The male (left) is smaller than the female (right), which is laden with eggs during brumation.
Shh… it’s brumation time.
Brumation – as Darren Smy, senior aquarium biologist, explains it – is like hibernation but for reptiles and amphibians. The endangered Oregon spotted frogs (Rana pretiosa), currently living behind the scenes at the Vancouver Aquarium Marine Science Centre as an assurance population, are currently catching some shut-eye.
Darren says this is part of their survival mechanism. As cold-blooded animals, frogs can’t maintain their body temperature like humans. When the temperature dips so does their body temperature and their metabolism slows. This, coupled with a decreased food supply, means its best for these frogs to hunker down and take it easy instead of expending energy.
During this time, the frogs find a cozy corner underwater in the exhibit and settle down for the winter.
Frogs take oxygen, plentiful in the very cold water, through their skin so there’s no need to rise to the surface for a breath of air during this period.
Darren explains the year-cycle for this species: the frogs put on weight by eating crickets and other insects all summer, their bodies start slowing down in October as the outside temperature drops, they brumate from about mid-November to February, and then breeding begins. The females are easily identified by their bigger bodies (the cold stimulates egg production); the males, by dark pads on their thumbs that become pronounced as breeding season nears (they’re used for hanging onto the female).
While it’s quiet for now, Darren is expecting to see lots of action as the temperature starts to rise. Stay tuned for more updates on the Oregon spotted frogs in the spring.
Learn more about the Aquarium’s work conserving endangered frog species by visiting our Frogs Forever? gallery or learning more online.
Written by Karen Horak, writer-editor, content and digital experience at the Vancouver Aquarium.