Resurveying Primate Populations: A Comparison of Methods toMonitor Change Over Time

摘要

Although long-term monitoring of wildlife populations is fundamental in understanding how populations respondto changes in their environment, particularly in areas affected by habitat disturbance, long-term monitoring programs are lacking for many species and sites. Using newer methods to estimate population density may limit comparison with estimatesobtained in the past at the same study site. Our aim is to evaluate whether resurveys could be used to monitor changes in population trends over time by comparing population density estimates obtained in the past with subsequent population densityestimates obtained using the same methods to collect and analyze the data. We performed line-transect surveys in mature andregenerating forest in the Otoch Ma’ax yetel Kooh protected area, Yucatán, Mexico, to determine the spider monkey (Atelesgeoffroyi) population density in 1997–1998 and 2015. We estimated population density by calculating the size of the sampledarea (effective strip width) using the Kelker, King and Maximum Perpendicular Distance methods. We compared populationdensity estimates obtained using the same method in 1997–1998 and 2015. Although population density estimates differedacross methods, each method consistently showed no change in population density over time in either mature or regenerating forest, suggesting that changes in population trends can be monitored using the same method over time. Given that largegaps remain in the distribution and size of populations for the majority of Neotropical primates and long-term monitoringprograms are scarce, resurveys may be a useful method to provide updated information on populations surveyed in the past.Such updated information is urgently needed, especially in areas that have undergone landscape-scale modifications betweensurvey periods.