Virginia’s Amphibians: Status, Threats and Conservation

Virginia’s diverse environments support 84 amphibian species (anurans and caudates), making it the third highest state in terms of species richness. However, the Commonwealth matches the global trend in declining amphibian populations with over one-third of its amphibian species in conservation need. The Species of Greatest Conservation Need included in the most recent Virginia Wildlife Action Plan cut across amphibian families and ecoregions. It is challenging to ascertain the exact cause of most of the population declines. In one degree or another, all of the global threats to amphibians exist within Virginia’s borders. While an active research program on amphibians exists in the Commonwealth, there are an abundance of data deficient topics where research can help detect and inform the cause of these declines, as well as evaluate management efforts. On a positive note, there are a large number of existing conservation efforts being undertaken across Virginia that directly or indirectly benefit local amphibians. “These foal and loathsome animals are abhorrent because of their cold body, pale color, cartilaginous skeleton, filthy skin, fierce aspect, calculating eye, offensive smell, harsh voice, squalid habitation, and terrible venom; and so their Creator has not exerted his powers to make many of them.” Carolus Linnaeus 1758 INTRODUCTION Some people would likely still describe amphibians as Linnaeus once did, but today we know they are a diverse class of vertebrates, many in number and integral components of ecosystems (Hocking and Babbitt 2014). They are ecologically recognized for their energy efficiency and nutrient cycling. Amphibians serve as prey to many different organisms and as predators consuming vast numbers of insects, including those species that are vectors for diseases or cause agricultural damage. 1 Corresponding author: jennifer.sevin@gmail.com Virginia Journal of Science, Vol. 66, No. 3, 2015 https://digitalcommons.odu.edu/vjs/vol66/iss3 278 VIRGINIA JOURNAL OF SCIENCE People have, and continue, to use amphibians for a variety of purposes, including as food, pets and cultural icons. Additionally, the applications of amphibians for human health are wide ranging, including serving as important research subjects and for the treatment of all kinds of ailments (Burggren and Warburton 2007, O'Rourke 2007, Hocking and Babbitt 2014). Amphibians are the earliest terrestrial Tetrapods, first appearing during the late Devonian Period about 360 million years ago. Their physiological, biological, behavioral and ecological adaptations have enabled them to inhabit every continent except Antarctica. Over 7,400 species of amphibians have been described globally across three orders: Anura (frogs and toads), Caudata (salamanders and newts) and Gymnophiona (caecilians) (refer to www.amhibiaweb.org for the most up to date species list). Amphibians are ectothermic organisms mostly known for their permeable skin, complex life cycles, limited mobility, and strong site fidelity. They have anamniotic (jelly-like) eggs with dozens of reproductive modes, ranging from internal to external fertilization, and small clutches of guarded eggs on land to thousands of eggs deposited in standing water. The same characteristics which make amphibians unique are the very attributes which also make them susceptible to changes in the environment. For these reasons, amphibians are considered good indicator species of ecosystem health (Blaustein et al. 1994, Welsh and Droege 2001, Davic and Welsh 2004, Hopkins 2007). However, if the responses of these organisms are truly indicative of what is happening in the environment, there is great cause for continued concern. Over the past few decades, amphibian populations across the globe have experienced declines, local extirpations and species extinctions (Blaustein and Wake 1990, Gibbons et al. 2000, Stuart et al. 2004, Lannoo 2005, Bishop et al. 2012). Amphibians are now considered one of the most threatened groups of organisms globally, with approximately 40% of species threatened (Stuart et al. 2004, Bishop et al. 2012). This paper explores the status of amphibian populations across Virginia, their potential threats, and actions taken to conserve them. VIRGINIA’S AMPHIBIANS Noted for their loud calls, the first printed record of frogs in Virginia is from Robert Beverley’s The History and Present State of Virginia in 1705 (Mitchell 2013). However, it was not until the early 1900s when Emmet Reid Dunn conducted his seminal work on Virginia’s amphibians that the true diversity was realized (Mitchell 2013). Even today, studies using genetic techniques are describing new species (Tilley et al. 2008, Fienberg et al. 2014). There are currently 84 documented species of anurans (referred to as frogs throughout the remainder of paper) and caudates (referred to as salamanders throughout the remainder of paper) in the Commonwealth of Virginia (Appendix). The Big Levels