Abstract:
Recent years have seen a rapid increase in the number of Afrotropical endotherms known to avoid mismatches
between energy supply and demand by using daily torpor and/or hibernation. Among mammals, heterothermy has been
reported in 40 species in six orders, namely Macroscelidea, Afrosoricida, Rodentia, Eulipotyphla, Primates and
Chiroptera. These species span a range in body mass of 7–770 g, with minimum heterothermic body temperatures ranging
from 1–278C and bout length varying from 1 h to 70 days. Daily torpor is the most common form of heterothermy, with
true hibernation being observed in only seven species, Graphiurus murinus, Graphiurus ocularis, Atelerix frontalis,
Cheirogaleus medius, Cheirogaleus major, Microcebus murinus and Microcebus griseorufus. The traditional distinction
between daily torpor and hibernation is blurred in some species, with free-ranging individuals exhibiting bouts of
424 h and body temperatures 5168C, but none of the classical behaviours associated with hibernation. Several species
bask in the sun during rewarming. Among birds, heterothermy has been reported in 16 species in seven orders, and is
more pronounced in phylogenetically older taxa. Both in mammals and birds, patterns of heterothermy can vary dramatically
among species occurring at a particular site, and even among individuals of a single species. For instance,
patterns of heterothermy among cheirogalid primates in western Madagascar vary from daily torpor to uninterrupted
hibernation for up to seven months. Other examples of variation among closely-related species involve small owls,
elephant shrews and vespertilionid bats. There may also be variation in terms of the ecological correlates of torpor
within a species, as is the case in the Freckled Nightjar Caprimulgus tristigma.
