The thermal ecology of burying beetles: temperature influences reproduction and daily activity in Nicrophorus marginatus

1. Understanding how organisms respond to thermal stress can help predict long‐term population viability under projected climate change models. Behavioural plasticity can mediate the impact of thermal stress; however, some behavioural modifications in response to novel environments act maladaptively and could implicate population persistence. 2. Burying beetles (Silphidae: Nicrophorus) have been found to modify traits related to individual fitness to be favourable in their perceived environments. To reproduce, breeding individuals of the nicrophorine genus work together to bury and prepare a suitable vertebrate carcass as food for their developing larvae. 3. Here, we explore how sustained temperature treatments influence traits that closely tie to individual fitness in Nicrophorus marginatus. We measure carcass handling, reproductive output, and activity levels in controlled and elevated temperature treatments. 4. At only 27.5 °C, we observed significantly reduced reproductive success rates, extended carcass handling time, and increased levels of activity when compared to the baseline temperature treatment of 26 °C. Additionally, at 26.5 °C, we document reduced brood size. 5. These findings indicate that slight incremental increases in temperature could have profound effects on burying beetle fitness when experienced for extended periods. To understand how subterranean‐breeding organisms respond to projected climate change and thermal stress, we investigated locomotion, reproduction, and fitness in the burying beetle, Nicrophorus marginatus, under three temperature treatments. At the highest temperature we tested (27 °C), reproductive success was significantly reduced, while carcass handling time and locomotor activity significantly increased. At the midrange temperature (26.5 °C), we documented reduced brood size. Incremental thermal shifts could have profound effects on fitness and recruitment, and have long‐term implications for population viability in areas with predicted temperature increases associated with climate change.