved rabies vaccine for the
domestic ferret, restrictions on their use as pets have been lifted
in many parts of the United States. However, in some localities,
even if the ferret is appropriately vaccinated, it can be seized

and destroyed if it bites a human being. Veterinarians should
therefore be familiar with legislation in their localities regarding the keeping of ferrets before they engage in ferret veterinary
care.

ANATOMY AND PHYSIOLOGY
The following is a brief overview of the important anatomic
and physiologic features of domestic ferrets for the practitioner.
The extensive literature on the anatomy and physiology of the
ferret provides a more detailed discussion. The skeletal anatomy
is depicted in Fig. 1-2, and the visceral anatomy is presented in
Fig. 1-3, 1-4, and 1-5.

Body Morphology

Figure 1-1
ferret.

Ferreter in the United Kingdom hunting rabbits with his

Ferrets have a long tubular body with short legs; this body
shape allows them to get in and out of small holes in the ground
during hunting. The ferret’s spine is very flexible, enabling the
animal to easily turn 180 degrees in a narrow passageway. The
ferret’s neck is long and thick and of approximately the same
diameter as the mandibular area; this anatomic feature makes it
difficult for owners to use collars on their pets. Even though their
legs are short and their claws are primarily used for traction and
digging, ferrets can climb along surfaces such as screen or wire
mesh and may reach dangerous heights.
If male ferrets are allowed to reach sexual maturity before

they are neutered, their body size is normally twice that of
female ferrets. This discrepancy in size is repeated throughout
the mustelid family. One theory for the large size of males is
that it facilitates defending their territories against other males
and allows them to successfully overpower and mate with

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6

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26

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32

Figure 1-2 Skeletal anatomy of a ferret. 1, Calvaria; 2, hyoid apparatus; 3, larynx; 4, seven cervical vertebrae; 5, clavicle; 6, scapula; 7, 15 thoracic vertebrae; 8, five lumbar vertebrae; 9, three sacral vertebrae; 10, 18 caudal vertebrae; 11, first rib; 12, manubrium; 13, sternum; 14, xiphoid process; 15, humerus; 16, radius; 17, ulna; 18, carpal bones; 19, accessory carpal bone; 20, metacarpal bones; 21, ilium; 22, ischium; 23, pubis; 24, femur; 25, patella; 26, fabella; 27, tibia; 28, fibula; 29, tarsal bones; 30, calcaneus; 31, metatarsal bones;
32, talus; 33, os penis. (Adapted from An NQ, Evans HE: Anatomy of the ferret. In Fox JG, ed: Biology and Diseases of the Ferret. Philadelphia, Lea & Febiger, 1988, pp 14-65.)

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Basic Anatomy, Physiology, and Husbandry

1

2

Figure 1-3

A, Ventral aspect of the viscera of
a ferret in situ. B, Anatomy of the viscera and
most important blood vessels as seen after
removal of the lungs, liver, and gastrointestinal
tract. 1, Larynx; 2, trachea; 3, right cranial lobe
of lung; 4, left cranial lobe of lung; 5, right
middle lobe of lung; 6, right caudal lobe of lung;
7, left caudal lobe of lung; 8, heart; 9,
diaphragm; 10, quadrate lobe of liver; 11, right
medial lobe of liver; 12, left medial lobe of liver;
13, left lateral lobe of liver; 14, right lateral lobe
of liver; 15, stomach; 16, right kidney; 17,
spleen; 18, pancreas; 19, duodenum; 20, transverse colon; 21, jejunoileum; 22, descending
colon; 23, uterus; 24, ureter; 25, urinary bladder;
26, right common carotid artery; 27, left
common carotid artery; 28, vertebral artery; 29,
costocervical artery; 30, superficial cervical
artery; 31, axillary artery; 32, right subclavian
artery; 33, right internal thoracic artery; 34, left
internal thoracic artery; 35, branch to thymus;
36, left subclavian artery; 37, brachiocephalic
(innominate) artery; 38, cranial vena cava; 39,
aortic arch; 40, right atrium; 41, pulmonary
trunk; 42, left atrium; 43, right ventricle; 44, left
ventricle; 45, caudal vena cava; 46, aorta; 47,
esophagus; 48, hepatic veins; 49, celiac artery;

50, cranial mesenteric artery; 51, left adrenolumbar vein; 52, left adrenal gland; 53, right adrenal
gland; 54, left renal artery and vein; 55, left
kidney; 56, suspensory ligament of ovary; 57, left
ovarian artery and vein; 58, left ovary; 59, left
deep circumflex iliac artery and vein; 60, caudal
mesenteric artery; 61, broad ligament of uterus;
62, left external iliac artery; 63, right common
iliac vein; 64, left internal iliac artery; 65, rectum.
(Adapted from An NQ, Evans HE: Anatomy of the
ferret. In Fox JG, ed: Biology and Diseases of the
Ferret. Philadelphia, Lea & Febiger, 1988, pp 1465.)

