CHS Blog

Riding waves with Canada’s most endangered amphibian

March 01, 2022
Briar Hunter, MSc Candidate, co-supervision by David Lesbarrè res, Laurentian University, and Gabriela Mastromonaco, Toronto Zoo

While most of us have seen our social lives struggle over these past two years, not all species were following social distancing rules. One species, in particular, has made significant leaps and bounds in their relational lives—the Oregon Spotted Frog.

The past two years have certainly been filled with devastating lows and ecstatic highs for these endangered frogs—but none of these waves have been related to COVID-19.

With only six wild populations remaining in Canada, located exclusively in British Columbia, Oregon Spotted Frogs (OSF) have been part of an extensive conservation breeding and reintroduction program since 2009. Partners from the Vancouver Aquarium, Toronto Zoo, Greater Vancouver Zoo, and Wildlife Preservation Canada (WPC) have released thousands of tadpoles year after year into a restored wetland in hopes of establishing a new self-sustaining population of this highly aquatic frog. Unfortunately, year after year, despite extensive surveys, no egg masses were found. Until…

Until spring 2020!

While the world was in disarray, reeling from the lack of toilet paper (which, let’s be honest, is what tipped us over the edge amongst so many other stressors), one pair of OSF decided this was their year. And then another. And then another.

Three beautiful, utterly sublime egg masses were laid next to one another, nestled by the mud and grasses around them in a balmy bubble bath of bliss—bubbles not included.

Blissful hope coursed through the biologists who had anxiously watched fluctuating population numbers year after year. Yet a silent killer threatened to dampen their bliss. Many female OSF were dying in zoos of a condition called “egg binding”, where retained eggs clog up internal organs and cause health complications. This phenomenon was not new and not unique to OSF, but the cause(s) of its occurrence were unknown. Furthermore, questions regarding the genetic sustainability of these conservation breeding programs were rising in urgency. The small, isolated nature of the few remaining wild populations whispered of the risks of inbreeding and warnings of tadpoles unable to adapt to ever-changing environments.

And so, in the spring of 2021 I traveled to British Columbia—wielding cotton swabs all the way. One for my covid test, and one for every OSF cheek who consented to the collection of their DNA-filled saliva. This is how I would tackle the question of their genetic health.

While wading through wetlands silhouetted by snow-capped mountains to collect these samples, I was privy to yet another type of peak. In nearly the same soft shallows as the year before, lay the wriggly orbs of OSF embryos sitting contentedly in the encompassing hug of their jelly coat. And not just one egg mass. Not two, or even three …

Six egg masses lay glistening in the morning sun. Their very existence a testament of patient perseverance.

Not only was there huge success in the wild populations, but a truly unparalleled breeding season by WPC staff at the Greater Vancouver Zoo led to over 20,000 tadpoles hatching and entering the wild—more than all other years combined!

Riding this wave of success, I endeavoured to analyze one of the altered components of that year’s breeding program in hopes of unveiling what had caused this enormous success. I designed and implemented a study on the overwintering conditions of OSF to see how it impacts their breeding behaviour and reproductive output. We suspect males and females influence one another if not separated during the overwintering period, but we hope to learn exactly how (whether visually, chemically, or physically) and what aspect of their breeding is affected. This will allow improving and optimizing of these breeding programs and hopefully lead to as much success as in 2021.

Alas, I cannot leave us on an entirely optimistic note because the world endures too much turmoil for a true happily-ever-after.

The flooding and mudslides in British Columbia in late 2021 have been utterly devastating and life-altering for so many—the OSF included. Many of the remaining wild populations lay within the major flooding zones. While the frogs ought to have been tucked away for their winter nap, their residing in river sloughs and floodplains means their homes were the perfect runway for mudslides and runoff from surrounding agriculture. We will not know the totality of the destruction and loss until the waters recede and the frogs emerge. There will be many an anxious biologist’s heart, awaiting the thaw of spring with imploring ears aching for the low cluck-cluck of surviving Oregon Spotted Frogs.

We are hopeful because we must be. I, at least, take this as a stark reminder of the importance of partnering with zoological institutions who can house and shelter some of our most vulnerable species. I await, with bated breath, the answers that spring will bring, but until then I strive to aid and improve current recovery actions for Oregon Spotted Frogs in Canada.

Congratulations to Briar for her 2021 field work successes and for her awarded best lightning talk of the 2021 CHS Conference! Well wishes and please keep us up-to-date about the ongoing findings from the in situ and ex situ OSF programme (we’re biting our nails in anticipation of spring 2022)!