Status Assessments of the Southern Hog-Nosed Snake, Florida Pinesnake, Short-Tailed Kingsnake, and Eastern Diamond-Backed Rattlesnake in Florida
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Status Assessments of the Southern Hog-nosed Snake, Florida Pinesnake, Short-tailed Kingsnake, and Eastern Diamond-backed Rattlesnake in Florida Final Report September 2016 Kevin M. Enge, Jonathan D. Mays, Ryan Butryn, and E. Pierson Hill Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute, Wildlife Research Section, Lovett E. Williams Jr. Wildlife Research Laboratory, 1105 SW Williston Road, Gainesville, Florida Table of Contents EXECUTIVE SUMMARY............................................................................................................. 4 INTRODUCTION........................................................................................................................... 5 Objectives ................................................................................................................................... 6 Southern Hog-nosed Snake ......................................................................................................... 6 Short-tailed Kingsnake ................................................................................................................ 6 Florida Pinesnake ........................................................................................................................ 7 Eastern Diamond-backed Rattlesnake ........................................................................................ 8 METHODS ..................................................................................................................................... 9 Locality Records ......................................................................................................................... 9 Surveys ...................................................................................................................................... 10 Habitat Modeling ...................................................................................................................... 12 RESULTS ..................................................................................................................................... 15 Locality Records ....................................................................................................................... 15 Road Surveys ............................................................................................................................ 17 Drift-fence Surveys ................................................................................................................... 17 Potential Habitat Models........................................................................................................... 17 DISCUSSION ............................................................................................................................... 20 Southern Hog-nosed Snake ....................................................................................................... 20 Distribution and Habitat ..................................................................................................................... 20 Upland Snake Status Assessments 2 Threats ................................................................................................................................................ 21 Short-tailed Kingsnake .............................................................................................................. 23 Distribution and Habitat ..................................................................................................................... 23 Threats ................................................................................................................................................ 24 Florida Pinesnake ...................................................................................................................... 25 Distribution and Habitat ..................................................................................................................... 25 Threats ................................................................................................................................................ 26 Eastern Diamond-backed Rattlesnake ...................................................................................... 27 Distribution and Habitat ..................................................................................................................... 27 Threats ................................................................................................................................................ 30 ACKNOWLEDGMENTS ............................................................................................................ 32 LITERATURE CITED ................................................................................................................. 33 FIGURES ...................................................................................................................................... 41 TABLES........................................................................................................................................ 58 PHOTOS ....................................................................................................................................... 83 APPENDIX I ................................................................................................................................. 91 Upland Snake Status Assessments 3 EXECUTIVE SUMMARY We conducted Florida status assessments for the southern hog-nosed snake (Heterodon simus), short-tailed kingsnake (Lampropeltis extenuata), Florida pinesnake (Pituophis melanoleucus mugitus), and eastern diamond-backed rattlesnake (Crotalus adamanteus), all of which have been petitioned for federal listing as threatened. By perusing museum collections and various databases, conducting drift-fence and road surveys, and soliciting sightings via webpages, we compiled recent records (2000−2016) for the species. We compiled 183 recent records of the southern hog-nosed snake from 21 counties and 37 conservation lands (53% of records), 91 recent records of the short-tailed kingsnake from 11 counties and 18 conservation lands (70% of records), 451 recent records of the pinesnake from 45 counties and 97 conservation lands (68% of records), and 1,663 recent records of the diamond-backed rattlesnake from 66 counties and 345 conservation lands (78% of records). We used many of these records to create potential habitat models using MaxEnt, which provided the acreage of potential habitat by county and conservation land. The three nonvenomous species are primarily restricted to xeric upland habitats, particularly sandhill, whereas the rattlesnake is more of a habitat generalist. All species except the short-tailed kingsnake are found in some ruderal habitats, such as old fields and semi-improved pastures. Ocala National Forest and Withlacoochee State Forest have the most high-quality potential habitat in the peninsula for all four species, whereas Eglin Air Force Base has most high-quality habitat in the panhandle for the three species that occur there. The proportion of high-quality potential habitat within each species’ range that occurs on conservation lands was 28% for the southern hog-nosed snake, 43% for the short-tailed kingsnake, 44% for the pinesnake, and 35% for the diamond-backed rattlesnake. The southern hog-nosed snake is still locally common on the Brooksville Ridge, uplands along the Suwannee River, and on Eglin Air Force Base, but populations are apparently scarce or extirpated in counties at the southern extent of its range. Little is known regarding the fossorial short-tailed kingsnake, but populations appear to remain abundant on the Brooksville Ridge and in Ocala National Forest, but only one recent record exists from the southern half of its range. The pinesnake still occurs over much of its historical range but has always been uncommon or absent from the southern peninsula because of unsuitable habitat. Little information is available on abundance, but we trapped 31 pinesnakes along drift fences. Recent records are lacking from counties along the northern Atlantic Coast. The diamond-backed rattlesnake still occurs throughout its historical range, including parts of the Florida Keys, but populations have been extirpated from some large urban areas, particularly in the southeastern peninsula. Primary threats to these species are habitat loss, habitat degradation (e.g., fire suppression and silviculture), and road mortality. Sufficient habitat is present on public lands for long-term conservation of all four species, provided habitats are properly managed (e.g., prescribed burning of pinelands) and road construction is limited. However, >55% of high-quality habitat identified for all four species occurs on private land, and this figure is >70% for the southern hog-nosed snake. Populations of the endemic short-tailed kingsnake apparently persist in subdivisions with native ground cover and in fire-suppressed sandhill habitat, but the paucity of recent records from highly fragmented habitats (mostly scrub) in the southern half of its range is cause for concern. Upland Snake Status Assessments 4 INTRODUCTION The southern hog-nosed snake (Heterodon simus), short-tailed kingsnake (Lampropeltis extenuata), Florida pinesnake (Pituophis melanoleucus mugitus), and eastern diamond-backed rattlesnake (Crotalus adamanteus) are upland snake species whose populations are suspected to be declining in Florida (Timmerman 1994, Tuberville