New Publication: Developing and Testing a Siren eDNA Assay

Environmental DNA (eDNA) assays have become a major aspect of surveys for aquatic organisms in the past decade. These methods are highly sensitive, making them well-suited for monitoring rare and cryptic species. Current efforts to study the Rio Grande Siren in southern Texas have been hampered due to the cryptic nature of these aquatic salamanders. Arid conditions further add to the difficulty in studying this species, as many water bodies they inhabit are ephemeral, sometimes constraining sampling efforts to a short window after heavy rain. Additionally, sirens are known to cease activity and reside underground when ponds begin to dry or as water temperatures increase. Conventional sampling efforts require extensive trap-hours to be effective, which is not always possible within the required sampling window. This study presents the development of a novel eDNA assay technique for this elusive species using conventional PCR and Sanger sequencing and compares eDNA sampling results with simultaneous trapping at multiple sites to assess the relative effectiveness of the procedure. Rio Grande Siren detection via eDNA sampling was significantly higher at all sites compared to trapping, confirming the utility of this assay for species detection. This methodology gives promise for future work assessing the distribution and status of the Rio Grande Siren and has potential for use on other southern Texas amphibians. 

Ruppert KM, Davis DR, Rahman MS, Kline RJ. 2022. Development and assessment of an environmental DNA (eDNA) assay for a cryptic Siren (Amphibia: Sirenidae). Environmental Advances 7:100163. [PDF]

New Publication: Revised South Dakota Field Guide

The Field Guide to the Amphibians and Reptiles of South Dakota (second edition) is now available! This newly-revised guide describes and illustrates all reptile and amphibian species in South Dakota in one reference. Color photos, updated distribution maps, and descriptions of life history and habitats help the reader identify 45 known and two possible species and understand the role these interesting animals play in nature. The second edition includes new illustrations and additional identification keys and reflects updated taxonomy and recent knowledge gained from university and community scientists. This field guide provides a glimpse into the lives of these intriguing members of South Dakota’s diverse natural heritage. Click here to purchase it ($20, shipped)

Kiesow AM, Davis DR. 2020. Field Guide to the Amphibians and Reptiles of South Dakota. Second edition. South Dakota Department of Game, Fish and Parks, Pierre, South Dakota. vii + 161 pp.

New Publications: New Notes on Texas and South Dakota Amphibians and Reptiles

Twelve new, short notes were involving amphibians and reptiles in Texas and South Dakota were published from December 2020–December 2021 in Herpetological Review. Six are single Geographic Distribution Notes, three are far larger collections of distributional records (containing 12, 17, and 31 records), and three are Natural History Notes. All Texas distribution records were from south Texas (e.g., Guadiana et al. 2020) and along the Gulf Coast (e.g., Davis 2021c), while those from South Dakota are from the south-central region (Davis. 2021a). The Natural History Notes include a report of a new diet record for Masticophis flagellum (Robinson and Davis 2020), information of reproductive timing for Kinosternon flavescens (Davis et al. 2021), and information on aquatic escape behavior and time spent submerged by Anolis sagrei (Davis 2021d). 

Davis DR. 2021a. New amphibian and reptile distribution records from eastern South Dakota, USA. Herpetological Review 52:97–99. [PDF]

Davis DR. 2021b. Geographic distribution: Anolis carolinensis (Green Anole). Herpetological Review 52:795. [PDF]

Davis DR. 2021c. New distributional records of amphibians and reptile from the Western Gulf Coastal Plain of Texas, USA. Herpetological Review 52:807–809. [PDF]

Davis DR. 2021d. Anolis sagrei (Brown Anole). Aquatic escape behavior. Herpetological Review 52:853–854. [PDF]

Davis DR, Robinson PS, LaDuc TJ. 2021. Kinosternon flavescens (Yellow Mud Turtle). Reproduction. Herpetological Review 52:391–392. [PDF]

Guadiana CJ, Davis DR. 2021. Geographic distribution: Salvadora grahamiae (Eastern Patch-nosed Snake). Herpetological Review 52:580. [PDF]

Guadiana CJ, Robinson PS, Schalk MS, Davis DR. 2020. New county records of amphibians and reptiles from south Texas, USA. Herpetological Review 51:799–803. [PDF]

Oyervides M, Sosa-Gutierrez CG, Davis DR. 2020. Geographic distribution: Ophisaurus attenuatus (Slender Glass Lizard). Herpetological Review 51:541. [PDF]

Rash RS, Davis DR. 2020. Geographic distribution: Rana sphenocephala (Southern Leopard Frog). Herpetological Review 51:71–72. [PDF]

Robinson PS, Davis DR. 2020. Masticophis flagellum (Coachwhip). Diet. Herpetological Review 51:148. [PDF]

Robinson PS, Davis DR, Kline RJ. 2020. Geographic distribution: Notophthalmus meridionalis (Black-spotted Newt). Herpetological Review 51:531. [PDF]

Salmon GT, Davis DR. 2021. Geographic distribution: Tropidoclonion lineatum (Lined Snake). Herpetological Review 52:348–349. [PDF]

