Aardwolf adaptations: a review

Abstract

The aardwolf Proteles cristatus has developed a number of anatomical and morphological adaptations for feeding on its termite prey. These adaptations preclude the aardwolf from feeding on other, larger (vertebrate) prey, especially during the winter months, when the T_a drops below 9°C and when Trinervitermes termites are largely unavailable. Winter is therefore a stressful period for aardwolves, as evidenced by increased juvenile mortality, a 20% decline in body mass and depletion of subcutaneous fat reserves. The aardwolf uses both physiological and behavioural means to overcome this period of food stress. An increased period is spent underground in the thermally-stable environment of the den. Den sharing is more common in the winter months and social thermoregulation may result in energy savings. While inactive the aardwolf lowers its T_b (to an average of 34.1±1.6°C during the middle of the inactive period during winter) and in some individuals this results in energy savings of up to 18%. Seasonal changes in pelage density and thermal conductance allow for more passive heat transfer during summer and improved heat retention during winter. Laboratory and field measurements of metabolic rate showed that the aard-wolf has a low BMR and a low FMR (between 40 and 78% of that predicted by allometric equations). The aardwolf's metabolic rate is 11% lower during the winter months, resulting in reduced energy requirements during the period of limited food availability. Evaporative water loss rates are low, further reduced during the winter months, adaptations to survive in a desert environment and on a seasonally-unavailable food source. The aardwolf is therefore well adapted to feed on a diet of Trinervitermes termites, a food niche that has been largely unexploited by other animals, and it uses various ecological, behavioural and physiological adaptations to cope with this seasonally unavailable food source.