Demographics of a ringed salamander (Ambystoma annulatum) breeding migration

摘要

Breeding migrations of the ringed salamander (Ambystoma annulatum) occur in autumn during rainy nights, when adults move in phalanxes toward small, fishless ponds. We intercepted ringed salamanders on their breeding migration in 1997 and 1998 as they crossed a paved road close to their 0.11-ha breeding pond. In 1997, we measured over 100 salamanders and found larger individuals of both sexes moved earlier in the migration, and females averaged larger than males in both weight and length. In 1998, we counted 1,096 salamanders moving towards the pond and 135 post-breeding animals as they emigrated back to their woodland habitat. Males dominated the first migration event of the 1998 season (73%) and females the last major phalanx (72%), but by the end of the migration season sex ratios were equal. A model predicted 9,848 ringed salamanders crossed the road to breed in this pond in 1998. Our sampling accounted for only 12% of post-breeding salamanders moving away from the pond, suggesting emigration is less directed than immigration. We found 61 ringed salamanders dead on the highway in 1998, indicating a 0.62% mortality due to vehicles.