Physiological thermoregulation in the heat is costly for endotherms, entailing large and rapidly increasing water expenditure, risks of blood chemistry changes associated with panting, and performance costs of adaptive hyperthermia. Changes in behaviour (e.g. reduction in activity) and microsite selection (choosing shaded, cool locations in the landscape) can reduce some of these costs by reducing the animal’s ‘heat load’. However, there is no such thing as a free lunch and these strategies (collectively called ‘behavioural thermoregulation’) carry their own baggage. This is because they require animals to alter their patterns of behaviour, and these alterations can carry significant fitness consequences.

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In my research group, we study the effects of temperature on, and the knock-on consequences of this for various fitness proxies, including reproductive success and body mass changes. We look at species traits that may exacerbate or reduce these costs, for behaviour example foraging strategies that place individuals under excessive heat loads, or interactions between heat stress and already costly breeding systems. We are very interested in life-history strategies that may buffer individuals from the costs of thermoregulatory behavioural trade-offs, for example, group-living in arid zone birds, and how the structure of social groups is affected by heat stress.

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We work on a range of Kalahari species including southern fiscals, southern yellow-billed hornbills, sociable weavers, white-browed sparrow-weavers and southern pied babblers. In the Fynbos biome, we address similar questions looking at cape rockjumpers and cape sugarbirds.