The effects of temperature on offspring provisioning in a cooperative breeder

Abstract

While most current predictive models agree that the climate is changing, it is not yet clear what impact these changes will have on animal populations. It is vital to determine the potential consequences in order to develop future management and conservation strategies. Climate change may impact population stability by prompting changes in breeding behaviour. For example, if above-average temperatures negatively affect adult body condition, this will increase the cost of parental care. Theory suggests that under this scenario, individuals may trade off their own body condition and survival against that of their young. Despite convincing evidence that this parental care trade-off exists in nature, the potential impact of climate change on parental investment strategies has rarely been investigated. In cooperatively breeding species, group-living adults can gain group size benefits, such as assistance with raising young. These benefits may mediate the effects of climate change on adult condition and subsequent investment in young. Here, we investigated the extent to which high temperatures and rainfall variation affect (1) adult provisioning rates to dependent nestlings, (2) offspring development and (3) the cost of offspring care in the cooperatively breeding pied babbler, Turdoides bicolor. We found that overall, adults provisioned young significantly less on hot days. However, this pattern was affected by rank: dominant individuals provisioned significantly less while subordinates did not. Offspring development was negatively affected by heatwave events, suggesting that young suffer from reduced investment on hot days. However, there was no evidence that the cost of provisioning young increased during heatwave periods, perhaps owing to the reduction in investment by adults. This study provides some of the first evidence that higher temperatures affect investment decisions in cooperative breeders and that dominant and subordinate individuals respond differently to this stressor.