Population estimate and management options for introduced rhesus macaques

Abstract

ABSTRACTApproximately 12 rhesus macaques (Macaca mulatta) were introduced to the forests along the Silver River, central Florida, USA, between 2 introductions in the 1930s and 1940s to increase tourism; this land is now Silver Springs State Park (SSSP). By the mid‐1980s the population along the Silver River reached nearly 400 individuals. Approximately 1,000 animals were trapped and removed from 1984 to 2012 to reduce population growth and mitigate negative macaque‐human interactions. This practice was halted due to extensive public controversy, and consequently no population management has been implemented since 2012. To aid in informing management decisions related to rhesus macaques, we estimated the fall 2015 population size within SSSP, developed an age‐structured matrix model to estimate the population growth rate, and examined the efficacy of 4 management strategies to regulate this population, including culling (50% or 80% of subadults and adults) and sterilizing adult females (50% or 80% ≥3 years old). Our assessment suggested there were 176 macaques among 5 social groups within SSSP in fall 2015. We estimated this population was growing and will likely double in size by 2022 without management intervention. Management actions designed to eradicate the macaque population would be most effective by removing ≥50% of subadults and adults at least biennially. The population could be reduced to about a third of the fall 2015 size by sterilizing ≥50% of adult females annually or ≥80% biennially. The rhesus macaque population extends outside of our study site, and thus our results are a proxy for management implications in the region. Managers tasked with rhesus macaque management must carefully weigh the trade‐offs of these options in future management of this charismatic, invasive species. © 2018 The Wildlife Society.