Population ecology of the northern pinesnake, Pituophis melanoleucus, in New Jersey

Dane C. Ward

doi:10.17918/etd-7391

Estimating local population density for threatened and endangered species is critical for successful conservation and management. For a cryptic and fossorial species such as the northern pinesnake (Pituophis melanoleucus), this problem is not easily resolved with classic mark-recapture studies because of low detection probabilities, low recapture rates, and unknown geographic distributions of local populations. Pituophis melanoleucus is a threatened species in New Jersey where the current population size and local population densities remain unknown. Because P. melanoleucus demonstrates long-term site fidelity for communal hibernacula, I used census data from select hibernacula along with spatial ecology data to estimate local P. melanoleucus density at Warren Grove Gunnery Range, Burlington County, New Jersey. I used maximum distance dispersed from hibernaculum (Max-D) to create idealized concentric circles around each hibernaculum, delimited the potential area that could be used by each snake, and estimated the density per hectare. Adult Max-D ranged from 386 m to 2765 m (x̄ = 1535 m ±95 m) with no observed differences between sexes. Local adult density ranged from 0.003 snakes/ha to 0.008 snakes/ha (x̄ = 0.005/ha) among hibernacula. Total population density (adults, sub-adults, and neonates) ranged from 0.004/ha to 0.022/ha (x̄ = 0.011 /ha). There was a positive relationship (r^2 = 0.63) between the maximum distance egressed and the number of adult snakes occupying each hibernacula. I determined that P. melanoleucus densities were below one snake per hectare. I calculated that 33,836.2 ha (14%) of former pinesnake habitat (236,281.8 ha) had been lost to development from 1986 to 2007 and that 20,203.5 ha (59.7%) of habitat loss occurred within core habitat patches. I considered intact natural forest areas as core habitat and only used patches greater than 200 ha in my analysis. I considered patches less than 200 ha unable to sustain a long-term viable P. melanoleucus population and assumed these habitat sinks (< 200 ha) supported fewer snakes than larger patches (> 200 ha). I estimated that the current available habitat (202,445.6 ha) supported between 810 and 4454 P. melanoleucus. Although I set 200 ha as the habitat patch size threshold, smaller patches, provided they are not degraded, still have ecological value to buffer larger patches and for snakes to "island hop" to larger patches. In addition, I measured the movement rate (m/s) of adult pinesnakes across three road substrate types (asphalt, concrete, sand) to determine resistance values between habitat patches. Adults traveled faster on sand (x̄ = 0.12 m/s) compared to asphalt (x̄ = 0.09 m/s) or concrete (x̄ = 0.03 m/s). My metric for estimating population size, that incorporated road resistance values between habitat patches will be important for determining where to maintain or establish landscape conservation areas for this declining threatened species in New Jersey.

Population ecology of the northern pinesnake, Pituophis melanoleucus, in New Jersey

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Population ecology of the northern pinesnake, Pituophis melanoleucus, in New Jersey

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