Abstract:
Numerous avian taxa use torpor, which involves pronounced
reductions in body temperature (Tb) to below normothermic
levels. However, the occurrence of this phenomenon in owls
(Strigidae) remains largely unknown. We investigated winter
patterns of thermoregulation in the crepuscular 80-g pearlspotted
owlet Glaucidium perlatum and the strictly nocturnal
61-g African scops-owl Otus senegalensis by obtaining telemetric
measurements of skin temperature (Tskin) from free-ranging
individuals in the Kalahari Desert of southern Africa. Pearlspotted
owlets remained homeothermic throughout the study
period, whereas African scops-owls routinely used shallow torpor,
with Tskin reduced by 3.3 –8.6 C (pooled mean, 5.3
1.1 C) below normothermic levels for 3–4 h after sunrise. The
mean lowest Tskin recorded in three African scops-owl individuals
was 29.0 0.1 C. The thermoregulatory differences between
these two species may be related to their diets and activity
patterns. African scops-owls are almost exclusively insectivorous
and experience a marked reduction in food availability on
cold winter nights. In contrast, pearl-spotted owlets have more
flexible activity patterns and include larger or diurnal vertebrate
prey in their diet.
