Population density varies with habitat quality, but studies linking density to particular habitat characteristics are lacking. In some areas, population densities have declined steadily over the past several decades (Schwartz and Schwartz, 1974; Stickel, 1978). Some investigators attribute the decline to increasing habitat fragmentation and obstacles (e.g., highways) that prevent females from reaching or returning from appropriate nesting areas (Stickel, 1978; DeGraaf and Rudis, 1983).
Sexual maturity is attained at about 4 or 5 years (Ernst and Barbour, 1972) to 5 to 10 years of age (Minton, 1972, cited in DeGraaf and Rudis, 1983). One to four clutches may be laid per year, depending on latitude (Oliver, 1955, cited in Moll, 1979; Smith, 1961). Clutch size ranges from three to eight eggs, averaging three to four in some areas (Congdon and Gibbons, 1985; Ernst and Barbour, 1972; Smith, 1956). Juveniles generally comprise a small proportion of box turtle populations, for example, 18 to 25 percent in one population in Missouri (Schwartz and Schwartz, 1974) and 10 percent in a study in Maryland (Stickel, 1950). Some individual box turtles may live over 100 years (Graham and Hutchinson, 1969, cited in DeGraaf and Rudis, 1983; Oliver, 1955, cited in Auffenberg and Iverson, 1979).
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