Sickness communication in swamp sparrows (Melospiza georgiana)
Fall 2020 Graduate Student Award in Social and Biological Determinants of Health
Although it is almost always advantageous for an animal to be able to identify and avoid infectious disease in others, it may not always be advantageous for an infected animal to reveal their sickness. This is particularly true for males during mate choice, when revealing sickness may cost a mating opportunity. To overcome conflicting interests between senders and receivers, most animals utilize “honest” signals that are maintained as reliable through costs that unhealthy animals are unable to meet. However, many of these signals depend on long-term investment, and it’s unclear whether transient disease affects this communication system in a way that is detectable by receivers. This may affect both mate choice and the spread of disease through a population. In this project we will determine whether a temporary infection, as mimicked with an immune stimulant, affects a long-term signal of male health, song in the swamp sparrow. To measure the effects of infection on song we will record song both when males are healthy and after injection with the immune stimulant. We will then play both versions of song to female swamp sparrows and measure their response. We also will correlate female response to song with a male’s level of inflammation and his levels of corticosterone and testosterone, which are known to play a role in the expression of secondary sex characteristics and the regulation of immune function.