Behavioral biologists from Münster University have been able to establish for the first time that male guinea pigs are still able to adjust their hormone systems to alterations in their environment, even in adulthood.

It has been previously known that guinea pigs' social environment during adolescence had a measurable impact on how they behaved later in life. But now, the new research says their adaptability can continue later during adulthood.

According to researchers, a vital step to examining hormonal functioning in guinea pigs is to give a primary impression on the animal's behavior. With this, they can then make adaptations to different possible social circumstances.

For instance, male guinea pigs that grew up only with a female during the time could become notably aggressive later on towards unrecognized males. The findings of the study were published in the journal Proceedings of the Royal Society B on June 10, 2020.

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Mixed-Sex Colonies Studies in Guinea Pigs

According to the Royal Society for the Prevention of Cruelty to Animals (RSPCA), guinea pigs are highly social animals. They are accustomed to living in close family groups of five to ten members of the colony in the wild.

The study used male guinea pigs that grew up in varied social housing circumstances.

The animals either belonged to huge mixed-sex colonies together other guinea pigs or paired with a female. Once they reached adulthood, the researchers relocated the males separately paired with an unfamiliar female.

An interesting shift in the social niche was observed in males coming from colony housing, while males who were used to living with a female partner remained unchanged. To assess the reactions of males to their new social atmosphere, the scientists determined the concentrations of the hormones testosterone and cortisol in the newly adjusted guinea pigs.

In addition to analyzing their hormone levels, their behavior in response to their new social setting was also noted. According to the researchers, after a month following the males' transfer, those who had previously been accustomed in colonies demonstrated a decrease in their testosterone levels. On the contrary, their cortisol levels increased.

Social Adaptability of Guinea Pigs

The researchers were able to identify that the hormone systems of the male guinea pigs used to living in colonies became comparable to those in pair housing. According to Alexandra Mutwill, the first author of the study, their findings revealed that the rodents were able to adjust their behavior to the new environment.

As for the males who had already been in previous pair housing with females, the researchers observed no change in their hormone systems. Furthermore, they have found that their testosterone levels remain low, and their cortisol responsiveness remains high.

The researchers have established that it is favorable for guinea pigs that live in colonies to have hormonal statuses with a less combative behavioral ploy. Nevertheless, after being transferred to pair housing with a female, they say another hormonal status would be profitable.

Scientists believe that if males in pair housing developed more aggressive tactics, it would be more beneficial as they could defend their female partner against unknown males. Additionally, they say that changes in the hormone systems of males from colony housing built the basis for such an adjustment in behavioral tactics. The researchers believe that it echoes an evolutionary adaptation.

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