Interactions of photoperiod, size-rank in the litter, and sex on development, stability and fitness components of the behavioural phenotype
Final Report Abstract
An important aspect of animal personality is temporal consistency of behavioural traits. At the same time, behavioural traits develop over ontogeny. We studied how environmental (photoperiod, maternal effects, litter composition and litter size) and genetic components (sex, heritable variation) influence the ontogenetic trajectory of behavioural and physiological (maturation, stress responsiveness and metabolic rate) traits and tested how these traits influence fitness in the cavy. Our results suggest that early life plasticity in behavioural traits is indeed adaptive, allows major adjustments in response to photoperiodic cues in both sexes, and plays a major role especially in the period of adolescence. The heaviest pup in a litter developed differently from its smaller siblings, a difference that arises as a maternal effect. This difference can be substantially modified by crossfostering, but the causality of cross-fostering effects that include reduced growth and increased metabolic rate is hard to disentangle and needs further study. Based on a pedigree spanning four to five generations of typed individuals, stress-related traits and birth mass show a strong heritable component, whereas traits associated with novelty seeking, growth rate and mass at weaning showed less heritable variation. In a series of match-mismatch experiments, we were able to show that animals born into a spring photoperiod suffered reduced growth rate when transferred into autumn conditions while the reverse did not apply. Behavioural traits varied in response to mismatch: boldness and exploration were only influenced by conditions before weaning and therefore unaffected by the change into matching or non-matching environments, whereas stress-related traits remained plastic. Animals brought into matching or mismatching conditions in outdoor enclosures where they could reproduce, showed no response to mismatching conditions in growth, survival and reproductive output in spring, but appear to respond negatively to mismatching conditions when transferred from spring into autumn conditions. In addition to the planned experiments, we studied (together with V. Brust in the group of L. Lewejohann) the relationship between personality traits and cognition, a newly developing field. Bold, aggressive animals were faster to learn, but found reversal learning more difficult than shy animals. Less aggressive and bold guinea pigs, the domesticated form of the cavy, proved faster at learning and reversal learning and showed a different correlation structure among personality traits than the wild ancestor as well as a different correlation between cognitive and personality traits. The proof of temporal consistency in associative learning of guinea pigs is one of the first demonstrations of consistency in an animal cognitive trait. Our experiments have greatly enhanced the knowledge about environmental factors influencing the ontogeny of behavioural, cognitive and physiological traits and their impact on adult behaviour and fitness consequences. Furthermore, our results revealed plasticity of among trait correlations the proximate and ultimate functions of which need to be investigated in future research. By experimentally showing adaptive adjustments of traits in match-mismatch experiments and costs of mismatching conditions, we conclusively prove the importance of considering early life conditions for the explanation of adaptive differences in behaviour and physiology. Haustiere der Zukunft. Sendung „Erde an Zukunft“, Kika http://www.kika.de/erde-an-zukunft/sendungen/sendung82482.html. - Wie Tiere fühlen. Interview zu einem Artikel für die TV-Zeitschrift „Hörzu“. - Vom Käfer bis zum Affen: Tiere haben Persönlichkeiten, dpa Interview, veröffentlich in "Focus" (u.a.). - Meerschweinchen – schlau und sozial? Wissensmagazin Xenius, Arte (2012).
Publications
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2013. Photoperiod influences the behavioral and physiological phenotype during ontogeny. Behav. Ecol. 24, 402—411
Guenther A, Trillmich F
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2014. Learning and personality types are related in cavies (Cavia aperea). J. Comp. Psychol. 128, 74-81
Guenther A, Brust V, Dersen M & Trillmich F
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2014. Prenatal social conditions shape offspring adult phenotype and reproductive success. Behav. Ecol. Sociobiol. 68: 1661-1667
Guenther A, Kowalski G, von Engelhardt N
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2014. The ontogeny of personality in the wild guinea pig. Anim. Behav. 90, 131-139
Guenther A, Finkemeier M-A, Trillmich F
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2015. Domestication effects on behavioural traits and learning performance: comparing wild cavies to guinea pigs. Anim. Cogn. 18, 99-109
Brust V, Guenther A
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2015. Within-litter differences in personality and physiology relate to size differences among siblings in cavies. Physiol. Behav. 145, 22-28
Guenther A & Trillmich F
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2016. Match–mismatch experiments using photoperiod expose developmental plasticity of personality traits. Ethology 122, 80-93
Finkemeier M-A, Guenther A, Trillmich F
