Making the best of a bad job: effects of state and social context on reproductive decisions in a burying beetle
Richardson, Jon Edward
Animals must make strategic decisions about how to allocate their limited resources towards reproduction. These decisions can include who to mate with, how many eggs or offspring to produce, and how much to allocate to current reproduction at the expense of survival and/or future reproduction. These decisions can be complicated by factors such as an individual’s own state or the social context they breed under. In this thesis, I investigated how individuals adjust their reproductive decisions in response to their own state or the social context of reproduction in the burying beetle Nicrophorus vespilloides – a species that uses small carcasses as a breeding resource. First, I found that variation in an individual’s body size and nutritional state influenced their allocation to different reproductive traits. I then found that mating decisions are influenced by nutritional state as food-deprived females preferred to mate with well-fed males. Next, I found that food-deprived females adjust their decisions by delaying egg laying, providing less parental care, and consuming more carrion themselves. Surprisingly, these decisions had no detrimental effect on the performance of their offspring. I then showed that being inbred impaired a female’s decisions about how many offspring to rear when resource availability fluctuated during breeding. Next, I examined how the social context influenced reproductive decisions. I found that partner quality influenced reproductive decisions as females that mated with a male in poor condition adjusted the size of their brood after hatching. Next, I found that females decided to increase their allocation to egg laying when breeding communally compared to breeding alone. Furthermore, females adjusted their decisions about the timing and duration of egg laying when breeding as either a host or a brood parasite. Finally, I found that an individual’s state and the social context can interact. Females gained less weight when they cared for an enlarged brood in an initial breeding attempt. This change in state was costly as these lighter females were subsequently less likely to win fights with other females over a second carcass required for future reproduction.