27
28
29
30
31
34
36

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32
33
3

35
37
38


4

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41

40
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8

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10

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44

43
45

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58

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3

1

45

2

7

6
Colon

10
Ureter

Figure 1-4 Pelvic arteries and structures of the male. 1, InterCaudal rectal a. nal iliac artery; 2, internal pudendal artery; 3, medial sacral
artery; 4, iliolumbar artery; 5, cranial gluteal artery; 6, caudal
gluteal artery; 7, lateral caudal artery; 8, prostatic artery; 9, urethral branch; 10, umbilical artery; 11, ureteral branch; 12, caudal
Anal sac
vesicle artery; 13, artery of the bulb; 14, deep artery of penis; 15,
Bulb of penis
dorsal artery of penis. (From Fox JG, ed: Biology and Diseases of
the Ferret. 2nd ed. Baltimore, Williams & Wilkins, 1998, p 67.)

13

8

11

Testicular
a.+v.

Prostate

Deferent
duct

12

914
15

Bladder

Os penis

Testis
Spermatic
cord

4

1

3

2


Pelvic
symphysis

5

Epididymis

Cd 1

Figure 1-5

6
7
Colon
18

8
10
9

19

11
12

Bladder

13


14

15
21
20

16

Pelvic viscera of the female (left lateral
view). 1, Internal iliac artery; 2, internal pudendal
artery; 3, medial sacral artery; 4, iliolumbar artery; 5,
cranial gluteal artery; 6, caudal gluteal artery; 7, lateral
caudal artery; 8, vaginal artery; 9, uterine horn; 10,
umbilical artery; 11, uterine artery; 12, ureteral branch;
13, urethral artery; 14, artery to vestibular bulb; 15,
caudal rectal artery; 16, perineal artery; 17, artery of the
clitoris; 18, uterine horn; 19, ureter; 20, vagina; 21, anal
sac. (From Fox JG, ed: Biology and Diseases of the Ferret.
2nd ed. Baltimore, Williams & Wilkins, 1998, p 64.)

17

females.13 A theory for the small size of the females suggests that
because they are confined near a nest for the energy-intensive
task of raising young, which they do entirely on their own, a
small body size means the female needs less to feed herself and
thus more of the food is available to the young.13 In other
words, the male’s reproductive success may be determined by
his ability to defend his territory and mate with many females,
and the female’s reproductive success may be determined by her

ability to secure food.13 The body weight of intact male ferrets
ranges from 1 to 2 kg and that of females from 0.6 to 1 kg.11 If
neutered before weaning, female ferrets become larger and male
ferrets stay smaller than intact individuals of the same sex.
Ferrets neutered before sexual maturity weigh between 0.8 and
1.2 kg. Males that have been neutered early do not develop the
heavy muscular neck and shoulder area that is characteristic of
intact males.
Ferrets experience a normal seasonal change in body fat—that
is, they lose weight in the summer and regain it in the winter. In
intact animals, the weight change is most dramatic: the weight

difference that occurs from season to season may be as great as
40%.

Hair Coat and Skin
The “wild” coat color of the domestic ferret most closely
resembles that of the European ferret. This color is referred to as
fitch-ferret, polecat-ferret, or sable and consists of black guard hair
with a cream undercoat, black feet and tail, and a black mask on
the face (Fig. 1-6). The other two naturally occurring colors are
albino, which is denoted by yellow-white fur and unpigmented
eyes, and cinnamon, which is also called sandy. Interestingly, the
cinnamon coloring—with its beige guard hair, cream undercoat,
and faint mask—closely resembles the natural coloring of the
Siberian ferret. In the United States, more than 30 color variations are recognized by the American Ferret Association. Color
variations include silver (dark gray guard hair with a cream
undercoat and little or no mask), black-eyed white (white body
hair but pigmented irises), chocolate (similar to sable but with


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Figure 1-6

7

hair may not grow back for weeks to months, which should be
explained to the owner. In addition, the regrown hair can be a
different texture or shade than the previous hair and it may
suddenly appear under the skin, giving a bluish appearance that
can be misinterpreted as a skin disease.
The skin of the ferret is thick, especially over the neck and
shoulders where it protects the ferret during fights with other
ferrets or during mating when vigorous biting of the back of the
neck occurs. Healthy skin should have a smooth appearance
without flakes or scales. Ferrets do not have sweat glands in their
skin and thus quickly succumb to heat prostration.14 Ferrets
have very active sebaceous glands, which account for their body
odor. During the breeding season, intact animals have increased
sebaceous secretions; this increase results in a noticeable
increase in body odor, yellow discoloration of the undercoat,
and oily fur.
Ferrets have a pair of well-developed anal glands, as do all
members of the mustelid family. These glands produce a serous
yellow liquid with a powerful odor. Ferrets that are frightened or

threatened can express their anal glands frequently but are
unable to project the fluid over a long distance, as can skunks.
The odor only lasts a few minutes, and as ferrets mature and
become accustomed to their environment they rarely express
these glands. Routine removal of the anal glands (a procedure
known as descenting; see Chapter 12) is not necessary because
the anal gland secretion is not responsible for the musky body
odor of ferrets. Rather, the sebaceous secretions of the skin
produce these animals’ overall odor. Nevertheless, pet ferrets
originating from large breeding farms in the United States are
routinely descented when they are 5 to 6 weeks of age.

