Introduced species of the month

  • May. 8, 2006 4:00 p.m.

Pacific Tree Frog (Hyla regilla)
Red-legged Frog (Rana aurora)

In just over 35 years, the Pacific tree frog has become widespread on Haida Gwaii. Two frogs were collected from the Port Coquitlam area and released into Beaven’s Pond, near Port Clements, in the summer of 1964. Although it was believed, at the time that two species were introduced, one type was transported as tadpoles, and the other was a pair of adults. Since this time, it was assumed that these two “species” were actually the same but at different stages of their life cycle. However, in 2002, a second species, the red-legged frog (Rana aurora) was identified in several locations around Port Clements and Juskatla.
By 1966 frogs had spread as far as Woodpile Creek and Kumdis slough and in 1967, frogs were observed in Tlell, Juskatla, and Mayer Lake. Around 1970, frogs were taken from Beaven’s Pond to Sandspit where populations continued to expand. Prior to this, in 1933, six frogs were released at Swan Lake, on the way to Copper Bay. It is not known which of these introductions populated the area, but by the 1980s they were widespread on Northern Moresby Island. There has been limited information gathered on the distribution of amphibians on Haida Gwaii and no systematic surveys have been conducted.
The impact of the tree frog hasn’t been studied and there is little understanding of the effects of introduced frogs. They may be competing directly or indirectly with the native toad as well as with riparian or aquatic invertebrate populations. Further study is required to determine abundance and distribution of amphibian species. There have been observations of large tadpoles and adult frogs that could be green frog or bull frog. These have been seen at Mayer Lake, Cumshewa Inlet and Pacofi Inlet but have not been verified. The determination of species presence, the extent of their range and population status is important information that is not currently available for any amphibian species.

This article was submitted by The Research Group on Introduced Species, as part of a series highlighting the history and status of introduced animals on the islands. For more info, contact Barb Rowsell, Program Manager, RGIS, Box 867, Queen Charlotte, BC, V0T 1S0,;; or Barb Johnston, Terrestrial Ecologist, Gwaii Haanas, Box 37, Queen Charlotte, BC, V0T 1S0.