New Publication: Drone Surveys for Freshwater Turtles

Conservation concerns are increasing for numerous freshwater turtle species, including Pseudemys gorzugi, which has led to a call for more research. However, traditional sampling methodologies are often time consuming, labor intensive, and invasive, restricting the amount of data that can be collected. Biases of traditional sampling methods can further impair the quality of the data collected, and these shortfalls may discourage their use. The use of unmanned aerial vehicles (UAVs, drones) for conducting wildlife surveys has recently demonstrated the potential to bridge gaps in data collection by offering a less labor intensive, minimally invasive, and more efficient process. Photographs and video can be obtained by camera attachments during a drone flight and analyzed to determine population counts, abundance, and other types of data. In this study we developed a detailed protocol to survey for large, freshwater turtle species in an arid, riverine landscape. This protocol was implemented with a DJI Matrice 600 Pro drone and a SONY ILCE α6000 digital camera to determine P. gorzugi and sympatric turtle species occurrence across 42 sites in southwestern Texas, USA. The use of a large drone and high resolution camera resulted in high identification percentages, demonstrating the potential of drones to survey for large, freshwater turtle species. Numerous advantages to drone-based surveys were identified as well as some challenges, which were addressed with additional refinement of the protocol. Our data highlight the utility of drones for conducting freshwater turtle surveys and provide a guideline to those considering implementing drone-mounted high-resolution cameras as a survey tool.

Bogolin AP, Davis DR, Kline RJ, Rahman AF. 2021. A drone-based survey for large, basking freshwater turtles species. PLoS ONE 16:e0257720. [PDF]


Funding awarded to survey for threatened Eastern Hog-nosed Snakes in South Dakota

I was recently awarded a Wildlife Diversity Small Grant from South Dakota Game, Fish and Parks to survey for the state-threatened Eastern Hog-nosed Snake (Heterodon platirhinos)The Eastern Hog-nosed Snake (Heterodon platirhinos) is a medium-sized, state-threatened snake that is distributed across most of the eastern USA, throughout the Great Lakes region, and into the Great Plains. Within the Great Plains, Eastern Hog-nosed Snakes reach their northernmost extent in South Dakota. Previously, the Eastern Hog-nosed Snake was thought to be restricted to extreme southeastern South Dakota along the Missouri River in Clay and Union counties, until two additional records greatly expanded the putative distribution of this species in the state. The first was a specimen collected from Chamberlain, Brule County in 1943 (Biodiversity Collections, University of Texas at Austin [TNHC] 106094) that was part of a recently accessioned voucher specimen collection from South Dakota State University. The second was a photograph of an Eastern Hog-nosed Snake from Rosebud Reservation, Todd County taken in 2017 (HerpMapper [HM] 193175). These new records are ca. 221 and 324 km west of the nearest record of Eastern Hog-nosed Snake in Clay County (University of Nebraska State Museum [UNSM] ZM-16478), represent the only known records for this species in central and western South Dakota, and provide evidence that populations of Eastern Hog-nosed Snakes occur along the Missouri River and riparian corridors in south-central South Dakota. To better understand the distribution and occurrence of Eastern Hog-nosed Snakes, I will conduct a series of targeted surveys for this species in south-central South Dakota.

Grant Title: Surveys for the state-threatened Eastern Hog-nosed Snake (Heterodon platirhinos) in south-central South Dakota

Eastern Hog-nosed Snake distribution map from

New publication: Effects of COVID-19 on herpetologists

The emergence of a global pandemic due to the spread of COVID-19 has had profound effects on how research and scholarly activities are conducted for many professional herpetologists. Responses to COVID-19 and mitigation efforts vary by country and institution but have largely resulted in the closures of academic campuses and research areas, travel restrictions, and interruptions in research funding. These responses have forced herpetologists to change the way they manage their professional responsibilities.

Davis DR, Allen B. 2020. Effects of the COVID-19 pandemic on herpetologists. World Congress of Herpetology Newsletter 1(2):26–31. [PDF]


New publications: new notes on South Dakota amphibians and reptiles

Three new, short notes were involving amphibians and reptiles in South Dakota were published in the December 2020 issue of Herpetological Review. The first was the description of two new county records for Wood Frogs (Rana sylvatica) in northeastern South Dakota. Wood Frogs have recently been expanding its range into and along the Prairie Coteau in recent years (see link). These specimens were collected by regional biologists in April 2020 represent two of eight new localities where individuals were seen or heard chorusing in April 2020. The second is a new record of Plains Hog-nosed Snake (Heterodon nasicus) from Gregory County. Though this specimen was collected in 1925, erroneous locality information recorded the individual from nearby in Nebraska, though the snake was actually collected near Fort Randall, along the Missouri River in present day Gregory County, South Dakota. The third is a note reporting an additional, previously unreported predator of the Smooth Greensnake (Opheodrys vernalis), the Wild Turkey, after an adult Smooth Greensnake was discovered in the crop of a Wild Turkey that was harvested in April 2020

Davis DR, Schardin B. 2020. Opheodrys vernalis (Smooth Greensnake). Predation. Herpetological Review 51:874. [PDF]

