Dwarf Mongooses Lose Body Mass in Hot Weather due to Limited Behavioural Plasticity

High temperatures associated with climate change can have adverse effects on wildlife, but behavioural plasticity may buffer such negative effects. Using long-term data from wild dwarf mongooses (<i>Helogale parvula</i>), we investigated the impact of high temperatures on daily activity patterns, movement and body mass. On hot days (≥ 35°C) compared with matched cooler ones (≤ 33°C), groups emerged from their overnight sleeping burrow and commenced foraging earlier in the morning and arrived at their overnight sleeping burrow later in the evening. However, there was no evidence that the time spent above ground at the burrow, the proportion of time inactive or the distance moved when foraging were altered on hot days. Consequently, the negative effects of high temperatures were not fully mitigated, as both adults and pups gained less body mass on hot days compared with cooler days. This loss was not compensated fully in the day after a hot day, and evening body mass of adults decreased with an increasing number of consecutive hot days. Together, these results suggest that there are potentially escalating consequences of hot weather for wildlife, especially those species that exhibit limited behavioural plasticity, in an ever-warming world.