The interplay between ecological and anthropogenic factors: a longitudinal study on gastrointestinal parasites in a social group of wild Macaca maura.

The ecological role of parasites is an emergent topic in conservation biology due to its significant impact on fitness and sustainability of threatened populations. In primates, both ecological and anthropogenic factors, likely involved in infection patterns, have been investigated by gastrointestinal faecal parasites as a non-invasive estimate of overall health conditions. Time spent on ground by hosts, especially in feeding activities, population size and dynamics (i.e., immigrations) and interactions with humans may all affect parasite richness and prevalence, particularly for parasites with faecal-oral transmission. In Bantimurung Bulusaraung National Park (South Sulawesi, Indonesia), we monitored nematode and protozoa infections over three-years (2014/15, 2016, 2017) in a social group of moor macaques (245 stools, 27 adults), experiencing natural dispersal events (as for immigrations, 5 in 2016; 3 in 2017; 3-year fixed core of 10 adult individuals). Over the years, a growing macaques' indirect contact with humans occurred, by means of both eating food tossed by motorists on the road – bisecting their home range - and foraging in trash pits. The time spent on the road showed a significant increasing trend, characterised by an inverse relationship with the time spent on the forest ground. Eight out of 14 parasite taxa found were reported in South Sulawesi human populations as well. Overall parasite richness had a significant increase in the last year especially due to Protozoans which showed an increasing prevalence of particular taxa (e.g., Balantidium coli, from 25% to 67%, p<0,03; Chilomastix mesnili, from 8% to 75%, p<0,01). On the contrary Trichuris prevalence decreased over the years (from 83% to 4%, p<0,01). Remarkably, new protozoan taxa with high prevalence (e.g., Endolimax nana 96%, Entamoeba histolitica/dispar 58%, Isospora sp. 71%) were detected in the last year, the first two reported in South Sulawesi human populations the last two found in at least one immigrant macaque. Anthropic contacts and immigration events likely contributed to the complex pattern observed, emphasising faecal parasite analysis as an important step in the infection risk assessment of threatened primate populations.