{"id":149,"date":"2018-03-05T17:02:21","date_gmt":"2018-03-06T01:02:21","guid":{"rendered":"https:\/\/sites.evergreen.edu\/urbanecologyw18\/?p=149"},"modified":"2018-03-16T13:22:37","modified_gmt":"2018-03-16T20:22:37","slug":"preserving-red-legged-frogs-and-other-stillwater-breeding-amphibians-in-an-urbanizing-puget-sound","status":"publish","type":"post","link":"https:\/\/sites.evergreen.edu\/urbanecologyw18\/preserving-red-legged-frogs-and-other-stillwater-breeding-amphibians-in-an-urbanizing-puget-sound\/","title":{"rendered":"Preserving Red-legged Frogs and Other Stillwater Breeding Amphibians in an Urbanizing Puget Sound"},"content":{"rendered":"
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Urbanization is likely to increase as population continues to grow rapidly in Puget Sound<\/p><\/div>\n

Urbanization is a growing force in Puget Sound where population is expected to grow by 1.8 million people by 2050 (PSRC, 2017). This rapid growth represents an increase of 42%, from 3.9 million in 2015 to 5.8 million people and will drive land use changes including the conversion of forestland to suburban and urban development. Additionally, mean household size is expected to decrease from 2.5 to 2.36, which in conjunction with population increase will fuel the demand for 830,000 more dwellings. Such land use changes transform the ecological function and composition of the landscape. In the Puget Sound these changes and more roads will lead to the degradation and fragmentation of forest and wetland habitats that native amphibian species rely on.\u00a0<\/p>\n

Northern Red-legged frogs<\/strong> (Rana auora<\/em>) breed in still water and rely on adjacent conifer forests during summer months (HerpAtlas, WADNR). While some natural and engineered wetlands can provide breeding habitat, careful consideration of development patterns that preserve connection to upland habitat may be essential to maintain viable populations in urbanizing areas.<\/p>\n

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Northern red-legged frogs are native to the lowland Puget Sound<\/p><\/div>\n

\n Northern red-legged frogs are a medium-sized frog distinguished by the orange-red undersides of the legs and margins of the abdomen. They are associated with lowland forested habitats ranging from southern British Columbia to northern California. They are recognized as vulnerable or threatened across most of their range. In lowland Thurston County they are known to breed starting in late-January or early February and hatch in 3-5 weeks. Tadpoles start to metamorphose in late June. During summer months they disperse into upland forests where they are associated with dense understory vegetation. As the most terrestrial member of the Ranid family in the Puget Lowlands, they are particularly vulnerable to changes in lands adjacent to wetlands<\/p>\n

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Northern red-legged frogs are one dependent on forested uplands as adults.<\/p><\/div>\n

Northern red-legged frogs are seen as an umbrella species<\/strong> for other still water breeding amphibians because of their reliance on diverse habitats. This means that if land use successfully protects red-legged populations, other lentic-breeding amphibians such as Northwestern salamanders and long toed salamanders are also likely to be protected (Hayes et al. 2008).
\n Wetland buffers are required by Washington State Department of Ecology that help provide adjacent habitat, but buffer size may not provide enough habitat. Red-legged frogs are known to disperse over 1 km into uplands, a distance far greater than any required buffer. In order to preserve populations of enhance breeding sites, a broader suite of landscape variables should be considered including hydroperiod of wetlands, land adjacent to wetlands, and connective corridors to suitable upland habitats further fro wetlands.<\/p>\n

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Wetlands that are well connected to forested uplands may be necessary to maintain populations of Northern red-legged frog<\/p><\/div>\n

\n Corridors<\/strong> that connect still water habitats to uplands may provide a critical landscape element to maintain viable populations of red-legged frog. Grand and colleagues (2017) found that the land cover in surrounding areas had a significant effect on site occupancy and abundance of red-legged frogs. Specifically, the amount of forest that is connected to wetlands but located >200 m from water were found to be of greatest significance. This effect was stronger than the presence of the invasive bull frog, an aggressive predator known to impact native amphibians.<\/p>\n

\n Urban development also brings new roads that fragment otherwise suitable habitats. Road mortality<\/strong> can be a major factor when busy highways bisect critical habitat corridors. For example, 70 red-legged frogs were found dead near Highway 30 near Portland, OR. This led to a community effort near Forest Park, in which local residents capture and move animals across the highway. The effort has led to collaboration with Oregon Department of Fish and Wildlife, the City of Portland, and Forest Park Conservancy among others. The group is currently advocating for ODOT to consider constructing an underpass that would all for migration of frogs and reduce road mortality. (Read the whole story here<\/a>)<\/p>\n

\n Hydroperiod<\/strong>, meaning the duration in which a wetland contains surface water is also an important factor for maintaining red-legged frog populations. Development often disrupts the hydrology of wetlands leading to altered hydroperiods. If a seasonal wetland becomes a perennial water body it may allow for the establishment of warm water fishes that predate larval amphibians. Alternatively, diversion of surface water may lead to early drying of important breeding habitats that can cause mortality of egg masses.
\n As the anthropogenic pressures associated with urbanization consider to impact native amphibians, it is important to consider strategies to maintain viable populations on the landscape. As an umbrella species for other native amphibians, considering land use policies and development patterns that foster the resilience of red-legged frog populations to urbanization could help to maintain a suit of native amphibians in the Puget Lowlands.<\/p>\n

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Larval amphibians are particularly vulnerable to desiccation and predation. Urbanization can alter hydroperiods of wetlands making tadpoles more vulnerable.<\/p><\/div>\n

\n More resources on amphibians in the Puget Sound:<\/strong><\/p>\n