Beyond patch size: The impact of regional context and habitat quality on three endangered primates

Abstract

Deforestation has carved tropical forest landscapes into millions of different-sized patches worldwide. Research has focused on the effect of patch size on biodiversity, while neglecting patch quality effects and leaving geographic and interspecific variance to patch attributes largely unexamined. Here, we assess how patch size and quality affect the encounter rate (ER) and immature-to-female ratio (IFR) of three endangered primates – Mexican mantled howler monkey (Alouatta palliata mexicana), black howler monkey (Alouatta pigra), and spider monkey (Ateles geoffroyi) – in three rainforest regions with different forest cover. ER of spider monkeys in the best preserved region (50% forest cover) was positively related to both patch size and quality (i.e., species richness of top food species). ER of mantled howlers in the 17% forest cover region was also positively related to patch size. Yet, both ER and IFR of black howlers in the 50% forest cover region and mantled howlers in the 5% forest cover region were mainly related to patch quality. Our results demonstrate that conservation actions in human-modified landscapes must go beyond considering the effect of patch size, as animal populations can be better predicted by patch quality in some regions.