Optimizing temperament through litter size in short‐lived, iteroparous mammals in seasonal environments

Abstract

A number of short-lived, iteroparous animal species have small broods in the early breeding season and larger broods in later breeding season. Brood size affects not only offspring size, but as recent results suggest, may also affect offspring's temperament, hormonal status, and aggression as adults. Most populations of short-lived, iteroparous mammals fluctuate predictably over the season, with low densities in winter, increasing densities in summer and a population peak in late summer followed by a population breakdown. If animals live only through parts of the season, possibly such differences in density and hence also in social environments among seasons require different personality types to increase individual fitness. We present data on behavior of European rabbits from a field enclosure study. These data clearly show that aggressiveness is higher in young from smaller litters than in young from larger litters, and smaller litters are usually born during the early breeding season. Moreover, our data suggest that behavioral types of the young rabbits are stable over time, at least during their subadult life. We suggest, that changes in mean litter size over the course of the breeding season may not only be a product of mothers' age or food availability, but may also have an adaptive function by preparing offspring characteristics for adulthood in a social environment undergoing predictable density changes within the season.

Unfolding personalities: The importance of studying ontogeny

“…These might be found in the influences on BPs by: (1) the interplay of genetic effects with brain, HPA and SAM development where a slightly higher stress response may feed back on BP development by, for example, changing HPA sensitivity and incorporating experience related to stress; (2) metabolic physiology and condition dependency, that may change priorities of risk aversion and foraging which in turn will feed back on condition, (3) situation choice (niche picking) and social feedbacks that may, via cognition and learning, influence the situations into which animals get themselves, thereby exposing individuals of different BPs to different environmental and social feedback; finally, (5) life histories that may differ for animals born into different population densities (e.g., Eccard & Rödel, 2011) or into a season where immediate reproduction is possible versus the ones that have to survive an initial nonreproductive period. Several of these mechanisms have been characterized quite well, but have as yet not been brought in productive connection with the theory of behavioral ecology and evolution.…”

Early development influences ontogeny of personality types in young laboratory rats

“…Ultimately, such a mechanism might help prepare the young for the current social situation in seasonally changing environments (cf. Eccard & Rödel, 2011).…”

“…These studies show that individuals can be assigned to distinct groups or at least can be ordered along a continuum with respect to parameters such as, for example, their levels of boldness, aggressiveness, or tendency to explore novel environments. This gives rise to several questions on the proximate causes (Hudson et al, 2011), physiological correlates (Kralj-Fišer, Weiß, & Kotrschal, 2010), adaptive value (Boon, Réale, & Boutin, 2007;Eccard & Rödel, 2011;Réale, Martin, Coltman, Poissant, & Festa-Bianchet, 2009), and evolution of this phenomenon (Wolf, Van Doorn, Leimar, & Weissing, 2007), which is often referred to as animal personality, behavioral Developmental Psychobiology Heiko G. Rö del 1 syndrome, temperament, or coping style Mason, 1984).…”

The effect of siblings on early development: A potential contributor to personality differences in mammals

“…This led us to consider the possibility that siblings, by influencing each other's early development, might contribute to shaping long-term differences in the suits of behavior variously referred to as personality, temperament, disposition, coping style, behavioral syndrome, or behavioral style. This interest has been reinforced by the increasing acceptance of the concept of animal personality among behavioral biologists, increasing evidence for the reality of such from a broad range of taxonomic groups (see reports in this issue), and by accounts as to how animal personality might be understood from a theoretical, evolutionary, and more recently, from a developmental perspective (Carere, Drent, Koolhaas, & Groothuis, 2005;Dall, Houston, & McNamara, 2004;Dingemanse & Réale, 2005;Eccard & Rödel, 2011;Gosling, 2001;Réale, Dingemanse, Kazem, & Wright, 2010;Roulin, Dreiss, & Kölliker, 2010;Sih, Bell, & Johnson, 2004;Trillmich & Groothuis, 2011;Stamps & Groothuis, 2010;Wolf, van Doorn, Leimar, & Weissing, 2007).…”