Does habitat disturbance affect stress, body condition and parasitism in two sympatric lemurs?

Abstract

Understanding how animals react to human-induced changes in their environment is a key question in conservation biology. Owing to their potential correlation with fitness, several physiological parameters are commonly used to assess the effect of habitat disturbance on animals' general health status. Here, we studied how two lemur species, the fat-tailed dwarf lemur (Cheirogaleus medius) and the grey mouse lemur (Microcebus murinus), respond to changing environmental conditions by comparing their stress levels (measured as hair cortisol concentration), parasitism and general body condition across four habitats ordered along a gradient of human disturbance at Kirindy Forest, Western Madagascar. These two species previously revealed contrasting responses to human disturbance; whereas M. murinus is known as a resilient species, C. medius is rarely encountered in highly disturbed habitats. However, neither hair cortisol concentrations nor parasitism patterns (prevalence, parasite species richness and rate of multiple infections) and body condition varied across the gradient of anthropogenic disturbance. Our results indicate that the effect of anthropogenic activities at Kirindy Forest is not reflected in the general health status of both species, which may have developed a range of behavioural adaptations to deal with suboptimal conditions. Nonetheless, a difference in relative density among sites suggests that the carrying capacity of disturbed habitat is lower, and both species respond differently to environmental changes, with C. medius being more negatively affected. Thus, even for behaviourally flexible species, extended habitat deterioration could hamper long-term viability of populations.

Keywords: Body condition; Madagascar; habitat disturbance; lemurs; parasitism; stress.

Figure 1:

Density of potential shelter trees (a) and food trees (b) of Microcebus murinus and Cheirogaleus medius at the four study sites in Kirindy Forest. *P < 0.05.

Figure 2:

Variation in hair cortisol concentrations in M. murinus (a) and C. medius (b) among the four study sites. Numbers indicate the total number of hair samples analysed for each site.

Figure 3:

General body condition (measured as scaled mass index) of M. murinus and (a) C. medius (b) across the four study sites. ***P < 0.001. Numbers indicate the sample size for each site.