Metabolism and thermoregulation in the springhare (Pedetes capensis)

Abstract

Springhares are large, nocturnally active, diurnally fossorial rodents that typically inhabit arid and semi-arid areas. This lifestyle means that they need to balance excessive heat loss when foraging at night against insufficient heat loss in a potentially warm, humid burrow and both of these against the need to minimize water turnover and energy requirements. In this study we investigated metabolism and thermoregulation in these animals. Basal metabolic rate averaged 8.62+/-1.37 J g(-1) h(-1) and minimum thermal conductance 0.386+/-0.062 J g(-1) h(-1) degrees C(-1). These were higher and lower than expected, respectively. This, along with a relatively low, lower critical temperature and broad thermal neutral zone indicate that springhares are physiologically well suited to the low night-time temperatures, which they typically encounter. Body temperatures were quite labile but springhares became hyperthermic at temperatures above 30 degrees C suggesting that they are poor thermoregulators at high temperatures. This is attributed to their seldom, if ever, encountering temperatures in this range. Insufficient heat loss under normal resting conditions does not appear to be a problem, as springhares inhabit deep burrows in which the temperature never exceeds the upper critical temperature. Excess heat generated during vigorous underground exercise is presumably stored and dissipated to the cool night air or the cooler soil when subsequently resting. Water turnover and energy expenditure are presumably adequately addressed by other physiological and behavioural characteristics.

The jaw is a second-class lever inPedetes capensis(Rodentia: Pedetidae)

“…Moreover, even if not quite a second-class lever these bites are very efficient, so high bite forces can be produced without having to massively increase the overall adductor muscle mass. It is likely that P. capensis has evolved this highly efficient feeding system in order to cope with the demands of the arid environment in which it lives (Peinke & Brown, 2003). Springhares are herbivorous, feeding almost exclusively on grasses (Peinke & Brown, 2006).…”

“…P. capensis is a nocturnal, bipedal, saltatorial rodent that inhabits arid and semi-arid areas of southern Africa (Peinke & Brown, 2003). It is large for a rodent (3–4 kg) and feeds principally on grasses, especially the rhizomes of Cynodon dactylon and the tubers of Cyperus esculentus (Peinke & Brown, 2006).…”

Numbats and aardwolves—how low is low? A re-affirmation of the need for statistical rigour in evaluating regression predictions

“…No correctly statistically analysed papers were found during this search, but the following 23 recent studies are examples of a common approach whereby a physiological variable for a species (e.g. BMR, C, EWL etc) is subjectively judged to be different from the allometrically expected value (Baudinette et al 2000, Geiser and Brigham 2000, McNab 2000, Merola-Swartjes and Ligon 2000, Weathers et al 2000, Anava et al 2001, McNab 2001, Williams 2001, Schleucher 2002, Bonaccorso and McNab 2003, Burton and Weathers 2003, Cortes et al 2003, Kalin et al 2003, Lindstrom and Klaassen 2003, Lovegrove and Smith 2003, McKechnie and Lovegrove 2003, Peinke and Brown 2003, Song and Wang 2003, Bozinovic et al 2004, Mathias et al 2004, Williams et al 2004. The percentage of the species' value relative to the expected value (obtained from the allometric equation for an animal of equivalent mass) was interpreted to be high (somewhat greater than 100%), low (somewhat less than 100%) or as expected (around 100%).…”

Putting the Spring back into the Hare (Pedetes capensis): Meat Chemical Composition of an Underutilized Protein Source

“…The weights were the same as those reported for New Zealand and Phendula meat rabbits [22]. Mature springhares typically weigh 3-4 kg [23,24], which are at the higher end of the dead weights recorded for the springhare of this study (Table 1). Dress out percentage and the weight of the tails were the only two characteristics that differed significantly due to the effect of season.…”