Behavior Basics: Clinical Approach to the Guinea Pig

Key Points

  • Guinea pigs are docile, prey species.
  • Like most prey species, the guinea pig can hide signs of pain and illness extremely well.
  • The guinea pig’s tendency to freeze when frightened or stressed, compounds the difficulty of observing valuable clues during the visual exam.
  • In an effort to minimize stress and increase clinical success, transfer the guinea pig to a quiet exam room as needed and approach the patient slowly and speak softly.
  • The hospitalized guinea pig can benefit greatly from the presence of a bonded cage mate.
  • Guinea pigs establish food preferences early in life, therefore offer hospitalized guinea pig patients their regular diet whenever possible.
  • Monitor appetite and eliminations carefully as this rodent tends to stop eating in stressful situations.
  • Provide vitamin C daily to ill, hospitalized guinea pigs to prevent scurvy, which can develop quickly.

Introduction

Guinea pigs (Cavia porcellus) are small, docile rodents, that must be approached with great care. Accurate evaluation of patient health status requires a thorough history, careful visual examination, and a detailed physical exam.

There are three standard breeds of the domestic guinea pig: American or English, Abyssinian, and Peruvian (Quesenberry et al 2012). Although up to 13 breeds have been recognized by the American Rabbit Breeder’s Association (Quesenberry et al 2012), no substantial differences in behavior have been studied or described among guinea pig breeds.

 

Minimizing stress before the exam

The clinician can glean much more information from evaluation of a relaxed patient when compared to a tense, fearful individual. The frightened or stressed guinea pig tends to freeze or exhibit tonic immobility (Dunbar et al 2016, Bradley Bays 2006). Stampede behavior can also be observed in the fearful guinea pig. Therefore, every effort must be made to create and maintain a stress-free environment for this gentle, prey species in a hospital setting.

In an effort to minimize stress, guinea pigs should be presented to the veterinary hospital in an enclosed, well-ventilated travel cage and protected from temperature extremes (Murray & Crane 2016). If the waiting room is busy, transfer this shy rodent to a quiet examination room to maintain a low-stress environment (Murray & Crane 2016).

 

Visual examination

Observe the guinea pig from a distance to evaluate behavior, mentation, and the respiratory rate or rhythm. There are a variety of additional clues that can potentially be gleaned from the visual exam, including posture, gait, as well as evidence of appetite or eliminations.

  • The healthy, relaxed guinea pig will appear inquisitive, active, and vocal, with clear, open eyes (Murray & Crane 2016, Quesenberry et al 2012, Bradley Bays 2006). Self-grooming is commonly observed (Manning et al 1976).
  • The normal guinea pig produces a large amount of stool and urine, and a number of fecal pellets should be visible within the enclosure (Murray & Crane 2016, Quesenberry et al 2012, Bradley Bays 2006).
  • The normal guinea pig bears weight evenly on all four limbs, walking with only the pads of the feet touching the ground (Bradley Bays 2006).
  • The healthy guinea pig will also display a vigorous appetite, accepting a treat such as fresh greens, even while in the carrier (Murray & Crane 2016, Quesenberry et al 2012, Bradley Bays 2006).

 

Clinical signs of pain or illness

As with many prey species, guinea pigs tend to hide signs of pain and illness in the presence of a human observer (Dunbar et al 2016). Subtle clinical signs can go undetected by the primary caretaker until the guinea pig begins to suffer from the secondary effects of illness, such as weight loss, dehydration, or a dull, rough hair coat (Dunbar et al 2016).

Signs of illness that can be reported by the owner or observed during the visual exam include any change in food or water consumption, oculonasal discharge, difficulty breathing, coughing or sneezing, certain vocalizations, such as urgent, repetitive squealing, exercise intolerance, a stiff or hunched posture, fecal staining of the perineum, as well as any change in fecal output, size, smell, and/or consistency (Table 1) (Oglesbee 2011, Bradley Bays 2006, Donnelly & Brown 2004, Morton & Griffiths 1985).

Clinical Tip: Any change in the quantity or consistency of stool should be monitored carefully. Advise owners to seek veterinary care if changes persist more than 12 hours (Bradley Bays 2006).

