ecology of host-parasite interactions in a wild mammalian host community in mudumalai, southern india

Abstract

Summary and Conclusions

A method for comparative quantitative study of faecally dispersed parasites of wild mammals was standardized. Twelve species of mammalian hosts-blacknaped hare, chital, elephant, gaur, langur, leopard, porcupine, sambar, sloth bear, tiger, wild boar, and wild dog-were studied. A few species with previously unreported morphological characteristics or host specificities are described.

The distribution of faecal propagule densities was highly aggregated in all host species. Positive correlations were observed between prevalence and parasite intensities in many host species.

Elephants exhibited increased parasite loads in the dry season compared to the wet season. Parasite loads of chital remained unchanged across seasons. The presence of domestic ungulates did not increase worm burdens in chital but did increase species richness at the componentcommunity level.

A negative association was found between relative tusk length in elephants and faecal parasite densities, compatible with the theory of parasiterelated secondary sexual characters and sexual selection in males.

Wild dogs selectively killed chital with higher parasite loads, particularly young individuals with Strongyloides infection.

In interspecific comparisons, species experiencing higher predation pressures showed lower median parasite loads. Population density, diet, gregariousness, body weight, or homerange size did not show the predicted effects on median parasite loads across host species.

Faecal odour tolerance by humans for different species was negatively correlated with the prevalence of potentially zoonotic parasites. Faecal odour of species not carrying zoonotic parasites was tolerated more.

Elephants, unlike chital, gaur, and sambar, preferred to defaecate in water and on salt licks-potential sites for parasite transmission. Considering several alternative explanations, the most plausible appears to be the evolution of spiteful parasitespreading behaviour. As a result, parasite betadiversity in elephants was low (i.e., higher faunal similarity among individuals) compared to all other species studied. In elephants, unlike chital and wild dogs, intergroup similarities were not different from intragroup similarities.

The possible role of parasites in shaping ecological and behavioural phenomena is speculatively explored. These include faecal territorial marking, seasonality of breeding, allogrooming, niche separation among predators, and potential predator-parasite mutualism.

This study was exploratory in nature. Several important questions have been identified that require further research, both through empirical data collection and through theoretical development.