Biodiversity Science ›› 2019, Vol. 27 ›› Issue (3): 243-248.doi: 10.17520/biods.2018327

• Special Feature: Analysis of Wildlife Camera-Trapping Data • Previous Article     Next Article

Limitations of relative abundance indices calculated from camera-trapping data

Chen Lijun1, Xiao Wenhong1, Xiao Zhishu1, 2, *()   

  1. 1 State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101
    2 University of Chinese Academy of Sciences, Beijing 100049
  • Received:2018-12-12 Accepted:2019-04-11 Online:2019-03-20
  • Xiao Zhishu

Abundance is an important parameter used to estimate the population size of various wildlife species. With the growing application of camera-traps (movement or heat activated) to monitoring wildlife, the relative abundance index (RAI) has become one of the most popular indicators of population abundance for inventories and assessment. Despite a simple and convenient indicator of population size, RAI obtained from camera-trapping data can be greatly affected by many factors such as species traits, detection rates and environmental factors. Therefore, we need verify the correlation between RAI and population density prior to its general application. So far, several types of RAIs have been developed based on camera-trapping data, and it is critical to compare these RAI indices and their applications. In this paper, we summarized the methods calculating RAI with camera-trapping data and reviewed their applications in wildlife monitoring and inventories in China. Four main types of RAIs were identified including (1) the number of days when one animal is photographed, (2) the number of photographs of focal species per 100 trap days, (3) the number of photographs of focal species per trap day, and (4) the proportion of photos from the focal species compared to all photos of all animals. Among them, the second RAI type is the most widely used (72.5%) in wildlife monitoring and inventories in China, and the fourth RAI type is used to compare species components in communities. Consequently, we recommend the second RAI type for estimating population abundance in particular when camera-trapping data are used for broad-scale comparisons over different spatial and temporal scales.

Key words: population size estimation, relative abundance index, camera-trapping, species monitoring and inventory

Fig. 1

Summary about the papers of species inventory with the relative abundance index based on camera trapping data across China (from 1997 to 2018). (A) The camera-trapping papers in each year (N = 109); (B) These inventory papers with two key categories and six subtypes: one is to get the RAI based on the independent photo each unit of trapping effort (N = 79) with the unit of 1,000 h (1,000/Th, N = 4), 1,000 d (1,000/Td, N = 13), 100 d (100/Td, N = 60) and 1 d (100%/Td, N = 2); the other is to get the relative composition (N = 30), including species composition from 100 or 1,000 independent photo from a given site (100/Np, N = 18), and the proportion of each species among all independent photo from a given site (100%/Np, N = 12)."

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