Feeding habits of the northern water snake, Natrix sipedon sipedon Linnaeus

TitleFeeding habits of the northern water snake, Natrix sipedon sipedon Linnaeus
Publication TypeJournal Article
Year of Publication1958
AuthorsBrown E.E
JournalZoologica
Volume43
Issue2
Pagination55-71
KeywordsVERTEBRATES
Abstract

Contents of the stomachs of 207 New York and Michigan water snakes (Natrix sipedon sipedon) were tabulated according to frequencies, volume and habitats of collection. Fishes comprised 79 per cent of the food items taken (with minnows, darters, sculpin and suckers predominant), amphibians 21 per cent. Food is listed for 73 young snakes of the first year. Minnows, darters and amphibians together comprised 80 per cent of tbe food items captured. Capture of prey involves so-called groping and direct attack methods. Prey may be taken in relatively deep water. Prey may, or may not, be brought ashore for swallowing. Food organisms were swallowed headfirst in 80 per cent of 200 cases. This snake appears to be well fitted for either diurnal or nocturnal feeding activity, apparently being more diurnal in cooler habitats, more nocturnal in warmer ones. It seems to be most active at temperatures between 70 and 80 F. Food amounting to 40 per cent of the weight of the snake may be taken at one time, but a meal is usually considerably smaller. Two hundred and seven stomachs in nature contained 1 to 7 food items, but averaged only 1.2 items per stomach. Examples are presented of amounts of food taken experimentally by good feeders during a period of a number of weeks. Four first-year specimens consumed food averaging 61 per cent of the original weight of tbe snake per week, or 247 per cent per month. Corresponding figures for 4 adult snakes were 43 per cent of the original weight of the snake per week or 174 per cent per month. Increases in gross length during this experimental feeding period averaged about the same for first-year specimens as for tbe fifth and sixth year adults: 7 mm. per week or 28 mm. per month. Increase in gross weight was much more rapid in tbe adults than in the young. However, weight increase in terms of percentage increase over tbe original weight of the snake was approximately twice as rapid in tbe young. Young individuals consumed about 3 grams of food for each gram of gain in weight. Tbe adults consumed half again as much (4.5 grams) per gram of gain in weight. Moderate meals required about 2 days for gastric digestion to be completed at midsummer temperatures. Post-gastric digestion required somewhat less time. In the central New York region June, July and August were tbe months of heavy feeding by snakes in nature, with much more moderate food consumption during late April, May and September.