Summer Food of Chrysemys picta marginata, in Chautauqua Lake, New York

Abstract

N INETY specimens of the central painted turtle, Chrysemys picta marginata (Agassiz), were captured during the period from August 17 to 29, 1941, in three trap nets of the New York Conservation Department, located just north of Stow and at Prendergast Point, Chautauqua Lake, Chautauqua County, New York. The nets were set in water from 5 to 8 feet deep over weed beds consisting largely of waterweed, Anacharis canadensis, yellow water lily, Nuphar variegatum, and several species of Potamogeton. These nets were lifted and reset daily at 8 to 10 A.M. The turtles were killed immediately and after the plastrons were removed they were preserved in 10 per cent formalin. All 90 specimens were adults (62 males and 28 females) and ranged in length of carapace from 106 to 175 mm., with a mean of 135.6 (standard deviation 14.7). The stomachs of 76 (55 males and 21 females) contained food, while 14 were empty. Each stomach was considered as a unit in the estimates of the percentage by volume occupied by each food item. An exploratory attempt at estimating the relative volume of the different organisms in the intestines indicated that large errors would result because of more rapid digestion of certain animal tissues, such as large soft-bodied insects. Furthermore, since no organisms were found in the intestines which were not found in at least one of the stomachs, only the stomach contents were considered. These data on stomach contents are analyzed in Table I. They supplement the studies of Surface (1908), Pearse, Lepkovsky and Hintze (1925), and Lagler (1941), made in Pennsylvania, Wisconsin, and Michigan on Chrysemys picta marginata, C. picta picta, C. picta belli, or intergrades of these subspecies. When percentage by volume is considered, the food items were about equally divided between plants and animals. However, 15 more stomachs contained animal material than plants, and only one of the 76 stomachs held no animal food. Of the animals eaten, snails were most abundant (16 per cent). The most common species were Amnicola limosa, Physa heterostropha, Valvata tricarinata, and Heliosoma campanulatus. An occasional snail was undoubtedly engulfed incidentally with plants, but in many stomachs the snails occupied a much greater volume than the plants. Even when plants were present, they were usually separated from the snails in a manner which suggested that they were probably eaten at different times. About 14 per cent of the volume was fishes. Of the four individual game and pan fishes that were eaten, three were yellow perch, Perca flavescens, and one was a young largemouth bass, Huro salmoides. These were swallowed whole. Two of the three forage fish taken were the spottail shiner, Notropis h. hudsonius, while the third was also a cyprinid. Considerable fish carrion was engulfed and was easily recognized in the stomach by the semi-solid irregular mixture of flesh and bone. Insects occupied 11.6 per cent by volume. The only three