Table 1. Potential signs of illness in the guinea pig (Mayer & Donnelly 2012, Oglesbee 2011, Bradley Bays 2006, Donnelly & Brown 2004, Morton & Griffiths 1985)

  • Depression/lethargy or agitation

  • Urgent, repetitive squealing

  • Change in food and/or water consumption

  • Poor body condition, reduced body weight

  • Stiff, hunched posture

  • Reluctance to move

  • Dull, unfocused eyes

  • Difficulty breathing

  • Scaly skin, hair loss, skin masses or lesions

  • Absence of chewed food in the mouth


  • Ocular and nasal discharge

  • Cough

  • Sneezing

  • Change in fecal output

  • Fecal staining of perineum

  • Dragging hind limbs

  • Difficulty urinating, blood in urine

  • Hypersalivation

Clinical Tip: Guinea pigs tend to be messy eaters; therefore, an absence of food or water spillage can indicate anorexia or a reduction in water intake (Bradley Bays 2006, Donnelly & Brown 2004, Morton & Griffiths 1985).

Clinical Tip: The itchy guinea pig typically appears like any other itchy mammal, however pruritus associated with heavy mite infestation can be so severe the animal may begin to seizure as it scratches (Bradley Bays 2006).

Sign of pain in the guinea pig can mirror those seen with illness, however a host of additional findings can be observed (Bradley Bays 2006):

  • Owners often report a change in demeanor, such as depression or agitation, but aggression may also be seen in a previously mild-mannered individual. Of course, guinea pigs may also bite when fearful.
  • The painful guinea pig may stand with the head extended, displaying a strained expression with dull, bulging, or unfocused eyes and partially closed eyelids.
  • Respirations may be rapid and shallow.
  • The animal may press its painful abdomen into the floor or table.
  • Gastrointestinal pain can also be associated with polydipsia.
  • Some individuals may demonstrate “barbering”, or pulling and chewing hairs at the site of pain. Barbering must be differentiated from overgrooming of conspecifics.
  • Orofacial problems, such as dental disease, may be associated with the guinea pig exhibiting interest without eating food (Bradley Bays 2006) and hypersalivation. The animal may even pick up a food items before allowing it to fall from its mouth.

Evidence of post-surgical pain in the guinea pig can be particularly subtle. A recent study (Dunbar et al 2016) found no obvious behavioral changes indicating pain in the guinea pig during the first 24 hours after surgery (Dunbar et al 2016). Only subtle behaviors, described as “small, transient body motions performed in a stationary position”, such as weight-shifting and back arching, were associated with post-operative pain (Dunbar et al 2016). These findings can all be seen with tonic immobility.

Clinical Tip: Clinicians should administer pre-emptive analgesia to guinea pigs based on the assumption that a procedure or condition is painful, instead of relying on the observation of signs. A recent study (Dunbar et al 2016) recommends analgesia be administered to guinea pigs for at least 24 hours after castration or surgeries of similar invasiveness. The coauthors (Bradley Bays et al) believe analgesics should be provided for up to 7 days postoperative for any prey species.

Handling and restraint

Guinea pigs are gentle animals that do not tend to bite, although young animals may nip. Individual adults may also bite when fearful or when an annoying procedure, like a toenail trim, is performed (Bradley Bays 2006, Donnelly & Brown 2004).

Normal, healthy guinea pigs are vocal and will often push up vigorously against the hand that pets the top of their head. Standard guinea pig handling requires only minimal restraint as most individuals will sit quietly on the exam table. Use a towel or mat to provide traction and warmth (Bradley Bays 2006). Guinea pigs typically respond well to gentle restraint. A slow, calm approach is particularly important for shy individuals unaccustomed to frequent handling (Table 2) (Murray & Crane 2016, Bradley Bays 2006). Never scruff a guinea pig or handle it roughly (Murray & Crane 2016).

Like the horse, guinea pigs are grazers with laterally-placed eyes that allow them to watch out for predators as they feed. Since guinea pigs cannot see directly in front of them, they may readily walk off the edge of an exam table or some other high structure. Therefore, exercise caution to prevent falls (Bradley Bays 2006). To prevent patient injury, the handler should also be prepared for the fearful guinea pig to make an explosive attempt to escape, particularly when startled by a sudden noise (Quesenberry et al 2012, Bradley Bays 2006, Manning & Wagner 1976).

As grazers, guinea pigs also possess extremely sensitive hairs or vibrissae on their chins and muzzles, which allow them to “feel” their food as they eat.

Clinical Tip: The presence of sensitive vibrissae on the nose means that guinea pigs do not like to have their noses touched and doing so may cause them to startle.

Table 2. General principles for guinea pig restraint (Bradley Bays 2006)

  • DO approach the guinea slowly

  • DO speak quietly

  • DO approach the guinea pig at eye level, whenever possible

To pick up the guinea pig, do not chase the animal around the enclosure. If your patient is unaccustomed to handling, use a small towel much as you would for a bird. To access the ventrum or feet, place one hand beneath the rump to support body weight while the other hand supports the mid-body (Fig 1) (Murray & Crane 2016, Bradley Bays 2006). The guinea pig may wiggle and squeal if not well supported (Bradley Bays 2006), however it helps if the animal’s back is gently braced against the handler’s body. If the guinea pig continues to squirm, try a minor alteration in position to settle the patient more comfortably (Bradley Bays 2006).

