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| Domestic guinea pig (Cavia porcellus) |
Guinea pigs (Cavia aperea f. porcellus)
originated in the highlands of South America where they were domesticated from
wild cavies (Cavia aperea) approx. 3000-6000
years ago for food. During domestication there was a tremendous increase in
population densities. While cavies live in large home ranges (200m2 –
1000m2) guinea pigs can be kept in groups of up to 20 individuals in
6m2 enclosures without any problems.
Domestication removes some pressures of natural
selection and replaces them with new selection pressures created from an artificial
environment. This, along with direct artificial selection by humans can result
in marked alterations in the biobehavioural profile of a species. These profiles
are also influenced by heritage and an ontogeny phase: adolescence; which is the
gradual transition from infancy through stages resulting in sexually mature
adults. During adolescence there is an extensive alteration in anatomy,
endocrine systems, neural circuits and behaviour. This is especially important
in the development of guinea pigs as development is heavily influenced by the
social circumstances the individual is exposed to during adolescence.
Zipser et al (2014) analysed differences in
emotional and social behaviours and cortisol reactivity across adolescent male guinea
pigs and cavies. Major differences in behavioural and endocrinological parameters
were found. Young individuals show that adaptations that reflect the
differences between the natural habitat of cavies and manmade housing
conditions guinea pigs emerge early in ontogeny well before attainment of
sexual maturity.
Differences in emotional behaviour found
cavies to be more explorative, risk-taking and socially less active. From an
evolutionary standpoint, extensive exploration is crucial for wild animals in
order to obtain access to vital recourses such as water, food, shelter and
mates. Cavies also consistently showed higher cortisol reactivity. In highly demanding
circumstances energy is expensive, therefore appropriate physiological
adaptations to provide the necessary energy quickly is required. High cortisol
reactivity can be interpreted as the energy provisioning mechanism that meets
these demands.
In contrast, the biobehavioural profile of
guinea pigs is characterised by higher levels of social activity and lower
levels of risk-taking, exploration and cortisol reactivity. They are more social
interactive with lower cortisol reactivity levels than cavies as they are adapted
to a less challenging environment with much higher population densities. Higher
degrees of agreeableness, sexual behaviour and lower levels of aggression are
common in domestication as dangerous and challenging environmental factors (hence
selection pressures) are removed, such as in manmade housing systems which
provide all relative resources for guinea pigs to thrive.
image accessed 25/04/2014: http://www.vetwest.com.au/pet-library/guinea-pig-care
image accessed 25/04/2014: http://www.vetwest.com.au/pet-library/guinea-pig-care
This is an interesting study. What methods did they use to test emotion, social behaviour and cortisol reactivity? How did they quantify risk-taking behaviour?
ReplyDeleteHey Tasmin,
ReplyDeleteEmotionality: there were three types of tests:
-Open field test: how long they stayed stationary on starting point in the open (anxiety like behaviour) and how far they travelled in the open (explorative behaviour). Dark light test: how long they stayed within the enclosed dark box (anxiety like behaviour) and the time taken to emerge into the open (explorative behaviour). Step down test: tested risk-taking behaviour by time taken to jump from an elevated platform.
Social Behaviour: there were two types of tests; male vs. unfamiliar infant interaction test & male vs. unfamiliar female courtship test where both male cavies and male guinea pigs had a choice between an empty control cage and the one with the stranger in it.
Cortisol Reactivity: tested elevation of plasma cortisol titres using a stress reactivity test; comparing initial Cortisol levels when in a familiar home, then transferring them to a strange unfamiliar environment and again testing the cortisol reaction (level of stress).
Generally, this experiment involved a lot of observation and video-recordings (as to ensure human presence didn’t influence either species). The methods are proven successful from previous studies and were based on tests commonly used to characterise behaviour in mice and rats that have now been adapted for guinea pigs and cavies.