Long-term declines in nutritional quality of tropical leaves

Global change is affecting plant and animal populations and many of the changes are likely subtle and difficult to detect. Based on greenhouse experiments, changes in temperature and rainfall, along with elevated CO2, are expected to impact the nutritional quality of leaves. Here, we show a decline in the quality of tree leaves 15 and 30 years after two previous studies in an undisturbed area of tropical forest in Kibale National Park, Uganda. After 30 years in a sample of multiple individuals of ten tree species, the mature leaves of all but one species increased in fiber concentrations, with a mean increase of 10%; tagged individuals of one species increased 13% in fiber. After 15 years, in eight tree species the fiber of young leaves increased 15%, and protein decreased 6%. Like many folivores, Kibale colobus monkeys select leaves with a high protein-to-fiber ratio, so for these folivores declining leaf quality could have a major impact. Comparisons among African and Asian forests show a strong correlation between colobine biomass and the protein-to-fiber ratio of the mature leaves from common tree species. Although this model, predicts a 31% decline in monkey abundance for Kibale, we have not yet seen these declines

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

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. [...] 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

Nabugabo vervet observations

Observational data collected in the field at Lake Nabugabo, Uganda of Vervet monkeys (Chlorocebus aethiops) between June 2011 and April 2014. The data is stored created using excel and stored as a .xlsx. The column names are kept intuitive. Further codes used in the file can be found in the "Read Me" file

Data from: Social behaviours and networks of vervet monkeys are influenced by gastrointestinal parasites

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

Social Behaviours and Networks of Vervet Monkeys Are Influenced by Gastrointestinal Parasites - Fig 1

<p><b>The nearest neighbour network of the primate population (A) before and (B) after de-worming</b>. The layout of the nodes and edges were determined by using the ForceAtlas2 algorithm [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0161113#pone.0161113.ref061" target="_blank">61</a>] with identical parameterization. The well-connected nodes occupy central positions in the graph. The size of the nodes are scaled to the sum of the weights of all edges incident upon it. The nodes are also shaded such that nodes with a higher degree are lighter in color.</p

The number of individuals each individual interacts with (Degree) as well as the total number of associations (strength) that were observed during the period before and after deworming.

<p>The number of individuals each individual interacts with (Degree) as well as the total number of associations (strength) that were observed during the period before and after deworming.</p