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7 recordsLinked to original sources
USGS2015

Wetland occupancy of pond-breeding amphibians in Yosemite National Park, USA

We estimated wetland occupancy and population trends for three species of pond-breeding anurans in Yosemite National Park from 2007-2011. We used a double survey technique in which two observers independently surveyed each site on the same day. Double surveys allowed us to calculate detectability for the three most common anurans within the park: Rana sierrae, Anaxyrus canorus, and Pseudacris regilla. Annual estimates of detectability were generally high; mean detectability ranged from 73.7% + 0.6 (SE) for any life history stage of A. canorus to 86.7% + 0.7 for sites with P. regilla reproduction (eggs or larvae present). Detectability was most variable for Anaxyrus canorus, which ranged from 45.9% to 99.7%. The probability of occupancy for R. sierrae was highest in larger, low-elevation wetlands that lacked fish. Anaxyrus canorus were more common in shallow high-elevation ponds; their occurrence was minimally impacted by the presence of fish. Finally, occurrence of P. regilla was largely unrelated to wetland size and elevation, but like R. sierrae, they were less likely to occupy sites with fi sh. Occupancy showed no trend over the five years of our study for R. sierrae or A. canorus when considering either sites with any life stage or only sites with reproduction. However, P. regilla showed a modest downward trend for sites with any life stage and sites with reproduction. Our results for R. sierrae run counter to expectations given recent concern about the decline of this species, while our findings for P. regilla raise concerns for this widespread and generally common species.

California↗
USGS2017

Nocturnal arboreality in snakes in the swamplands of the Atchafalaya Basin of south-central Louisiana and Big Thicket National Preserve of Southeast Texas

The southeastern United States is home to a diverse assemblage of snakes, but only one species, the Rough Greensnake ( Opheodrys aestivus ), is considered specialized for a predominantly arboreal lifestyle. Other species, such as Ratsnakes (genus Pantherophis ) and Ribbonsnakes/Gartersnakes (genus Thamnophis ), are widely known to climb into vegetation and trees. Some explanations given for snake climbing behavior are foraging, thermoregulation, predator avoidance, and response to flood. Reports of arboreality in snake species typically not associated with life in the trees (such as terrestrial, aquatic, and even fossorial species) usually come from single observations, with no knowledge of prevalence of the behavior. Here, we report on arboreality of snake species detected during 8 years of night surveys in the Atchafalaya Basin of south-central Louisiana and 5+ years of night surveys in Big Thicket National Preserve in southeast Texas. We recorded a total of 1,088 detections of 19 snake species between the two study areas, with 348 detections above ground level (32%). The Rough Greensnake and Western Ribbonsnake ( Thamnophis proximus ) accounted for nearly 75% of total arboreal detections among the two study areas. However, with one exception, all snake species detected more than once between both study areas had at least one arboreal detection. These observations demonstrate that snakes with widely varying natural histories may be found in the trees at night, and for some species, this behavior may be more common than previously believed.

Louisiana, Texas↗
USGS2014

Call broadcasting and automated recorders as tools for anuran surveys in a subarctic tundra landscape

Relatively little is known about population ecology of anurans in arctic and subarctic tundra regions, in part because it is difficult to survey anurans in these landscapes. Anuran survey protocols developed for temperate regions have limited applicability in arctic and subarctic tundra landscapes, which may lack roads and vehicle access, and experience variable and inclement weather during short anuran breeding seasons. To evaluate approaches to address some of the limitations of surveying anurans in tundra landscapes, we assessed the effectiveness of using breeding call broadcasts to increase detection of Boreal Chorus Frogs ( Pseudacris maculata ) and Wood Frogs ( Lithobates sylvaticus ) near Cape Churchill, Manitoba, Canada. We also evaluated how counts of anurans derived from automated audio recorders compared with those obtained simultaneously by observers. We detected on average 0.4 additional Wood Frogs per survey when we broadcasted calls ( x̄ = 0.82, SD = 1.38), an increase of > 40% compared to surveys without broadcasts ( x̄ = 1.24, SD = 1.51; Wilcoxon test; Z = 2.73, P = 0.006). In contrast, broadcasting Boreal Chorus Frog calls did not increase the number of chorus frog detections (Wilcoxon test; Z < 0.001, P > 0.90). Detections of Wood Frogs in a 100-m radius were lower via automated recorders ( x̄ = 0.60, SD = 0.87 SD) than by observers during simultaneous surveys ( x̄ = 0.96, SD = 1.27 Z = 2.07, P = 0.038), but those of Boreal Chorus Frogs were not different (x = 1.72, SD = 1.31; x̄ = 1.44, SD = 1.5; Z = 1.55, P > 0.121). Our results suggest that broadcasting calls can increase detection of Wood Frogs, and that automated recorders are useful in detecting both Wood Frogs and Boreal Chorus Fogs in arctic and subarctic tundra landscapes.

