Abstract:

Context: Estimating the population size of large and medium-sized mammals is a fundamental issue in animal ecology, attracting great attention from researchers, managers, and the public. However, despite the fact that it has been explored from the mid-20th century to now, the population sizes of numerous species worldwide are unknown. In China, the research targeting large and medium-sized mammals have been explored since 1980s. Although it has made great progress, the population size of many species in China are still unknown.
Aims: We aim to establish a framework to categorize existing estimation methods and further summarize the research development of population size estimation in China while highlighting strengths and trends under this framework.
Results & Conclusions: First, we establish a concise hierarchical framework according to the estimation theory, data resources, and models used. This framework indicates that there are four classes of methods including distance sampling method, capture-recapture method, encounter-based method, and direct count method from remotely sensed imagery according to estimation theory. Then for each of the four methods, we illustrate the basic model and its assumptions, explaining how existing data resources (including insight, camera trap, DNA microsatellite, satellite tracking, acoustic monitor, and remote sensing data) realize each theory respectively. We summarize unique features, advantages, and disadvantages of each method and compare size or density estimation resulted from different methods. Secondly, we summarize the development of population size estimation methods in China in the context of this framework while highlighting trends and strengths. Numerous data obtained from infrared cameras in many study areas during the last decade can be used to estimate the population size by employing distance sampling, capture-recapture models, and encounter-based methods. Meanwhile, the pellet distance sampling method, fecal-DNA capture-recapture method and direct count method from remotely sensed imagery are suggested to be developed. Finally, a guide to select the estimation methods appropriate for their studies is provided as a reference for future researchers.

Key words: population size, population density, large and medium-sized mammals, distance sampling, capture-recapture method, encounter-based method, direct count method from remotely sensed imagery