A Guide to Sexing Salamanders in Central Appalachia, United States

Quantifying aspects of population structure, such as sex ratio and age class, is important for studying and managing wildlife (Skalski et al. 2005). Data at the individual level can provide insight into spatial and temporal dynamics of populations, resulting in more robust assessments of population health than abundance estimates alone (Kurose et al. 2005; Koons et al. 2006; Reid et al. 2006). For example, it is common that environmental changes affect ages and sexes differently because of differences in physiology, size, behavior, and space use (Steen et al. 2006; Popescu and Hunter 2011; Cayuela et al. 2016). Improved understanding of these differential effects broadens the ecological understanding of species and the ability to manage them.

Determining the sex of animals in the field depends on the presence of distinguishable primary or secondary sex characters at the time of observation, and observer awareness of them. For many salamander species, sexing individuals is inherently difficult because secondary sex characters are often subtle or only visible during the breeding season (e.g., Sever 1975; Marvin 2009; Morgan et al. 2014). This challenge is compounded by a lack of widely available guidance for sexing salamanders. Most field guides for salamanders in the United States provide little or no information on distinguishing between sexes (e.g., Dodd 2004; Powell et al. 2016). Although several natural history books (e.g., Bishop 1943; Petranka 1998; Pfingsten et al. 2013) and internet sites (e.g., AmphibiaWeb [https://amphibiaweb.org/]) provide useful information on sexual dimorphism, none are comprehensive and all are lacking in visual examples, a critical tool for training in identification (Branson et al. 2010; Tirkaz et al. 2015). Thus, determining all the sexually dimorphic characters for a particular salamander species or group of species may require renting or purchasing books, having access to scientific literature databases, and spending a substantial amount of time searching for and compiling the information.

The lack of easily available resources and guidance for identifying sex of salamanders creates a barrier for inclusion of this information in research projects and monitoring programs. Although many wildlife biologists and student researchers are likely familiar with some prominent sexually dimorphic characters (e.g., mental glands, cirri), it is unlikely that the majority of nonprofessional herpetologists are knowledgeable about the characters that are useful for every species they could encounter in their projects, or when the characters are likely to be visible. In addition, it is likely that most biologists and nonsalamander experts would benefit from visual examples of sexually dimorphic characters to assist with identification in the field.

The purpose of this guide is to provide a reference to assist nonprofessional herpetologists with identifying sex of adult salamanders in the field. Species coverage is constrained to the Central Appalachian region, including portions of southern New York, Pennsylvania, eastern Ohio, eastern Kentucky, western Maryland and Virginia, and all of West Virginia (Stephenson 2013; Figure 1). This region is a global biodiversity hotspot for salamanders (Buckley and Jetz 2007; Rissler and Smith 2010), and contains many endemic species of conservation concern, such as Cheat Mountain salamander Plethodon nettingi, Shenandoah salamander Plethodon shenandoah, Cow Knob salamander Plethodon punctatus, and Peaks of Otter salamander Plethodon hubrichti. Many of the species covered in this guide also occur in other geographic regions. Thus, while our species coverage is restricted to Central Appalachia, this guide has broad value for biologists in eastern and central North America.

We used distribution boundaries in Powell et al. (2016) to delineate salamander species occurring in the Central Appalachian region. For each species, we compiled and reviewed published literature and graduate theses that investigated sex identification. We attempted to include all primary literature and avoided citing gray literature when feasible. We also reviewed literature on size-at-maturity and breeding season because many characters that distinguish sexes of adults are only visible during the breeding season. Data for size-at-maturity and breeding season provided here should be considered approximations because they are spatially and temporally variable. We created tables to serve as quick references in the field, and included illustrations and images to show examples of sexually dimorphic characters. The Text S1 (Supplemental Material) file contains individual species accounts with additional information and images.

We identified seven morphological characters that are broadly useful for sexing live, nonanesthetized, adult salamanders in the field (Table 1). These characters include presence or prominence of swollen nasolabial grooves or cirri in males (Figures 2a, 2b, 3b), presence of a visible mental gland in males (Figures 2b, 3a), squared snout in males (Figures 2c, 3b), swollen jaw musculature in males, swollen cloaca in males (Figures 2d, 2e, 3c, 3e, 3f), cloacal papillae, and visibility of testes (males) or eggs (females) through the abdominal wall. Individual species exhibited one to five of these characters (Table 1). For many species, eggs and testes can be seen by pressing the dorsal surface of the abdomen against a light, referred to as “candling.” In addition, eggs often are visible through the abdominal wall even without a light (Figure 3d). Most characters are only visible or prominent during the breeding season. Information on species-specific size at maturity and breeding season is provided in Table 2. Additional species-specific information is available in Text S1 (Supplemental Material).

Two characters, enlarged premaxillary and maxillary teeth (Figure 2f), are strongly sexually dimorphic for some species (Table 3), but these characters are difficult to distinguish in the field unless animals are first anesthetized. For some species, males and females can be distinguished by their size (Table 3), with females typically being larger (Figure 2f; see Supplemental Material for species-specific information). However, male and female size distributions overlap, so size is only a reliable character when females exceed the maximum size of males. Additional species-specific sexually dimorphic characters have been reported in the literature for many Central Appalachian species, which are summarized in Table 4 and discussed in the individual species accounts (Supplemental Material).

Salamanders in Central Appalachia display a wide variety of sexually dimorphic characters, but no characters are present in all species and most species can only reliably be sexed in the field during the breeding season. Our guide serves as the most robust synthesis of sexually dimorphic characters available for salamanders in Central Appalachia to-date that we are aware of, and provides helpful guidance for the periods when species may display sexual dimorphism. However, we emphasize that size at maturity and breeding season can vary across the distribution of species, and recommend that additional research on local populations be consulted when available. Unfortunately, information needed for reliable sex determination is lacking or unpublished for many species, and we encourage researchers to address these biological and natural history information gaps.

Please note: The Journal of Fish and Wildlife Management is not responsible for the content or functionality of any supplemental material. Queries should be directed to the corresponding author for the article.

Text S1. Individual species accounts with information on size at maturity, breeding season, and sexually dimorphic characters for salamanders in Central Appalachia, United States, 1907–2020.

Available: https://doi.org/10.3996/JFWM-20-042.S1 (13.55 MB PDF)

Reference S1. Marcum C Jr. 1994. Ecology and natural history of four plethodontid species in the Fernow Experimental Forest, Tucker County, West Virginia. Master's thesis. Huntington, West Virginia: Marshall University.

Available: https://doi.org/10.3996/JFWM-20-042.S2 (17.3 MB PDF)

We thank the many individuals who have devoted themselves to improving our understanding of the biology and natural history of salamanders in the Appalachian region, without whom this review paper would not have been possible. We thank four anonymous reviewers and the Associate Editor for their suggestions, which greatly improved the quality of this manuscript. We thank Brett Skelly, Sara Crayton, Stephen Nelson, and Wayne Van Devender for providing photographs showing sexually dimorphic characters. Donald Brown and Lacy Rucker were supported by the U.S. Department of Agriculture (USDA) National Institute of Food and Agriculture, McIntire Stennis project WVA00122, and the West Virginia Agricultural and Forestry Experiment Station. This is Scientific Article No. 3410 of the West Virginia Agricultural and Forestry Experiment Station, Morgantown, West Virginia. Donald Brown was also supported by the USDA Forest Service Northern Research Station.

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