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

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

Common parasite species found in faecal samples collected from <i>A. forsteri</i> males.

<p>Common parasite species found in faecal samples collected from <i>A. forsteri</i> males.</p

Descriptive statistics of behavioural observations for the territorial, non-territorial transient and resident male categories.

<p>Descriptive statistics of behavioural observations for the territorial, non-territorial transient and resident male categories.</p

Hierarchical clustering of male behavioural profiles using Ward's linkage of Euclidean distances.

<p>The method builds the hierarchy from the individual elements by progressively merging clusters. The amount of clustering structure that has been found for each node is interpreted by the Agglomerative Coefficient (0.9759) (<a href="http://www.wessa.net/rwasp_agglomerativehierarchicalclustering.wasp/" target="_blank">http://www.wessa.net/rwasp_agglomerativehierarchicalclustering.wasp/</a>). The y-axis represents the male ID.</p

Descriptive statistics of testosterone levels in <i>A. forsteri</i> males displaying the territorial and non-territorial transient and resident mating tactics.

<p>*not relevant when n = 2.</p

Descriptive statistics of parasite loads (eggs per gram of faeces) found in faeces of territorial and non-territorial males.

<p>The egg counts per gram of faeces in a female sample were used as reference sample and contained 500 <i>Diphylobothrium</i> and 100 <i>Ascaris</i> eggs/g. UID: unidentified.</p