The social modulation of behavioural profile and stress responsiveness during adolescence: an adaptive mechanisms?
Zusammenfassung der Projektergebnisse
Adolescence is the gradual transition from childhood to adulthood. From an evolutionary perspective, this time may be an opportunity for adaptation. However, data in support of this hypothesis are largely lacking. Our previous work in guinea pigs showed a conspicuous environment-dependent canalization of behavioural profiles and stress responsiveness during this phase of life. If males live in large mixedsex colonies (CM) throughout adolescence, they were characterized by low aggressiveness and low stress responsiveness. In contrast, males housed in pairs (PM; one male/one female) were aggressive and showed high cortisol responses. During the 1st funding period we focused on underlying mechanisms and discovered a heretofore undescribed neuroendocrine pathway. The overall aim of this funding period was to elucidate whether the behavioural alterations that occur during adolescence represent adaptations to the social environment in which the individuals live. More specifically, we argue that the low-aggressive profile may be part of a “queuing strategy” that enables CM to live peacefully with unfamiliar conspecifics. The highly aggressive profile is supposed to be part of an “early reproduction strategy” that helps PM to compete for female partners aggressively. To test this hypothesis, two match-mismatch experiments were conducted. In experiment 1, situations were created (1 CM /1 PM / 2 females) that reflect a low-density situation, in which reproductive success is determined primarily by the outcome of male-male competition. We hypothesized that PM will be dominant over CM and will sire a higher number of offspring. In the corresponding experiment 2, PM and CM were introduced into large mixed-sex colonies. This situation reflects a high-density situation where male reproductive success is determined by a “queuing strategy”. We hypothesized that CM cope better with this situation than PM and will hence sire a higher number of offspring. Experiment 1 confirmed our hypotheses impressively: PM directed more aggression towards the male competitor, they attained the dominant position more often and consequently sired significantly more litters and pups than CM. These effects appeared mediated by endocrine mechanisms: PM showed more pronounced increases in plasma concentrations of both cortisol and testosterone, which likely promoted enhanced aggressiveness while mobilising necessary energy. Taken together, these results clearly show that PM were indeed better adjusted to the low-density situation than CM. During the initial phase of Experiment 2 PM were more aggressive than CM and showed higher cortisol and testosterone concentrations than PM. However, this strategy did not lead to reproductive success. Hereupon PM changed their strategy and could no longer be distinguished from CM who displayed an energy saving queuing strategy right from the start. Accordingly, over the whole time of the experiment PM and CM did not differ in their reproductive success. Thus at late adolescence the males were still able to readjust their behavioural strategy. Notably, our previous work shows that such a change of strategy seems much more difficult or even impossible when the males are fully adult. In summary, our project provides the clearest evidence to date for adaptive shaping of the behavioural and neuroendocrine phenotype by social influences during adolescence. Furthermore, the combined insights from both funding periods make a significant new contribution to the understanding of how and why the environment and hormones interact during this phase of life to shape behavioural profiles. Alarm im Hamsterrad / FAZ / 17.05.2015. Mensch, Kaninchen! / Süddeutsche Zeitung / 29.08.2014. Echte Persönlichkeiten / Wissen & Leben / Juli 2014. Vom Käfer bis zum Affen: Tiere haben Persönlichkeiten / Focus / 22.05.2014. Mamasöhnchen, Memmen und Mannweiber / Hamburger Abendblatt / 08.05.2014. Mamasöhnchen, Memmen und Mannweiber / Die Welt / 09.05.2014. Was ein Hausmeerschweinchen von einem wilden unterscheidet / der Standart / 12.04.2014. Was Haus- und Wildmeerschweinchen unterscheidet / bild der wissenschaft / 10.04.2014. Hausmeerschweinchen mögen es ruhig / Münstersche Zeitung / 14.04.2014. Meerschweinchen – als Haustier gesellig / Westfälische Nachrichten / 10.04.2014. SWR2 Wissen / Schmusekatzen und Streuner / Wie Tiere “Persönlichkeit” entwickeln (gesendet: 25.11.2015).
Projektbezogene Publikationen (Auswahl)
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(2013): Behavioural profiles are shaped by social experience: When, how and why. Philos. Trans. R Soc. B 368: 20120344
Sachser, N., Kaiser, S., Hennessy, M.B.
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(2013): Dimensions of Animal Personalities in Guinea Pigs. Ethology 119: 970-982
Zipser, B., Kaiser, S. & Sachser, N.
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(2014): Effects of domestication on biobehavioural profiles: a comparison of domestic guinea pigs and wild cavies from early to late adolescence. Front. Zool. 11: 30
Zipser, B., Schleking, A., Kaiser, S., Sachser, N.
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(2015): Domestication affects the structure, development and stability of biobehavioural profiles. Front. Zool. 12 Suppl. 1: 19
Kaiser, S., Hennessy, M.B., Sachser, N.
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(2015): New perspectives in behavioural development: adaptive shaping over the lifetime? Front. Zool. 12 Suppl. 1: 1
Trillmich, F., Günther, A., Müller, C., Reinhold, K., Sachser, N.
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(2015): Stability and change: stress responses and the shaping of behavioral phenotypes over the life span. Front. Zool. 12 Suppl. 1: 18
Hennessy, M.B., Kaiser, S., Tiedtke, T., Sachser, N.
