- The guinea pig is a gentle, docile, rodent.
- Guinea pigs do not tolerate dietary or enrichment changes well.
- Food preferences are established early in life, and a guinea pig can refuse to eat if their food type or presentation is changed. Therefore juvenile guinea pigs should be exposed to a variety of chows and vegetables in small amounts.
- The guinea pig’s response to perceived danger is immobility or, less commonly, flight.
- Guinea pigs are highly social, vocal animals.
- Guinea pigs practice coprophagy.
The guinea pig or “cavy” (Cavia porcellus) is a rodent, belonging to suborder Hystricomorpha and family Caviidae (Fig 1) (Kimura et al 2016).
The guinea pig was first domesticated in South America between 500 and 1000 AD, possibly as early as 1000 BC (Quesenberry et al 2012, Weir 1974). Guinea pigs primarily served as a food source for wealthy families, and they were also sacrificed by the Inca during spiritual rituals (Kimura et al 2016). To this day, the guinea pig is still used as a food source in many South American countries (Fig 2) (Quesenberry et al 2012).
Guinea pigs were brought to Europe approximately 500 years ago where these gentle animals were primarily kept as pets. Since the 19th century, the guinea pig has also been used in biomedical research (Dunbar 2016, Quesenberry et al 2012, Padilla-Carlin et al 2008). Today, guinea pigs are both a popular pet and laboratory animal throughout the world. The number of guinea pigs in biomedical research has declined significantly with the advent of genetically engineered mice and rats, but guinea pigs remain the most prevalent regulated species by the United States Department of Agriculture (Fig 3) (Dunbar 2016, Quesenberry et al 2012).
Free-ranging guinea pigs are crepuscular (Asher et al 2004), while captive cavies are active during most of the day, spending only a small amount of time napping (Clemons & Seeman 2011). Guinea pigs at rest will lie on their sides with the feet extended or they will sit in sternal recumbency with the feet tucked underneath (Bradley Bays 2006). No distinct circadian rhythm has been observed in laboratory guinea pigs, but it has been shown they prefer not to be out when intense light is present (Clemons & Seeman 2011).
The guinea pig’s response to perceived danger is immobility or, less commonly, flight (Quesenberry et al 2012). When exposed to a novel sound or placed in a new environment, the guinea pig will in most cases freeze. This freezing is accompanied by an arched back, extended forelimbs, with the head held high, and eyes wide open (Manning et al 1976). When exposed to a sudden movement, guinea pigs tend to make an explosive attempt to reach shelter. When multiple guinea pigs are housed in one enclosure, animals tend to scatter in different directions when frightened, possibly to cause confusion in the predator (Manning et al 1976). Providing a shelter can minimize this behavior.
Guinea pigs are highly social animals. Free-ranging guinea pigs live in small groups, consisting of several to several dozen individuals in a male-dominated hierarchy (Manning et al 1976).
Domesticated guinea pigs seek physical contact with others when housed together. While at rest, they will often lie side by side, sometimes resting their chins or feet on one another (Manning et al 1976). Guinea pigs will also crowd together at feeders, however little mutual grooming is observed.
Guinea pigs can be extremely vocal (Manning et al 1976). Many of these vocalizations have been described in the literature (Quesenberry et al 2012, Bradley Bays 2006, Manning & Wagner 1976). These sounds include, but are not limited to:
- The “chutt” is a sound made in one to two calls and is related to general exploration and activity.
- The “purr” is made in approximately 50 fast bursts of noise and is related to mating and/or filial behavior.
- The “drr” is usually made in 6-7 bursts of sound, although anywhere from 3-14 is possible. This vocalization is a warning signal related to sudden changes in the environment like a novel sound.
- The “chirp” is a low intensity call designed to communicate distress or a warning. Visit Wikimedia:
- The “chutter” consists of two to four calls created in response to danger. Chutters are generally associated with flight, evasion, or defense.
- A “squeal” is a single call produced in response to injury.
- The “tweet” is a vocalization consisting of a variable number of calls that is related to maternal licking of the pups’ anogenital region.
- The “whistle” occurs in two stages, beginning with the “low whistle” and increasing in frequency to the “full whistle”. This sound is related to maternal separation and/or caretaker feeding.
- The “grunt” is related to dominance in males when interacting with underlings.
- The “scream” is produced by an underling during a fight and is variable in the number of calls created.
- “Tooth chattering” is another sound that a subordinate guinea pig may produce in response to a threat or conflict.
