Mortality risk affects mating decisions in the spider Nephila clavipes

Abstract

Risk assessment is a fundamental component of any decision-making process, including mate choice. For males, one element of risk that is rarely considered is that a female mate may not survive to offspring independence, resulting in total reproductive failure. This element of risk could be particularly important in short-lived species where all individuals, regardless of condition, attempt to reproduce, and developing mature eggs is a time and energetically expensive process during which females are at risk of predation, starvation, and disease. I evaluate whether males use female survival probability as a mate choice criterion in the golden orb-web spider Nephila clavipes by assessing how male reproductive investment changes depending on female proximity to oviposition. Using a field experiment and a controlled mating experiment, I show that males mate at higher frequencies, transfer more sperm, and father more offspring in the first clutch when mated with nonvirgin females close to oviposition compared with younger nonvirgin females. Furthermore, females close to oviposition have a lower probability of mortality prior to egg deposition compared with virgin females and young nonvirgin adult females. These findings support the hypothesis that males invest more reproductive effort as a female approaches oviposition, possibly because these females are a low-risk mating investment. Copyright 2011, Oxford University Press.