Sable coloring of a domestic ferret.

dark brown rather than black guard hair), Siamese (guard hairs
that are a lighter brown than chocolate and a light-colored
mask), panda (white hair on the head and shoulders and body
hair of various colors), and shetland sable (sable body coloring
but with a white stripe running vertically on the face from the
nose to the top of the head).
Ferrets molt in the spring and the fall, concomitantly with
their change in weight. The molting can be subtle or dramatic.
The hair itself may vary in length from season to season, typically being shorter in the summer and longer in the fall. Hair
color also may change, usually being lighter in the winter and
darker in the fall. In intact females, hair loss will follow the first
ovulation of the season followed by hair regrowth after successful mating.6 The regrown hair usually is sleeker and darker
then the original coat. This loss and regrowth can be repeated
if more than one mating occurs during the season.6 If a female
molts the coat and does not successfully mate, areas of alopecia may result. If a ferret is in estrus when an ovariohysterectomy is performed, a new coat will grow in within a month after
surgery. Neutered ferrets of either sex have a less dramatic molt

and color change than intact ferrets. A large percentage of silver
ferrets become black-eyed whites as they mature in years. Ferrets
may lose or change their mask configuration from season to
season and from year to year; for this reason, dependence on
photographs alone for pet identification is unreliable. A more
permanent form of identification, such as a microchip or tattoo,
should be used.
The clinician should consider the hair coat cycles of the ferret
when removing hair for surgery or diagnostic procedures. The

Special Senses
Ferrets have good binocular vision and they can see fairly well
in low-light levels because their ancestors were twilight or night
hunters.21 The retina contains cones and ganglions, but it is
unknown how well colors are distinguished.21 An experiment
with moving targets indicated that ferrets consistently followed
and attacked the “prey” when it was moving at 25 to 45 cm/sec,
which is the approximate escape speed of a mouse.3
Ferrets have an elaborate turbinate system like other carnivores and appear to develop their olfactory preferences for food
items during the first 3 months of life. By the fourth month,
when in the wild they would be leaving the nest, these preferences are set.2 This may explain why it can be difficult to change
a ferret’s diet as an adult.

Skeletal System
The long narrow skull of the ferret has no suture lines in the
adult.1 The dental formula for the ferret is 2(I 33 C11 P 33 M 21) = 34.
The deciduous teeth erupt at 20 to 28 days of age, and the permanent teeth erupt at 50 to 74 days of age.1 The upper incisors
are slightly longer than the lower incisors and cover the lower
ones when the mouth is closed. The canines are prominent as
in other members of the order Carnivora. In some ferrets, the

tips of the upper canines extend beyond the most ventral portion
of the chin. The canine roots are longer than the crown; this fact
must be considered when extraction is necessary. Upper premolars 1 and 2 and all three of the lower premolars have two roots.
The third upper premolar, or carnassial tooth, and the first upper

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molar have three roots. The second lower molar is very tiny and
has only one root.1
The ferret’s long, flexible spine has a vertebral formula of C7,
T15, L5 (6 or 7), S3, Cd18.1 Ferrets normally have 15 pairs of
ribs (occasionally 14), and some ferrets have 14 on one side and
15 on the other.1 The first 10 ribs are attached to the sternum,
and the remaining 4 to 5 become the costal arch. In ferrets, the
thoracic inlet is bordered by the first pair of ribs and the sternum
and is very small.1 The presence of anterior thoracic masses or
megaesophagus can result in dysphagia or dyspnea.
Each of the ferret’s four feet has five clawed digits. The first
digit on each foot has only two phalanges, whereas each of the
other digits has three.1 The claws are not retractable as in cats
and thus must be trimmed periodically. Ferrets should not routinely be declawed, in part because this causes difficulty with
traction.


Thoracic Cavity and Pharyngeal Anatomy
The heart lies approximately between the sixth and eighth
ribs. It is cone shaped, and, on a ventrodorsal view of the chest,
its apex is directed to the left of midline.1 The ligament that connects the heart to the sternum can be surrounded by a varying
amount of fat. On lateral radiographic views, this gives the
impression that the heart shadow is raised above the sternum.
Loss of this raised effect (i.e., the heart shadow is in direct contact
with the sternum) is one of the early signs of cardiac enlargement.
The lungs of the ferret have six lobes. The left lung is composed of two lobes—the left cranial and the left caudal lobes;
the right lung is composed of four lobes—the right cranial, the
right middle, the right caudal, and the accessory lobes.1
The thymus can vary in size depending on the age of the
ferret. It can be quite prominent in the young ferret and is found
within the thoracic inlet in the cranial mediastinum.1 In my
experience, it can be a common site of neoplasia presenting with
a prominent cranial mediastinal mass in ferrets younger than 1
year.
The anatomy of the major arteries exiting the aorta in the
direction of the head is unusual. In place of bilateral carotid
arteries, ferrets have a single central artery, the innominate artery
or the brachiocephalic artery, that exits the aortic arch just proximal to the left subclavian artery. The brachiocephalic artery
divides into the left carotid, the right carotid, and the right subclavian arteries at the level of the thoracic inlet. This central
artery may be an anatomic adaptation that allows the ferret to
maintain blood flow to the brain while it turns its head 180
degrees.22
Ferrets have five pairs of salivary glands: the parotid, the zygomatic, the molar, the sublingual, and the mandibular.1 Mucoceles are uncommon in ferrets. The mandibular lymph node lies
cranial to the mandibular salivary gland and closer to the angle
of the jaw. This lymph node can become enlarged, particularly
in some cases of lymphoma, and thus may be confused with the
salivary gland. A fine-needle aspirate of the mass should be

obtained and examined to cytologically differentiate the two.

