Thermoregulation in two population of the Matabeleland mole‐rat (Cryptomys hottentotus nimrodi) and remarks on the general thermoregulatory trends within the genus Cryptomys (Rodentia: Bathyergidae)

Abstract

The social Matabeleland mole‐rat Cryptomys hottentotus nimrodi occurs in both the high‐and lowveld of Zimbabwe. The population in the highveld has a mean (± S. D.) resting metabolic rate (RMR) when acclimated for three months in the laboratory of 0.83 ± 0.04cm3 O2 g‐l h‐l (n=12) within the thermoneutral zone (TNZ) of 31‐32°.The body temperature (Tb) within the thermoneutral zone is low 34.4 ± 0.18 (n= 12) and remains stable at ambient temperatures (Ta s) from 25‐32°. Above 32°, Tb increases albeit slightly to 36.6 ± 1.46° (n= 12). The conductance is high 0.17 0.02cm3 O2 g‐1 h‐°‐1 (n= 24) at the lower limit of thermoneutrality. The mean RMR at 18° (the lowest Ta tested) was 2.29 ± 0.11 cm3 O2 g‐1 h‐1, which is 2.75 times that of the RMR in the TNZ.The population in the lowveld has a mean (± S.D.) resting metabolic rate (RMR) when acclimated for three months in the laboratory of 0.95 ± 0.07 cm3 O2 g‐1 h‐1 (n= 12) within the themoneutral zone (TNZ) of 28‐30 °.The body temperature within the thermoneutral zone is low 34.0 ± 0.23 (n= 12) and remains stable at Tas from 25‐30 °. Above 32 °, Tb increases, albeit slightly, to 37.8 ± 1.14 ° (n= 12).The conductance is high 0.14 ± 0.09cm3 O2 g‐1 h‐1°‐1 (n= 24) at the lower limit of thermoneutrality. The mean RMR at 18 ° (the lowest Ta tested) was 1.96 ± 0.12cm3 O2 g‐1 h‐1, which is 2.0 times that of the RMR in the TNZ.These thermoregulatory parameters are compared with published data on other species of Cryptomys from Southern and Central Africa.