Social Behaviours and Networks of Vervet Monkeys Are Influenced by Gastrointestinal Parasites

Abstract

Substantial research has shown that while some parasite infections can be fatal to hosts, most infections are sub-clinical and non-lethal. Such sub-clinical infections can nonetheless have negative consequences for the long-term fitness of the host such as reducing juvenile growth and the host’s ability to compete for food and mates. With such effects, infected individuals are expected to exhibit behavioural changes. Here we use a parasite removal experiment to quantify how gastrointestinal parasite infections affect the behaviour of vervet monkeys (Chlorocebus aethiops) at Lake Nabugabo, Uganda. Behavioural profiles and the structure of nearest neighbour relationships varied significantly. As predicted, after deworming the duration of the resting events decreased, which is consistent with the idea that parasite infections are energetically costly. In contrast to what was predicted, we could not reject the null hypothesis and we observed no change in either the frequency or duration of grooming, but we found that the duration of travel events increased. A network analysis revealed that after deworming, individuals tended to have more nearest neighbours and hence probably more frequent interactions, with this effect being particularly marked for juveniles. The heightened response by juveniles may indicate that they are avoiding infected individuals more than other age classes because it is too costly to move energy away from growth. We consider that populations with high parasite burden may have difficulties developing social networks and behaviours that could have cascading effects that impact the population in general.

Comparison of gastrointestinal parasite communities in vervet monkeys

“…To some degree, the increased parasite richness observed in this study may be due to our larger sample size. It is also possible that the higher parasite richness observed in the Lake Nagubabo population results from the highly anthropogenically disturbed nature of the study group's habitat: vervets at Lake Nabugabo have frequent interactions with humans, dogs and livestock (Chapman et al 2016). However, living in a highly disturbed habitat does not alone explain the higher parasite species richness observed in this study, as 4 of the 7 other vervet populations sampled also live in highly disturbed habitats (Table 4).…”

“…With respect to the condition of the host, while stress is known to be a factor influencing parasitic infection (Chapman et al 2006), host condition is difficult to quantify and compare. Our study group was likely chronically stressed by frequent interactions with humans -who are known to chase and kill group mem- bers-and dogs, which are a known predator of vervets in this population (Chapman et al 2016). However, this stress may have been mitigated by the year-round availability of food sources, namely crops planted by humans.…”

“…Vervets are often found living in urban, peri-urban or agricultural environments, sometimes co-existing with humans, as well as in undisturbed savanna, and woodland, riverine systems. Vervet monkeys are considered pests because they frequently crop raid or steal human food (Boulton et al 1996;Saj et al 2001;Gillingham & Lee 2003;Chapman et al 2016). Because of their proximity to (and frequent interaction with) humans and their ability to live in habitats ranging from old-growth forest to cities, vervet monkeys are a good model for understanding parasitic infections in wildlife populations inhabiting highly anthropogenic habitats.…”

Direct estimate of the spontaneous germ line mutation rate in African green monkeys

“…As a consequence, a comparison of de novo mutation rates between an Old World monkey and great apes can help to better illuminate variation in mutation rates across primates, presenting a significant step forward in our understanding of the molecular clock. Furthermore, this estimate provides a more correct scaling factor for characterizing the population history of the African green monkey itself-a species, which stands as one of the most important nonhuman primate models in biomedical research (e.g., Broussard et al 2001;Lemere et al 2004;Emborg 2007;Chapman et al 2016).…”

Peer Review #1 of "Adaptive genetic variation at three loci in South African vervet monkeys (Chlorocebus pygerythrus) and the role of selection within primates (v0.2)"

“…These primates are listed as 'Least concern' in the Red list of mammals of South Africa, Swaziland and Lesotho (Turner et al 2016a). The genus Chlorocebus is a taxon of significant scientific interest within research areas such as immunodeficiency virus pathology (Ma et al 2013), parasite ecology (Gaetano et al 2014;Wren et al 2015;Chapman et al 2016),…”