Late-Season Movement and Habitat Use by Oregon Spotted Frog (Rana pretiosa) in Oregon, USA
Many amphibians use multiple habitats across seasons. Information on seasonal habitat use, movement between seasonal habitat types, and habitats that may be particularly valuable is important to conservation and management. We used radio-telemetry to study late-season movement and habitat use by Oregon Spotted Frog (Rana pretiosa) at nine sites from four populations along the Cascade Mountains in Oregon. Movement rates declined with date and were the lowest at the end of tracking in December and January. Frogs across our sites used vegetated shallows in late summer and early fall. In fall, frogs used a range of habitat types, and at several sites moved to distinctive habitats such as springs, interstices in lava rock, and semi-terrestrial beaver channels. Distance between first and last tracking location was <250 m for 84.5% (49/58) of frogs, ranged up to 1145 m, and was greater for frogs in ditch habitats than those not in ditches. Distinctive features like springs or semi-terrestrial retreats can host multiple frogs and may represent particularly valuable wintering habitat for R. pretiosa in some sites in their Oregon range.
Study sites for radio-telemetry of Oregon Spotted Frog (Rana pretiosa) in Oregon, USA. Pink shaded areas are the approximate historic range of R. pretiosa (http://www.iucnredlist.org, accessed 12/4/17).
Displacement distance (straight-line distance from release site, in meters) for individual R. pretiosa in fall and early winter. We tracked R. pretiosa at three sites in 2011, four sites in 2012, and three sites in 2016. Two females in a ditch site in 2012 were last located 1145 m and 949 m from their respective release locations (off top of figure).
Interaction between size (snout–urostyle length, in mm) and sex as predictors of distance between release site and last location for adult R. pretiosa in Oregon.
Late-season movement rate (meters/day) of R. pretiosa in ditch (n = 2) and non-ditch (n = 7) sites in Oregon. Lines are modeled rates (±95% CI) from model-averaged coefficients (Table 5).
Ordination of habitat attributes at telemetry locations of R. pretiosa that were Wintering (=yes) or Pre-Wintering (=no) in Oregon, USA. Data are from telemetry locations at nine sites in Oregon, USA. Proportions of habitat attributes at locations of pre-wintering frogs differed from locations of wintering frogs (MRPP; A = 0.067, P = 0.001).
Ordination of habitat attributes at all late-season locations of female and male R. pretiosa. Data are from telemetry locations at nine sites in Oregon, USA. Habitat attributes did not differ significantly between sexes (MRPP; A = 0.002, P = 0.322).
Contributor Notes
Associate Editor: J. Kerby.