Frogs Sing Again at Beaver Lake

On an evening stroll around Beaver Lake, you may be fortunate enough (as SPES’ Conservation Projects Manager recently was during a wildlife survey) to hear the classic calls of the Pacific chorus frog, a species that was thought to be extirpated from Stanley Park!

Pacific chorus frogs (also known as Pacific tree frogs) make a louder sound than expected  in comparison to their size. These tiny amphibians are only 3 to 5 cm in length, but they can call louder than other frogs which are over twice their size! Listen to their call here.

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Pacific chorus frog – green colour morph (Photo by The High Fin Sperm Whale – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=19041749)

They have beautiful colors that vary from a bronze tan to pale grey, or the classic bright green. Along with wood frogs, Pacific chorus frogs have a distinguishable dark stripe, or “mask”, that starts from their nostril and goes past their eye to almost their shoulder.  Some of the same coloring can be seen as stripes or small spots on their backs, and their undersides are usually a pale cream.

So why relate a frog to trees? Well! These frogs have less webbing in-between their toes so consequently they have longer, slimmer limbs and at the end of their toes they have small, sticky pads which assist them to grip to vegetation and climb trees. Though they normally remain closer to the ground, they can still evade predators with their agility to climb and hide.

During the breeding season, Pacific chorus frogs prefer to use shallow wetlands with abundant aquatic and emergent vegetation to lay their eggs and they utilize ground cover for protection. Certain streams and pools around Beaver Lake are ephemeral (drying up in the summer months) which could favour the survival of these tiny amphibians. Some of their main predators, certain fish and the invasive bullfrog (Lithobates catesbeiana), require permanent water bodies to live and breed. By breeding earlier than their predators and using these ephemeral ponds, the Pacific chorus frogs may have a slightly better chance of survival.

Photo credit: Karla Uemeto

Beaver Lake (Photo by Karla Uemeto)

Stanley Park Ecology Society and students from UBC are working collaboratively to map and inventory the bio-diversity of these ephemeral ponds so that potential Pacific chorus frog habitat can be monitored and protected and hopefully help the Pacific chorus frogs’ survival in the Park as they charm our late night spring walks with their beautiful frog chorus.

– By Paul Higginson, SPES Conservation Technician