Vancouver’s treefrog
Filed Under: Uncategorized on April 24, 2009
Long before there were people in Vancouver, communities of birds, deer, reptiles and many other animals called this place home.
One of them was the Pacific Treefrog. A small amphibian that spends much of its time hiding under rocks, tree stumps and forest detritus. Although other members of it’s family enjoy climbing trees, our Pacific treefrog seldom spend much of it’s time in tree branches. For this reason, some have renamed it’s common name to Pacific chorus frog. Chorus is an apt description, as these frogs produce some of the most delightful and most recognizable “frog” sounds - the “wreck-it, wreck-it” calls many of us associate frogs with.
Today, Pacific treefrogs are found in fragmented populations throughout the metro Vancouver area. But they are not a localized species, as their coverage is vast – covering much of the northwest region of the north american continent.
From the province of British Columbia website “Frogwatch BC“:
At a Glance
The Pacific Treefrog is a very appealing little frog, and quite common in B.C. They are small frogs, up to 5 centimetres long, and may be any colour from pale grey or tan to bronze or bright emerald green. Pacific Treefrogs have a conspicuous dark “mask” or stripe extending from the nostrils through the eye as far as the shoulder. They are often marked with dark patches or stripes on the back, and are usually pale cream underneath. Their legs are long and slender; their toes have round pads, which help the frog grip and climb, and there is very little webbing between the toes, making them look quite long. Females are slightly larger than males, a feature common to most frogs.
Other similar-appearing frogs in B.C. include the Wood Frog and the Boreal Chorus Frog. Wood Frogs have a dark mask, but may be distinguished from Pacific Treefrogs by their toes, which do not have pads, and their dorsolateral folds (ridges running from the eye down the back). Pacific Treefrogs have no dorsolateral folds. Boreal Chorus Frogs are treefrogs as well. They resemble Pacific Treefrogs but have much smaller toe pads, have an eyestripe which continues along the body, and usually have three stripes on their backs. Boreal Chorus Frogs are only found in a small segment of northeastern B.C., so any treefrog found in the southern part of the province is almost certain to be a Pacific Treefrog.
Home Sweet Home
The Pacific Treefrog is quite cosmopolitan in its choice of homes. Outside the breeding season, in early spring, Pacific Treefrogs may be found in woodlands, meadows, pastures, and even urban areas, often quite far from the nearest body of water. City dwellers on the coast are often pleasantly surprised to find that a Pacific Treefrog has made itself at home in their garden or even in plant pots on a balcony. The sticky pads on their toes allow these frogs to climb about on plants with great agility, though they usually stay fairly close to the ground.
During the breeding season, the Pacific Treefrog makes its way to shallow wetlands where there is a lot of plant cover. Often these wetlands or ponds are temporary, drying up by midsummer; they are called “ephemeral” wetlands. By using these wetlands for breeding, the Pacific Treefrog can avoid predatory fish and amphibians, such as Bullfrogs, which require permanent water bodies.
This is the Life
Early in the spring, Pacific Treefrogs begin to breed. Males make their way to the breeding ponds and call in unison to attract females. The choruses can be startlingly loud considering the size of the frog! The breeding call of the male is a two-syllable krek-ek, instead of the one-syllable c-r-r-ick heard the rest of the year. After mating, the females lay small clusters of eggs, attaching them to bits of vegetation in quiet, shallow water. The egg clusters are irregular in shape and may contain 10 to 70 eggs. The embryos develop rapidly, hatching two or three weeks after the eggs are laid, and the tadpoles metamorphose in approximately two months. Newly metamorphosed Pacific Treefrogs may be only one centimetre long! The young frogs mature quickly and may be ready to breed the year following transformation.
What’s on the Menu?
Adult Pacific Treefrogs eat spiders and a wide variety of insects, which they hunt while climbing about on plants. Tadpoles graze on algae and detritus. In turn, treefrogs are preyed on by snakes, Bullfrogs, and many birds and mammals, and tadpoles are eaten by larger frogs and fish.
Where and When
In British Columbia, the Pacific Treefrog is found in the southern part of the mainland and on Vancouver Island. It has been introduced to Haida Gwaii (Queen Charlotte Islands). Pacific Treefrogs are found southward along the U.S. west coast as far as Mexico, but are not found east of the Rocky Mountains.
Pacific Treefrogs can be heard calling throughout the year, especially during rainstorms, and the spring mating choruses are impossible to miss. It’s very difficult to spot these little fellows, though, since they will cease calling if they feel threatened.
How Are They Doing?
The Pacific Treefrog is quite abundant in B.C. and can use a variety of habitats, so it is not considered to be of conservation concern. This species is on the provincial Yellow List of species managed at the ecosystem level. Populations may decline in the future, however, if the loss of wetlands continues. Pacific Treefrogs are protected under the British Columbia Wildlife Act.
How You Can Help
Even though Pacific Treefrogs are doing well in B.C., loss of wetland habitats can mean loss of local populations of these tiny frogs. Learn about wetlands and how important they are to our environment.
Take part in BC Frogwatch and let us know when and where you hear treefrogs (and other amphibians) begin their spring chorus. Since the time when frogs begin to call can depend on the weather, scientists think that keeping track of this information may help us learn more about climate change. Environment Canada’s EMAN program (the Ecological Monitoring and Assessment Network) coordinates the national Frogwatch program, as well as other monitoring programs.
