Annual Reproductive Potential, Diet, and Growth of the Map Turtle, Graptemys Geographica (Le Sueur)) in a Missouri Stream
The annual reproductive potential, diet, and growth of the common map turtle (Graptemys geographica) was studied from April 1988 through June 1988 in the Niangua River, Dallas County, Missouri. The examination of reproductive tracts from 18 females indicate that two-thirds laid two clutches of eggs annually and one-third laid three. The average clutch size is 10.1. The annual reproductive potential is 23.3. Age and minimum size at maturity are tentatively estimated at 3 years, 60mm plastron length for males, and 9-10 years, 170-180mm plastron length for females. Adaptive significance of body size and clutch size is discussed. Quantitative analysis of gut contents of 32 adult specimens indicate that Graptemys geographica is a carnivore specializing on mollusks; mollusks made up 94.1% by volume of all the food items eaten. Growth rates were determined from growth rings of the right abdominal plastral lamina. Limited data indicate that growth is most rapid in the season of hatching, thereafter growth becomes profressively slower each year.
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