关键词: 空间标记-重捕模型, 种群密度, 活动节律, 相机陷阱, 小型猫科动物, 食肉目, 香港

Abstract

Aim: Reliable estimates of population density are fundamental to wildlife conservation and management. Although the leopard cat is the most common and widespread wild felid in China, little is known about the ecology and population biology of this species in the country. Using spatially explicit capture-recapture (SECR) modelling derived from extensive camera-trapping data, we estimated the population density and activity patterns of leopard cats in a well- protected private nature reserve in southern China.
Methods: Between June 2020 and May 2021, we conducted a camera-trap survey across a pre-determined grid system in Kadoorie Farm and Botanic Garden (KFBG), Hong Kong. KFBG was established on a barren hillside following sustained anthropogenic disturbances. After six decades of protection, secondary forest currently covers approximately 80% of the site. We deployed a total of 19 camera trap stations across our small 1.5 km² study area, with two opposite-facing cameras at each station to obtain images of both flanks of leopard cats. The consecutive 12-month survey yielded 113 independent capture events of the leopard cat, of which 61 events were clear enough to facilitate individual identification. Based on closed population assumptions for capture-recapture models, we also divided the 12-month survey into six two-month sampling periods, and estimated the population density for each sampling period using Maximum Likelihood SECR modelling. We also examined activity kernel densities to estimate the difference in diel activity patterns between wet and dry seasons.
Results: Our analyses revealed that results from two sampling periods were robust and precise enough (i.e., low standard error and narrow 95% confidence intervals) to estimate leopard cat density. We estimated leopard cat density between June and July 2020 as D = 0.64 ± 0.31 (0.26-1.55) individuals/km², and between February and March 2021 as D = 0.87 ± 0.48 (0.31-2.40) individuals/km², which are among the highest density estimates for this species reported in any region. We also found that the diel activity pattern of leopard cats in the study site is arrhythmic during the wet season, but became more nocturnal-crepuscular during the dry season, though they also exhibited some diurnal activity. Kernel density analyses however suggested no significant differences in diel activity patterns occurred between wet and dry seasons.
Conclusions: Our study provides important early data on the population density of leopard cats in southern China, the results of which allow for comparisons with other studies elsewhere using capture-recapture modelling approaches. We further demonstrate the utility of SECR methods for estimating population density over short and long sampling periods across necessarily small sampling areas. We further provide practical recommendations for conducting camera trap surveys to enhance the success rates of individual identification and “recapture” of leopard cats. In accordance with the conclusion of other studies, our results show that leopard cats are highly adaptable, exhibit great plasticity in daily activity, and thrive well in human-modified landscapes.

Key words: spatially explicit capture-recapture (SECR), population density, activity pattern, camera traps, small felid, Carnivora, Hong Kong