Physical Examination of Small Exotic Mammals

Key Points

  • Before you start the hands-on portion of your examination, perform a visual exam. The visual examination should include information about the cage as well as the appearance and mentation of the animal.
  • Obtaining the patient’s weight and temperature should be the first part of the physical examination.
  • Auscult the heart and lungs using an infant or pediatric stethoscope.
  • The primary deviation from the typical “head to tail” method of physical examination is the oral exam in rabbits and rodents. The oral examination can be very stressful for many small mammals and is generally performed last.
  • One of the most effective ways to perform an oral examination on a small mammal is with an illuminated bivalve nasal speculum.
  • Look for any dental abnormalities such as malocclusion, tooth overgrowth, fractured teeth, or points on the lingual or buccal surfaces of the premolars or molars.

Introduction

Physical examination in exotic small mammals is performed similarly to examinations in dogs and cats, however many small mammals can easily become stressed. Approach these patients calmly, gently, and quietly. Gather all items that may be needed during the physical exam beforehand since it is essential to keep handling time to a minimum. Ideally schedule examination of nocturnal species such as sugar gliders (Petaurus breviceps), rats (Rattus norvegicus), and mice (Mus musculus) during the evening hours (Fig 1). It can also be helpful to dim the lights while examining these species.

rat exam Nugent

Figure 1. Physical examination of a pet rat (Rattus norvegicus). Photo credit: Jody Nugent-Deal. Click image to enlarge.

Visual examination

Perform a visual examination before beginning the hands-on portion of your exam. Gather visual information about the pet’s caging: note the bedding and the degree of cleanliness, the diet offered, as well as the presence of any toys or cage furniture.

The visual examination is particularly important in small, pugnacious rodents like the hamster that will allow only a quick physical exam. Gather information about the appearance and mentation of the pet. What is the appearance of the stool? Does the skin and hair coat appear healthy? Or is there evidence of fur or quill loss? Are there signs of respiratory disease such as increased respiratory effort, increased respiratory rate, sneezing, coughing, chattering, or congestion? As obligate nasal breathers, open-mouth breathing is a sign of respiratory distress in rabbits (Oryctolagus cuniculus) and many rodents.

Many small mammals like rabbits and rodents tend to mask pain and discomfort, especially when frightened. Signs of fear in the rabbit may include the body flattened in a crouched, motionless position with the feet tucked underneath and the head extended. The ears are often tucked tightly against the head, and the eyes may bulge. Signs of pain may include teeth grinding in a slow, loud crunching fashion in rabbits and ferrets (Mustela putorius furo), reluctance to move, decreased interest in the environment, and a hunched posture.

 

Physical examination

Obtain heart rate and respiratory rate as soon as the animal is removed from the cage (Table 1). If you suspect respiratory problems, supplemental oxygen may be warranted. Since many exotic mammals are very small, obtain weight using a scale that weighs to the nearest gram (Fig 2). Obtain body temperature using a small, quick-acting, flexible digital thermometer when appropriate. If the patient appears overly stressed at any time during the examination, halt the exam and allow the animal to relax.

Syrian hamster

Figure 2. Syrian hamster (Mesocricetus auratus) in a weight bucket. Photo credit: Dr. Lauren Thielen. Click image to enlarge.

 

Table 1: Reported Normal Vital Signs for Exotic Small Mammals.
Temperature °C (°F) Pulse (bpm) Respiration (bpm)
Chinchilla 37-38 (98.5-100.4) 150-350 40-80
Degu 38.3 (100.9)
Ferret 37.8-39.4 (100-103) 180-250 30-40
Gerbil 37.4-38.2 (99.3-100.8) 260-600 85-160
Guinea pig 37.2-38.6 (99-101.5) 230-380 40-100
Hamster 36.1-38.9 (97-102.3) 250-500 34-114
Hedgehog 35.4-37 (95.7-98.6) 180-280 25-50
Mouse 37.1 (98.8) 400-700 90-200
Rabbit 38.0-39.6 (101.3-103) 180-325 30-60
Rat 37.7 (99.9) 300-500 70-150
Sugar glider 32 (89.6) 200-2300 16-40

