RESEARCH THEMES
APPLIED HERPETOLOGICAL CONSERVATION
A central tenant in my research is to collect data that can be used to help conserve amphibians, reptiles, and their habitats. My work integrates field ecology, population monitoring, habitat assessment, and modern analytical tools to develop practical, evidence-based conservation strategies. I help generate species detections across the landscape using traditional methods and emerging technology, such as environmental DNA surveys and drone surveys, which can then be used to understand current distributions of species and guide management actions. With occurrence data in hand, conservation measures can be implemented that hopefully enhance individual health, reduce threats and stressors, and support the long-term persistence of populations. This theme reflects our commitment to bridging science and management to conserve herpetological biodiversity.
INTERACTIVE EFFECTS OF MULTIPLE STRESSORS
Due to increasing levels of anthropogenic disturbance, it is important to understand how these act as stressors. Anthropogenic disturbances such as habitat modification, contaminants, introduced species, and pathogens are all recognized as stressors that act on individuals and act in combination with natural stressors. The combinations of multiple stressors can have additive, synergistic, or antagonistic effects on organisms. Even if the effects of a particular stressor are known, it may be difficult to anticipate its effects when additional stressors are present. I am interested in investigating the interactions of stressors on native species and using this information to help inform management decisions.
NATURAL HISTORY OF AMPHIBIANS AND REPTILES
While many people favor ‘hypothesis-driven’ studies, there is a paucity of information about a vast number of amphibian and reptile species. Particularly, little is known about species which have limited geographic ranges, are infrequently encountered, or are of conservation concern. Further, many ecological questions can only be fully understood with an intimate knowledge about the species involved and often, this information is lacking. As part of on-going research projects, I attempt to increase our understanding of the natural history of species. With increases in our understanding of species’ natural history, we can better manage populations and species of interest.
Current PROjects
ASSESSING THE DISTRIBUTION AND THREATS OF SGCN FROGS IN EASTERN NEW MEXICO
Without updated field data, the current conservation status of Blanchard’s Cricket Frogs (Acris blanchardi), Rio Grande Leopard Frogs (Rana berlandieri), and Plains Leopard Frogs (Rana blairi) remain uncertain. All three anuran species are listed as a SGCN in the New Mexico Department of Game and Fish State Wildlife Action Plan (SWAP), emphasizing the urgent need for updated field data to inform management and conservation actions. Anecdotal reports suggest that these species may have declined in recent years, particularly in areas affected by drought, groundwater depletion, and river management practices. The combined survey and management proposed here will generate contemporary occurrences data for these species and help address the threat and risk posed by invasive American Bullfrogs (Rana catesbeiana). The resulting data will guide effective habitat management, restoration, and species recovery efforts—directly supporting the goals of the New Mexico SWAP and the conservation of biodiversity in the Pecos River basin.
INCREASING OUR UNDERSTANDING OF THE RIO GRANDE COOTER TO INFORM FUTURE RECOVERY OPTIONS
There is a paucity of information on the Rio Grande Cooter (Pseudemys gorzugi) given its limited range, recent species designation, and elusive behavior. This overall lack of information on this species of turtle, combined with numerous threats due to climate change and anthropogenic pressures, highlights an urgent need for data and research on this species. Despite not being federally protected in 2022, there is continued support to better understand this species as it continues to face threats to its persistence across its range and future listing petitions seem likely. Recovery options such as reintroductions or translocations, either supplementing declining populations or establishing new populations, may be important conservation strategies to help protect and sustain this species. We propose to conduct a series of studies to help fill in information gaps on the Rio Grande Cooter to help guide species management.
ENVIRONMENTAL DNA SURVEYS FOR NEW MEXICO SNAKES OF CONSERVATION CONCERN
The Mexican Gartersnake (Thamnophis eques) and the Plain-bellied Watersnake (Nerodia erythrogaster) are two imperiled species in New Mexico with limited recent occurrence records. This project aims to update the known distribution of both species using environmental DNA (eDNA) surveys in the Gila River watershed (for T. eques) and the Lower Pecos River system (for N. erythrogaster). In addition to confirming species presence, this work will help identify habitat characteristics associated with occupancy and inform future monitoring efforts. Species-specific eDNA assays are being developed and validated as part of this research. Funding is provided by the New Mexico Department of Game and Fish through the Share With Wildlife program.
