What’s that frog?

Kristina Robbins holding Oregon Spotted Frog. Photo: Isabelle Groc

American Bullfrog

Juvenile Western Toad. Photo: Isabelle Groc

Pacific Northern Tree Frog

Oregon Spotted Frog and Northern Red-legged Frog side by side. Photo: Isabelle Groc

Monica Pearson and Celia Serrano inspecting eggs in the field. Photo: Isabelle Groc.

Identifying amphibians in the Lower Mainland can be complex, but our identification guide to frogs and toads
provides useful tips and guidelines to help you identify frogs and toads in the low-elevation wetlands of the Fraser Valley. It focuses on features that will help you distinguish between similar species.

Commonly encountered native species in British Columbia are the Western Toad (Anaxyrus boreus) and the Pacific Northern Tree Frog (Pseudacris regilla), both found in a wide variety of wetland habitats and forested habitats. Tailed frogs, found in steep mountain streams, are not covered in the guide.

Native or invasive?

The first step distinguishes between introduced and native amphibian species. Introduced frogs include the American Bullfrog (Lithobates catesbeianus) and the Green Frog (Lithobates clamitans). Both are now common in the Fraser Valley.

Check the tympanum: does the frog have an obvious tympanum (ear drum) as big or bigger than the eye? If yes, then your frog is likely an invasive species, American Bullfrog or Green Frog. If no, it is likely a native species.

Identifying Western toads

Western toads are easy to recognize. Adults have stocky bodies with short legs, and tend to walk rather than hop. Their thick skin appears dry and bumpy and can range in colour from pale green to grey, dark brown, and red.

They typically have pale-coloured bellies mottled with black, and a pale coloured stripe down their backs. Their beautiful gold-flecked eyes have distinctive horizontal oval pupils. Behind each eye is a prominent oblong or kidney-shaped swelling called a parotoid gland.

Identifying Pacific Northern Tree Frogs

The Pacific Northern Tree Frog also known as the Pacific Chorus Frog is small frog, up to 5 centimetres long, and may be any colour from pale grey or tan to bronze or bright emerald green. These frogs ave a distinctive dark eye band from eye to forearm. 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.

Oregon Spotted Frog or Northern Red-legged Frog?

Those two native frogs are similar, easy to confuse, and overlap in their range. Look for the features that differentiate between the two species. For example:

– Northern Red-legged Frogs have eyes that are angled outward; Oregon Spotted Frog eyes are oriented upwards.

– Oregon Spotted Frogs generally sit in crouched position, unless preparing to jump. Red-Legged Frogs generally sit in upright position, with forearms pushing body upwards.

– Northern Red-legged Frogs have flecks/freckles rather than spots and much brighter, pink-red legs than Oregon Spotted Frogs.

– Oregon Spotted Frogs have no yellow on their sides, and the belly may be grey-white to bright red. Red-legged Frogs often have bright yellow patches on sides at the hip.

– Oregon Spotted Frogs have raised bumps on their sides and other their back as well, while Red-Legged Frogs have smooth sink on their sides and back.

– Oregon Spotted Frogs have completely webbed feet because they spend most of their time in or around water, whereas Northern Red-legged Frogs have partially webbed feet reflecting their semi-terrestrial habits.

Identification of Oregon Spotted Frog and Red-Legged Frog egg masses can be equally tricky. Tightly clustered egg masses are always produced by Oregon Spotted Frogs. However, single egg masses are more difficult to identify.

To learn more about egg mass identification and survey techniques, consult our printable guide.