Bullsnakes and Their Control on a Nebraska Wildlife Refuge

long been known as an important breeding and resting ground for wild ducks. These lakes vary from small temporary potholes and ponds to large permanent lakes of two or three square miles. The usual depth is from one to four feet, but a few are much deeper. There are extensive bullrush marshes and good hay meadows around most of them (P1. 12, C) Studies by the U. S. Fish and Wildlife Service revealed that ducks nesting on Crescent Lake Refuge were subjected to heavy predation by bullsnakes (Pituophis sayi). The reptiles were reducing the nesting success to far below that on other comparable refuges in the United States (Kalmbach, N. Amer. Wildl. Conf. Trans., 4: 591-604, 1939). Of 274 duck nests under observation in 1938, bullsnakes completely destroyed 114 (42%) besides taking some eggs from many others. On 16 occasions they were actually caught in the act of swallowing duck eggs (Pl. 13, C). Accordingly, studies in 1939, 1940, and 1942 included experiments to control these reptiles. Various methods, including pitfalls, poisoned eggs, and glass eggs, were tested but the only successful means was by the live trap here described. NATURAL HISTORY OF BULLSNAKES