Abdominal Viscera
The ferret spleen varies greatly in size, depending on the
animal’s age and state of health. The spleen is located along the
greater curvature of the stomach and is attached to the stomach

and liver by the gastrosplenic ligament.1 The caudal splenic tip
can be located anywhere from the cranial pole of the left kidney
to the caudal pole of the right kidney, depending on its size.
When enlarged, the spleen extends in a diagonal fashion from
the upper left to the lower right of the abdominal cavity.
The ferret’s relatively large liver is composed of six lobes. The
pear-shaped gallbladder is located between the quadrate lobe
and the right medial lobe.1 The opening of the bile duct is
located in the duodenum in common with the pancreatic duct1
(see Fig. 12-6). The pancreas is V shaped with a right and left
limb connected at the midline near the pylorus.1 The right limb
is longer than the left and extends along the descending
part of the duodenum. The left limb extends along an area
between the stomach and the spleen.1 Ferrets have a simple
stomach that can expand greatly to accommodate large
amounts of food.1 It fits into the curve of the liver in the cranial
abdomen. The pylorus is well developed and is easily distinguished grossly. Ferrets have the ability to vomit but do not
always do so in the presence of gastric foreign bodies. Before
vomiting, a ferret will back up, hold its head low, squint its
eyes, and salivate excessively.
The small intestine is short, approximately 182 to 198 cm in
length.1 This length results in a short gastrointestinal transit time
of about 3 to 4 hours in the adult animal.4 The gut flora is

simple, and therefore gastrointestinal upset with use of antibiotics is rare.4 The ileum and jejunum are indistinguishable on
gross examination. Ferrets do not have a cecum or ileocolonic
valve. The large intestine of the ferret is approximately 10 cm in
length.1
The adrenal glands (Fig. 1-7) of ferrets older than 2 years
are frequently affected by disease. The left adrenal gland lies in
fatty tissue just medial to the cranial pole of the left kidney. It is
approximately 6 to 8 mm in length and is usually crossed by the
adrenolumbar vein on the ventral surface.9 Two or more
branches of the left adrenolumbar artery supply blood. The right
adrenal gland lies more dorsal than the left and is covered by
the caudate lobe of the liver. It is intimately attached to the

Caudal vena cava
Celiac a. and cranial
mesenteric a.
L. adrenal gland

R. adrenal gland

Right
kidney
Left
kidney

Fat
Renal a.+v.
Aorta

Figure 1-7 Ventral view of the abdominal cavity showing the arterial

supply and venous drainage of the kidneys and adrenal glands. (From
Fox JG, ed: Biology and Diseases of the Ferret. 2nd ed. Baltimore, Williams &
Wilkins, 1998, p 60.)

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caudal vena cava. The caudal vena cava may lie over part or all
of the gland. The right adrenal gland is slightly larger than the
left one and is longer, approximately 8 to 11 mm in length.9 In
another study, the adrenal gland length in females ranged from
5.0 to 10.0 mm for the left and 5.0 to 10.0 mm for the right; in
males, it was 7.0 to 10.5 mm for the left and 7.5 to 13.5 for the
right.15 The right adrenal gland is supplied by three to five separate vessels that come from a combination of the right renal
artery, the right adrenolumbar artery, and the aorta.9 In two
studies, accessory nodules of adrenal cortical tissue were found
in 11 of 135 ferrets and 10 of 26 ferrets, respectively.9,15 The accessory adrenal tissue was usually found either embedded in or
adjacent to the adrenal gland.15

Urogenital Tract
The right kidney lies cranial to the left kidney in the retroperitoneal fat. The cranial end of the right kidney is covered by the
caudate lobe of the liver. The bladder is small and easily holds
10 mL of urine at a low pressure.21
Male ferrets have a small prostate gland that is located at the
base of the bladder and surrounds the urethra.1 When the
prostate is grossly enlarged, as in the presence of paraurethral
or prostatic cysts, it appears on lateral radiographic views as a

round mass just dorsal to the neck of the bladder. Male ferrets
have a J-shaped os penis, which can complicate urethral
catheterization.
Female ferrets have paired ovaries located just caudal to the
kidneys and attached to the wall of the abdominal cavity by the
broad ligament and by the suspensory ligament.1 The uterus is
bicornate with a short body and one cervix, similar to the cat
uterus. The vulva becomes extremely enlarged during estrus.

Physiologic Values
Physiologic values for domestic ferrets are presented in
Table 1-1.

HUSBANDRY
The following discussion of husbandry is an overview of the
keeping of ferrets as pets. A wealth of information is now available on all these topics, providing more details. The literature
also contains ample information about maintaining ferrets as
laboratory animals; thus this topic is not addressed here.

