Hormone systems can still be adapted in adulthood

Date:
June 16, 2020
Source:
University of Mu"nster
Summary:
Behavioral biologists have now been able to demonstrate for the
first time that male guinea pigs are still able to adapt their
hormone systems to changes in their social environment in adulthood.



FULL STORY ==========================================================================
How do animals adapt their behaviour during life in order to assure
survival and reproduction? This is a question of great interest for
behavioural biologists worldwide. An essential step is to examine
hormonal mechanisms which have a fundamental impact on the animal's
behaviour and thus make adaptations to various social situations possible.


==========================================================================
It has been known for some time now -- especially as a result of research
in guinea pigs -- that the social environment during adolescence,
i.e. the period from late childhood through puberty into adulthood,
has a considerable impact on how individuals behave in later life. Male
guinea pigs, for example, which grew up only with a female during this
period, are particularly aggressive towards unfamiliar males. Behavioural biologists at Mu"nster University have now been able to demonstrate for
the first time that males are still able to adapt their hormone systems
to changes in their social environment in adulthood. The study has been published in the journal Proceedings of the Royal Society B.

Methodological approach The male guinea pigs used in the study grew
up in different social housing conditions -- either in large mixed-sex
colonies with many other guinea pigs, or in pairs with a female. When
the guinea pigs reached adulthood, the researchers transferred the
males individually to pair housing with an unfamiliar female. This way
in males stemming from colony housing a change of the social niche was
induced. In contrast, in males which were previously housed in pairs
the female partner was changed, but the social niche -- i.e.

pair living -- remained the same. In order to assess immediate reactions
of males to their new social environment, the researchers observed
the behaviour of males and determined concentrations of the hormones testosterone and cortisol.

"We were able to demonstrate that one month after transfer to pair housing
with an unfamiliar female, males which had previously been housed in
colonies displayed a decrease in their testosterone levels and an increase
in their cortisol responsiveness. Consequently, their hormone systems
became similar to those of males in pair housing. This way, the animals
were most likely also able to adapt their behaviour to the new situation," explains Alexandra Mutwill, first author of the study and PhD student
being supervised by Prof. Dr Norbert Sachser at the Institute for Neuro-
and Behavioural Biology at the University of Mu"nster. "As in the case of
males which had previously been housed in pairs, the female partner but
not the social niche was altered, the hormone systems did not change: the
low testosterone levels and the high cortisol responsiveness persisted."
When guinea pigs live in colonies with a large number of conspecifics,
it is advantageous to have a hormonal status which favours a less
aggressive behavioural tactic. However, after transfer to pair housing
another hormonal status is beneficial which enables the male to adopt
a more aggressive tactic in order to defend the female partner against unfamiliar males. In males from colony housing, the change in hormone
systems built the basis for such a change in the behavioural tactic and probably reflects an evolutionary adaptation.


========================================================================== Story Source: Materials provided by University_of_Mu"nster. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Alexandra M. Mutwill, Tobias D. Zimmermann, Antonia Hennicke,
S. Helene
Richter, Sylvia Kaiser, Norbert Sachser. Adaptive reshaping of
the hormonal phenotype after social niche transition in adulthood.

Proceedings of the Royal Society B: Biological Sciences, 2020;
287 (1928): 20200667 DOI: 10.1098/rspb.2020.0667 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200616135800.htm

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