Effect of socio-ecological factors and parasite infection on body condition of Brown Mouse Lemur Microcebus rufus (Mammalia: Primates: Cheirogaleidae)

Abstract

Various studies in ecology have shown the relationship between body condition and parasitic loads in nonhuman primates, however, little information is available regarding prosimians such as lemurs.  In this study, the synergistic effect of parasite infection and socio-ecological factors on the body condition of Microcebus rufus in the family Cheirogaleidae was analyzed in Ranomafana National Park in southeastern Madagascar.  This lemur species is characterized by its ability to adapt to different types of forest, and by seasonal fattening.  Based on the factors considered, this species is, therefore, a good model for the study of body condition and ecology of infectious diseases in lemurs. Floatation and direct observation techniques were used for examination of parasite infection.  Two indices considering body condition were analyzed: volume index (VI) and condition index (CI), the residual between the mass observed and the corrected mass.  The generalized linear mixed model (GLMM) was used to model the synergistic effect of parasite infections and socio-ecological factors on variation in body condition, with the identity of individuals used as a random factor.  We identified five species of helminths, one species of protist, and one species of lice which infected the 204 mouse lemurs captured.  There was a sexual difference for all measures of the parasite infection.  The more parasite species an individual was infected with, the smaller was its body size according to the Volume Index that reflects deposits of subcutaneous fat.  Individuals with more positive Condition Index values, particularly females, excreted more parasite eggs or oocyst in their faecal matter.  The results suggest that an individual’s body condition constitutes an indicator of risk of parasite infection and transmission.