On Tuesday May 2nd, 2023 The Greater Vancouver Zoo alongside Wildlife Preservation Canada released approx. 5,900 Oregon Spotted Frog tadpoles into a local release site.
After a cold and challenging winter season in 2022/23 the frogs came back with a vengeance in the spring. As soon as the water warmed to just above freezing the native frogs began breeding and breeding they did. Of the 17 females in the breeding program run by Wildlife Preservation Canada at Greater Vancouver Zoo, twelve egg masses were produced. This is an amazing number considering our captive breeding colony spent much of the winter battling illness brought about by a chytrid infection. Chytrid is a disease introduced to wild frogs that can and unfortunately did get transmitted to our captive colony. Through treatment, which took two months and application of novel techniques (see our newsletter for details) we were able to recover the health of our population while saving their breeding season, which was no small task. Overall our captive breeding colony produced 6180 tadpoles, or 515 tadpoles per egg mass. Of these animals we retained 200 to rear over the summer into froglettes for release in the late summer.
Alongside rearing our captive born tadpoles are rearing an additional 800 wild collected tadpoles as part of a comparative growth study which ensures our captive produced tadpoles are developing at the same rate as their wild bred counterparts.
Additionally we are rearing one tub of native Red Legged frogs as part of a collaborative project with Fraser Valley Conservancy to develop a photographic differential ID catalogue for Red Legged and Oregon Spotted frogs which often live alongside each other but can be hard to tell apart as the tadpole stages in the field. This field ID resource will prove invaluable for biologists and other professionals identifying these species in the field, hopefully leading to more comprehensive ID of frog species and potentially the discovery of new populations.
“Being able to breed and release these tadpoles as such a high number consistently gives us increased reassurance that we will have a positive impact on the populations of this critically endangered species” says Wildlife Preservation Canada Lead Biologist Andrea Gielens, “ Having an ex-situ colony provides assurance of the production of tadpoles for release and protects breeding animals allowing them to reproduce over more seasons and contribute to population recovery.”
Andrea Gielens, Wildlife Biologist
Check out this episode of Conservation Corner!
https://www.youtube.com/watch?v=gEmS1GNxml4
