Rose-ringed Parakeets in Kauai, Hawaii
Rose-ringed parakeets (Psittacula krameri) are one of the most invasive bird species in the world, having established non-native populations in over 35 countries. While these birds are beautiful, intelligent, and charismatic, they can devastate native species and ecosystems where they are introduced. Further, they cause significant agricultural damage by eating farmed fruits and vegetables. Rose-ringed parakeets were introduced on the island of Kauai, Hawaii, in the 1960s. What began as only a few animals is now in excess of 10,500 birds. Through funding from the U.S. Department of Agriculture, I am currently studying the ecology and distribution of this population as well as sustainable and humane methods to reduce the rose-ringed parakeet population size on Kauai. My goal is for my research to help alleviate some of the impacts these birds are having on the island.
Evaluation of potential contraceptive use Contraceptives are used to control pest bird populations. The contraceptive Diazacon has been demonstrated to reduce reproduction of captive rose-ringed parakeets, providing inference that it may be effective in reducing wild population sizes. However, because this contraceptive is also effective in other bird species, it must be delivered in a manner that only parakeets can access it.
Researchers from the USDA APHIS WS National Wildlife Research Center developed a parakeet-selective feeder, designed to prohibit feed access to non-target species. Collaborating with the NWRC, we are testing strategies to acclimate rose-ringed parakeets on Kauai to feeders. Should this effort prove successful, future use of contraceptives via the parakeet-selective feeder may allow this strategy to be used in an integrative pest management plan for rose-ringed parakeets on Kauai.
Evaluation of roost culling Rose-ringed parakeets on Kauai congregate nightly in large roosts, ranging from 800 – 6,500 birds. While in other habitats these roosts can be found in a variety of places, on Kauai they are predominately in developed and urbanized areas. The large number of birds are extremely loud and produce a tremendous quantity of droppings. This in turn threatens human health through the potential of pathogen exposure, causes property damage, and increases abundance of rodents that forage on seeds within the droppings. Culling parakeets at the roost has historically been avoided. Parakeets will abandon roosts if they are disturbed. Roost abandonment is problematic because we depend upon the roosts for population monitoring. Further, the parakeets have thus far not moved into native forests, and driving them from urban areas may cause them to shift into more sensitive environments. Roost culling has further been avoided due to safety concerns of the number of humans in the area. However, the COVID-19 pandemic provided an optimal time to test roost culling, as travel restrictions and a temporary curfew vastly reduced the number of people outdoors.
From March – October 2020, the County of Kauai funded a private wildlife control company to cull parakeets at two of the known roost sites on Kauai. Working with these collaborators, we evaluated the number of birds removed per roost and per hour of effort. We collected >3,000 parakeet carcasses from this effort to collect morphometric data, genetic samples, and conduct necropsies to evaluate the age and sex ratio of culled birds. We will use this information for modeling the future rose-ringed parakeet population size on Kauai and inform management strategies.
Ocelots in South Texas
Ocelots (Leopardus pardalis) are a medium-sized felid native throughout Central and South America. Once widespread throughout Texas, Louisiana, and Arkansas, the U.S. population of the federally endangered ocelot is now restricted to the Lower Rio Grande Valley (LRGV) of South Texas. It is estimated <80 individuals remain between two genetically isolated breeding populations. While the population decline is due to several factors, vehicle collisions have been found to be one of the leading contemporary causes of ocelot mortality in the LRGV. Wildlife crossing structures may provide a viable mitigation strategy but must be placed in locations that maximize likelihood of use by ocelots. I am currently leading a team contracted by the Texas Department of Transportation to provide guidance on optimal locations to build wildlife crossing structures to protect ocelots in the LRGV. My team and I are analyzing an ocelot telemetry dataset spanning 35 years coupled with current and planned transportation data to conduct several studies to address this goal:
Road Crossing Patterns of Ocelots in South Texas Placing wildlife crossing structures in locations where animals frequently cross roads can help promote habitat connectivity. Using the telemetry dataset, we are determining locations where ocelots have successfully crossed roads. We are evaluating how these crossing frequencies have varied by road type (high traffic paved, low traffic paved, gravel, and dirt) and how these crossing patterns varied by ocelot sex, duration of monitoring period, and within home-range road density. Further, we will evaluate land cover structure at locations where ocelots have crossed paved roads to determine if there are landscape patterns at crossing locations.
Recently Completed Projects
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, my collaborators and 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. The purpose of this study was to estimate the distribution and range of rhesus macaques along the Ocklawaha River. Using baited camera traps and regular boat surveys, we identified six previously unidentified groups of macaques, expanding approximately 20km north and 11km south of the confluence of the Silver River. This study provided inference of the metapopulation status of rhesus macaques in central Florida. Role: PI Manuscript in Preparation: Wilson, A.C., Anderson, C.J, Romagosa, C.M., & C. Carter. Abundance of Introduced Rhesus Macaques (Macaca mulatta) in Central Florida
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 developed 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. Our models indicated the climatic conditions within Florida and throughout much of the southeastern U.S. are similar to those of each species’ native range. Interestingly, this suggests climate is not the limiting factor of squirrel monkey survival or vervet monkey spread in Florida. It also suggests climate will not limit continued spread of rhesus macaques. This information can be used to prioritize use of limited research and management funds. Manuscript in Preparation: Anderson, C.J., Loiselle, B.A., Bankovich, B., & C.M. Romagosa. Climate Does Not Dictate Invasion Success of Non-Human Primate Populations in Florida.
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 used genetic sequencing to characterize the mitochondrial genetic composition of this population. We described five haplotypes within the population, supporting the notion all members of the current population came from small, isolated introductions. Further, we collected a sample from an adult male rhesus macaque captured >100km from the Silver Springs population and determined he had a haplotype identical to members of the population. This indicates males may be dispersing great distances from the source population. Manuscript in Preparation: Klegarth, A.R., C.J. Anderson, and S.A. Johnson. Population genetics of an invasive rhesus macaque (Macaca mulatta) population.
Estimating Invasion Potential of Capybaras in Florida. Native throughout South America, the capybara (Hydrochoerus hydrochaeris) is the world’s largest rodent. This species has recently expanded its native range in Paraguay. Further, it has been regularly observed since 1992 throughout Florida, U.S.A, where at least one introduced population included ~60 individuals. Given the potential impacts capybaras could have on native species and demonstrated ability to establish in Florida, we sought to evaluate whether climate throughout Florida and the southeastern U.S. is conducive to capybara requirements. We developed a climate envelope model (methodology described above) and determined climatic conditions expanding Florida and much southeastern U.S. are unlikely to curtain capybara establishment. Our results suggest managers should make efforts to quickly control future capybara introductions. Manuscript in Preparation: Anderson, C.J., B.A. Loiselle, C.M. Romagosa, D. Pearson, and E. Suarez. Establishment potential of introduced capybaras (Hydrochoerus hydrochaeris) in Florida, U.S.A.
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 detect different species. Given the potential for capybaras to establish populations in Florida, managers need a low-cost and efficient mechanism to detect potential future introductions. In this study, we sought to develop an eDNA assay for the detection of capybaras in novel environments. 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 initial collection. To determine if this method would work under varying environmental conditions and water body sizes, we collected samples of capybara scat from the Jacksonville Zoo and placed it in water bodies in the lab and in the field. We found we were able to detect eDNA in all water bodies, but the duration of detection varied. Future research can expand these results in environments where capybara have been introduced to better understand how the assay works in natural habitats.