Scent marking is common among both male and female cavies (Bradley Bays 2006, Manning & Wagner 1976). Anal and supracaudal gland marking is observed during introductions to a new environment or in mating situations and is performed by squatting and dragging the rump on the cage floor (Iburg et al 2013, Clemons & Seeman 2011).
Wild guinea pigs tend to be more aggressive than their domesticated counterparts (Clemons & Seeman 2011). In captivity, access to mating privileges, food resources, and space appear to be the primary reasons these normally docile rodents may exhibit aggressive behavior (Clemons & Seeman 2011). Forms of aggression include ear nibbling and hair pulling or barbering, in which a tuft of hair is removed from a subordinate animal and consumed (Quesenberry et al 2012, Manning & Wagner 1976). Male guinea pigs may also bite.
Change is bad
Guinea pigs have been described as “neophobic”, and as a general rule, they do not tolerate changes in diet or environment well (Quesenberry et al 2012). Food preferences are established early in life and even a slight change in the type of diet or presentation of food can result in an adult refusing to eat (Quesenberry et al 2012). To minimize the risk of future problems, expose young animals to to a wide array of formulated foods and produce in small amounts so they become accustomed to variety in their diet (Quesenberry et al 2012).
Clinical Tip: Always instruct owners of the guinea pig’s tendency to establish strong food preferences. This will minimize the risk of a potentially dangerous, self-imposed fast when the pet is offered a new food later in life.
Although guinea pigs are inquisitive by nature, new environments or individuals can also be daunting. When exposed to something new, the guinea pig will react by stretching its body and making initial contact with only its whiskers (Clemons & Seeman 2011). Environmental changes can sometimes result in altered moods and a reduction in appetite, but fortunately these effects tend to be mitigated by the presence of a cage mate (Donnelly & Brown 2004).
Like other rodents, guinea pigs display a wall-following strategy (thigmotaxis), using their whiskers to feel walls and avoiding open spaces (Lee et al 2014).
In addition to being neophobic (see “change is bad” above), guinea pigs also tend to eat in groups, with little to no competition observed (Fig 4). Additionally, guinea pigs do not cache or store their food (Manning et al 1976).
Water bottles with drinking or sipper tubes provide a form of environmental enrichment for guinea pigs as they require jaw movements similar to chewing, which guinea pigs enjoy. Use of water bottles may also reduce the risk of urinary concretions such as uroliths (Fig 5) (Balsiger et al 2016). When a guinea pig is first exposed to a drinking tube, their first instinct is not to lick, but instead to pull or chew on the tube. Gradually the guinea pig should learn how to drink properly by licking, accompanied by slight chewing. If the guinea pig continues to struggle over time, the drinking tube may need to be pulled directly flush to the cage wall, so that the only solution is for the guinea pig to lick (Manning et al 1976). Guinea pigs are also known to inject a slurry of pellets into the tubes of their sipper bottles (Quesenberry et al 2012), therefore water bottles must be cleaned and disinfected regularly. Plugging the spout or sipper tube can also result in cage flooding. Guinea pigs that play with the sipper tube regularly may be bored and should be provided with forms of environmental enrichment to limit this behavior.
Clinical Tip: Unfortunately, water consumption can decrease when a water bowl is offered to the guinea pig. Insufficient water intake can increase the risk of concentrated urine and urolithiasis (Balsiger et al 2016).
Free-ranging guinea pigs do not dig burrows, but instead use the dens of other animals to avoid predators (Manning & Wagner 1976). Provide companion and laboratory guinea pigs with some form of visual security, which can range from a simple cardboard box to a commercially available hide box (Fig 6).
Guinea pigs normally eat vitamin B and protein-rich feces directly from the anus. If ingestion of these nutrient-rich fecal pellets is prevented, this can result in inefficient digestion of fiber and weight loss (Quesenberry et al 2012). Guinea pigs housed together or with other species may also eat each the other animal’s fecal pellets, which can cause problems if parasites are present (Donnelly & Brown 2004).
Clinical Tip: Geriatric guinea pigs may suffer from fecal impactions, possibly due to loss of muscle tone or an inability to practice coprophagy. Affected elderly pigs will require regular (e.g. weekly) manual expression (Quesenberry et al 2012).
The guinea pig is a gentle, highly social rodent, that commonly serves as a companion animal and an experimental model in North America and Europe. Food preferences are established early in life, and a guinea pig can refuse to eat if their food type or presentation is changed. For this reason, small mammal veterinarians recommend exposing juvenile guinea pigs to a variety of chows and vegetables. Guinea pigs also do not tolerate environmental changes well. When exposed to something perceived as dangerous, the response of the guinea pig is generally to freeze, or less commonly flight.