Is diet flexibility an adaptive life trait for relictual and peri-urban populations of the endangered primate Macaca sylvanus?

Abstract

Habitat loss, fragmentation and urban expansion may drive some species to marginal habitats while others succeed in exploiting urban areas. Species that show dietary flexibility are more able to take advantage of human activities to supplement their diet with anthropogenically abundant and accessible resources. The Barbary macaque (Macaca sylvanus) is an endangered species due to the loss of its habitat, and human pressure. The population of Gouraya National Park (Algeria) lives in a relictual habitat that constitutes about 0.6% of the species range. In addition, this population is a unique case where urban expansion favours contact zones between Barbary macaque habitats and a big city (Bejaia). We quantified the dietary composition of Gouraya macaques over an annual cycle with the objective to understand how diet flexibility of this species may help it adapt to a relictual habitat or cope with urban expansion. We recorded the phenology of plant species every month. This study shows that Gouraya macaques, compared to those living in other forest types of the distribution area, are under lower seasonal constraints. They consume a greater amount of fruit and seeds that are available throughout much of the year, and a lesser amount of costly to find and extract subterranean foods. Therefore the Gouraya relictual habitat appears as a favourable environment compared to other major habitats of that species. This study also shows that colonizing peri-urban zones increases the availability and species richness of diet resources for Barbary macaques as they consume more human foods and exotic plants than in farther sites. Adult males eat more human foods than adult females and immatures do. The exploitation of high-energy anthropogenic food could favour macaque population growth and expansion towards the city center associated with human/macaque conflicts. We recommend applying management actions to restore macaques back to their natural habitat.

Fig 1. Location of the study site and of the two “Les Oliviers” (peri-urban) and “Cap Carbon” (non-urban) groups.

Fig 2. Number of available plant species in each phenological stage at “Les Oliviers” (peri-urban) and “Cap Carbon” (non-urban) sites.

Fig 3. Plant species richness of the macaques’ diets in the two sites.

Rarefaction curves represent the cumulative numbers of observed eaten species. Randomized species richness is represented as a function of the number of eaten food items we sampled. Symbols are plotted every 10 hours of observation. Dashed lines indicate 95% confidence intervals.

Fig 4. Monthly variation in the specific diversity of the macaques’ diets in the two peri-urban and non-urban groups.

Fig 5. Overlap of the macaque groups’ diets.

Monthly variation of Schoener’s indices.

Fig 6. Variation in the percentage of feeding time spent on 11 food categories according to month and group.

Leaves also included stems.

Fig 7. Scatter plots of the discriminant function analysis among three age-sex categories of individuals.

A: Scatter plot of two discrimination functions based on samples from adult males, adult females and immatures. The largest symbols indicate the mean of the cloud for each age-sex category; B: Scatter plot of the canonical weight of the discriminant analysis. Variables are the 11 food categories of macaques’ diets.