Surviving the Cold, Dry Period in Africa: Behavioral Adjustments as an Alternative to Heterothermy in the African Lesser Bushbaby ('Galago moholi')

Abstract

Behavioral and physiological adaptations are common and successful strategies used by small endothermic species to adjust to unfavorable seasons. Physiological adaptations, such as heterothermy, e.g., torpor, are usually thought to be more effective energy-saving strategies than behavioral adjustments. The African lesser bushbaby, 'Galago moholi', is physiologically capable of torpor but expresses heterothermy only under conditions of extreme energy limitation, suggesting that it has evolved alternative strategies to compensate energetic bottlenecks. We hypothesized that 'Galago moholi' survives the unfavorable winter period, without-or only rarely-employing torpid phases to save energy, by using behavioral thermoregulation. We compared the ecology and behavior of 'Galago moholi' in summer and winter by telemetric tracking and examined food availability by determination of arthropod and gum availability. We found a significant increase in huddling behavior and a significant increase in the use of enclosed and insulated sleeping sites during winter, as well as a reduction in nightly activity. 'Galago moholi' hunted for insects significantly less in winter than in summer, and increased gum intake in winter, when gum showed an increase in energy content. The availability of high-quality food, albeit in low quantities, presumably enables 'Galago moholi' to stay normothermic throughout the cold, dry period and to focus on reproduction activities. We propose that 'Galago moholi' favors ecological and behavioral adjustments over torpor because these are sufficient to meet energy requirements of this species, and their advantages (flexibility, unrestricted activity, and reproduction) outweigh the energetic benefits of heterothermy.