Population surveys of the ice rat Otomys sloggetti robertsi in the Lesotho Drakensberg

Abstract

Increasing environmental temperatures may lead to better survival of organisms that are usually susceptible to low temperatures. We investigated whether the numbers of the ice rat Otomys sloggetti robertsi, whose populations are regulated by low temperatures, have increased in the recent past as a consequence of current environmental warming in the Lesotho Drakensberg. Ice rats are endemic to the southern African alpine zone, are exclusively herbivorous, have a diurnal activity profile, and live in underground burrows. We predicted that ice rat numbers would remain stable or increase since winters have become milder. We monitored ice rat numbers in three locations, separated by 70, 80 and130 km. The results show that the population density of ice rats has increased over threefold to 352 ice rats per hectare over the past decade. Our findings suggest that higher temperatures could have improved habitat productivity and reduced thermal stress, and thus improved winter survival of ice rats.

Key words:

• Population density
• Environmental warming
• Primary productivity