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Ministry of Environment

Key to B.C. Frogs and Toads

Tailed Frog (Ascaphus truei)

How to use the key:

Dichotomous keys are very commonly used in biology – you may have seen one before. Dichotomous means two-branched, and these keys are a useful way to break down an identification process into a number of simple steps. There are paired descriptions of different traits, each numbered. For each pair (beginning at no. 1), click the option (a) or (b) that best fits your animal, and go to the numbered characteristic given by that option. Choose the best option again, and so on until you come to a species. Click on the name to see the species description, and see whether the description fits what you saw. If it doesn’t, try the key again, especially if you were not sure of one or more of your choices.

For example, suppose I have seen a small frog in the Lower Mainland. I look at its eyes and see that it has horizontal pupils, so I click on 1(b). This directs me to no. 3; I choose (b) again because my frog has smooth skin. In no. 4 I choose (a) because my frog has a dark eye stripe and sticky pads on its toes. I discover that I have seen a Pacific Chorus Frog (and a cute little creature it was, too).


Illustrations taken from: Green, D.W. and R.W. Campbell. 1984. The Amphibians of British Columbia.
British Columbia Provincial Museum, Handbook 45. Used with permission of RBCM.

1a. Pupil of eye vertical when contracted … go to 2
1b. Pupil of eye horizontal when contracted … go to 3
2a. Sharp-edged, horny spade on underside of foot, body squat and toad-like
  » Great Basin Spadefoot (Spea intermontana)
2b. No spade on sole of foot, male with tail-like copulatory organ
  » Pacific Tailed Frog (Ascaphus truei) or Rocky Mountain Tailed Frog (A. montanus)
3a. Parotoid glands and rough warts present, body squat
  » Western Toad (Anaxyrus boreas)
3b. No parotoid glands or warts present, skin smooth or with scattered tubercles … go to 4
4a. Conspicuous adhesive toe-pads present, dark eye stripe ending at shoulder
  » Pacific Chorus Frog (Pseudacris regilla)
4b. Toe-pads absent or inconspicuous … go to 5
5a. Body elongate with dark side stripes extending to groin; three dorsal stripes or series of spots also present
  » Boreal Chorus Frog (Pseudacris maculata)
5b. Dark side and dorsal stripes absent, dorsolateral folds and/or skin fold around ear membrane present … go to 6
6a. Large rounded spots with light halos present on a green or brown background, belly white, dorsolateral folds present
  » Northern Leopard Frog (Lithobates pipiens)
6b. No large, rounded spots on back … go to 7
7a. Colour green or olive green, no dark facial mask present. Adult males with deep yellow throats and ear membranes larger than diameter of eye. … go to 8
7b. Colour brown or tan, may have black, irregular spots on back, dark facial mask more or less obvious … go to 9
8a. Dorsolateral folds present
  » Green Frog (Lithobates clamitans)
8b. Dorsolateral folds absent, skin fold around ear membrane present
  » Bullfrog (Lithobates catesbeiana)
9a. Distinct, black facial mask present, no black dorsal spots, white belly, white mid-dorsal stripe may be present
  » Wood Frog (Lithobates sylvaticus)
9b. Red, orange or yellow colouration underneath, especially in older individuals, dark spots present on back, facial mask present but not intensely dark … go to 10
10a. Eye upturned, salmon colour on white background on belly and under legs, distinct dark spots on back, no green area in groin
  » Oregon Spotted Frog (Rana pretiosa) or a Columbia Spotted Frog (Rana luteiventris)
10b. Eye not upturned, yellow or red underneath; red-coloured underparts, bones of lower leg may be visible through skin, area of green in groin
  » Northern Red-legged Frog (Rana aurora)

This key is used here by permission of the Royal British Columbia Museum. It is modified from the key appearing in their handbook, The Amphibians of British Columbia by David Green and R. Wayne Campbell, which was published in 1984.

Photo © Russ Haycock. No reproduction or distribution without permission.