Select a link above for additional species-specific information in our Basic Information Sheets

A general rule of thumb is to begin the physical examination at the head and work your way down to the tail to ensure nothing is overlooked. The primary deviation from the “head to tail” method is the oral exam in rabbits and rodents. Since this procedure can be very stressful for small prey species, it is generally performed last. In predator species, such as dogs, cats, and ferrets, the mouth is usually evaluated at the same time the head is examined. Broken canines are a common finding in adult ferrets. Gingivitis and periodontitis are frequently seen in African pygmy hedgehogs (Atelerix albiventris).

Continue the examination by looking at the nares, eyes, and ears. Ferrets often have dark, waxy debris in the ears, however they should be evaluated if there is excessive debris or a history of scratching. Most ferrets in the United States have two small round tattoos on the inside of the pinna. These tattoos indicate the ferret is from a facility called Marshall Farms. One dot indicates the ferret has been descented and the second dot indicates neutering (Fig 3).

Ferret with two small round tattoos on the inside of the pinna.

Figure 3. Most ferrets (Mustela putorius fur) in the United States are from Marshall Farms, a facility that places two small round tattoos on the inside of the pinna. One dot indicates the ferret has been descented and the second dot indicates neutering. Photo provided by Nugent-Deal. Click image to enlarge.

Auscult the heart and lungs using an infant or pediatric stethoscope (Figs 4A and 4B), noting the presence of any potential heart murmurs, arrhythmias, harsh lung sounds, or any other abnormalities. When compared to the cat or dog, the ferret heart is located more caudally (Fig 5). Also a prominent sinus arrhythmia is frequently ausculted in the normal ferret.

Physical exam of a hamster with an infant stethoscope.

Figure 4A. Auscultation of small mammals with an infant stethoscope. A, Golden hamster (Mesocricetus auratus). Photo provided by J. Nugent-Deal. Click image to enlarge.

Auscultation of a rat

Fig 4B. Auscultation of a rat (Rattus norvegicus) Click image to enlarge.

Physical exam auscult ferret

Figure 5. Auscultation in a ferret (Mustela putorious furo) illustrating the more caudal location of the heart when compared to the cat or dog. Photograph provided by J. Nugent-Deal. Click image to enlarge.

Palpate all peripheral lymph nodes. Normal ferrets may have a significant amount of fat around the peripheral lymph nodes that may be confused with lymphadenopathy.

Evaluate the hair coat and skin for evidence of skin lesions, hair loss, or ectoparasites. Progressive hair losson the tail, tail base, and trunk is the most common sign of hyperadrenocorticism in ferrets (Fig 6). Normal hedgehog skin is relatively dry and flaky but excess crust or scale, quill loss, or redness is associated with skin disease such as dermatophytosis or mange. Guinea pigs often have mild to moderate dark sebaceous debris on the skin overlying the back. Older boars may develop a collection of debris at the base of the spine.

Physical exam of bald ferret tail

Figure 6. Alopecia on the tail, tail base, and trunk is the most common sign of hyperadrenocorticism in the ferret (Mustela putorius furo). Photograph by C. Pollock. Click image to enlarge.

Also check for any masses, especially in rats and mice. Be aware of normal glandular structures. The male sugar glider has a ventral chest gland as well as a scent gland on top of the head that may resemble a “bald spot”. There is also a dark brown, fur-covered flank gland in male and female hamsters. This gland tends to be larger and more prominent in males.