Behavior
The domestic ferret maintains the physiology and behavior
of its predator ferret ancestors. Domestication has made ferrets
unafraid of human beings and able to handle new environments
without fear. The alertness for danger among feral relatives also
is decreased.16 In addition, their ancestors are solitary animals
that do not interact with others except to mate. Ferrets, on the
other hand, appear to be able to live in communal groups peacefully, particularly if neutered. Ferrets still maintain the instinctive behaviors for play, territory marking, and hunting.
Aggressive play behavior can serve as a tool to teach aggression and protection skills as well as hunting skills. Aggressive
play begins at around 6 weeks of age and eventually merges into
more serious adult aggressive behavior as ferrets mature.17 Ferrets


9

TABLE 1-1
Selected Physiologic Values for Domestic Ferrets7,11
Parameter

Normal Values

Body weight, intact male
Body weight, intact female
Body weight, neutered; both sexes
Life span
Sexual maturity
Gestation period
Litter size
Normal weight at birth
Eyes and ears open
Weaning age
Body temperature
Average blood volume

1-2 kg
0.6-1.0 kg
0.8-1.2 kg
5-11 yr
6-12 mo of age
41-43 days
1-18 kits, average 8
6-12 g

32-34 days
6-8 wk
37.8-40ºC (100-104ºF)
Mature male, 60 mL;
mature female, 40 mL
200-400 beats/min
33-36 breaths/min
26-28 mL/24 hr
6.5-7.5

Heart rate
Respirations
Urine volume
Urine pH

will still exhibit bouts of play behavior as adults, particularly
during courtship or within their familiar group. Serious aggression occurs primarily when strangers are introduced or during
periods when the animal feels fearful. Neck biting by both sexes
is the most common aggressive and play behavior seen.17 This
behavior is also used by males to control females during mating.
Ferrets have very thick skin over the back of the neck and they
can sustain very aggressive biting without serious injury. In addition, the neck bite serves to quickly kill prey when used in
hunting. Other offensive aggressive behaviors include lunging,
sideways attack, dancing, and a staccato clucking sound.18 Defensive threats include hissing, screaming, and snapping of the
jaws.18 A ferret scream can be quite loud, high-pitched, and
alarming, but it is associated with fear and not pain.18 To minimize biting among ferrets, a bitter-tasting product can be applied
to the necks of ferrets. This type of product is also helpful when
sprayed on an owner’s hands, feet, or shoes to prevent nipping
by a playful pet.
The polecat ancestors of the ferret lived in underground

burrows. They usually took over other animals’ burrows and
then modified them by digging additional entryways and
rooms.20 In the home, the domestic ferret thoroughly enjoys
digging in soft materials, including carpeting, furniture stuffing,
and litter box material. Ferrets also appreciate being able to
explore tunnel-like areas and having an enclosed sleeping area.
Polecats are very fastidious about their dens and never defecate
or urinate in or near the burrow. They use urine, stool, and anal
gland secretions to mark their territory. Ferrets, like the polecats,
prefer to back up to a vertical surface to defecate or urinate and
then proceed to leave their scent with anal gland secretions by
dragging their anus over the surrounding area.20 In addition, an
intact male ferret may mark his territory by rubbing his abdomen
or side around the perimeter, leaving the scent of skin oils in the
area.18

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Ferrets appear to use olfactory clues rather then visual clues
when searching for prey.3 However, once the prey is located they
are stimulated by a range of movement somewhere between 25
and 45 cm/sec, which is the escape speed of a small rodent.3 In
addition, ferrets learn to attack the neck area of the prey as they

experience success with an efficient kill.3 Ferrets in the home like
to run after and sometimes grab moving targets such as feet,
objects rolling across the floor, and other pets.
Because they are close to the ground, ferrets spend a great
deal of time with their noses to the floor investigating their
environment. This behavior results in the inhalation of dust
and debris and subsequent sneezes. A ferret’s sneeze, which is
very loud and sounds like a combination of a cough and a
sneeze, may be alarming to its owner. Unless sneezing is frequent or associated with other clinical signs, owners need not
be concerned.

Reproduction
Ferrets are easily sexed. The preputial opening in the male
ferret is located on the ventrum, as in male dogs, just caudal to
the umbilical area. The os penis is readily palpable. In female
ferrets, the urogenital opening is located in the perineal region
ventral to the anus. The urogenital opening looks like a slit in
nonestrous females; during estrus, the vulva becomes swollen
and protuberant, appearing like a doughnut of tissue.
Both male and female reproductive cycles are controlled by
the photoperiod; they become fertile as the days get longer.6 The
natural breeding season for ferrets in the northern hemisphere
is from March to August. Under artificial lighting conditions,
they can be induced to breed year-round.6 Spermatogenic activity occurs in the seminiferous tubules from December to July,
and the testicles enlarge during this time. In addition, both sexes
have an increase in the intensity of the odor of the skin oils and
urine during the fertile period. White ferret fur becomes yellow
with these oily secretions.
Female ferrets are seasonally polyestrous and induced ovulators. Ovulation occurs 30 to 40 hours after copulation. Copulation is a noisy, violent affair in which the male ferret grasps the
female by the neck and drags her around, repeatedly mating with

