City sloths and marmosets in Atlantic forest fragments with contrasting levels of anthropogenic disturbance

Abstract

Urbanization is a major threat to wildlife with its cohort of environmental stressors. Urban remnant vegetation can help mitigate these impacts, but such remnants are subject to stressors that might be detrimental for some species. Habitat generalists have flexible diets and broader habitat tolerances that could favour their persistence in these remnants. Marmosets (Callithrix jacchus) and sloths (Bradypus variegatus) differ in their ecological and behavioural plasticity and both occur in urban areas. We predict marmosets to be less affected than sloths, a specialist species, by anthropogenic disturbance. We estimated their densities in urban forest fragments of semi-deciduous Atlantic forest in Paraiba, NE Brazil, with contrasting levels of urbanization. Using the distance sampling methodology, we surveyed 12 trails in a larger and less impacted fragment (515 ha) and 13 trails across nine smaller forest patches (2.1–8.0 ha) with a greater level of anthropogenic disturbance. Density of marmoset’s groups was higher in the area with lower anthropogenic disturbance, whereas sloths’ density was significantly higher in the more urbanized fragments. Marmosets seemed to be more impacted by noise than sloths. The density of both species in forest patches with higher level of anthropogenic disturbance was similar or even higher than densities from non-urban and less disturbed areas. Despite the negative impacts on wildlife, urbanization seems to cause a reduction of predators and an increase in availability of food resources that favour some species. Our results show the importance of small urban forest fragment for the persistence of marmosets and sloths in Neotropical cities.