Estimating Rhesus Macaque Abundance in the Ocklawaha River Floodplain
Rhesus macaques were introduced along the Silver River, central Florida, in the mid-1930s and 1940s. Since that time, this population has demonstrated pervasive growth, and with it, potential impacts to native flora and fauna and the local human community. In previous research with this population, I evaluated potential impacts on nesting birds, determined the winter home range and habitat selection, estimated the fall 2015 population size, and modeled future population growth under varying management scenarios.
The Silver River flows east into the Ocklawaha River. Rhesus macaques were first observed along the Ocklawaha River in the 1970s. However, no population estimates or ecological studies have been conducted with macaques in this habitat. Rhesus macaques have been observed over 100 times in locations outside of the Silver River, and we believe the land along the Ocklawaha River may be serving as a corridor for macaque dispersal from the Silver River. I am currently conducting research funded by the Florida Fish and Wildlife Conservation Commission to study the rhesus macaques in the floodplain along the Ockalwaha River. Using baited camera traps and regular boat surveys, we aim to estimate the distribution and abundance of rhesus macaques in this habitat. This will allow us to better understand the metapopulation of rhesus macaques in central Florida and how they may be dispersing and impacting native natural resources.
Comparing Invasion Potential of Introduced Primates in Florida
Florida is among the states that has experienced the greatest number of introductions of non-native wildlife species. These introductions threaten native wildlife and ecosystems and are estimated to cost over $500 million annually in mitigation and management expenses. Florida is particularly at-risk for species introductions due to the peninsular geography, subtropical climate, large tourism industry, and several major ports of entry. Three species of primates have been introduced into Florida: rhesus macaques (Macaca mulatta), vervet monkeys (Chlorocebus sabaeus), and squirrel monkeys (Saimiri sciureus). In a previous research study, I led a team that described the history and status of these species. We noticed an interesting trend; despite having the most introduced populations, squirrel monkeys had had the least success in establishment in the state. Conversely, the vervet monkey population had remained remarkably stable, and introduced rhesus macaque populations in both the forests of central Florida and the mangrove islands of the Florida Keys had thrived.
Climate envelope models are a unique tool to understand the climatic variables that defines a species’ range. In this study, we are developing climate envelope models to characterize the climatic conditions in which these species occur in their native range, and then compare these to the conditions in Florida. We will use these models to understand whether climate may have been a limiting factor for squirrel monkey establishment in state. Further, we will use it to understand whether and where rhesus macaques may be able to spread throughout Florida and the southeastern U.S. if populations continue to grow unmanaged. This information can be used to prioritize use of limited research and management funds.
Characterizing Rhesus Macaque Genetics in Central Florida
Approximately 10 rhesus macaques (Macaca mulatta) were introduced in what is today Silver Springs State Park, central Florida, in the 1930s and 1940s in an effort to increase tourism. This population has demonstrated considerable growth and reached ~400 individuals in the initial introduction site by the mid-1980s. From that time until 2012, the population was controlled through a trapping and removal program, but no population control has been implemented for the past ~5 years. From 2011 – 2016, there were ≥38 observations of rhesus macaques in Florida outside of Silver Springs State Park. It is unknown whether these individuals represented separate introductions, or if they were emigrants from the Silver Springs population. In this study, we presented cotton swabs soaked in sucrose to the macaques; the macaques chewed the swabs until they lost flavor, then spit out the swabs. We then collected the swabs and extracted DNA from the residual macaque saliva. We are using genetic sequencing to characterize the mitochondrial genetic makeup of this population. This will allow managers and researchers to sample any macaque in Florida to determine if it came from the Silver Springs population.
Developing an eDNA Assay for the Detection of Capybaras (Hydrochoerus hydrochaeris)
When an animal enters an environment, it leaves bits of its DNA through hair, skin, or bodily fluids; this is referred to as environmental DNA (eDNA). Detecting eDNA in water or soil is a novel technique for detecting cryptic species. Essentially, it allows us to determine whether an animal has entered a habitat without actually observing the animal. Researchers are now refining this tool to understand how long eDNA persists in different environments and how to best use to to detect different species.
Native throughout South America, capybaras (Hydrochoerus hydrochaeris) are the world’s largest rodent. This cryptic species can be difficult to detect, as it often alters its normally-diurnal lifestyle to become nocturnal when disturbed by humans. This species has recently expanded its native range in Paraguay. Further, it has been regularly observed since 1992 throughout Florida, U.S.A. Developing an eDNA assay to detect capybaras in novel habitats would provide a reliable and cost-effective method to determine whether they have established in non-native habitats. In summer 2017, we conducted a pilot study using water from a capybara exhibit from the Rolling Hills Zoo, preserved with Longmire’s solution; we were able to successfully extract capybara DNA from the water sample, even after leaving it untouched for 85 days after sampling it. We are now further evaluating this method to determine the degradation rate of capybara eDNA in water bodies (i.e, how long after a capybara has been in a body of water we are still able to detect their DNA) and how this rate varies by water body size.