her. If the female is receptive, she will become limp in his grasp.
The normal gestation is 41 to 43 days, and the female raises the
kits entirely on her own. Pregnancy can be determined at around
14 days with gentle palpation or ultrasound. If fertilization does
not occur, pseudopregnancy lasting 41 to 43 days will result. If
not bred, females can stay in estrus indefinitely unless the photoperiod changes, she is bred, she is treated with hormones, or
she dies from hyperestrogenism. (See Chapter 4 for a discussion
of this disease.)
The kits are born blind and deaf, with a thin coat of white
hair. By about 3 days of age, the hair starts to change color unless
the kit is an albino. Kits start moving around actively and can
eat soft food by 21 days of age, even before their eyes are open.
The eyes and ears open at 32 to 34 days of age and they are
weaned at 6 to 8 weeks. It is very difficult to raise neonate
orphaned kits.

Housing
Ferrets can be housed either indoors or outdoors depending
on the climatic conditions of the area. Ferrets are intelligent,

curious animals that should not be continuously confined in a
small cage. Pets need a safe play area where they can investigate
a variety of objects, such as boxes, bags, and plastic pipes. Ferrets
should be allowed a minimum of 2 hours a day of exercise. Lewington12 has an extensive description of an entire “ferretarium”
and other outside enclosures for ferrets that are rich in environmental stimuli.
A play or living area for ferrets must first be “ferret proofed”—
that is, all holes to the outside or to areas from which the ferrets
cannot be retrieved must be blocked off. In addition, ferrets like
to burrow into the soft foam rubber of furniture and mattresses.
Owners should be advised to cover the bottom of all couches,

chairs, and mattresses with a piece of thin wood or hardware
cloth. The burrowing is not only destructive but also potentially
life threatening because ferrets may swallow the foam rubber
and develop gastrointestinal obstructive disease. Reclining chairs
have been implicated in the deaths of many ferrets and should
be removed from the environment. In addition, all access to any
foam or latex rubber items, such as dog and cat toys, athletic
shoes, rubber bands, stereo speakers and headphones, and pipe
insulation, should be eliminated. Ferrets will often chew these
substances, and ingestion of rubber foreign bodies is the most
frequent cause of gastrointestinal obstruction, particularly in
ferrets younger than 1 year.
Up to two ferrets can use a wire cage of 24 ¥ 24 ¥ 18 inches
in height as a home base when it is necessary to confine them.
The floor can be either solid or wire. Glass tanks are not suitable
for caging ferrets because they provide poor ventilation. Custombuilt wooden cages can also be used, but care must be taken to
protect corners, the lower third of walls, and the floor from contamination with urine. If ferrets are kept outdoors, a portion of
the cage should be shaded for protection from extremes of heat
and cold and a well-insulated nest box should be provided. They
do not tolerate temperatures above 90°F (32°C), especially in
the presence of high humidity, and may need to be brought
indoors. In climates where the temperature drops below 20°F
(-7°C), a heated shelter is necessary. When caring for ferrets in
a clinical setting, ensure that cages are escape proof. Ferrets have
been known to squeeze between the bars of a standard dog or
cat hospital cage.
Ferrets need a dark, enclosed sleeping area. This is essential
in the clinical setting as well because the patient may become
more anxious and stressed if denied access to such a “safe” area.
Towels, old shirts, and cloth hats can be used in addition

to specific products designed for ferrets to sleep in, such as
cloth tubes and tents. For the occasional ferret that insists
on eating its cloth sleeping material, use a small cardboard,
plastic, or wooden box with an access hole cut into it. Some
owners use slings, hammocks, or shelves that are built into the
cage to provide additional sleep and play areas. In a multipleferret household, at least one sleep area should be provided
per ferret.
Toys for ferrets should not include any latex rubber toys
intended for dogs or cats. Instead, paper bags, cloth toys for cats
or babies, or hard plastic or metal toys can be used. Ferrets love
to run through cylindrical objects, such as polyvinyl chloride
pipe, large mailing tubes, and dryer vent tubing; these items
make good toys and promote exercise.
Ferrets can be trained to use a litter box relatively easily.
Because ferrets like to back up in corners to defecate or urinate,
the litter box sides should be high enough to contain the

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Basic Anatomy, Physiology, and Husbandry
excreted material. Pelleted litter material is recommended
instead of clay or clumping litter. Because of the ferret’s short
digestive transit time, the pet may not always reach the cage to
use the litter box if it is not close by. Therefore owners should
be advised to have several litter boxes available in various rooms
of the house for use by the pet when it is uncaged.


