Literaturdatenbank
Literaturdatenbank |
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Iverson, J. B., Higgins, H., Sirulnik, A., & Griffiths, C. (1997). Local and geographic variation in the reproductive biology of the snapping turtle (chelydra serpentina). Herpetologica, 53(1), 96–117.
Added by: Sarina Wunderlich (18 Nov 2012 17:43:33 UTC) |
| Resource type: Journal Article BibTeX citation key: Iverson1997b View all bibliographic details  |
Categories: General Keywords: Fortpflanzung = reproduction, Habitat = habitat, Nordamerika = North America, Schildkröten = turtles + tortoises Creators: Griffiths, Higgins, Iverson, Sirulnik Collection: Herpetologica |
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| Abstract |
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We studied female snapping turtles at two shallow lakes on the Crescent Lake National Wildlife Refuge from 1990-1994, most intensively during the nesting seasons of 1993 and 1994. Females matured at 28-29 cm carapace length (CL), 22-23 cm plastron length (PL), 5.5- 6.5 kg body mass, and 10-12 winters of age. Nesting was recorded from 1-28 June, but in a given year season length was 13-18 days and its start may be inversely related to spring temperatures. Nesting began between 0400 and 0930 h and between 1800 and 0100 h. During the warm June of 1994, nesting was equally divided between morning and evening, but during the relatively cold June of 1993, smaller females apparently shifted predominately to evening nesting. It was not determined whether all females reproduced every year. Reproducing females produced one clutch per year of 20-73 eggs (x = 46.8) weighing 6.4-19.1 g each (x = 11.4). Egg size, clutch size, and clutch mass were each positively correlated with female size. However, relative to female body size, large females produce smaller eggs and smaller clutches, but the same total clutch mass, as small females. No differences in reproductive output were detectable between 1993 and 1994. Geographic variation in female size across the species range is significant. In temperate regions, mean female size is correlated with latitude, longitude, and elevation, with the largest females found in Nebraska and South Dakota. Females in the tropics are as large as the largest temperate females. Egg size does not vary with average female body size across populations or with latitude. Eggs in the tropics average nearly twice the mass of those in temperate regions, but relative to female body size, egg size in the tropics is not significantly different. Clutch size is positively correlated with female body size within and among populations, as well as with latitude. However, relative to body size, clutch size does not vary among temperate populations, although it is larger there than in the tropics. No trade-off between average egg size and clutch size was evident among populations. Clutch mass was correlated with female body size and varied geographically along with body size. However, relative to body size, there was no significant geographic variation in clutch mass. Variation in growth rate to maturity among temperate populations suggests that at northern, western, and high elevation locations a greater selective advantage accrues from maturing at a larger body size than from maturing at an earlier age, perhaps because of the strong body size-clutch size correlation.
Added by: Sarina Wunderlich |