Coastal Tailed Frog

The habitat of the tailed frog is cold, fast-moving streams with cobblestone bottoms. They are mostly aquatic, but adults may emerge during cool, wet conditions to forage terrestrially. Breeding season lasts from May through September, and females deposit their eggs in strings under rocks in fast-moving streams. Larvae take one to four years to metamorphose in the cool, fast-moving mountain streams. The amount of cobbles and fines (sand and similarly sized fine particles) in streams have been shown to be good indicators of tadpole abundance, with tadpole abundance being inversely proportional to concentration of fines and proportional to concentration of cobbles. Thermal tolerance range in adults is exceptionally low relative to other North American anurans, with eggs rarely found above 20 °C and adults and larvae regularly migrating along microhabitats to reach temperatures below 20 °C whenever possible. It would appear that they prefer temperatures 16 °C and below. Eggs develop best at temperatures between 5° and 13.5 °C. Because of this very narrow thermal tolerance, adults may exhibit philopatry where temperatures are stable and low. However, it has also been hypothesized that they may migrate to colder waters in autumn. …

When attempting to mate, males will lunge at the female, wrapping a forelimb around them to secure them initially in an inguinal amplexus formation (males wrap their digits around female anterior to the pelvic region, placing their head on the back and close to the rear of the female) and then in a ventral amplexus formation (female is flipped over and male and female venters face each other). From here, the male inserts the "tail" into the female, and squeezes the female to gain leverage before thrusting. During this process the female is relatively still, occasionally kicking during the insertion process. In some situations there is male-male competition for the female. In these situations, both males compete to enter the amplexus formation, eventually one establishing a better hold on the female and expelling the other male from the breeding process. Usually the male that is larger is more likely to succeed.