IMPERILED TURTLE SURVEYS IN SOUTHWESTERN INDIANA
We received funding to conduct visual and trapping surveys for four species of turtles (River Cooters [Pseudemys concinna], False Map Turtles [Graptemys pseudogeographica], Smooth Softshells [Apalone mutica], and Eastern Mud Turtles [Kinosternon subrubrum]) in southwestern Indiana. This research will primarily involve surveys in the Wabash, Ohio, Patoka, and White rivers, as well as their surrounding drainages. Surveys aim to collect data in order to estimate population size and record demographic data on these four focal species, but other turtle species as well. In addition, I will identify quality nesting sites and areas of high species abundance and diversity that may aid in future conservation action. Funding for this research is provided by the Indiana Department of Natural Resources, Division of Fish and Wildlife.
WESTERN RIBBONSNAKE DISTRIBUTION AND CONSERVATION IN NEW MEXICO
The Western Ribbonsnake (Thamnophis proximus) is a state-threatened species in New Mexico with few historic occurrence records. Though well-studied in other portions of its range, it is poorly understood in New Mexico. The primary goal of this research is to update and better describe the full distribution of this species in the state, as well as identify habitat features that correlate with occupancy. Additionally, we are investigating threats that the species may face, including habitat loss, invasive species, water quality declines, and snake fungal disease. Funding for this research is provided by the New Mexico Department of Game and Fish.
On-GOING RESEARCH
DISTRIBUTION AND CONSERVATION OF THE BLACK-SPOTTED NEWT
The Black-spotted Newt (Notophthalmus meridionalis) is a candidate species for federal listing by the U.S. Fish and Wildlife Service. Habitat loss and degradation have contributed to the decline of this species and the expansion of urbanization and agriculture may threaten remaining populations. Understanding the current distribution of this species is challenging due to the ephemeral nature of the aquatic habitats used and long periods when this species is underground. We are using environmental DNA (eDNA) assays to survey for this species across their historic distribution in the state, characterizing the habitats they use, and attempting to better understand their threats in order for best management practices to be developed for this species.
VARIATION AMONG WESTERN SLIMY SALAMANDER POPULATIONS
The Western Slimy Salamander (Plethodon albagula) is recognized as having two disjunct ranges, one on the Edwards Plateau of Central Texas and the other within the Interior Highlands of Missouri, Oklahoma, and Arkansas. Morphological and genetic variation has been found within the Edwards Plateau among several different lineages, though less is known about the Interior Highlands population. Currently, I am examining both morphological and genetic variation within the Interior Highlands populations and between these two broadly distributed populations, and plan to expand these studies to include ecological perspectives.
STATUS AND DISTRIBUTION OF THE RIO GRANDE COOTER
The Rio Grande Cooter (Pseudemys gorzugi) was recently denied listing by the U.S. Fish and Wildlife Service under the Endangered Species Act. Information on the status and distribution of this species is still lacking, and interested remains in attempting to better understand the ecology of this species. We are using novel approaches to census and detect the Rio Grande Cooter across its distribution in Rio Grande, Pecos River, and their tributaries in Texas and New Mexico. We have used drone-based imaging and environmental DNA (eDNA) to survey and detect this species with success. Data shows that drone-based surveys can produce identifiable images of turtles in a wide range of habitat utilized by this species and eDNA surveys have yielded important detections of this species.
OCCURRENCE OF FALSE MAP TURTLES IN SOUTH DAKOTA
In 2017 I have become involved in survey work examining the status of False Map Turtles (Graptemys pseudogeographica) in South Dakota. Specifically, we’re looking to see if this species is still present in Lake Oahe, a large reservoir along the Missouri River, north of Pierre. Daming of the Missouri River and the formation of large reservoirs has resulted in habitat degradation and loss, and likely the extirpation of this species form a large part of their historic range. Initial results suggest this species is extirpated from most of Lake Oahe; however, this species still remains abundant from free-flowing, more natural segments of the Missouri River, such as the 59-mile Missouri National Recreational River from Yankton, South Dakota, to Sioux City, Iowa.
