Road proximity increases risk of skeletal abnormalities in wood frogs from National Wildlife Refuges in Alaska.
BACKGROUND
Skeletal and eye abnormalities in amphibians are not well understood, and they appear to be increasing while global populations decline. Here, we present the first study of amphibian abnormalities in Alaska.


OBJECTIVE
In this study we investigated the relationship between anthropogenic influences and the probability of skeletal and eye abnormalities in Alaskan wood frogs (Rana sylvatica).


METHODS
From 2000 to 2006, we examined 9,269 metamorphic wood frogs from 86 breeding sites on five National Wildlife Refuges: Arctic, Innoko, Kenai, Tetlin, and Yukon Delta. Using road proximity as a proxy for human development, we tested relationships between skeletal and eye abnormalities and anthropogenic effects. We also examined a subsample of 458 frogs for the trematode parasite Ribeiroia ondatrae, a known cause of amphibian limb abnormalities.


RESULTS
Prevalence of skeletal and eye abnormalities at Alaskan refuges ranged from 1.5% to 7.9% and were as high as 20% at individual breeding sites. Proximity to roads increased the risk of skeletal abnormalities (p = 0.004) but not eye abnormalities. The only significant predictor of eye abnormalities was year sampled (p = 0.006). R. ondatrae was not detected in any Alaskan wood frogs.


CONCLUSIONS
Abnormality prevalence at road-accessible sites in the Kenai and Tetlin refuges is among the highest reported in the published literature. Proximity to roads is positively correlated with risk of skeletal abnormalities in Alaskan wood frogs.
Reeves
Mari K
MK
US Fish and Wildlife Service, Anchorage Fisheries and Ecological Services Office, Anchorage, Alaska 99501, USA. mari_reeves@fws.gov
Dolph
Christine L
CL
Zimmer
Heidi
H
Tjeerdema
Ronald S
RS
Trust
Kimberly A
KA
D000413:Alaska; D000818:Animals; D001842:Bone and Bones / Q000002:abnormalities*; D003247:Conservation of Natural Resources; D004450:Echinostomatidae / Q000502:physiology; D004781:Environmental Exposure; D005124:Eye Abnormalities / Q000139:chemically induced / Q000662:veterinary*; D005843:Geography; D011898:Ranidae / Q000002:abnormalities* / Q000469:parasitology; D012307:Risk Factors