The Oregon spotted frog may be Canada’s most endangered amphibian, but we have seen firsthand how resilient this species can be.

The Oregon spotted frog recovery program continued its record streak last year with an astounding 23,527 tadpoles produced from 39 egg masses. Most were released in spring to continue their development in the wild, but ~1000 were retained in our breeding facility for release later in the summer. This allows us to monitor the condition of the tadpoles held back, to ensure that our lab conditions mirror what is occurring in their natural habitat and we are producing healthy frogs.

Egg laying season in the wild begins in early spring so while our frogs were getting busy in the lab, our teams went out to visit a restored natural site to see how the wild animals were faring. We were thrilled to see wild egg masses for the third year in a row! This confirms that released frogs from our conservation program are breeding and thriving. This specific site that we have been monitoring produced two egg masses, and though that is down from five masses the previous year, field crews noted that numbers of egg masses were down at all sites and this is likely the result of natural yearly fluctuations.

 After a winter of unknown outcomes, Oregon spotted frog egg masses are a welcome sign this spring.

Due to our incredible breeding success last year, our research this year will shift to exploring the role of exogenous hormones, which are hormones that are in the environment from other frogs, and how they can play a role in triggering breeding.

Moving into fall, frogs went into hibernation, their tanks wrapped in heaters and insulation to keep them cold but prevent them from freezing solid during the winter.

About halfway through December, disaster struck. Staff checked on the frogs in the morning and found many of them in one tank were visible on top of the detritus layer. Given the time of year, frogs are almost never visible having buried themselves for the winter months. Further investigation revealed the animals had in fact died, rather quickly overnight. We gathered our thoughts about how to handle the situation. This type of mortality is not common in conservation breeding programs and we needed to determine the cause.

The investigation process was intensive and involved tearing apart beautifully constructed naturalized enclosures but resulted in the recovery of live animals that had not succumbed to whatever had affected their tank mates. We decided to place them in artificial hibernation in fridges, both for easy access and care as well as control over their environment.

We took swabs and samples from both deceased and live animals and sent them to the provincial pathology lab which soon sent back the second least desired result, after unknown – it was chytrid. Chytrid is a fungus found in wild frog populations, including many in BC, that prevents frogs from being able to breathe through their skin, an incredible process and critical especially during hibernation. This fungus affects amphibian populations worldwide and is considered a significant culprit in mass extinction events, specifically in tropical areas.

The frogs in our conservation breeding program are good sports when it comes to being swabbed for pathology tests.

We had to decide if we should wake the frogs, treat them, and potentially lose breeding for the following year. Or, if we should treat them in hibernation, hoping they didn’t lose too much weight and could rally for breeding season. We chose the latter option, though this was uncharted territory. Only a handful of conservation organizations in the world have done this type of treatment for chytrid.

We consulted members of the recovery team, gathered medication, supplies and sterilization equipment and began the treatment process, involving daily baths in antifungal solution. We treated 55 frogs, one by one, knowing that their fate was in our hands. After treatment, each frog has its skin surface swabbed and screened for DNA markers of the fungus. This screening needs to be done twice, one week and two weeks post treatment and both screens need to come back negative.

After the first round, we still had positive results for the presence of chytrid. Since the frogs were doing well we decided to increase the concentration and length of the baths and begin the whole process again. Another 55 baths. After the second round of treatment, they received negative test results for chytrid and the breeding season was upon us.

We quickly moved on to our usual preparation for the breeding season, hoping the frogs would continue their natural process. After the winter chaos, we were all relieved when the remaining seventeen females produced twelve egg masses. The egg masses are developing well and we should still have a significant number of tadpoles to release, though perhaps not a record-breaking year. But certainly a year to remember.
Onward to rebuilding, learning, and species recovery!

Andrea Gielens

Lead Biologist – Fraser Valley Wetlands Wildlife Recovery Program

Andrea manages our 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 on Denman Island in BC.

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