Torpor on Demand: Heterothermy in the Non-Lemur Primate Galago moholi

Abstract

BackgroundHibernation and daily torpor are energy- and water-saving adaptations employed to survive unfavourable periods mostly in temperate and arctic environments, but also in tropical and arid climates. Heterothermy has been found in a number of mammalian orders, but within the primates so far it seems to be restricted to one family of Malagasy lemurs. As currently there is no evidence of heterothermy of a primate outside of Madagascar, the aim of our study was to investigate whether small primates from mainland Africa are indeed always homeothermic despite pronounced seasonal changes in weather and food availability.Methodology/Principal FindingsOne of the nearest relatives of Malagasy lemurs, the African lesser bushbaby, Galago moholi, which inhabits a highly seasonal habitat with a hot wet-season and a cold dry-season with lower food abundance, was investigated to determine whether it is capable of heterothermy. We measured skin temperature of free-ranging individuals throughout the cool dry season using temperature-sensitive collars as well as metabolic rate in captured individuals. Torpor was employed by 15% of 20 animals. Only one of these animals displayed heterothermy in response to natural availability of food and water, whereas the other animals became torpid without access to food and water.Conclusions/SignificanceOur results show that G. moholi are physiologically capable of employing torpor. However they do not use it as a routine behaviour, but only under adverse conditions. This reluctance is presumably a result of conflicting selective pressures for energy savings versus other ecological and evolutionary forces, such as reproduction or territory defence. Our results support the view that heterothermy in primates evolved before the division of African and Malagasy Strepsirhini, with the possible implication that more primate species than previously thought might still have the potential to call upon this possibility, if the situation necessitates it.

Hiding from the Moonlight: Luminosity and Temperature Affect Activity of Asian Nocturnal Primates in a Highly Seasonal Forest

“…Many of these primates undergo periods of torpor or heterothermy to conserve energy to cope with low ambient temperatures [25], [26], [27], [28], [29], [30], [31]. Fernández-Duque et al [68] reported that the activity of a lunar philic primate was reduced during cooler temperatures, despite luminance.…”

“…Torpor and hibernation have been studied extensively in these species, showing some of the most remarkable specialisations of any nocturnal mammal, such as extreme lowering of the body temperature, and heavy storage of fat in the tail [29], [30]. Torpor has also been observed in a captive sub-adult Galago moholi [31], although it was not observed in two long-term field studies of this species [15], [21], [32]. Indeed, the opposite was the case, when galagos became active in the daytime to feed on valuable gum resources [15].…”

Hibernation Patterns of Dwarf Lemurs in the High Altitude Forest of Eastern Madagascar

“…In this context, the evolution of energy-saving metabolic strategies, particularly in small-bodied primates, could be seen largely as a result of selective environmental forces during major climatic changes in the history of Madagascar. In favor of the traditional position, Nowack et al (2010) point out that hibernation is expressed in members of all major mammalian lineages, and that some expression of heterothermy (albeit not true hibernation) has been reported in the sister taxa of lemurs, the galagos and lorises. Heterothermy, according to this view, is a plesiomorphic trait present in the ancestral strepsirrhine (Dausmann et al 2012).…”

The hustle and bustle of city life: monitoring the effects of urbanisation in the African lesser bushbaby

“…The traps were set late in the afternoon and checked hourly between 17:00 h and 05:00 h. All individuals spent ≤ 1 hour within a trap before removal. After removal, trapped individuals were aged, sexed, weighed and body length was measured from nose to the base of the tail with a flexible measuring tape following Nowack et al (2010), and all fresh faeces within the traps were collected. Individuals were handled for less than five minutes, without the use of anaesthesia, before being released at the exact spot of capture.…”

“…We then averaged the ten IORs to achieve an average IOR between the two observers (89.9 ± SE 0.03 %). Although free-ranging populations from both sites were accustomed to humans, due to previous biological studies (NNR; Mzilikazi et al 2006;Nowack et al 2010;Nowack et al 2013;Pullen et al 2000) or frequent human interaction (OP), observers were never closer than five metres to an individual being followed.…”