Proper guinea pig restraint requires two hands.

Figure 1. Proper guinea pig restraint requires two hands. Support the rump with one hand, while the other hand is gently placed around the mid-body. The guinea pig shown here would be more secure and less likely to struggle if its back was gently braced against the handler’s body. Photo credit: Jake Rikki’s Refuge via Flickr Creative Commons.

When handled by a stranger, guinea pigs can be quiet and immobile, particularly shy or frightened individuals (Donnelly & Brown 2004). Well-socialized animals tend to make many vocalizations during restraint (Donnelly & Brown 2004). A relaxed guinea pig, habituated to handling, may also enjoy being scratched behind the ears and petted beneath the chin with one finger (Bradley Bays 2006).

Guinea pigs most often respond to oral exams with loud vocalizations and fear. Oral examination can be facilitated by making your movements slow and deliberate, talking softly to the patient as you proceed. To alleviate stress, an assistant can also place one hand on the rump and the other hand around the shoulders to stabilize the animal (Darbo-McClellan 2014). Alternatively, loosely wrap the guinea pig in a towel, leaving the head free for examination (Fig 2) (Donnelly & Brown 2004).

To examine the guinea pig oral cavity, an assistant may place one hand around the shoulder and chest and another hand around the rump. In this case, a towel is loosely wrapped around the hindquarters

Figure 2. To examine the guinea pig oral cavity, an assistant may place one hand around the shoulder and chest and another hand around the rump. In this case, a towel is loosely wrapped around the hindquarters. Photo credit: Heather Darbo-McClellan.

Visit LafeberVet’s web-based seminar “Restraint and Handling of Small Exotic Companion Mammals” for additional information. Go to timestamp 09:02 for guinea pig-specific information.

Physical examination

Much of the guinea pig exam is typical for that of any small mammal. Unique behavioral considerations include:

Eliminations

Guinea pigs often urinate when nervous or frightened, so there is frequently evidence of fresh urine in the transport cage. Guinea pigs also commonly urinate while handled (Bradley Bays 2006). Urination is a relatively passive process, in which the animal squats a small amount and slightly raises its head (Bradley Bays 2006). The normal, alkaline urine of the guinea pig varies in appearance, ranging from creamy white to thick, yellow, and turbid (Quesenberry et al 2012, Bradley Bays 2006). Bloody urine often indicates a bladder problem, whereas pink or red-tinged urine at the end of micturition indicates reproductive pathology. Additionally, porphyrin staining, or a brown or orange tinge to the urine, can occur with stress, ingestion of certain legumes, or administration of certain antibiotics (Bradley Bays 2006).

Clinical Tip: Placing a guinea pig on a white towel during physical examination will often allow the practitioner to evaluate urine color.

Vital signs

Stress may increase patient body temperature, so obtaining vitals should be one of the first tasks performed during the physical examination (Table 3) (Quesenberry et al 2012).

Table 3. Reported normal vital signs in the guinea pig (Nugent-Deal 2010)
ParameterUnits of measurementReported values
Temperature °C (°F) 37.2-38.6 °C (99-101.5 °F)
PulseBeats per minute230-380
RespirationBreaths per minute 40-100

Skin

Barbering can occur as a response to stress associated with overcrowding or insufficient enrichment, such as free-choice grass hay or chew items, such as cardboard boxes or untreated paper towel rolls (Bradley Bays 2006). Consider self-barbering if only the head and neck are unaffected (Bradley Bays 2006). Barbering can be distinguished from other causes of alopecia by careful evaluation of the skin and fur. Barbered fur is chewed near the skin creating a coarse, stubbly texture, however the underlying skin appears normal (Bradley Bays 2006).

Clinical Tip: When alopecia is noted dorsally, laterally, or in the flank area, but remaining fur and skin is normal, consider barbering as a response to pain and palpate for masses or evidence of abdominal pain (Bradley Bays 2006). Alopecia noted laterally may have a hormonal etiology.

Abdomen

Auscult the abdomen in all guinea pig patients (Fig 3). Healthy herbivores typically have one or two gut sounds or borborygmi per minute (Nugent-Deal 2010). Disease or stress can slow gastrointestinal motility.

Disease or stress can reduce the frequency of gut sounds or borborygmi ausculted during the physical exam.

Figure 3. Disease or stress can reduce the frequency of gut sounds or borborygmi ausculted during the physical exam.

