Christopher A Pearl

Despite the high profile of amphibian declines and the increasing threat of drought and fragmentation to aquatic ecosystems, few studies have examined long-term rates of change for a single species across a large geographic area. We analyzed growth in annual egg-mass counts of the Columbia spotted frog (Rana luteiventris) across the northwestern United States, an area encompassing 3...

Biological invasions can have dramatic effects on freshwater ecosystems and introduced crayfish can be particularly impacting. We document crayfish distribution in three large hydrographic basins (Rogue, Umpqua, Willamette/Columbia) in the Pacific Northwest USA. We used occupancy analyses to investigate habitat relationships and evidence for displacement of native Pacifastacus...

Oviposition timing, behaviors, and microhabitats of ambystomatid salamanders vary considerably (Egan and Paton 2004; Figiel and Semlitsch 1995; Howard and Wallace 1985; Mac-Cracken 2007). Regardless of species, however, females typically oviposit using sites conducive to embryo development and survival. For example, the results of an experiment by Figiel and Semlitsch (1995) on Ambystoma...

Invasive species directly threaten freshwater biodiversity, particularly in regions of high aquatic richness like the Pacific Northwest (PNW). Crayfish are among the most impactful of aquatic invasive species. Invasive crayfish are considered ecosystem engineers due to their ability to alter basic wetland properties, such as reducing vegetation and bank integrity and increasing turbidity...

Non‐native fish and bullfrogs (Lithobates catesbeianus) are frequently cited as contributing to the decline of ranid frogs in the western United States, so we hypothesized that non‐native species, habitat, or a combination of these relate to the probability of local extinction for northern red‐legged frogs (Rana aurora) in Oregon, USA. We also hypothesized that the probability of...

The Columbia spotted frog (Rana luteiventris) occupies a large range in western North America and is comprised of at least three genetic units. Concern exists regarding the status of the Great Basin populations in Oregon, Idaho, and Nevada. We surveyed target and nearby alternate sites on public lands in southeastern Oregon where there was evidence that Columbia spotted frogs were...

The Oregon spotted frog (Rana pretiosa) is the most aquatic of the native frogs in the Pacific Northwest. The common name derives from the pattern of black, ragged-edged spots set against a brown or red ground color on the dorsum of adult frogs. Oregon spotted frogs are generally associated with wetland complexes that have several aquatic habitat types and sizeable coverage of emergent...

Batrachochytrium dendrobatidis is a fungal pathogen that is receiving attention around the world for its role in amphibian declines. Study of its occurrence patterns is hampered by false negatives: the failure to detect the pathogen when it is present. Occupancy models are a useful but currently underutilized tool for analyzing detection data when the probability of detecting a species...

High-resolution macroscopic charcoal and pollen analysis were used to reconstruct an 11??000-year-long record of fire and vegetation history from Beaver Lake, Oregon, the first complete Holocene paleoecological record from the floor of the Willamette Valley. In the early Holocene (ca 11??000-7500 calendar years before present [cal??yr??BP]), warmer, drier summers than at present led to...

Solar ultraviolet radiation (UV) has received much attention as a factor that could play a role in amphibian population declines. UV can be hazardous to some amphibians, but the resultant effects depend on a variety of environmental and behavioral factors. In this study, the potential effects of UV on the Northwestern Salamander, Ambystoma gracile, from three lakes were assessed in the...

Livestock grazing is a common land use across the western United States, but concerns have been raised regarding its potential to affect amphibian populations. We studied the short-term effects of full and partial livestock grazing exclosures on Rana luteiventris (Columbia Spotted Frog) populations using a controlled manipulative field experiment with pre- and posttreatment data (2002...

The pathogen Batrachochytrium dendrobatidis (Bd) has been associated with amphibian declines in multiple continents, including western North America. We investigated Bd prevalence in Oregon spotted frog (Rana pretiosa), a species that has declined across its range in the Pacific Northwest. Polymerase chain reaction analysis of skin swabs indicated that Bd was prevalent within populations...