Amphibians and Reptiles in Human-dominated Landscapes

Amphibians and reptiles are taxa especially susceptible to any number of stressors given their ecology, life history, behavior, and how humans view them. Habitat modification, degradation and loss as a result of urban development is a factor in amphibian and reptile declines worldwide. Given future projections about the number of people inhabiting urban areas, the stress of urban development on amphibians and reptiles shows no decline. However, relatively little is known about these animals in urban areas. This symposium will highlight research into how amphibians and reptiles respond to urbanization and survive in a human-dominated landscape.  In recognition of our TWS conference being jointly held with the AFS, our symposium will include a number of aquatic or semi-aquatic species from across North America.

8:00AM Spatial Ecology of Turtle Populations within an Urban Landscape
  Travis Ryan
The development of infrastructure to support a growing human population within urban areas can have a profound impact on the abundance and distribution of wildlife within cities. Indianapolis, IN is the 16th largest city in the United States in terms of both population size and spatial extent. Approximately 60% of the city’s drinking water is moved from the White River to a water treatment facility via the Central Canal. This canal was constructed in the 1830’s and in addition to its current use, it is vital habitat for six species of freshwater turtles. The distribution of varying upland habitats (including commercial districts, residential areas, remnant woodlots, roads, etc.) influence habitat use and movement of turtles within the canal. Suburbanization over the last 50 years has led to a reliance on retention ponds and other created wetlands to manage rainfall drainage. These created wetlands can also serve as habitat for freshwater turtles with factors such as size and age of the wetland as well as surrounding habitat characteristics (e.g., distance from roads and road density) influencing colonization and persistence.
8:20AM Urbanization, Wildfire, and Drought Effects on Native Stream Breeding Amphibians in Southern California
  Katy Semple Delaney, Rosi Dagit, Lee Kats, Seth Riley
At Santa Monica Mountains National Recreation Area (SAMO), the largest urban national park in the U.S., native stream breeding amphibians are exposed to many different stressors, including habitat fragmentation, roads, urban water run-off, extreme drought, and wildfires. Together with our partners, the National Park Service has been monitoring native stream breeding amphibians in SAMO for almost 20 years. In this talk, we will examine trends in amphibian occupancy and abundance as related to the amount of urbanization in watersheds, year-to-year fluctuations in temperature and precipitation levels, fire and resulting debris flows, and co-occurrence with non-native invasive fishes and crayfish.
8:40AM Urban Patches Provide Critical Small Vertebrate Diversity Value within the California Floristic Province Hotspot
  Robert Fisher, Staci Amburgey, Carlton Rochester, Cheryl Brehme, Stacie Hathaway, Katy Semple Delaney, Seth Riley, Jean-Pierre Montagne, Emily Perkins, David Miller
Over the past 25 years there has been a major shift in the development process of the biodiversity reserve system in coastal southern California. This Mediterranean ecosystem is one of three hotspots in the United States for endangered species. With data on 45 terrestrial vertebrate species representing 47,156 individuals, we assessed the responses to habitat loss and fragmentation. Data were collected at 698 pitfall arrays across 97 patches ranging in size from 0.42 to 81,402.48 hectares. We determined the relationship between species richness and patch size, and then assessed what this means for the conservation landscape with regards to maintaining biodiversity. Of 9,321 patches (1,388,854 ha) of open space left in southern California, 2,242 patches (524,970 ha) are currently conserved. We found that patches greater than 5,000 ha contained about 80% of the predicted richness within these species based on species distribution models, but that in patches between 30 ha and 5,000 ha there was 27-39% less richness than predicted, and below 30 ha the missing richness was close to 55%. Fortunately, these smallest patches, although the most numerous, represent only about 2-3% of the total land remaining as open space or conserved land. Our results indicate that the percentage of area in conservation is dominated by larger patches which contain greater species diversity. Future conservation could benefit from adding non-conserved open space to existing conserved patches to enlarge them to over 5,000 ha to reduce species loss, versus placing more small “insular” patches into the network.