The Journal of North American Herpetology↗
USGS2015

Decadal changes in phenology of peak abundance patterns of woodland pond salamanders in northern Wisconsin

Woodland ponds are important landscape features that help sustain populations of amphibians that require this aquatic habitat for successful reproduction. Species abundance patterns often reflect site-specific differences in hydrology, physical characteristics, and surrounding vegetation. Large-scale processes such as changing land cover and environmental conditions are other potential drivers influencing amphibian populations in the Upper Midwest, but little information exists on the combined effects of these factors. We used Blue-spotted (Ambystoma laterale Hallowell) and Spotted Salamander (A. maculatum Shaw) monitoring data collected at the same woodland ponds thirteen years apart to determine if changing environmental conditions and vegetation cover in surrounding landscapes influenced salamander movement phenology and abundance. Four woodland ponds in northern Wisconsin were sampled for salamanders in April 1992-1994 and 2005-2007. While Blue-spotted Salamanders were more abundant than Spotted Salamanders in all ponds, there was no change in the numbers of either species over the years. However, peak numbers of Blue-spotted Salamanders occurred 11.7 days earlier (range: 9-14 days) in the 2000s compared to the 1990s; Spotted Salamanders occurred 9.5 days earlier (range: 3 - 13 days). Air and water temperatures (April 13- 24) increased, on average, 4.8°C and 3.7°C, respectively, between the decades regardless of pond. There were no discernible changes in canopy openness in surrounding forests between decades that would have warmed the water sooner (i.e., more light penetration). Our finding that salamander breeding phenology can vary by roughly 10 days in Wisconsin contributes to growing evidence that amphibian populations have responded to changing climate conditions by shifting life-cycle events. Managers can use this information to adjust monitoring programs and forest management activities in the surrounding landscape to avoid vulnerable amphibian movement periods. Considering direct and indirect stressors such as changing habitat and environmental conditions simultaneously to better understand trends in space and time can help improve monitoring programs for this taxa, which is at major risk of continued declines.

Wisconsin↗
USGS2007

Occurrence of the amphibian pathogen Batrachochytrium dendrobatidis in Pacific Northwestern USA

Chytridiomycosis (infection by the fungus Batrachochytrium dendrobatidis ) has been associated with amphibian declines in at least four continents. We report results of disease screens from 210 pond-breeding amphibians from 37 field sites in Oregon and Washington. We detected B. dendrobatidis on 28% of sampled amphibians, and and we found - > 1 detection of B. dendrobatidi s from 43% of sites. Four of seven species tested positive for B. dendrobatidis , including the Northern Red-Legged Frog ( Rana aurora ), Columbia Spotted Frog ( Rana luteiventris ), and Oregon Spotted Frog ( Rana pretiosa ). We also detected B. dendrobatidis in nonnative American Bullfrogs ( Rana catesbeiana ) from six sites in western and central Oregon. Our study and other recently published findings suggest that B. dendrobatidis has few geographic and host taxa limitations among North American anurans. Further research on virulence, transmissibility, persistence, and interactions with other stressors is needed to assess the potential impact of B. dendrobatidis on Pacific Northwestern amphibians.

Oregon↗
USGS2005

Modeling anuran detection and site occupancy on North American Amphibian Monitoring Program (NAAMP) routes in Maryland

One of the most fundamental problems in monitoring animal populations is that of imperfect detection. Although imperfect detection can be modeled, studies examining patterns in occurrence often ignore detection and thus fail to properly partition variation in detection from that of occurrence. In this study, we used anuran calling survey data collected on North American Amphibian Monitoring Program routes in eastern Maryland to investigate factors that influence detection probability and site occupancy for 10 anuran species. In 2002, 17 calling survey routes in eastern Maryland were surveyed to collect environmental and species data nine or more times. To analyze these data, we developed models incorporating detection probability and site occupancy. The results suggest that, for more than half of the 10 species, detection probabilities vary most with season (i.e., day-of-year), air temperature, time, and moon illumination, whereas site occupancy may vary by the amount of palustrine forested wetland habitat. Our results suggest anuran calling surveys should document air temperature, time of night, moon illumination, observer skill, and habitat change over time, as these factors can be important to model-adjusted estimates of site occupancy. Our study represents the first formal modeling effort aimed at developing an analytic assessment framework for NAAMP calling survey data.

Maryland↗
USGS1989

Distribution, habitat, and future of Harter's water snake, Nerodia harteri, in Texas

Detailed studies of the distribution and habitat use of the endemic Texas snake Nerodia harteri were conducted from 1979 to 1987. The Brazos water snake N. h. harteri is restricted to the upper Brazos River drainage; it is found in about 303 km of stream plus two reservoirs, Possum Kingdom Lake and Lake Granbury. The Concho water snake, N. h. paucimaculata occupies 396 stream-km in the Concho-Colorado River drainage, and about 25 km of lake. As such, Harter's water snake has one of the smallest ranges of any North American snake species. Medium to large, flat rocks on an unshaded shore for hiding places and rocky shallows for feeding grounds appear to be important for juveniles. There is an ontogenetic habitat shift in N. harteri that may also be common in many other Nerodia. We found that adult N. harteri are not restricted to rocky riffles in flowing rivers but can inhabitat a much wider range of habitats in pools and lakes. Several sections of both the Brazos and Colorado rivers are uninhabited by N. harteri, apparently because juvenile habitat is lacking or scarce. Riffles are more isolated on the uninhabited stretches, and they may be too far apart to recolonize after catastrophic local population extinctions. Past dam projects have eliminated populations of Nerodia harteri through habitat destruction by inundation and siltation. Fragmentation of populations may also prevent recolonization after local extinctions. A major dam being constructed on the Colorado River near Stacy, McCullough County, will inundate about 18% of the known habitat of Nerodia h. paucimaculata and perhaps degrade another 8% or more. A unique agreement whereby the dam-constructing authority will construct artificial habitats and fund biological studies could ameliorate the negative effects of the dam and reservoir on populations of the Concho water snake.

Journal of Herpetology↗