Political borders and natural boundaries of wildlife populations seldom coincide, often to the detriment of conservation objectives. Transnational monitoring of endangered carnivores is rare, but is necessary for accurate population monitoring and coordinated conservation policies. We investigate the benefits of collaboratively monitoring the abundance and survival of the critically endangered Amur leopard, which occurs as a single transboundary population across China and Russia. Country-specific results overestimated abundance and were generally less precise compared to integrated monitoring estimates; the global population was similar in both years: 84 (70-108, 95% confidence interval). Uncertainty in country-specific annual survival estimates were approximately twice the integrated estimates of 0.82 (0.69-0.91, 95% confidence limits). This collaborative effort provided a better understanding of Amur leopard population dynamics, represented a first step in building trust, and lead to cooperative agreements to coordinate conservation policies. K E Y W O R D SAmur leopard, camera traps, carnivore, China, mark-recapture, monitoring, Panthera pardus orientalis, Russia, transboundary conservationThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Southwest Primorsky Krai retains the sole remaining population of critically endangered Amur leopards, but and also holds an isolated population of Amur tigers. This small group of tigers plays a key role as a core breeding population for potential Amur tiger recovery in neighboring Jilin and Heilongjiang Provinces of Northeast China. A large scale camera-trap monitoring program initiated by the United Administration of the State Nature Biosphere Reserve Kedrovaya Pad and Land of the Leopard National Park in 2013 provides a more precise means of tracking dynamics of animals' abundance than previous snow-track counts and is to act «early warning system» in a case of dramatic decreases in tiger numbers. Surveys were conducted over three years, beginning in August 2013 and ending in July 2016. During each survey year, we planned to select a survey period of no more than 92 days when no less than 80% of camera-trap stations were active. However, as the camera-trap stations were not simultaneously deployed and checked during the last year (2015)(2016), using the 80% cut point substantially was not feasible, so we lowered the limit to 55%. To estimate detection rates for adults, we used only those animals that were present in a given year both before and after the survey period, with the assumption that if a tiger were present both before and after, most likely it was present during the survey period as well. From the 320 photographic captures obtained over three years we identified 39 adult Amur tigers and 22 cubs. Among them only seven adult individuals (18%) were captured in all three years, while sixteen adult individuals (41%) were captured only in one of the three years; the rest (41%) were captured in two of the three years. Females demonstrate greater fidelity, and a greater likelihood or being present in all three years. Tigers were more frequently captured during the cold season from October to March with the peak numbers recorded in December. However, there were only ten instances in which adult/subadult tigers were photographed both before and after the survey period in all years combined. Of those, in only six instances (60%) tigers also photographed during the survey period, suggesting a relatively low detection probability. However detection of cubs was even lower: twenty-two cubs were photographed during the three years of the study but only three (14%) were photographed during the three survey periods. These results suggest that capture rates of cubs are much lower than those of adults/subadults reaffirming recommendations to not include cubs in formal population abundance estimates.