One of the most interesting aspects of frog biology is their unique breeding behavior, which is often highly adapted to their specific habitat and environmental conditions.

Frog breeding is a complex process that involves several stages, including courtship, mating, and egg-laying. The timing and nature of these behaviors can vary widely depending on the species of frog, their geographic location, and the environmental conditions in which they live. In conservation breeding programs like that for the Oregon spotted frog at WPC’s facility at the Greater Vancouver Zoo, making sure we get these timings and habitat features right ensures our programs success and the production of thousands of tadpoles for release.

Breeding season begins with male frogs will calling out to females using a distinctive mating call, which for Oregon spotted frogs sounds very much like someone knocking at a door, like they are saying “hello ladies! Are you home?”

Once a female frog has been attracted to a male’s call, the two frogs will engage in a grip like hold called amplexus where the male frog grasps the female with his front legs to prevent her from leaving while he fertilizes her eggs. Multiple males may grasp onto one female making a ball of frogs as each vies to fertilize the females eggs as they emerge.

Oregon spotted frog in amplexus in the breeding ponds at Greater Vancouver Zoo.

The egg-laying stage of frog breeding occurs in a suitable breeding habitat.  For Oregon spotted frogs this occurs in a communal location, which helps to increase the chances of survival for the offspring. The location is often the same or close year after year. Females choose a warm shallow area, often supported from below by submerged vegetation. The floating rafts of eggs maintained close to the waters surface, help to keep the eggs in the warmest part of the water while allowing the egg mass jelly to act like a mini greenhouse keeping the eggs and tadpoles even warmer.

Once the eggs have been laid, the adult Oregon spotted frogs role in the breeding process is usually complete. The adults typically leave the breeding habitat and return to her normal habitat, leaving the eggs to hatch and develop on their own. As the tadpoles develop those on the top of the egg mass hatch first. As they grow and the tadpoles below them begin to hatch they slowly eat their way through the jelly mass. By the tame the break through the bottom of the jelly mass to swim out into the open pond, they are larger and strong enough to maintain themselves in the water column.

Frog breeding is an amazing process that is essential to the survival of these important and unique creatures. By understanding the behaviors and adaptations that enable frogs to reproduce successfully, we can work to restore populations of these amazing animals for future generations.

Andrea Gielens

Lead Biologist – Fraser Valley Wetlands Wildlife

Andrea manages WPC’s captive breeding and release programs for the Oregon spotted frog and the coastal western painted turtle. Andrea has studied at-risk reptiles and amphibians in Canada and abroad, including a term at the Durrell Wildlife Conservation Trust in Jersey. Andrea also manages the Taylor’s checkerspot butterfly recovery program in BC.

Andrea Gielens

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