Davis DR. 2020. Geographic distribution: Heterodon nasicus (Plains Hog-nosed Snake). Herpetological Review 51:780. [PDF]

Davis DR, McElroy OD, Skadsen DR. 2020. Geographic distribution: Rana sylvatica (Wood Frog). Herpetological Review 51:770–771. [PDF]

New publication: redescription of a new non-pentadactyl Philippine skink

The diversity of Philippine amphibians and reptiles has increased over the last few decades, in part due to re-evaluation of species formerly believed to be widespread. Many of these investigations of widespread species have uncovered multiple closely related cryptic lineages comprising species complexes, each restricted to individual Pleistocene Aggregate Island Complexes (PAICs). One group in particular for which widespread cryptic diversity has been common is the clade of Philippine skinks of the genus Brachymeles. Recent phylogenetic studies of the formerly recognized widespread species Brachymeles bonitae have indicated that this species is actually a complex distributed across several major PAICs and smaller island groups in the central and northern Philippines, with numerous species that exhibit an array of digit loss and limb reduction patterns. Despite the recent revisions to the B. bonitae species complex, studies suggest that unique cryptic lineages still exist within this group. In this paper, we resurrect the species Brachymeles burksi Taylor 1917, for a lineage of non-pentadactyl, semi-fossorial skink from Mindoro and Marinduque islands. First described in 1917, B. burksi was synonymized with B. bonitae in 1956, and has rarely been reconsidered since. Evaluation of genetic and morphological data (qualitative traits, meristic counts, and mensural measurements), and comparison of recently-obtained specimens to Taylor’s original description support this species’ recognition, as does its insular distribution on isolated islands in the central portions of the archipelago. Morphologically, B. burksi is differentiated from other members of the genus based on a suite of unique phenotypic characteristics, including a small body size, digitless limbs, a high number of presacral vertebrae, the absence of auricular openings, and discrete (non-overlapping) meristic scale counts. The recognition of this central Philippine species further increases the diversity of non-pentadactyl members of the B. bonitae complex, and reinforces the biogeographic uniqueness of the Mindoro faunal region.

Siler CD, Freitas ES, Sheridan JA, Maguire SN*, Davis DR, Watters JL, Wang K, Diesmos AC, Brown RM. 2020. Additions to Philippine slender skinks of the Brachymeles bonitae complex (Reptilia: Squamata: Scincidae) IV: resurrection and redescription of Brachymeles burksi. Philippine Journal of Systematic Biology 14:10.26757/pjsb2020b14005. [PDF]

New publication: new records of Wood Frogs from the Prairie Coteau, South Dakota

Historically, only six records of Wood Frogs (Rana sylvatica) existed from South Dakota, all represented by museum specimens from the 1920s. No other Wood Frogs were reported in South Dakota for the next six decades, and the species was presumed extirpated until 1997 when Wood Frog calls were recorded at two sites in northeastern Roberts County. Since 1997, numerous individuals have continued to document Wood Frogs in northeastern Roberts County. It was not until 2016 that Wood Frogs were detected outside of northeastern Roberts County. Here, we report additional records of Wood Frogs from the Prairie Coteau, ca. 50 km southwest of previously known populations.

Skadsen DR, Davis DR. 2020. A population of wood frogs (Rana sylvatica) in southwestern Roberts County and a new county record for Grant County, South Dakota. The Prairie Naturalist 52:31–32. [PDF]

New Publication: a new algae-mediated shell disease process in Yellow Mud Turtles

Christiansen.etal.2020_Fig1While shell diseases may be often encountered in captive aquatic turtles maintained in less than optimum conditions, cases of nonulcerating shell disease in wild populations are rare. We discovered lesions on the carapace of individual Kinosternon flavescens (Yellow Mud Turtle) adapted to a highly aquatic existence in the artificial ponds of a cattle ranch in the Chihuahuan Desert of west Texas. Because the carapacial lesions seemed to represent a continuum of a single process, we followed the gross changes in the lesions on turtles over a 13-yr period, testing the hypothesis that we were seeing a progressive shell disease. We confirmed our working hypothesis as we observed Arnoldiella chelonum, a common, filamentous alga, protruding from enlarged pores in newly formed shell and growing under translucent shell lamellae. As the disease advanced, our gross and histological studies revealed that algae were found between more of the shell lamellae, eventually culminating with sloughing of lamellae. Erosion of lamellae led to a localized but complete loss of portions of the scute and exposure of underlying bone. We provide data on the occurrence of this condition among the marked population and progression of the lesions to more-severe forms in individual turtles. Studies of specimens in research collections provided evidence of our observed disease process in K. flavescens across time and throughout the distribution of the species in Texas. We suggest that, by capitalizing on permanent artificial water sources, K. flavescens has serendipitously allowed A. chelonum to invade and damage the nonliving portion of the shell.

Christiansen JL, Davis DR, Jacobson ER, LaDuc TJ. 2020. A potential new shell disease process revealed by a long-term field study of the yellow mud turtle, Kinosternon flavescens, in Texas. Journal of Herpetology 54:1–8. [PDF]