Reliance on Exotic Plants by Two Groups of Threatened Samango Monkeys, Cercopithecus albogularis labiatus, at Their Southern Range Limit

Abstract

Understanding how threatened species adapt their behavior to landscapes shaped by humans is increasingly important to ensuring they persist in a changing world. Matrix habitats can be shared spaces where human and non-human primates co-exist. We set out to determine how an endemic, nationally threatened forest specialist, the frugivorous, arboreal samango monkey (Cercopithecus albogularis labiatus), has responded to a matrix habitat made up of residential gardens and commercial plantations in Eastern Cape province, South Africa. We followed two groups from dawn to dusk for a mean of three days per month for 12 months (1 February 2011 to 31 January 2012) using scan sampling to collect data on their diet, activity and ranging patterns. We used resource abundance transects to describe the groups' home ranges and monitored tree phenology to calculate fruit and seed availability indices. Monkeys from both groups consumed large quantities of exotic plant species, 2 accounting for over 50% of their overall annual diet, with seeds of the invasive black wattle (Acacia mearnsii) the most commonly consumed exotic species followed by acorns of two oak species (Quercus robur and palustris.). However, monkeys responded to the availability of indigenous rather than exotic fruits and seeds and increased their consumption of exotics when indigenous fruits were less available. While monkeys spent less time moving when feeding on exotic species compared to indigenous species, eating exotics did not free up monkeys' time to rest or socialize as additional time was required to process exotic foods. To offset the possible negative consequences of the monkeys' reliance on exotic seeds, including escalating conflict between monkeys and people in gardens, we suggest gradual removal of exotic plant species in the habitat and replacement with indigenous species as one mitigation strategy.

Northern pigtailed macaques rely on old growth plantations to offset low fruit availability in a degraded forest fragment

“…Following optimal foraging strategies, macaques preferentially fed on highly nutritive fleshy fruit in the native forest, but included less preferred, although highly nutritive exotics seeds (i.e., high protein and calorie) during preferred native fruit scarcity (Lacher, Willig & Mares, 1982). These results are similar to those found in the closely related southern pigtailed macaque ( Macaca nemestrina ) and the arboreal samango monkey ( Cercopithecus albogularis labiatus ) which both rely on exotic plant species for survival: oil palm fruit ( Elaeis guineensis ) and black wattle seeds ( Acacia mearnsii ), respectively (Ruppert, Holzner, See, Gisbrecht, & Beck, 2018; Wimberger, Nowak, & Hill, 2017). During the lower fruit availability periods in the natural forest, northern pigtailed macaques relied on seeds characterized by high nutritive quality, which concomitantly occurred in large clumps in plantation forest, allowing high energy intake during enlarged ranging movement.…”

Variation in behavioral traits of two frugivorous mammals may lead to differential responses to human disturbance

“…Those fruits were found to be relatively nutritious and procured energetic advantages to chimpanzees (McLennan & Ganzhorn, 2017). This behavioral flexibility has also been observed in many other primate species, such as Colobus angolensis palliates (Dunham, 2017) and Cercopithecus albogularis labiatus (Nowak, Wimberger, Richards, Hill, & Roux, 2017; Wimberger, Nowak, & Hill, 2017). For these species, the risk of starvation and sensitivity to fruit availability may be more important than the risk of predation induced by human disturbance (McLennan, 2013; Nowak et al, 2017; Weterings, Moonen, Prins, Wieren, & Langevelde, 2018).…”

Here to stay. Recent advances and perspectives about Acacia invasion in Mediterranean areas

“…The tree density of A. saligna stands, together with other factors such as urban density or vegetation structure, contributed to the decline of birds diversity (Dures and Cummings 2010) and species of small mammals (Manor et al 2008), linking the decrease in biodiversity with a reduction in habitat quality or ecosystem integrity. Additionally, seeds of A. mearnsii are used as a nutrient source by the specialist primate Cercopithecus albogularis labiatus, altering its feeding behaviour and probably leading to consequences for A. mearnsii dispersion (Wimberger et al 2017).…”