There’s been a lot of activity on the Vancouver Aquarium rooftop lately. As you may have seen from an earlier blog post, the Oregon spotted frog (Rana pretiosa) eggs kept there have hatched, and Aquarium biologists have recently released many of them in the Fraser Valley. This is good news for the Oregon spotted frog, which is an endangered species in Canada.

In order to bring this endangered species back from  the brink of extinction in Canada, the Aquarium has been working with the Oregon Spotted Frog Recovery Team, which includes members from provincial, federal and regional district agencies, First Nations, universities and conservation organizations. Aquarium biologists currently care for approximately 60 adult Oregon spotted frogs, and approximately 6,000 eggs hatched this spring from 18 egg masses (though a few of those egg masses were not fertile). These eggs produced twice as many tadpoles as in the past two years.

An egg mass looks like a clump of clear JELL-O with black poppy seeds spread throughout. The “poppy seeds” are actually Oregon spotted frog eggs, and they’re encased in a jelly-like substance that expands when the eggs make contact with the pond water. The eggs take on different shapes as they grow from a circle, to a bean, to a rod shape (that’s when they start looking like tadpoles). The tadpoles hatch within two to three weeks of egg laying.

A gridded tray is an important tool used in counting frog eggs.

A gridded tray is an important tool used in counting frog eggs.

An important part of this conservation project is knowing just how many eggs are being produced. Kris Rossing, one of the Aquarium biologists working on this initiative, says there are two ways they do this: they can do a volume count by putting the eggs in a container and estimating the number of eggs based on the measurement that one egg equals one millilitre, or they can count the eggs one by one by putting them in a gridded tray (a grid is drawn onto the tray so the person counting doesn’t lose track). Although the volume method is considerably faster, it is not as accurate as counting on a gridded tray.

This is delicate work that requires specialized equipment. This year’s breeding program at the Aquarium is being supported by Bring Back the Wild, an Earth Rangers initiative. The Aquarium is also part of a worldwide effort, along with other zoos and aquariums, to conserve other amphibian species under the Amphibian Ark (AArk) project.

The tadpoles didn’t stay at the Aquarium very long – they were released into the wild to supplement populations there. It’s the first step in reversing this species’ endangered status. The species has vanished from 90 per cent of its range in British Columbia due to factors such as draining of wetlands, urban development and the arrival of invasive species.

Since 2007, Aquarium staff has been collecting Oregon spotted frog eggs to establish an aquarium-based assurance population. In 2010, Oregon spotted frogs were bred at the Aquarium for the first time ever in an aquarium environment.


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