Nutrition
Ferrets are strict carnivores that are designed to eat whole,
small prey animals. Their polecat ancestors would bring their
kill home and store the excess in the den and eat small frequent meals rather then gorging.4 They have a very short
gastrointestinal tract with minimal gut flora and few brush
border enzymes, so they cannot use carbohydrates efficiently
or digest fiber.4 Ferrets in nature would only encounter carbohydrates as found in the partially digested stomach contents
of their prey. Ferrets should therefore be fed a diet high in
fat for energy, high in good-quality meat protein, and minimal
carbohydrate and fiber. A whole prey diet or a balanced fresh
or freeze-dried carnivore diet is the most appropriate for a
ferret, and such diets are currently fed in some areas of the
world. Disease-free sources of prey food such as chicks, mice,
and rats are now available in many areas thanks to the reptile
market, which uses these foods for carnivorous pets. The
stools of a ferret on a whole prey diet are very firm and of low
volume.
The most common diet fed to pet ferrets in the United States
is dry kibble. Although there have been advancements in dry
ferret food formulation, these diets still contains high levels of
grain, which is necessary to hold the food in its solid shape.
Very high levels of plant proteins in the diet can lead to
urolithiasis.4 Furthermore, excess dietary carbohydrates can
affect the pancreas and may contribute to disease of the beta
cells. Unfortunately, ferrets seem to enjoy sweet foods, and
some commercial pet food companies have capitalized on this
preference by producing ferret treats that are little more than
sugar-coated grains. These treat foods are particularly dangerous to the health of the pet ferret. The stools of a ferret eating
a dry kibble diet is formed but soft, voluminous, and may
contain visible undigested grain.

If a dry diet is fed to the ferret, the owner should read the diet
ingredients carefully. The crude protein should be 30% to 35%
and composed primarily of high-quality meat sources, not
grains; the fat content should be 15% to 20%.4 Dry food ingredients are listed on the label in descending order of their amount
in the product. The first three ingredients of a ferret diet should
be meat products. Because the diet is dry, it can be left out at all
times. However, the ferret may establish stashes of food around
the house, mimicking the storage of extra prey in its ancestral
den. Growing kits need 35% protein and 20% fat, and lactating
females require 20% fat and twice the calories of the nonpregnant ferret.4
Acceptable supplemental foods to a dry diet include fresh raw
organ or muscle meat and raw egg. It is not necessary to cook
the meat or eggs if they are fresh and are suitable for human consumption. Omega-3 oils, fish oils, or meat fat can be added to
increase the fat content of the diet provided these additions are
not allowed to become rancid. Dairy products have also been
used as a fat and protein supplement, but some ferrets develop
soft stools when fed these products. Even though ferrets enjoy

11

eating fruits, they should be avoided because owners often overfeed these items, leading to a reduction in the consumption of
a healthier diet and the overfeeding of sugars and fiber. Ferrets
develop their dietary preferences by 4 months of age; therefore
changing an adult ferret’s diet can be difficult without some
innovation.
Because of the short gastrointestinal transit time, fasting a
ferret for longer than 3 hours is not necessary to check the
fasting blood glucose level. Six hours is more than sufficient
to empty the gastrointestinal tract for surgery. Ferrets older
than 2 years in the United States are prone to develop insulinoma, and a longer fast could result in a serious hypoglycemic

condition.
Water should always be available in either a sipper bottle or
a heavy crock-type bowl. Ferrets love to play in the water, so the
bowl should not be easy to overturn. Supplements should not
be added to the ferrets’ water supply.

REFERENCES
1. An NQ, Evans HE: Anatomy of the ferret. In Fox JG, ed. Biology
and Diseases of the Ferret, 2nd ed. Baltimore, Williams &
Wilkins, 1998, pp 19-69.
2. Apfelbach R: Olfactory sign stimulus for prey selection in polecats. Zeitschrift fur Tierpsychol 1973; 33:270-273.
3. Apflebach R, Wester U: The quantitative effect of visual and
tactile stimuli on the prey-catching behaviour of ferrets (Putorius furo L.). Behav Processes 1977; 2:187-200.
4. Bell JA: Ferret nutrition. Vet Clin North Am Exotic Anim Pract
1999; 2:169-192.
5. Fox JG: Taxonomy, history, and use. In Fox JG, ed. Biology and
Diseases of the Ferret, 2nd ed. Baltimore, Williams & Wilkins,
1998, pp 3-18.
6. Fox JG, Bell JA: Growth, reproduction, and breeding. In Fox JG,
ed. Biology and Diseases of the Ferret, 2nd ed. Baltimore,
Williams & Wilkins, 1998, pp 211-227.
7. Fox JG: Normal clinical and biologic parameters. In Fox JG, ed.
Biology and Diseases of the Ferret, 2nd ed. Baltimore, Williams
& Wilkins, 1998, pp 183-210.
8. Grzimek B, ed: Grzimek’s Encyclopedia of Mammals, Vol 3. New
York, McGraw-Hill, 1990, pp 401-405.
9. Holmes RL: The adrenal glands of the ferret, Mustela putorius. J
Anat 1961; 95:325-339.
10. Lewington JH: Classification, history and current status of
ferrets. In Ferret Husbandry, Medicine & Surgery. Oxford, Butterworth-Heinemann, 2000, pp 3-9.

11. Lewington JH: External features and anatomy profile. In Ferret
Husbandry, Medicine & Surgery. Oxford, ButterworthHeinemann, 2000, pp 10-25.
12. Lewington JH: Accommodation. In Ferret Husbandry, Medicine
& Surgery. Oxford, Butterworth-Heinemann, 2000, pp 2653.
13. MacDonald D: The Velvet Claw: A Natural History of the
Carnivores. London, BBC Books, 1992, pp 211-215.
14. Moody KD, Bowman TA, Lang CM: Laboratory management of
the ferret for biomedical research. Lab Anim Sci 1985; 35:272279.
15. Neuwirth L, Collins B, Calderwood-Mays M, et al: Adrenal ultrasonography correlated with histopathology in ferrets. Vet Radiol
Ultrasound 1997; 38:69-74.
16. Poole TB: Some behavioral differences between the European
polecat, Mustela putorius, the ferret, Mustela furo, and their
hybrids. J Zool 1972; 166:25-35.

