PREDATION BY GRASS SNAKES (NATRIX NATRIX) AT A SITE IN SOUTHERN ENGLAND

The prey and feeding frequency in free-living grass snakes was studied during 1993 and 1994 at a site in southern England. Individual snakes and common toads were recognized using PIT tags and a small number of adult snakes were radio-tracked over long periods to determine predat ion rates. Grass snakes fed, almost exclusively, on common toads (adul t, juvenile, and tadpoles). A positive correlation was found between p rey size and snake size. Large snakes did not appear to prey upon smal l toads, although clearly capable of doing so. Male and female ate lar ge meals (toads) approximately every 20 days between May and September , with females fasting for a period of about 45 days during gestation and egg-laying. After allowing for differences in the number and size of toads predated by male and female snakes, the mean amount of food c onsumed per day was estimated to be 2.3% and 1.6% of body weight.