Correlation between Male Social Status, Testosterone Levels, and Parasitism in a Dimorphic Polygynous Mammal

Sandra S. Negro,Abigail K. Caudron,Philippe Delahaut,Michel Dubois,Neil J. Gemmell,Dennis Marinus Hansen

doi:10.1371/journal.pone.0012507

Sandra S. Negro, Abigail K. Caudron + Show 4 more

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https://doi.org/10.1371/journal.pone.0012507

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Abstract

Life history trade-offs have often been assumed to be the consequence of restrictions in the availability of critical resources such as energy and nutrients, which necessitate the differential allocation of resources to costly traits. Here, we examined endocrine (testosterone) and health (parasite burdens) parameters in territorial and non-territorial New Zealand fur seal males. We documented intra-sexual differences in sexual behaviours, testosterone levels, and parasitism that suggest a trade-off exists between reproductive success and physical health, particularly susceptibility to helminths and acanthocephalans, in males displaying different mating tactics (i.e., territorial and non-territorial tactics). Levels of testosterone were higher in territorial males and correlated positively with reproductive effort (i.e., intra- and inter-sexual interactions). However, these territorial males also exhibited high levels of parasitic infection, which may impair survival in the long-term. Our study, while limited in sample size, provides preliminary evidence for a link between male mating tactics, testosterone levels and parasite loads, and potential effects on reproductive success and life history that should be explored further.

Highlights

Life history trade-offs have often been assumed to be the consequences of restrictions in the availability of critical resources such as energy and nutrients, necessitating differential allocation of resources to costly traits [1]
This study examined endocrine and health parameters in A. forsteri males employing the territorial mating tactic and nonterritorial mating tactics related to their relative reproductive success
We identified 12 topographically demarcated territories defended by territorial males

Summary

Introduction

Life history trade-offs have often been assumed to be the consequences of restrictions in the availability of critical resources such as energy and nutrients, necessitating differential allocation of resources to costly traits [1]. Increasing evidence implicates hormones as mediators of life history trade-offs [1,2]. Testosterone, the principal androgenic hormone, can raise male mating success by promoting the development of secondary sexual characters. A schematic model of interactions between endocrine system, immune system, secondary sexual characters and parasites has previously been proposed in Folstad and Karter [9]. Wingfield et al [8] proposed a 3-level model of testosterone in male birds: a non-breeding androgen baseline (level A), the breeding androgen baseline induced by environmental cues (level B), and the physiological testosterone maximum that an individual can achieve during intra- and intersexual interactions (level C). The above models described for birds are supported by other studies in pinnipeds [13,14,15]

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