9:00AM Assessing and Verifying Urban Habitat Connectivity for the Northern Red-Legged Frog
  Amanda Temple, Martin Lafrenz, Leslie Bliss-Ketchum, Catherine de Rivera, Lori Hennings
Urban habitats present unique challenges to species movements. The presence of alternative land cover and infrastructure such as residential lawns, fences, transmission lines and roads can reduce or completely block species movement, however understanding the degree to which movement is inhibited is a species-specific question. As a provision to the Metro Regional Habitat Connectivity Toolkit, movements of Northern Red-legged frogs (Rana aurora, RAAU) were tracked with radio telemetry in relatively intact habitat in Forest Park, and modeled for urban population locations in the city of Gresham with Circuitscape 4.0 and Least Cost Path Analysis. Telemetry data in Forest Park has provided detailed and fine scale information on how RAAU adults are utilizing habitat features and navigating the landscape. Frogs are heavily utilizing vegetative cover, particularly sword fern, within relatively dense Western Hemlock- Douglas fir forest. RAAU was also not found to show preference for particular topography features, such as ravines or riparian areas, and regularly moved along upland slopes where vegetation cover was adequate. Presence of RAAU has been previously verified through egg mass surveys in Gresham sites and were used as anchor points to model adult connectivity pathways from breeding ponds to adult terrestrial habitats, facilitating their seasonal migration. Findings illustrated locations where adult habitat presence was limited and/or restricted, and where barriers may be limiting adult dispersal. In addition to this work, we plan to verify modeling assumptions in the Gresham population with telemetry efforts in 2020. These results allow practitioners to devise habitat connectivity strategies for sensitive species in urbanizing places and can provide more detailed understanding of potential thresholds for sustaining RAAU population. In addition, urban connectivity models such as this can support the protection of location-specific wildlife movements in rapidly changing environments and can inform regional conservation strategies and planning efforts.
9:20AM Natural and Unnatural History: Habitat Use and Behavior of Amphibians in a Northern City
  Cynthia A. Paszkowski, Brett R. Scheffers, Murdoch E.D. Taylor, Benjamin L.S. Furman, Arthur V. Whiting
Edmonton, Alberta (population 1.2 million) straddles the North Saskatchewan River Valley in the Aspen Parkland of western Canada. The region supports 5 amphibian species: 4 anurans and 1 salamander. In 2008-2009 we began investigating amphibian populations within the city, conducting trapping, and auditory and visual surveys on 17 natural wetlands and 58 constructed stormwater ponds. We documented wood frogs (Lithobates sylvaticus) in 100% of natural and 60% of stormwater ponds, boreal chorus frogs (Pseudacris maculata) in 88% of natural and 48% of stormwater ponds, and western tiger salamanders (Ambystoma mavortium) in 40% of natural and 10% of stormwater ponds. Modelling showed that the presence of wood frog, the most widespread species, was best predicted by the amount of aquatic vegetation within ponds, and coverage by native vegetation and wetlands on the landscape. Only 3% of the 100 m surrounding stormwater ponds supported native vegetation, suggesting that suitable upland habitat limits populations, as all local amphibians forage and hibernate terrestrially. Trapping of 13 ponds found that densities of wood frog eggs, larvae, and metamorphs were indeed lower at stormwater than at natural ponds, but stormwater metamorphs were larger. Radio-tracking of 49 adult wood frogs on 3 natural and 8 stormwater ponds showed that, throughout the summer, adults remained near breeding ponds: mean relocation-distance = 13 m away, mean maximum relocation-distance = 27 m. Habitat selected by frogs was characterized by tall grass and shrubs. Despite evidence that adult frogs were relatively sedentary, analysis of 10 microsatellite loci from 182 wood frogs from 3 natural and 5 stormwater ponds detected no genetic bottlenecks or differentiation among sites. The long-term connectivity and persistence of amphibian populations within Edmonton remains uncertain. However, use of new monitoring techniques (automated recording units) and native plants to landscape stormwater ponds offer promise for urban amphibian conservation.

Organizers: David Drake, Seth Riley
Supported by: TWS Urban Wildlife Working Group

Location: Reno-Sparks CC Date: September 30, 2019 Time: 8:00 am - 9:40 am