Salamander (Plethodon sherando), Shenandoah Salamander (P. shenandoah) and Peaks of Otter Salamander (P. hubrichti) are endemic to the Commonwealth; meaning they are found only in Virginia and nowhere else in the world. The other 81 species are found in at least one other adjacent state. The most recent addition to Virginia’s species Virginia Journal of Science, Vol. 66, No. 3, 2015 https://digitalcommons.odu.edu/vjs/vol66/iss3 VIRGINIA’S AMPHIBIAN SPECIES 279 list came in 2015, with the Atlantic Coast Leopard Frog (Rana kauffeldi) (Feinberg et al. 2014). Virginia has the third highest amphibian diversity of the states (Stein 2002). Supported by a diverse array of habitats, these amphibians span the Commonwealth, from coastal wetlands to mountain top ridgelines. Some species of amphibians are habitat generalists, such as the ubiquitous American Bullfrog (Lithobates catesbeianus) which occupies every county in Virginia and a variety of freshwater aquatic habitats. Other species are habitat specialists, such as the rock outcrop residing Green salamander (Aneides aeneus). Virginia has six main ecoregions as described by The Nature Conservancy, including the Cumberland and Southern Ridge and Valley, Southern Blue Ridge, Central Appalachian Forest, Piedmont, Mid-Atlantic Coastal Plain, and the Chesapeake Bay Lowlands. Each region differs in topography, geology, climate and vegetation. Both frogs and salamanders occupy each ecoregion, but they display different patterns of species richness (Figure 1). In general, frogs predominate in the eastern ecoregions, while more salamanders reside in the western ecoregions. STATUS OF VIRGINIA’S AMPHIBIANS Species assessments are conducted by multiple organizations and for a variety of purposes. This paper uses established rating systems in discussing the status of Virginia’s amphibians (Appendix), including the IUCN Red List, NatureServe Conservation Status (global=GRank and state=SRank), U.S. Fish and Wildlife Service endangered species listing (ESA), State of Virginia endangered species listing (State) and the Virginia Wildlife Action Plan (2005 and 2015 WAP). The authors consider a species of concern to be one that has been ranked as imperiled by at least one of the known ranking systems. All 28 species of frogs found in Virginia also occur in at least one other state. According to the range-wide assessments (i.e. IUCN, NatureServe GRank and ESA), none of these species are imperiled. On the local level, eight of the 28 species (29% of total frogs) are of conservation concern in Virginia. Five species are listed by both NatureServe SRank and Virginia’s WAP, while an additional three species are listed only on the WAP. The Barking Treefrog (Hyla gratiosa), listed as State Threatened, is the only State listed species. The Atlantic Coast Leopard Frog is not considered in any ranking system because it is newly described (Fienberg et al. 2014) and therefore no previous data for comparison are available for assessment purposes. A different story holds true for the salamanders. According to the NatureServe GRank, ten species are of conservation concern across their entire range. The IUCN ranking is in agreement with the NatureServe GRank on eight of these species. According to the NatureServe SRank and Virginia’s WAP an additional 19 species are of conservation concern within Virginia. Four of these species, however, are only listed by NatureServe and one additional species only by the WAP. Including all listings, the total salamander species of conservation concern in Virginia is 29 (52% of total). Three of these species are listed as State Threatened or Endangered, including the Mabee’s Salamander (Ambystoma mabeei) (ST), Eastern Tiger Salamander (A. Virginia Journal of Science, Vol. 66, No. 3, 2015 https://digitalcommons.odu.edu/vjs/vol66/iss3 280 VIRGINIA JOURNAL OF SCIENCE FIGURE 1. Number of Virginia amphibians based on the six terrestrial ecoregions designated by The Nature Conservancy. A species may be represented in more than one ecoregion. Ecoregions include CSRV = Cumberland and Southern Ridge and Valley, SBR = Southern Blue Ridge, CAP = Central Appalachian Forest, PIED = Piedmont, CBL = Chesapeake Bay Lowlands and MACP = Mid-Atlantic Coastal Plain. tigrinum) (SE) and Shenandoah Salamander (SE)). The Shenandoah Salamander is the only amphibian in Virginia listed by the U.S. Fish and Wildlife Service as Federally Endangered. Virginia Journal of Science, Vol. 66, No. 3, 2015 https://digitalcommons.odu.edu/vjs/vol66/iss3 VIRGINIA’S AMPHIBIAN SPECIES 281 Of note are the discrepancies in the different assessments. There may be a number of contributing factors for the differences, but two considerations are worth mentioning in relation to rankings in Virginia. The NatureServe listings were last reviewed on average 11 years ago and in some cases may be outdated. In addition, useful information about species on a state or more local level are not always published in the peer-reviewed literature used i