Effects of male age and experience on bi-parental reproductive output and allocation in a burying beetle

Background/Question/Methods

In organisms that express bi-parental care, both males and females can incur costs associated with reproduction. Nicrophorus orbicollis is a burying beetle that serves as a model organism for studying life history and resource allocation. We evaluate the influence that male experience and age has on bi-parental reproductive output and allocation. We allowed 40 day old virgin males to reproduce with virgin females and then mated these same males a second time at 55-60 days of age with virgin females to test for effects of male experience on reproductive success.  We then mated 55-60 day old virgin males with virgin females to test for effects of age of males on reproductive success.

Results/Conclusions

There was a significant effect of reproductive experience on reproductive success: experienced males produced smaller broods compared to virgin males. There was a significant effect of age on male mass change during reproduction. Young males increased in mass and older males decreased in mass. The patterns of male mass change and final clutch size are consistent with both the terminal investment hypothesis (i.e., the tradeoff between future and current reproduction declines with age among males such that body mass increase during reproductive bouts would decrease as males age), as well as the cost-of-reproduction hypothesis (i.e., males that have reproduced before have decreased reproductive output for future reproductive bouts).