Hibernation Site Philopatry in Northern Pine Snakes (Pituophis melanoleucus) in New Jersey
Northern Pine Snakes (Pituophis melanoleucus) are one of the few snakes that spend the winter in underground hibernacula that they excavate. We report the use of hibernacula by Pine Snakes from 1986 to 2012 in the New Jersey Pine Barrens. We determined whether philopatry to a specific hibernaculum varied as a function of age, sex, and location of the hibernaculum. Three hibernacula were occupied nearly continuously for 27 yr by 1 to 27 snakes each year. With known-age snakes (N = 120), captured mainly as hatchlings and 2-yr-olds, we found that 23% were always philopatric. Philopatry was related to age of last capture, sex, and capture location. Philopatry was higher for 1) females compared with males, 2) snakes at two solitary hibernacula compared with a hibernaculum complex, and 3) snakes 6 yr old or younger, compared with older snakes. Of hatchlings found hibernating, 24% used the same hibernation site the next year, and 38% were located at year 4 or later. The number of snakes that always used the same hibernation site declined with the age of last capture. Snakes that entered hibernacula as hatchlings were found more often than those that entered as 2-yr-olds. For the seven snakes that were 14 yr or older, females were found 64–86 % of the time, whereas males were found 15 to 50% of the time. Understanding the behavior and habitat requirements of snakes during different seasons is central to life-history analysis and for conserving viable populations.Abstract
Schematic of use of hibernacula by Pine Snakes in New Jersey. Shown is information known for the species, including clutch size (Burger et al., 1987) and hatching success (Burger and Zappalorti, 2011b), and new information on how hatchlings move among hibernacula, on the basis of 152 hatchlings found in the three hibernacula from 1985 to 2012. For ease of reading, snakes that die during each year are connected by a dashed line. The number that no longer return to a hibernaculum could either have moved to an unknown one, or died.
Number of known-age Pine Snakes that switched hibernacula during the period until they were last encountered. Shown is the total number of snakes by the age when last encountered as a function of whether they switched or did not, the percentage of snakes that never switched sites, and the mean number of years that snakes used the same hibernacula as a function of age of last encounter. The dashed line indicates 100% philopatry at each age of last encounter. Snakes are represented only once (at the last age they were encountered). Snakes at any age could have lived longer, but not been captured, or could still be captured.
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