The Sound of Spring

The following was published in the Cranbrook Daily Townsman, Tuesday, May 4, 2010.

For most, the sound of spring is the clamour of bird song. After the long silence of winter, hushed by layers of snow (or maybe not, this year!), the return of songbirds from their lush tropical dreamland brings a welcome music to the early morning sunlight. The gathering chorus, added to daily by new arrivals, grows earlier as dawn heads steadily north. In the evening, the robin, soon joined by other thrush cousins, sings a vespers to the enclosing darkness.

But if you are lucky enough to live close to a pond or wetland, that evening song is soon joined by another voice. This one more rhythmic than melodic. Steady. Emphatic and determined. The steady krek-ek… krek-ek… of the Pacific tree frog is as much a sign of spring in the East Kootenay as any crocus or bluebird.

Pacific tree frogs are one of the more common amphibians in southern British Columbia, occurring from the coast east to the Rocky Mountain Trench. Highly variable in colour as a species, we here in the East Kootenay get the drab olive variety, with a black triangular mask behind their eyes. They’re small in size – rarely more than 5 cm long. Their range ends as the Lizard and Galton ranges climb from the valley into west slope of the Rockies. But many small ponds, sloughs and wetlands throughout the Trench are the site each spring of a ritual pilgrimage for the tiny amphibians.

For an animal that is reliant on the whims of fickle spring weather, frogs are remarkably adapted to cold. Some nights when the temperature battles hard to remain above freezing, we can still hear the frogs croaking away in late April.

As the snow melts and frost eases from the ground, tree frogs emerge from their hibernation – a winter spent under the chilly blanket of dead leaves and other forest floor cover. Many frogs have an physiology adapted to super-cooling that allows them to virtually freeze during the winter. Provided they are not disturbed, they literally thaw out the next spring and start their year anew.

They return to ponds each spring only to breed and lay eggs. As all amphibians, their larval stages are fully aquatic. Tree frog tadpoles or pollywogs develop rapidly, metamorphosing into terrestrial adults within two months. They have to grow quickly, for their pond is often ephemeral and dries out under the summer sun.

Like most tree frogs, their toes have suction cups on the end to facilitate climbing into their eponymous lair of small trees and shrubs where they spend most of the season, often quite distant from water. Here they feast on a typically froggy diet of insects, spiders and other bugs caught from their not-so-lofty perches. Unlike most frogs, which only call during the spring breeding season, Pacific tree frogs often just can’t hold back. Any particularly glorious night of rain and damp misery may elicit a song of apparent joy from a tree frog’s throat.

However, ours is not a particularly joyful time for amphibians. Species the world over are in decline, and BC is by no means sheltered. Chytrid fungus, originally from Africa, has been unwittingly spread worldwide with devastating effects on our frog populations. Reducing transmission by not handling frogs and not visiting different ponds is the best way to restrict the disease. Any mass die-offs of frogs should be reported to the British Columbia Ministry of Environment.

This year, the pond in our neighbourhood is dry. The water table lowered from lack of snow and too long without rain. We have not yet heard the frogs, though I know they are singing elsewhere. I miss the call, lying in bed with the window open at night listening for their spring ritual. Species fated to the whims of climate are well adapted to adjust to a occasional dry years. We just hope this is an anomaly and not a portend of conditions to come. A spring without tree frogs is far too silent.