Laura Burkholder
Green Diamond Resource Company
Korbel, California
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ABSTRACT
BURKHOLDER, LAURA L. and LOWELL V. DILLER
Green Diamond Resource Company, Korbel, CA
lburkholder@greendiamond.com
Population Parameters of Coastal Tailed Frogs in Northwestern California
Several studies have estimated the abundance of tailed frog (Ascaphus spp.) larvae within streams, but there has been no attempt to directly estimate the abundance of immature and adult frogs. We conducted a mark-recapture study of post-metamorphic coastal tailed frogs (A. truei) on a total of six streams from 2002-04 and used an open population model in Program MARK to estimate capture probabilities and population size within stream reaches. In 2003 probability of capture appeared to be constant over time (0.06 +- 0.01) and did not differ by age, sex, or creek. In 2004, capture probabilities of both creeks indicated a quadratic time trend depending on age (adults: mean = 0.11 +-0.02, immatures: mean = 0.13 +- 0.01) Captures were only adequate to estimate population size for two creeks during summer surveys from 2003 to 2004. Summer population estimates of females in both creeks indicated that there were on average 1.82 and 1.25 females per linear meter of stream in 2003 and 2004, respectively. Extrapolated to entire stream length with potential habitat, these estimates suggest potential total population sizes of 40,947 and 5,811 frogs for each creek. Our data indicated that tailed frogs have the potential to be a major biological component of headwater streams, but low capture probabilities limited our ability to estimate abundance for all streams. Because abundance estimates are important for management of this species, future studies should focus on methods that may increase capture probabilities in creeks with low population densities of frogs.
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