IWN Report — Sunday, 18 October 2026

The endangered lion-tailed macaques of the Western Ghats carry roughly twice as many kinds of parasite when they live beside human settlements, many of them species that normally infect cattle, and researchers think the burden may be one reason so few young macaques survive in the region’s shrinking forest patches.

The Centre for Wildlife Studies (CWS) returned to the finding in a science blog post on 16 October, drawing on a 2013 paper in PLOS ONE by researchers from CWS and the Centre for Cellular and Molecular Biology (CCMB). The team collected 91 fresh droppings from nine macaque troops on the Valparai plateau in the Anamalai ranges of Tamil Nadu between January and March 2010, sampling one troop in each of nine forest fragments, and found nine kinds of parasite.

According to the paper, troops in the five fragments with settlements nearby averaged 5.6 parasite types each, against 2.5 for troops farther from people, and six of the nine types turned up only near settlements. Cattle grazed in all five of those fragments. CWS singles out Haemonchus and Cotylophoron, both common in livestock, as examples, and says grazing cattle are the likely source. In four fragments, it adds, people, cattle and macaques drank from the same streams.

Troop size also played a part, with larger troops carrying more parasite types, but living near settlements raised the count whatever the size of the troop. A hookworm, Ancylostoma, behaved differently from the rest and was more common in smaller troops and away from settlements.

The Valparai plateau covers about 220 square kilometres at an elevation of roughly 1,000 metres. Most of its rainforest was cleared between the 1890s and 1930s for tea, coffee and cardamom, and what remains survives in patches ranging from 2 to 2,000 hectares. The paper counted about 20 macaque groups in those patches, most of them isolated, with one or two groups per fragment.

CWS describes the lion-tailed macaque as endangered and found only in the Western Ghats, and the 2013 paper put nearly 40 per cent of the population in small, isolated groups. The authors suggested that heavy parasite loads may partly explain the lower birth rates and poorer survival of young macaques in such fragments, alongside less nutritious diets.

Sources: Centre for Wildlife Studies: In the fragmented Western Ghats, lion-tailed macaques and people share land, water, and parasites · PLOS ONE: Human Presence Increases Parasitic Load in Endangered Lion-Tailed Macaques (Hussain et al., 2013)