Oral cavity, teeth

Like most small mammals, oral examination is stressful in the guinea pig and this procedure should always be performed last.

Clinical Tip: Guinea pigs enjoy mixing food and water in their mouths, and it is normal to find a green slurry within the oral cavity during the exam. Absence of particulate matter suggests the individual has been anorectic for some time (Bradley Bays 2006).

Some clinicians offer a treat, such as greens or hay, after the oral exam to assess the guinea pig’s overall health and to calm the nervous patient (Bradley Bays 2006). Remember that many guinea pigs are neophobic to new food items, so a familiar food item is preferable.

 

Diagnostics

Collection of diagnostic samples, including venipuncture, can be performed using gentle restraint, but in many cases light sedation or general anesthesia is preferable to reduce patient stress (Murray & Crane 2016).

 

Managing the hospitalized patient

Clinical Tip:  Guinea pigs do not adapt well to changes in their environments or routines and should be hospitalized only when necessary (Quesenberry et al 2012).

Not surprisingly, well socialized and well-adapted guinea pigs tend to do much better in a hospital setting, regardless of the underlying problem (Bradley Bays 2006), however there are measures that can be taken to reduce stress and improve outcome in even the most skittish patients:

Provide a cage mate

Guinea pigs isolated in a new environment initially respond by vocalizing and running around in circles. With more time, the guinea pig will enter a passive stage in which they will crouch with eyes closed, bristled fur, and may experience an increase in rectal body temperature (Bradley Bays 2006, Hennessy et al 2003). Housing the patient with a bonded cage mate significantly reduces stress in the ill, hospitalized guinea pig (Bradley Bays 2006, Donnelly & Brown 2004) and normal behaviors are noted sooner.

Food and water

Monitor food and water intake closely. The extremely high metabolic rate of the guinea pig means this animal needs to eat almost continuously (Bradley Bays 2006), however feeding activity increases at the beginning and end of the light cycle and in the middle of the dark period (Bradley Bays 2006, Horton et al 1975).

Make every effort to offer the hospitalized guinea pig their regular diet. Guinea pigs establish strong food preferences early in life, and will often refuse to eat or become depressed if there are any changes in the texture, color, shape, or taste of food (Quesenberry et al 2012, Bradley Bays 2006). Guinea pigs also tend to stop eating in stressful situations.

Guinea pigs and primates are among a small number of animal species that require exogenous or dietary L-ascorbic acid or vitamin C (Quesenberry et al 2012, Harkness et al 2010). Guinea pigs require 10-25 mg/kg of vitamin C per day in their diet; pregnant sows require 30 mg/kg/day (Quesenberry et al 2012, Harkness et al 2010). Provide vitamin C daily to ill, hospitalized guinea pigs via feed, tablet (Daily C, Oxbow Animal Health), water, or parenteral injection (5-10 mg/kg BW SC, IM) to prevent scurvy which can happen in 2 weeks or less (Quesenberry et al 2012, Harkness et al 2010). The risk of scurvy or hypovitaminois C is particularly high in young, growing animals up to 6 weeks of age (Harkness et al 2010).

Clinical Tip: Provide ill, hospitalized guinea pigs with vitamin C daily.

Normal water intake is approximately 100 ml/kg/day (Bradley Bays 2006). Bottles and dishes must be cleaned and sanitized daily as guinea pigs will pack chewed food up into the sipper tube and they will often defecate in food bowls .

Housing

House this gentle rodent in areas where noise is minimized (Bradley Bays 2006). Guinea pigs possess a relatively good sense of hearing, which makes this sensitive species susceptible to the stress of loud noises. To further minimize stress, offer some form of visual security, such as a hide box, a commercially available shelter, or even a towel for the guinea pig to burrow into and under for sleep and for retreat when startled (Fig 4) (Bradley Bays 2006).

Visit Basic Husbandry: Hospitalizing Non-Traditional Pets and Exotic ICU: Nursing Care for Exotic Companion Mammals for additional information.

Even a towel can offer some form of visual security for burrowing or to serve as a retreat when the guinea pig is startled.

Figure 4. Even a towel can offer some form of visual security for burrowing or to serve as a retreat when the guinea pig is startled.

Conclusion

Like most prey species, the guinea pig frequently hides signs of pain and illness. To improve clinical success, take measures to minimize stress by maintaining the animal in a quiet exam room and approaching the patient in a slow, quiet manner. The hospitalized guinea pig can also benefit greatly from the presence of a bonded cage mate. Monitor appetite and eliminations carefully in the guinea pig, and offer the same diet as fed in the patient’s home whenever possible as guinea pigs establish strong food preferences early in life.

 

References