CHIHUAHUAN DESERT MUD TURTLE ECOLOGY
I am actively working on several research projects examining different aspects of the ecology of the Yellow Mud Turtle (Kinosternon flavescens) in the Chihuahuan Desert of west Texas. We have been studying population demographics, growth, movement, phenology, and a novel shell disease in these turtles on C. E. Miller Ranch. Historically, these turtles relied on ephemeral pools that filled for short periods of time after summer rains and once these sites dried out, these turtles move back to upland terrestrial habitats. However, the presence of permanent, well-filled cattle ponds has allowed these turtles to remain in these habitats for prolonged periods of times, influencing growth their growth and subsequently the progression of an algae-mediated shell disease.
PHILIPPINE AMPHIBIAN AND REPTILE DIVERSITY
The Philippines is home to a remarkable diversity of amphibians and reptiles, the majority (~75%) of which are endemic to this island archipelago. Recent studies of the archipelago’s terrestrial biodiversity have dramatically increased the number of recognized species, often as the result of identification of unique genetic lineages. Species once recognized to have wide distributions that spanned multiple faunal regions have more recently been revealed to constitute complexes of multiple species, each of which is typically restricted to a specific faunal region, island group, or complex geographic regions. I have been collaborating with researchers to help describe this incredible species diversity and resolve taxonomic issues with newly collected morphological and molecular datasets. Two focal genera that I have been working with are Brachymeles (Scincidae) and Pseudogekko (Gekkonidae).
DISTRIBUTIONS OF AMPHIBIANS AND REPTILES IN SOUTH DAKOTA
Current understanding of the distributions of amphibians and reptiles in South Dakota is limited compared to that of many other vertebrate groups in the state. Continuing increases in human population, conversion of grasslands to agriculture, and habitat degradation all likely have strong negative impacts South Dakota’s amphibian and reptile species, but their effects are difficult to track because of limited historic and modern sampling. I am currently working to update the known distributions of all South Dakota amphibian and reptile species and have compiled a database of over 14,400 specimens to better map these distributions. For additional information on this project visit: www.sdherps.org.
AMPHIBIAN DISEASES
Emerging infectious diseases such as chytridiomycosis (caused by the fungus Batrachochytrium dendrobatidis) and ranavirosis are well-known factors which are contributing to global amphibian declines. I am interested in both the lethal and sub-lethal effects (i.e., behavioral changes, reduced growth, delayed development) of these pathogens on amphibians as well as the effects of infection on the stress hormone response of individuals. I have surveyed for these pathogens throughout the central USA, and am using both field-based and experimental studies to better understand their effects on amphibians. Additionally, I have expanded my involvement in efforts to screen amphibians for these pathogens in southeast Asia.
Throughout the Midwest, agricultural contaminants are present in wetlands and may be responsible in part for regional amphibian declines. A local factor contributing to elevated levels of contaminants in these wetlands is the presence of agricultural tile drains. These tile drains promote crop growth by removing excess water and salts from fields; however, it can also transport contaminants (e.g., pesticides, fertilizers, metals) directly into nearby wetlands at concentrations above benchmarks for the protection of aquatic life. Much of my dissertation aims to examine the effects of this tile drain effluent on water quality, wetland habitat quality, and wetland-dependent taxa (i.e., amphibians, aquatic invertebrates).
STRESS PHYSIOLOGY
Both natural and anthropogenic stressors are known to affect stress hormone production in amphibians. Traditionally, hormones have been measured via plasma collection or whole-body assays, but alternatives such as urinary collection have been developed. I have helped to develop novel methods to collect water-borne hormones from small aquatic salamanders and am using these methods to assess stress in individuals from both experimental laboratory comparing individual responses to stressors, and field settings to compare population-level responses to large-scale habitat disturbance. Projects examining how urbanization, agricultural development, predators, contaminants, and disease influence stress hormone levels are on-going.
PREDATOR-PREY INTERACTIONS IN AQUATIC AMPHIBIANS
Predation is a dominant element of ecological communities. The introduction of novel predatory fish into environments has been particularly problematic and has lead to significant declines in amphibian populations. I am broadly interested in how amphibians respond to novel predators and the sensory modalities mediating these interactions. Additionally, I am interested in the role of innate and learned predator recognition as well as predator generalization play in the recognition of novel predators. The majority of my work investigating these topics has involved fully-aquatic Eurycea salamanders of central Texas, most of which are highly endemic and are state and federally protected.
Drew R. Davis, Ph.D. 