CANOPY EFFECTS ON EARLY STAGE VITAL RATES FOR NORTHERN RED-LEGGED FROGS AND POTENTIAL IMPACTS TO POPULATION GROWTH RATES.
Kelcy W. McHarry; Institute for Wildlife Sutdies; PO Box 1104, Arcata, CA, 95518; (541) 505-2951; mcharry@iws.org; Brian R. Hudgens, Jessica M. Abbott
Habitat characteristics at breeding sites may influence amphibian vital rates and population persistence, but the impact may differ among populations. Our research investigated the effect of canopy cover on early stage vital rates for several populations of Northern red-legged frogs (Rana aurora). We evaluated if the effect of canopy cover differed among populations, and if so whether the effect varied with ambient air temperatures. We reared eggs and conducted mark-recapture surveys for tadpoles in enclosures with contrasting canopies. We built matrix models to evaluate if observed effects of canopy cover on tadpole survival impacted population growth rates. Egg hatch success did not differ between canopy treatments or among sites. The effect of canopy over on tadpole survival varied among populations but there was no evidence that there was an interaction between canopy cover and local air temperature. For the populations where a canopy cover effect was detectable, population growth rates varied from approximately stable assuming tadpole survival observed in the open canopy treatments, to 30% annual decreases assuming tadpole survival observed in closed canopy treatments. Our results demonstrate canopy cover availability can influence tadpole survival and alter population trajectories.
Ecology and Conservation of Amphibians and Reptiles II