Specifically, we tested the hypotheses that reduced basal metabolism and pulmocutaneous water loss, as measured in the laboratory, lead to a conservative field metabolic rate (FMR) and water flux in free-living aardwolves. Further, we quantified the activity budget of aardwolves during summer and winter to construct a time-energy budget for them, thereby examining their seasonal patterns of energy allocation.
We studied aardwolves for two years, from December 1988 to January 1991, on a 2015-ha study plot on the Benfontein Game Farm (28 [degrees] 50 [minutes] S, 24 [degrees] 50 [minutes] E), located [approximately]6 km southeast of Kimberley, South Africa.
The natural history of aardwolves has been described by Richardson (1987a), Koehler and Richardson (1990), Skinner and Smithers (1990), Anderson (1994), and Van Jaarsveld et al.
Within each territory, aardwolves construct 5-6 dens, usually by enlarging vacant springhare (Pedetes capensis) burrows (Richardson 1987b, Anderson 1994).
To facilitate locating individual aardwolves and to simultaneously monitor body temperature ([T.sub.b]), we implanted a temperature-sensitive radio transmitter into the abdominal cavities of six animals, two males and four females, to which we assigned names (Anderson and Richardson 1992).
In addition to the data for body mass of aardwolves used in our DLW experiments, we also obtained information on body masses of other aardwolves from several sources.
When feeding on Hodotermes mossambicus, aardwolves consume workers that harvest grasses on the soil surface (Richardson 1987a).
A general accounting of when aardwolves were active during each season was made by noting when radio-tagged animals exited their dens in the afternoon or evening, and when they returned (exit and entrance times were recorded for 2-3 d for each aardwolf each season).
Aardwolves were accustomed to our vehicle and would allow us to approach within 15-40 m, depending on the animal.
If we suspected that our presence was influencing the behavior of aardwolves, as was the case for several animals, especially the day after injection, we immediately terminated observations until the following evening.
We employed a two-part model to estimate energy expenditure from time-activity budgets of aardwolves:
We estimated the energy cost of walking from body mass and the average velocity of aardwolves when walking by the equation (Taylor et al.
Following Anderson and Richardson (1992), we captured aardwolves using a Telinject dartgun (Telinject, Randburg, South Africa) with darts containing a mixture of ketamine hydrochloride (15-20 mg/kg) and acetylpromazine (15-40 mg/kg).
Aardwolves spend a considerable portion of their day confined to a den, and it is known that C[O.sub.2] concentrations in burrows can rise to levels far above ambient air, at least for small rodents (2-10%; Darden 1972, Arieli 1979, Gettinger 1983).
Our original experimental design consisted of comparing the FMR and water flux of the same six aardwolves during two seasons.