Nature and science
The winter dens pine snakes left and returned to
Documented history and research · Sources compared
Decades of marked snakes showed why an apparently empty winter den could still matter. Site loyalty changed with age and could include long absences.
Following individuals across decades
Joanna Burger and Robert Zappalorti followed winter-den use from 1986 through 2012. Their 2015 analysis included 120 snakes of known age encountered at least twice. Only 23 percent always returned to the same hibernation site. Females showed greater fidelity than males, and older snakes were more likely to have changed sites. Burger and Zappalorti, hibernation-site philopatry (2015).
The denominator matters. These were repeatedly encountered individuals, not every snake in the Pines. A snake missing from a monitored den might have died or moved elsewhere. The researchers explicitly discuss that uncertainty, which prevents a simple conversion of absence into a mortality count. Burger and Zappalorti, hibernation-site philopatry (2015).
An empty den was not necessarily abandoned
A separate long-term paper followed seven hibernacula over 26 years. Some sites went unused for years, with gaps as long as a decade, before snakes occupied them again. Apparent abandonment sometimes followed intrusion by a predator. The authors argued that the long intervals made short surveys a poor guide to a den’s lasting value. Burger and colleagues, long-term hibernaculum use.
Together the studies distinguish loyalty by an individual snake from continued use of a place by a population. A den can remain valuable even as its occupants change, and an animal can return after intervening winters elsewhere. That is a conservation lesson grounded in repeated observation rather than a claim that every snake returns to one permanent underground home. Burger and colleagues, long-term hibernaculum use.
Sources and research limits
- Burger and Zappalorti, hibernation-site philopatry (2015) — Indexed full-text abstract, results and discussion read; direct PMC retrieval displayed a browser check.
- Burger and colleagues, long-term hibernaculum use — Indexed author-paper results and discussion read; hosted proof has incomplete printed bibliographic fields.
Exact den locations are unnecessary to this account. The papers share a research program and some observations; they are complementary analyses rather than two independent population censuses.