Sportive lemurs elevate their metabolic rate during challenging seasons and do not enter regular heterothermy

Abstract

Animals experience seasonal changes of environmental and ecological conditions in most habitats. Fluctuations in ambient temperature have a strong influence on thermoregulation, particularly on small endothermic mammals. However, different mammalian species cope differently with these changes. Understanding the physiological responses of organisms to different seasons and analysing the mechanisms that account for intra- and inter-specific differences and the ecological consequences of these variations is important to predict species responses to climatic changes. Consequences of climatic changes will be most pronounced in climatically already challenging habitats, such as the dry regions of western Madagascar. We aimed to identify the seasonal responses and adaptive possibilities in energy budgeting of Lepilemur edwardsi, a small primate of this habitat, by measuring metabolic rate (MR; open-flow respiratory) and skin temperature in the field during different seasons. Resting metabolism was generally low, but our study did not detect any signs of regular heterothermic episodes, despite the fact that these are known in other sympatrically living lemurs with a similar lifestyle. Surprisingly, L. edwardsi responded by elevating its resting MR in the poor-resourced dry season, compared to the better-resourced wet season, presumably to master detoxification of their increasingly toxic diet. As body mass decreased over this time, this strategy is obviously not energetically balanced on the long term. This is cause for concern, as it suggests that L. edwardsi has a very small leeway to adjust to changing conditions as experienced due to climate change, as dry season are expected to become longer and hotter, straining water budgets and food quality even more. Moreover, our findings highlight the importance of studying physiological parameters directly in the field and under differing climatic conditions.

Season and reproductive activity influence cortisol levels in the Malagasy primate Lepilemur edwardsi

“…Sportive lemurs inhabit almost all habitats in Madagascar and can survive even in the driest and harshest environments on this island, such as the extremely dry spiny forests in southern Madagascar and the seasonal deciduous dry forests in the West. However, individuals seem to be affected by the unfavorable conditions of the dry season, as previous studies show that L. edwardsi increases its resting metabolism to cope with these conditions and has a higher parasite prevalence towards the end of the dry season (Bethge et al, 2021, 2022).…”

“…Low HCC in L. edwardsi is in concordance with previous findings which show that plasma GC decreases with decreasing mass‐specific resting metabolic rates of mammals (Haase et al, 2016). Sportive lemurs have one of the lowest mass‐specific resting metabolic rates measured in mammals so far (Bethge et al, 2017, 2021; Schmid & Ganzhorn, 1996). Indeed, other nocturnal lemur species, such as the fat‐tailed dwarf lemur ( Cheirogaleus medius ) and the gray mouse lemur ( Microcebus murinus ), which also have comparatively low resting metabolic rates, also showed comparatively low HCC levels ranging from 0.15 to 24.33 pg mg −1 and 0.15 to 42.35 pg mg −1 HCC respectively (Rakotoniaina et al, 2016).…”

“…Arboreal folivores, such as L. edwardsi, depend on low nutritional food resources (particularly during the dry season), which seems to select for a more sedentary lifestyle and low metabolism (Bethge et al, 2017(Bethge et al, , 2021Lovegrove, 2000;McNab, 2008). As an adaptation to these energetic limitations, L. edwardsi may further have to inhibit the release of GC by their HPA-axis.…”

City comfort: weaker metabolic response to changes in ambient temperature in urban red squirrels

“…We processed data-files from the oxygen analyser with Clampfit 10.3.1.4 (Molecular Devices, Sunnyvale, USA) to account for zero checks and exclusion of periods where the individuals were outside of the nest boxes (Supplementary Figure S6 ). We corrected measured values to standard temperatures and pressure and calculated the rate of oxygen consumption with the following equation 93 , which is applicable for our set-up 52 , 94 : . FR e represents the excurrent flow rate and F i O 2 –F′ e O 2 accounts for the difference in fractional O 2 concentration when entering and leaving the nest box.…”

Seasonal changes in the parasite prevalence of a small Malagasy lemur species (Lepilemur edwardsi)

“…Ambient temperature during the dry season ranges between a daily maximum median of 33°C and a minimal median of 23°C during the night and there is no rainfall for about 6 months (Bethge et al . 2021).…”