Niche partitioning between two marsupials inhabiting the Yungas of Northwestern Argentina: overlapping diets in non-overlapping lifestyles?

Abstract Marmosa rapposa and Thylamys sponsorius were captured in syntopy in the locality of Isla de Cañas Salta province, Argentina. We studied the stomach contents of 7 M. rapposa and 10 T. sponsorius and identified arthropods and plant material as the main items. Niche overlap was studied using the Pianka index. We found that arthropods were the most abundant items in both species (67 % in M. rapposa , 63.5 % in T. sponsorius ), and plant material represented 29.6 % and 35.5 %, respectively. Insects were the main item in both species (45 % in M. rapposa , 58.5 % in T. sponsorius ), while spiders were more abundant in the diet of M. rapposa (21.7 % vs. 5 % in T. sponsorius ). The dietary overlap between the two species was high (91.1 %); a similar result was found between males and females of M. rapposa (74.2 %) and T. sponsorius (77.4 %). Non-parametric analyses using PERMANOVA and Principal Coordinate Analysis showed the same pattern, with broad overlap in the diets of the species. The coexistence of these two species may be due to temporal segregation (which we could not study) or different habitat use (more prominent palmar and plantar calluses in M. rapposa indicate a more arboreal lifestyle than that of T. sponsorius ).