SOURCES OF DATA -- AMPHIBIAN AND REPTILE DISTRIBUTION

Vertebrate Characterization Abstracts (VCA) Data

     VCA data, acquired from states' natural heritage programs, are the
foundation for Gap Analysis range data for amphibians and reptiles.  These
abstracts make up all of the source data for Connecticut, Rhode Island, and
Massachusetts. Range data for Vermont and New Hampshire also incorporate VCA
records, but have supplemental data described below.  No VCA data are included
for Maine, which is being handled separately at The University of Maine.  VCA
data consist of species-by-county occurrences.  The source of VCA data is
variable, from a mix of literature citations.  These VCA databases vary in size
with the Connecticut, Massachusetts, Rhode Island, and Vermont databases
containing 51, 461, 141, and 355 herptile records, respectively.  By-county
occurrences were translated to by-hexagon occurrences according to a single
decision rule:  If any portion of a hexagon fell within a county, the hexagon
was coded as "species present."  

New Hampshire Reptile and Amphibian Atlas Data

     New Hampshire Atlas data supplement our distributional data for New
Hampshire.  This atlas database, acquired with permission for its use from
Dr. Jim Taylor at The University of New Hampshire, consists of 2996 by-town
occurrence records.  1078 of these are vouchered records from literature
sources, from known experts, or from reports accompanied by photographs or
specimens, which have been verified by Dr. Taylor.  The remainder of the
records represent unvouchered sightings that Dr. Taylor accepted as probable
locations.  Amphibian occurrence records account for 2066 of the total, while
reptiles make up the remaining 930.  Vouchered records total 745 for amphibians
and 333 for reptiles.  
     We generalized the by-town occurrence records taken from the atlas project
to hexagon-level occurrence records.  Counties and hexagons received a
species-present code when any portion of a species-present town polygon
fell within their boundaries. 

Vermont Reptile and Amphibian Atlas Data

     Reptile and amphibian distributions for Vermont also include atlas data
supplied by Jim Andrews at Middlebury College in Middlebury, Vermont.  Andrews
has distributional data on amphibians and reptiles from museum records and
from field observations.  His data had been compiled by town and represented a
draft version of a Vermont Atlas of Amphibians and Reptile (to be published by
Vermont Nature Conservancy).  He delivered these data in the form of 1698
by-hexagon occurrences (1086 and 612 records for amphibians and reptiles,
respectively).  At our request, Andrews coded hexagons similar to the breeding
bird atlas data in that species-by- hexagon occurrences were coded as known
(confirmed), probable, or possible.