Population Ecology of the Lake Erie Water Snake, Nerodia sipedon insularum

摘要: Population ecology of the Lake Erie water snake, Nerodia sipedon insularum, is described based on a 5 yr capture-mark-recapture study involving 1449 captures 1247 individuals. Water snakes are widespread in island area but have declined numbers and disappeared from one within last 50 yr. estimates for adult range 25 to about 500 individuals seven islands. Snakes active late April until early October. Males caught most often during breeding season May June, while females taken more later summer. Females appear feed over longer portion than males, grow at faster rate (0.014 vs 0.012 cm/d mean growth rate) attain larger body size (82.1 62.5 cm snout-vent length). Weight gain occurs throughout restricted mid-summer males. Some reproduce annually smaller may skip opportunities reproduce. Number offspring positively correlated with female size. Comparisons data mainland populations elsewhere this species indicate that differ having sizes (mean length 10-16 greater males 13-14 females), lower rates (maximum 0.06 0.13 populations) shorter tails (by 2-5% 1-3% females). In addition, litter less strongly (r2 = 0.17 0.34-0.72 elsewhere). Differences also exist newborns newborn SVL population ranges 12% 4% populations), diet (mainland typically consume amphibians fewer fish) intensity predation (frequency stub two times populations).