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FERRETS

17. Poole TB: Aggressive play in polecats. Symp Zool Soc Lond
1966; 18:23-44.
18. Poole TB: Aspects of aggressive behavior in polecats. Zeitschrift
fur Tierpsychol 1967; 24:351-364.
19. Porter V, Brown N: The Complete Book of Ferrets. London,
Pelham Books, 1987.
20. Sleeman P: Stoats & Weasels, Polecats & Martens. London,

Whittet Books, 1989, pp 67-70.

21. Whary MT, Andrews PLR: Physiology of the ferret. In Fox JG, ed.
Biology and Diseases of the Ferret. 2nd ed. Baltimore, Williams
& Wilkins, 1998, pp 103-148.
22. Willis LS, Barrow MV: The ferret (Mustela putorius furo L.) as a
laboratory animal. Lab Anim Sci 1971; 21:712–716.
23. Zeuner FE: A History of Domesticated Animals. New York,
Harper & Row, 1963, pp 401-403.

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2
Basic Approach to Veterinary Care
Katherine E. Quesenberry, DVM, Diplomate ABVP, and
Connie Orcutt, DVM, Diplomate ABVP

RESTRAINT AND PHYSICAL EXAMINATION
Restraint
Physical Examination

RESTRAINT AND PHYSICAL EXAMINATION
Restraint

PREVENTIVE MEDICINE
Vaccinations
Canine Distemper

Rabies
Vaccine Reactions
Parasites
Endoparasites
Ectoparasites

HOSPITALIZATION
CLINICAL AND TREATMENT TECHNIQUES
Venipuncture
Reference Ranges
Intravenous Catheters
Fluid Therapy
Antibiotic and Drug Therapy
Pain Management
Nutritional Support
Urine Collection and Urinalysis
Urinary Catheterization
Splenic Aspiration
Bone Marrow Collection
Tracheal Wash
Blood Transfusion

Ferrets can easily be accommodated in an existing small
animal veterinary practice. Special equipment needs are
minimal, and the approach to handling ferrets is similar in many
ways to that for dogs and cats. Ferret owners regularly seek
veterinary care for a variety of reasons: ferrets need preventive
vaccinations for canine distemper and rabies; ferret owners generally are very attuned to their pets and are responsible pet
owners; ferrets have a relatively short life span compared with
that of cats and dogs; ferrets in the United States have a high

incidence of endocrine, gastrointestinal, and neoplastic diseases,
especially middle-aged and geriatric ferrets; and many of the diseases common to ferrets are not easily ignored by the pet owner
(e.g., alopecia resulting from adrenal disease and hypoglycemic
episodes caused by insulinoma).

Most ferrets are docile and can be easily examined without
assistance. However, an assistant is usually needed when taking
the rectal temperature, when administering injections or oral
medications, or if an animal has a tendency to bite. Young ferrets
often nip, and nursing females and ferrets that are handled infrequently may bite. Unlike dogs and cats, which growl, ferrets will
bite without warning. Therefore always ask the owner if the ferret
will bite before handling it and take precautions accordingly.
Also be aware of local laws pertaining to required procedures if
an unvaccinated ferret bites an employee or other person in
your clinic.
Depending on the ferret’s disposition, one of two basic
restraint methods can be used for physical examination. For a
very active animal or one that bites, scruff the ferret at the back
of its neck and suspend it with all four legs off the table (Fig.
2-1). Most ferrets become very relaxed with this hold, and the
veterinarian is able to examine the oral cavity, head, and body,
auscultate the chest, and palpate the abdomen easily.
For more tractable animals, lightly restrain the ferret on the
examination table. Examine the mucous membranes, oral cavity,
head, and integument. Then pick the ferret up and use one hand
for support under its body while using the second hand to
auscultate the thorax and palpate the abdomen. The ferret can
be scruffed at any time for vaccination, ear cleaning, or other
procedures that may elicit an attempt to escape or bite.
To restrain a ferret for procedures such as venipuncture or

ultrasound, hold it firmly by the scruff of its neck and around
the hips without pulling the legs back. Most ferrets struggle if
their legs are extended by pulling on the feet. Many animals can
be distracted during a procedure by feeding Nutri-Cal (Tomlyn,
Buena, NJ) or a meat-based canned food (a/d Prescription Diet,
Hill’s Pet Nutrition, Topeka, KS; Eukanuba Maximum-Calorie,
The Iams Company, Dayton, OH) by syringe. However, if a
blood sample is to be collected subsequently to measure the
blood glucose concentration, feeding Nutri-Cal or other products containing sugar, which will cause the blood glucose concentration to increase, should be avoided. Leather gloves are not
recommended because they interfere with the handler’s dexterity, they cannot be disinfected between animals, and a determined ferret can bite through them.

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