Competing pressures on populations: long-term dynamics of food availability, food quality, disease, stress and animal abundance

Abstract

Despite strong links between sociality and fitness that ultimately affect the size of animal populations, the particular social and ecological factors that lead to endangerment are not well understood. Here, we synthesize approximately 25 years of data and present new analyses that highlight dynamics in forest composition, food availability, the nutritional quality of food, disease, physiological stress and population size of endangered folivorous red colobus monkeys ( Procolobus rufomitratus ). There is a decline in the quality of leaves 15 and 30 years following two previous studies in an undisturbed area of forest. The consumption of a low-quality diet in one month was associated with higher glucocorticoid levels in the subsequent month and stress levels in groups living in degraded forest fragments where diet was poor was more than twice those in forest groups. In contrast, forest composition has changed and when red colobus food availability was weighted by the protein-to-fibre ratio, which we have shown positively predicts folivore biomass, there was an increase in the availability of high-quality trees. Despite these changing social and ecological factors, the abundance of red colobus has remained stable, possibly through a combination of increasing group size and behavioural flexibility.

Sociality and health: impacts of sociality on disease susceptibility and transmission in animal and human societies

“…Variation in survival is relatively straightforward to determine, provided individuals can be recognized and followed, but survival estimates are generally complicated by dispersal, and causes of mortality must be separated into those due to extrinsic causes (primarily predation) and those attributable to infection and non-infectious diseases. For example, Chapman et al [116] use demographic data collected over decades to make inferences about the effects of stress and new parasites on population dynamics in red colobus monkeys, and recent studies revealed that survival is affected by social relationships in female baboons [117] and male bottlenose dolphins [118].…”

The hustle and bustle of city life: monitoring the effects of urbanisation in the African lesser bushbaby

“…With limited area available for movement and foraging, primates turn to anthropogenic food sources, such as provisioned feeding spots or crop raiding, to survive within a highly humanized environment (Hoffman and O'Riain 2012). Food availability has been shown to be a key factor contributing to group dynamics, most notably population size and structure, as well as aggressive interactions among conspecifics (Chapman et al 2015;Oro et al 2004). As food provisioning in the urban habitat provides a constant source of nutrition, this can have a considerable impact on population ecology (Altmann and Muruthi 1988;Hill 1999).…”

The sociality–health–fitness nexus: synthesis, conclusions and future directions

“…Links between health, sociality and fitness also have important implications for conservation biology, as highlighted by the contribution to this theme issue by Chapman et al [10]. Conservation biologists often consider the problems that arise in small populations, which of course is characteristic of endangered species.…”

“…A final example of surprising results comes from Chapman et al's [10] contribution to the theme issue. In this paper, the authors investigated a series of predicted links involving food quality and availability, glucocorticoid levels as a marker of stress, and abundance of wild red colobus monkeys.…”

“…Other papers in this issue have investigated the fitness consequences of sociality and parasitism, for example in Columbian ground squirrels [8]. The papers also take a wide range of approaches, including broad-scale comparative and meta-analysis [3,7,9], long-term field research on food availability, stress and population density [10], social networks and disease spread in wild animals [4], and experimental studies of behaviour in captive primates [5].…”