| New Jersey Division of Fish and Wildlife |
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Maps depicting potential pine snake habitat have been completed for the entire southern New Jersey Pinelands. As a next phase in this project, biologists plan to compare known locations of pine snakes with the mapped habitat to help refine mapping criteria and to help guide habitat management plans.
The New Jersey Department of Environmental Protection lists the northern pine snake as a threatened species. This listing is based on the isolation of the New Jersey population, vulnerability to illegal collecting, and loss of habitat to development pressures. The United States Department of the Interior - Fish and Wildlife Service previously listed the northern pine snake as a candidate (C2) for listing under the federal Endangered Species Act. The C2 classification denoted taxa "for which the information now in possession of the Service indicates that proposing to list the species as threatened or endangered is possibly appropriate, but for which conclusive data are not available to support proposed rules at this point." Collection for the pet trade and habitat loss were cited as possible factors in local population declines that may warrant listing by the Service.
While the general distribution and habitat associations of northern pine snakes in New Jersey have been known for some time, only recently have researchers begun to investigate their more specific habitat requirements (Burger and Zappalorti 1989, 1988, 1986, Burger et. al. 1988, Zappalorti and Burger 1986, Zappalorti et. al. 1983). These studies have generally established that habitats required by P. m. melanoleucus in New Jersey are provided primarily within dry pine-oak forest types growing on very infertile sandy soils such as Lakehurst or Lakewood sands (Burger and Zappalorti 1988, 1989). Within these generalized habitats, pine snakes select open sandy clearings with little ground cover for nesting. Summer den sites are also typically located in clearings near fallen logs. Winter hibernacula are located in nearby areas providing more vegetation cover and leaf litter (Burger et. al. 1988, Burger and Zappalorti 1986). The greater spatial frequency and temporal persistence of clearings within sandy, infertile soils may partially account for association of pine snakes with these soils. Soil texture may also be important because pine snakes are among the only snakes known to excavate their own hibernacula and summer dens.
The information provided by these studies provides a basis for beginning to map potential northern pine snake habitat by overlaying maps of suitable soils with maps of suitable vegetation cover. Mapping the location and extent of potential habitat is a critical step in the development of a conservation plan for the northern pine snake in New Jersey. Maps depicting suitable habitat will provide a valuable tool for directing pine snake surveys. An understanding of available habitat is also needed to identify areas that may be depleted or unoccupied because specific critical habitat components such as hibernacula or nesting sites are absent or because of over-collecting. When these areas are identified, biologists can experiment with applying management techniques such as provision of artificial hibernacula, prescribed burning, etc. Information on the location of potential pine snake habitat will also assist permitting agencies such as the Pinelands Commission and the Land Use Regulation Program in the review of development permit applications.
The availability of land cover (vegetation) and soils coverages in digital Geographical InformationSystem (GIS) format provided us with the ability to create maps of suitable habitat by combining these data layers following specific criteria. Digitally mapped vegetation and soils information is available for New Jersey through the Integrated Terrain Unit (ITU) maps prepared by the New Jersey Department of Environmental Protection (NJDEP) - Bureau of Geographic Information and Analysis (BGIA). ITU maps comprise a series of digital maps that integrate the separate layers of land use/land cover, soils, geology, and flood prone areas into one seamless, sliverless digital coverage in the GIS.
Given the association of pine snakes with pine-oak forests we ranked as primary all polygons classified in the ITU land cover classification as coniferous forested uplands (>75% coniferous forest) and all areas mapped as mixed coniferous/deciduous forested uplands (>50% 75% coniferous trees). Because pine snakes also occasionally use oak-pine forests and other dry upland habitats such as the pine plains areas, we ranked as secondary all polygons mapped on ITU maps as mixed deciduous/coniferous forest (>25% <50%) or as coniferous shrubland (brush cover >25%, composed of >75% coniferous species) or mixed shrublands (brush cover >25% <75% of either coniferous or deciduous species). All remaining polygons of various non-preferred vegetation types were ranked as not suitable and eliminated from inclusion in areas mapped as pine snake habitat.
The Lakewood and Lakehurst soils found to be preferred by pine snakes (Burger and Zappalorti 1988) are characterized as highly leached, sandy, extremely infertile soils known as "sugar sands." Lakewood soils occupy higher upland portions of drainages. Lakehurst soils occupy lower areas with a fluctuating water table that typically reaches the subsoil in late winter (Markley 1979). Based on the association of northern pine snakes with these soils, we ranked them as primary. We also included Evesboro sands among primary soils because this series shares several important characteristics with Lakewood soils (sandy, xeric, excessively drained, acidic, very infertile). Together these three soils comprise the "Lakehurst - Lakewood - Evesboro association" (USDA 1971). Evesboro sands typically support a pine-oak cover, which provides the most widely used habitat for pine snakes. Further, known concentrations of northern pine snakes (e.g. in southeastern Cumberland County) occur on areas of Evesboro soils (R.T. Zappalorti pers. com. 1991). Notably, Evesboro soils are not common in the areas where published studies describing pine snake habitat associations were carried out. This may explain the lack of reference to Evesboro soils within areas of preferred habitat.
We ranked as secondary soils a group of sands and loamy sands having characteristics similar to the Lakewood, Lakehurst and Evesboro series. Secondary soils included Klej sands, Klej loamy sands, Hammonton loamy sands, Woodmansie sands, and abandoned sand mines. These soils also often support a pine-oak forest cover. All remaining polygons of various non-preferred soil types were ranked as tertiary.
