Behavioural and endocrine correlates to the mating system of the aardwolf Proteles cristata

Abstract

Mating systems are classifications of the outcome of individual strategies aimed at maximising reproductive success. These systems have two components; one describes how individuals socially relate and bond to mating partners and the other describes the genetic outcome of actual mating activities. Reproductive activity is under strong endocrine and behavioural regulation where inter-sexual discrepancies in the regulation of reproductive success have resulted in the majority of mammal species exhibiting polygynous mating systems, with only 5% of mammals being socially monogamous. However, in monogamous species there can be a discrepancy between social pair bonds and sexual mating activities. Aardwolves are extreme diet specialists ii on a temporally fluctuating resource, Trinervertermes spp. A number of studies have described them as socially monogamous but at the same time observed a high frequency of extra pair copulations (EPCs). A recent study also linked sex variation in den use to polygamous mating. However, it is unclear to what extent these EPC's contribute to individual fitness, and how these contrasting mating strategies influence space use and reproductive physiology. The aim of this project was to determine if there was seasonality in reproductive activity and to test if endocrine physiology, home range size and space use were similar between males and females as predicted for a socially monogamous species. We assessed reproductive endocrinology in zoo-housed aardwolves and quantified if physiological and behavioural data in wild aardwolves relate more to predictions based on social monogamy or polygamy. We found physiological support for previous behavioural observations of reproductive seasonality in both zoo-housed and wild aardwolves. We suggest that the seasonal breeding strategy in aardwolves is as a direct consequence of their strong dietary preference on a temporally fluctuating resource, where it is important for aardwolves to time periods of high physiological investment in reproduction with high seasonal abundance of these termites. Our data on zoo-housed aardwolves also showed that the social environment appeared to modify physiological responses to variation in environmental conditions. We suggest that due to strict seasonal breeding in wild aardwolves females are time constrained in receptivity which, combined with their largely solitary behaviour, implies that males have to be dynamic in the onset of their reproductive activity to closely match that of locally receptive females. Therefore, it may be adaptive for aardwolves to retain social receptivity even if resource distributions cause these animals to forage alone. We also found that physiological and behavioural traits correspond better to predictions based on social monogamy than polygamous mating in a population of wild aardwolves. However, earlier studies in the same population found that behavioural traits were more related to predictions based on polygamous mating. Therefore, our data and other studies show how a difference between traits can relate to either social monogamy or polygamous mating in wild aardwolves in the same study area. We suggest that social mating system components regulate the observed endocrine and behavioural parameters more than actual mating patterns, which implies that social components pose a stronger selective pressure on physiology and behaviour than sexual mating patterns. Overall, we conclude that due to the discrepancy in traits that correspond to predictions based on different mating systems, aardwolves do not fit discreetly into any current mating system classification. We suggest that the evolutionary causes for the potentially conflicting mating strategies as well as the fitness benefits of these strategies need to be further investigated.