Palpate the abdomen. In many small mammals, the stomach, kidneys, cecum (if present) and bladder (if full) can be easily palpated. The normal rabbit cecum should be soft and compressible. A mildly enlarged spleen is often palpable in the normal ferret. Even marked splenomegaly may merely indicate normal extramedullary hematopoiesis when associated with a normal texture. Auscult the abdomen in rabbits, guinea pigs (Cavia porcellus), and chinchillas (Chinchilla laniger) (Figs 7A and 7B). Healthy herbivores typically have one or two gut sounds or borborygmi per minute. Disease or stress can reduce gut movement.

Auscultation of the gastrointestinal tract in an herbivore

Figure 7A. Auscultation of the gastrointestinal tract in an herbivore. Photo by J. Nugent-Deal. Click image to enlarge.

Auscultation of the gastrointestinal tract in a rabbit

Fig 7B. Auscultation of the gastrointestinal tract in a rabbit (Oryctolagus cuniculus). Photo by J. Nugent-Deal. Click image to enlarge.

Palpate the limbs and joints and examine the feet. Hedgehogs may suffer from threads wrapped around digits or ingrown toenails. Check the bottoms of the feet for evidence of pododermatitis (Fig 8). Be sure to note the fur overlying the forelimbs since matted fur may build up when rabbits fastidiously groom oculonasal discharge.

Pododermatitis in a guinea pig

Figure 8. Pododermatitis in a guinea pig (Cavia porcellus); note the swelling and redness. Photograph by J. Nugent-Deal. Click image to enlarge.

Examine the genitalia, the perineal region, the prepuce, and the mammary glands. Assign a body condition to the patient using a system similar to that used in dogs and cats, with 1 out of 9 being emaciated and 9 out of 9 being grossly obese.

Examine the mouth last. Palpate the cheek and jaws for swellings or asymmetry, and look for evidence of drooling, which may also be seen with dental disease. Carefully evaluating the gums, tongue, and all of the teeth including the incisors. The oral examination can be difficult in a conscious patient, and light sedation or general anesthesia may be required in uncooperative or anxious individuals. Use a mouth speculum with a bright light source to examine the oral cavity of rodents and rabbits (Oryctolagus cuniculus). One of the most effective instruments is an illuminated bivalve nasal speculum (Fig 9 and Fig 10). A rigid endoscope along with a mouth speculum may also be used to examine the mouth. Less effective instruments include an otoscope with a long otoscope cone or a small vaginal speculum and a penlight. Look for dental abnormalities such as malocclusion, tongue entrapment (generally seen in guinea pigs with severe dental disease), incisor overgrowth, fractured teeth, or points on the lingual or buccal surfaces of the cheek teeth, common in guinea pigs, rabbits, and chinchillas.

Oral exam of a guinea pig using an illuminated bivalve nasal speculum.

Figure 9. Oral exam of a guinea pig (Cavia porcellus) using an illuminated bivalve nasal speculum. Photograph provided by J. Nugent-Deal. Click image to enlarge.

Intraoral view of a guinea pig using an illuminated bivalve nasal speculum.

Figure 10. Intraoral view of a guinea pig (Cavia porcellus) using an illuminated bivalve nasal speculum. Photograph provided by J. Nugent-Deal. Click image to enlarge.

Evaluate patient hydration status in a manner similar to that used in cats or dogs. Mucous membranes should be moist and pink, and capillary refill time should be between 1 to 2 seconds. A common sign of dehydration is dry or tacky mucous membranes. Severe dehydration may be associated with sunken eyes. Also tent or pull upward on the skin overlying the back to assess hydration since another sign of dehydration is a reduction in skin elasticity.

If the initial respiratory rate seemed exaggerated, recount the rate upon completion of the examination after the animal has been placed back into the cage.

 

Conclusion

Before you begin the hands-on portion of your examination, perform a visual examination to obtain information about the cage as well as the appearance and mentation of the animal. The primary deviation from the typical “head to tail” method of physical examination is the oral examination. The oral examination can be very stressful for small mammals and therefore is generally performed last. Once a complete physical exam has been performed and the animal is stable, diagnostic may be performed when indicated.

References