Thermal biology in the Upper Galili Mountain blind mole rat (Nannospalax galili) and an overview of spalacine energetics.

ABSTRACT

Several hundred mammalian species thrive in complex burrow systems, which protect them from climatic extremes and predation. At the same time, it is also a stressful environment due to low food supply, high humidity, and, in some cases, a hypoxic and hypercapnic atmosphere. To face such conditions, subterranean rodents have convergently evolved low basal metabolic rate, high minimal thermal conductance and low body temperature. Although these parameters have been intensively studied in the last decades, such information is far from being well-known in one of the most studied groups of subterranean rodents, the blind mole rats of the genus Nannospalax. The lack of information is particularly noticeable for parameters such as the upper critical temperature and the width of the thermoneutral zone. In our study, we analysed the energetics of the Upper Galilee Mountain blind mole rat Nannospalax galili and found its basal metabolic rate of 0.84 ± 0.10 mL O2×g-1 × h-1, thermoneutral zone between 28 and 35 °C, mean Tb within the zone of 36.3 ± 0.6 °C, and minimal thermal conductance equal to 0.082 mL O2×g-1 × h-1 × C-1. Nannospalax galili is a truly homeothermic rodent well adapted to face lower ambient temperatures, because its Tb was stable down to the lowest temperature measured (10 °C). At the same time, a relatively high basal metabolic rate and relatively low minimal thermal conductance for a subterranean rodent of such body mass, and the difficulty of surviving ambient temperatures slightly above upper critical temperature, indicates problems with sufficient heat dissipation at higher temperatures. This can easily lead to overheating, that is relevant mainly during the hot-dry season. These findings suggest that N. galili can be threatened by ongoing global climate change.