Based on their preference for a pine dominated cover growing on Lakewood-Lakehurst-Evesboro soils we ranked polygons created by the overlap of primary vegetation with primary soil types as the most suitable (preferred) pine snake habitat (1-A). However, because we suspect that habitat suitability of a parcel is enhanced by proximity to preferred habitat, inclusion and classification of other soils-vegetation combinations depended on the classification of adjacent polygons. This scheme for classification of remaining polygons attributes slightly greater importance to vegetation than to soils.
For polygons created by the overlap of primary cover types with secondary soils we assigned habitat suitability based on contiguity with 1-A parcels. Those polygons that were adjacent to 1-A habitat were also ranked as preferred (1-B) habitat. Those polygons that were not contiguous with 1-A habitat were ranked as suitable habitat (#2).
Similar "contiguity analysis" was performed for polygons created from the overlap of secondary vegetation with primary soils and where primary vegetation overlapped with tertiary soils. These areas were considered suitable when polygons were contiguous with areas of 1-A or 1-B habitat. When polygons were isolated from areas of primary habitat they were excluded. Areas where secondary vegetation overlapped with secondary soils were considered unsuitable whether or not they were contiguous with primary habitat.
Application of the described habitat mapping criteria and procedures resulted in mapping a total of 12,422.62 ha in the five counties as potential northern pine snake habitat. This represents approximately 2.54% of the total land area represented by the five counties.
Most of the mapped potential habitat occurred in scattered pockets in all of the counites. The only large areas of contiguous habitat occurred in Cumberland County. A relatively large area of "preferred" habitat was mapped in the western part of the county just west of the Manumuskin River. Several clusters of nearly contiguous habitat were mapped along both sides of the Maurice River. The five habitat categories we mapped should not be taken as an ordered ranking of habitat potential except for the distinction between "preferred" and "suitable" habitat. While we suspect that these five habitat categories may differ in their overall potential suitability, there is insufficient information from studies performed thus far to characterize their relative suitability. We elected to maintain the differentiation so map users can ascertain the reason that a particular area was included as mapped potential habitat and to illustrate the spatial distribution and relationship of the inclusion criteria.
Given additional criteria with which to define suitable habitat, further refinement in the classification of habitat suitability within these areas may be possible using existing ITU coverages. For example, landscape-scale variables such as minimum habitat patch size and distance between habitat patches should be examined and included in future refinements of habitat maps. Additional information not currently included on ITU mapping, but possibly available in GIS format, could also be used to further refine habitat suitability classifications. Locations of open sandy areas essential for nesting and denning could be superimposed on the habitat maps to detect the most highly suitable habitats and/or to modify the existing classifications. Using digitized aerial photography or other remote sensing coverages, we may be able to use GIS to perform this analysis.
Ground-proofing of ITU land cover classifications or use of other more accurate vegetation coverages may also result in reclassification of some habitat areas. Preliminary checking suggested that some areas of oak-pine forests may be misclassified as mixed coniferous/deciduous (pine-oak) on ITU maps. Consequently, many areas currently mapped as preferred (1A or 1B) habitat possibly should be mapped as suitable (2, 3 or 4). If this problem of land cover classification is pervasive, then the current habitat mapping would tend to "over-include" and/or "over-classify" suitable habitat.
There are few confirmed occurrences of northern pine snakes in this five-county area. We have not yet compared the distribution of occurrences with our habitat mapping. In future phases of this project, we plan to assess the correspondence between mapped habitat and pine snake distribution. Comparison of currently known pine snake occurrences with mapped habitat is likely to produce valuable insights that will help refine mapping criteria and also direct future field surveys. Caution will be necessary in this examination because Natural Heritage occurrences include imprecise and occasionally inaccurate location information. A further test of the maps and the habitat classification will also include directed field surveys of potentially suitable habitat. We are currently examining techniques that could be applied to quickly assess the presence/absence of pine snakes in a particular area.
Burger, J. and R.T. Zappalorti. 1988. Habitat use in free-ranging pine snakes (Pituophis melanoleucus) in New Jersey Pine Barrens. Herpetologica 44(1): 48-55.
Burger, J. and R.T. Zappalorti. 1986. Nest site selection by pine snakes (Pituophis melanoleucus) in the New Jersey Pine Barrens. Copeia 1986(1): 116-121.
Burger, J., R.T. Zappalorti, M. Gochfeld, W.I. Boarman, M. Ca-frey, V. Doig, S.D. Garber, B. Lauro, M. Mikovsky, C. Safina, and J. Saliva. 1988. Hibernacula and summer den sites of pine snakes (Pituophis melanoleucus) in the New Jersey Pine Barrens. J. Herpetol. 22(4):425-433.
Connant, Roger. 1975. A field guide to reptiles and amphibians of eastern and central North America. 2nd ed. Houghton Mifflin, Boston, MA. 429 pp.
Jenkins, C.D. and J. Smith. 1995. Delineating northern pine snake (Pituophis m. melanoleucus) habitat using Integrated Terrain Unit mapping: Burlington county pilot project. unpubl. report. New Jersey Department of Environmental Protection, Division of Fish, Game and Wildlife - Endangered and Nongame Species Program. 9 pp.
Markley, Marco L. 1979. Soil series of the Pine Barrens. pp. 81-93 in R.T.T. Forman, ed. Pine Barrens: ecosystem and landscape. Academic Press, New York, N.Y. 601 pp.
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Zappalorti, R.T., and J. Burger. 1986. The importance of man-made habitats to pine snakes. Environ. Cons. 12:358-361. Zappalorti, R.T., E.W. Johnson and Z. Lezcyznaki. 1983. The ecology of the northern pine snake (Pituophis m. melanoleucus) in southern New Jersey with special notes on habitat and nesting behavior. Bull. Chicago Herpetol. Soc. 18:57-72.
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