First camera-trap records of Tlacuatzin insularis (Didelphimorphia: Didelphidae) in the Islas Marías Biosphere Reserve, Nayarit, México

Abstract

The mouse opossum of the Islas Marías (Tlacuatzin insularis), characterized by well-defined black eye-rings, light brown limbs, and a uniformly brown tail, is an endemic species restricted to the Islas Marías Archipelago Biosphere Reserve, Mexico. Information on its biology, ecology, and population status remains limited, highlighting the need to generate updated data to inform its conservation. On María Madre Island, 17 camera-trap stations were installed along four non-systematically distributed trails, prioritizing sites with evidence of mammal activity. Cameras operated continuously for an average of nine days each. With a total sampling effort of 160 trap-days, two independent records of Tlacuatzin insularis were obtained, corresponding to a male individual and another of undetermined sex. Both records occurred within a time window between 20:00 and 23:00 h. In parallel, cameras documented other endemic species of the reserve, such as the Islas Marías rabbit (Sylvilagus graysoni) and the Islas Marías raccoon (Procyon lotor insularis). Additionally, invasive exotic species were recorded, including the domestic cat (Felis catus) and the black rat (Rattus rattus). This finding is the first record of T. insularis through camera trapping, which is a relevant step considering its endemic distribution and the limited information available on its ecology. Furthermore, the presence of invasive species in the archipelago underscores the need to strengthen conservation actions aimed at mitigating their potential impacts on this and other native species.