Ecology 6th Edition by Charles Krebs

Exercise 3

At Point Pelee National Park in Ontario, frog surveys showed that the bullfrog (Rana catesbeiana) disappeared in 1990, and from 1990 to 1994 the green frog (Rana clamitans) has increased in numbers fourfold (Hecnar and M'Closkey 1997). Suggest three possible interpretations for these natural history observations, and indicate how you would test these hypotheses experimentally.