The continuing development of improved capture–recapture (CR) modeling techniques used to study apex predators has also limited robust temporal and cross-site analyses due to different methods employed. We develop an approach to standardize older non-spatial CR and newer spatial CR density estimates and examine trends for critically endangered Sumatran tigers (Panthera tigris sumatrae) using a meta-regression of 17 existing densities and new estimates from our own fieldwork. We find that tiger densities were 47% higher in primary versus degraded forests and, unexpectedly, increased 4.9% per yr from 1996 to 2014, likely indicating a recovery from earlier poaching. However, while tiger numbers may have temporarily risen, the total potential island-wide population declined by 16.6% from 2000 to 2012 due to forest loss and degradation and subpopulations are significantly more fragmented. Thus, despite increasing densities in smaller parks, we conclude that there are only two robust populations left with >30 breeding females, indicating Sumatran tigers still face a high risk of extinction unless deforestation can be controlled.

No abstract

Niche partitioning is a result of interspecific competition between closely-related species to allow co-existence. Multiple species of small carnivores co-occur throughout their ranges in Sumatra, but they are among the lesser studied group of mammal species. This study aimed to collate occurrence records of small carnivores, model their island-wide spatial distribution, and assess their spatio-temporal niche partitioning in Sumatra. We collated camera trap records of small carnivores that were mainly bycatch data from widespread tiger surveys. We used Maxent to predict suitable habitat for nine small carnivore species in response to environmental variables, calculated pairwise spatial niche overlap, and then assessed temporal overlap using Kernel density estimation. In total, we detected 16 of the 21 small carnivore species known to occur in Sumatra. We predicted the suitable habitat of nine species that were found in ≥ 20 locations. Species with the smallest extent of predicted suitable habitat were the Malay civet (Viverra tangalunga) and short-tailed mongoose (Herpestes brachyurus). Of 36 pairwise comparisons, five species pairs had high overlaps and four species pairs had low overlap on spatiotemporal niche. High overlaps did not necessarily indicate high competition pressure because these species have different behaviour to allow coexistence, such as food preference and arboreality. Camera trap surveys are commonly conducted for species-specific studies, yet they also yield abundant records of non-target species. We therefore encouraged collaboration among institutions working in the same region to use bycatch data to fill the knowledge gaps in the ecology of other lesser known species.

In the original version of the Article, reference 18 was incorrectly numbered as reference 30, and references 19 to 30 were incorrectly numbered as 18 to 29. These errors have now been corrected in the PDF and HTML versions of the manuscript.