PUBLICATION: using eDNA to detect threatened newts

The Black-spotted Newt (Notophthalmus meridionalis) is a chronically understudied salamander species, with many aspects of its natural history, ecology, and distribution poorly known. Previous studies using traditional methodologies have had limited success documenting N. meridionalis on the landscape, detecting individuals at 6% (7 of 114) and 1% (2 of 221) of sites surveyed. A novel environmental DNA (eDNA) assay was designed and implemented with the goals of assessing the current distribution of N. meridionalis across south Texas, USA, and better understanding the conditions for positive eDNA detections. We conducted eDNA sampling and traditional surveys at 80 sites throughout south Texas. Notophthalmus meridionalis was detected at 12 localities in total: four localities using eDNA surveys, four localities using traditional methods, and four localities with both methodologies. eDNA detections were obtained from five counties, including one where N. meridionalis has never been reported and another where N. meridionalis has not been observed since the 1930s. eDNA detections were obtained in all four seasons, generally following moderate to heavy rainfall events. Our results support the increased use of eDNA surveys to detect rare and cryptic amphibians and to better understand the current distribution of this imperiled species. 

Robinson PS, Davis DR, Collins SM, Kline RJ. 2022. Defining the current distribution of the imperiled black-spotted newt across south Texas, USA. Global Ecology and Conservation 36:e02131. [PDF]


PUBLICATION: developing an eDNA survey for Himalayan anurans

Wildlife monitoring programs are instrumental for the assessment of species, habitat status, and for the management of factors affecting them. This is particularly important for species found in freshwater ecosystems, such as amphibians, as they have higher estimated extinction rates than terrestrial species. We developed and validated two species-specific environmental DNA (eDNA) protocols and applied them in the field to detect the Hazara Torrent Frog (Allopaa hazarensis) and Murree Hills Frog (Nanorana vicina). Additionally, we compared eDNA surveys with visual encounter surveys and estimated site occupancy. eDNA surveys resulted in higher occurrence probabilities for both A. hazarensis and N. vicina than for visual encounter surveys. Detection probability using eDNA was greater for both species, particularly for A. hazarensis. The top-ranked detection model for visual encounter surveys included effects of both year and temperature on both species, and the top-ranked occupancy model included effects of elevation and year. The top-ranked detection model for eDNA data was the null model, and the top-ranked occupancy model included effects of elevation, year, and wetland type. To our knowledge, this is the first time an eDNA survey has been used to monitor amphibian species in the Himalayan region.

Saeed M, Rais M, Akram A, Williams MR, Kellner KF, Hashsham SA, Davis DR. 2022. Development and validation of an eDNA protocol for monitoring endemic Asian spiny frogs in the Himalayan region of Pakistan. Scientific Reports 12:5624. [PDF]


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 http://www.sdherps.org.

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]