Abstract
BackgroundThe social environment the mother experiences during pregnancy and lactation can powerfully influence the offspring’s behavioural profile. Our previous studies in wild cavies show that two different social environments during pregnancy and lactation bring about different behavioural strategies of male offspring later in life: An unstable social environment leads to a behavioural camouflage strategy, hypothesised to be beneficial at times of socially challenging situations. A stable social environment during early phases of life, however, leads to an early reproduction strategy, expected to be more successful at times of social stability. In the present study, we observed the behavioural strategies of the two types of males in direct comparison in a socially challenging situation: Two adolescent males were placed simultaneously in an unknown social group consisting of one adult male and two females in a semi-naturalistic environment. Cortisol as well as testosterone concentrations and activity levels were compared. Furthermore, paternities were analysed after the males reached sexual maturity. We hypothesised that sons showing a behavioural camouflage strategy are better adapted to cope with this socially challenging situation compared to those displaying an early reproduction strategy.ResultsAt the beginning of the experiment, no differences in plasma cortisol concentrations between the males were found, both showed a highly significant increase due to the challenging situation. From day 5 until the end of the experiment (duration = 40 days) sons showing an early reproduction strategy had significantly higher plasma cortisol concentrations compared with those showing a behavioural camouflage strategy. Plasma testosterone concentrations did not differ significantly. Activity levels decreased significantly over time independently of the male’s behavioural strategy. Both types of males did not sire offspring during the observation period.ConclusionHigher cortisol values from day 5 until the end of the experiment in sons showing an early reproduction strategy indicate higher levels of stress in these males compared to those displaying a camouflage strategy. We conclude that the modulation of the males behavioural strategy due to an unstable social environment during early development facilitates the endocrine adaptation to a comparable social situation later in life.
Highlights
The social environment the mother experiences during pregnancy and lactation can powerfully influence the offspring’s behavioural profile
Minutes with at least one antenna contact were counted as active minutes (= active animal) while minutes with no antenna contact were considered as inactive minutes
The statistical analyses revealed that activity of social environment (SE)- and Unstable social environment (UE)-sons decreased significantly over time (Fig. 2, factor time: p = 0.008, F = 3.80, df = (5;35))
Summary
The social environment the mother experiences during pregnancy and lactation can powerfully influence the offspring’s behavioural profile. Our previous studies in wild cavies show that two different social environments during pregnancy and lactation bring about different behavioural strategies of male offspring later in life: An unstable social environment leads to a behavioural camouflage strategy, hypothesised to be beneficial at times of socially challenging situations. We hypothesised that sons showing a behavioural camouflage strategy are better adapted to cope with this socially challenging situation compared to those displaying an early reproduction strategy. Maternal hormones cross the placenta modifying organizational pathways of the offspring’s developing brain, which, in turn, affect physiological and behavioural responses later in life [1, 3]. This maternal control over the offspring’s development, called maternal effects [2, 4, 5] has received much attention in evolutionary biology (see [1, 6, 7]) and is discussed to increase the variance and quality of the generation
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