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Canadian Herpetological Society Société d'Herpétologie du Canada |
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Pacific Treefrog
Pseudacris regilla
Family: Hylidae
COSEWIC status:- Not Assessed
- No Status
- Least Concern
Description
The Pacific Treefrog is a small frog that reaches a maximum length of about 5 cm, with males being slightly smaller than females. The dorsal colouration is highly variably and can change based on temperature, light and substrate colour. Individuals are often varying shades of brown, tan or green, although some red, bronze and black colour morphs can occur. Pacific Treefrogs have a dark stripe that extends from the snout through the eye to the shoulder, distinct circular toe pads, and granular skin. Individuals may have a dark y or v-shaped marking between the eyes and dark blotches or stripes on the back and legs, although some or all of these markings may be absent. The belly is whitish or pale yellow, and the throat of males is light brown. Larvae (tadpoles) have long tails with a large fin, lack front legs (newly hatched tadpoles are legless), and are greenish-grey to brown, sometimes with gold flecking. Larvae can reach lengths of 5 cm before metamorphosis. The call of this species is the classic “ribbit” sound.
Similar Species
This species may be confused with the Boreal Chorus Frog and the Wood Frog. The Boreal Chorus Frog has smaller toe pads, disproportionately short legs and the eye stripe continues well past the shoulder to the groin. The Pacific Treefrog and Boreal Chorus Frog can also be differentiated based on location, as the distributions of these two species do not overlap. The dark markings on the face of the Pacific Treefrog can sometimes look like the dark mask of the Wood Frog, but Wood Frogs lack toe pads and have pronounced dorsolateral folds (folds of skin running down each side of the back).
Distribution
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In Canada, Pacific Treefrogs occurs in southern B.C. on Vancouver Island and the gulf islands, along the west coast adjacent to Vancouver Island, and in the southern interior, but is absent from southeastern B.C. Populations in the interior extend further north than those along the coast. This species occurs along the West Coast south to Baja California, and as far inland as western Montana and eastern Nevada.
Habitat
This species typically breeds in aquatic habitats that are fish-free, such as permanent and temporary wetlands, shallow bays of lakes and slow-moving creeks. Outside of the breeding season, Pacific Treefrogs forage in moist terrestrial habitats near lakes, wetlands, ponds and streams, such as wet meadows, open woodland and sparse forest. As the name implies, these individuals can be found in trees and shrubs, although most individuals forage on the ground. Individuals hibernate underground in mammal burrows, rocky crevices, or under rotten logs.
Biology
In Canada, Pacific Treefrogs hibernate during the winter and are typically active from March or April until September or October. Males call to attract females during the breeding season, which occurs in the early spring. During breeding, the male grasps the female (amplexus) and fertilization occurs externally in aquatic habitats as the female lays eggs. The female lays up to 1,200 eggs in small clusters of 5–120, which are attached to submerged vegetation. The eggs are olive-brown on one side and yellow to cream on the other and are surrounded by two clear jelly envelopes. The eggs typically hatch in about a month, and tadpoles undergo metamorphosis 2–3 months later. Individuals reach sexual maturity the year following metamorphosis, and most only mate once in their life. This species is very short-lived, with a maximum lifespan of only three years. Pacific Treefrogs are active during the day and night, and they forage in terrestrial habitats for a wide variety of invertebrates, including flies, beetles, wasps, ants, mites spiders, and snails. This species is able to survive moderate freezing temperatures by elevating their glucose levels, which prevents the cells from freezing.
Threats
Habitat loss and degradation, primarily resulting from logging and urban development, is the most significant threat to this species in Canada. Pesticides/herbicides, agricultural effluent, road salt and other environmental contamination can be detrimental to frog populations by causing direct mortality as well as developmental deformities. Road mortality can also be a significant threat when roads bisect this species’ habitat. Pathogens, such as chytrid fungus and Ranavirus, can cause mass mortality of frog populations and are a serious threat to frogs in Canada. Climate change may also pose future threats to Canada’s frog populations, particularly by increasing the frequency and severity of droughts.