Desmognathus Fuscus Research Articles

The herpetological legacy of Jacob Green and the nomenclature of some North American lizards and salamanders.

Jacob Green was born in 1790 to a prominent New Jersey family of scholars and theologians. He taught at the College of New Jersey (now Princeton University) from 1818 to 1822 before co-founding Jefferson Medical College (now Thomas Jefferson University) in 1825, where he taught Chemistry until his death in 1841. Between 1818 and 1831, he published a series of nine papers on lizards, salamanders, and snakes, authoring the original description of several well-known species of salamanders from the eastern United States. Many of his names are ambiguous; some have been adjudicated by the ICZN, while others are currently treated as nomina dubia. Here, we review all of Green's publications, report on newly re-discovered or re-interpreted material from several major natural history collections, and resolve most if not all remaining issues through a series of taxonomic actions. In particular, we first designate a neotype for Salamandra nigra Green, 1818. We then place S. sinciput-albida Green, 1818 and S. frontalis Gray in Cuvier, 1831 in synonymy with S. scutata Temminck in Temminck Schlegel, 1838 and invoke Reversal of Precedence under Article 23.9 to designate them nomina oblita. We also designate a lectotype for S. bislineata Green, 1818. Finally, we resurrect the name S. fusca Green, 1818 as the valid name for the species Desmognathus fuscus, assuming priority over Triturus fuscus Rafinesque, 1820, designating S. fusca Laurenti, 1768 a nomen oblitum, and placing S. nigra Green, 1818 in synonymy. While Green's herpetological legacy is not as expansive as that of some of his successors such as Holbrook, he is nonetheless a foundational early worker in salamanders, having described some of the most-studied species in the world.

Osseous pathologies in the lungless salamander Desmognathus fuscus (Plethodontidae)

AbstractThe majority of reported pathologies in lissamphibians (salamanders, caecilians and frogs) include limb deformities such as missing limbs, multiple extra limbs and digits, or incomplete limb formation. However, comparatively little is known about congenital vertebral malformations or posttraumatic pathologies (e.g. injuries, infections) in the vertebral column of salamanders. In the present study, we describe eight vertebral deformities in three cleared and stained specimens of Desmognathus fuscus. Two specimens display developmental deformities which range from a potential non‐segmented wedge vertebra to fully segmented hemivertebrae. The vertebral pathology in the third specimens possibly results from a parasitic infection. Apparently, these osseous deformities were not severe enough to prohibit survival of the specimens.

Towards rectifying limitations on species delineation in dusky salamanders (Desmognathus: Plethodontidae): An ecoregion-drainage sampling grid reveals additional cryptic clades.

Dusky salamanders (Desmognathus) constitute a large, species-rich group within the family Plethodontidae, and though their systematic relationships have been addressed extensively, most studies have centered on particular species complexes and therefore offer only piecemeal phylogenetic perspective on the genus. Recent work has revealed Desmognathus to be far more clade rich-35 reciprocally monophyletic clades versus 22 recognized species-than previously imagined, results that, in turn, provide impetus for additional survey effort within clades and across geographic areas thus far sparsely sampled. We conceived and implemented a sampling regime combining level IV ecoregions and independent river drainages to yield a geographic grid for comprehensive recovery of all genealogically exclusive clades. We sampled over 550 populations throughout the distribution of Desmognathus in the eastern United States of America and generated mitochondrial DNA sequence data (mtDNA; 1,991 bp) for 536 specimens. A Bayesian phylogenetic reconstruction of the resulting haplotypes revealed forty-five reciprocally monophyletic clades, eleven of which have never been included in a comprehensive phylogenetic reconstruction, and an additional three not represented in any molecular systematic survey. Although general limitations associated with mtDNA data preclude new species delineation, we profile each of the 45 clades and assign names to 10 new clades (following a protocol for previous clade nomenclature). We also redefine several species complexes and erect new informal species complexes. Our dataset, which contains topotypic samples for nearly every currently recognized species and most synonymies, will offer a robust framework for future efforts to delimit species within Desmognathus.

Phylogenomic data reveal reticulation and incongruence among mitochondrial candidate species in Dusky Salamanders (Desmognathus)

Gene flow between evolutionarily distinct lineages is increasingly recognized as a common occurrence. Such processes distort our ability to diagnose and delimit species, as well as confound attempts to estimate phylogenetic relationships. A conspicuous example is Dusky Salamanders (Desmognathus), a common model-system for ecology, evolution, and behavior. Only 22 species are described, 7 in the last 40 years. However, mitochondrial datasets indicate the presence of up to 45 “candidate species” and multiple paraphyletic taxa presenting a complex history of reticulation. Some authors have even suggested that the search for species boundaries in the group may be in vain. Here, we analyze nuclear and mitochondrial data containing 161 individuals from at least 49 distinct evolutionary lineages that we treat as candidate species. Concatenated and species-tree methods do not estimate fully resolved relationships among these taxa. Comparing topologies and applying methods for estimating phylogenetic networks, we find strong support for numerous instances of hybridization throughout the history of the group. We suggest that these processes may be more common than previously thought across the phylogeography-phylogenetics continuum, and that while the search for species boundaries in Desmognathus may not be in vain, it will be complicated by factors such as crypsis, parallelism, and gene-flow.

Salamander stress and duress: the relationship between CORT, autotomy and regeneration, and exploratory behaviour

Responses to stress are generally mediated through the production of glucocorticoids by the hypothalamic-pituitary-adrenal (or -interrenal) axis. The prolonged production of stress hormones can contribute to delayed wound healing and growth, but little is known about their influence on regeneration following tail autotomy, or exploratory behaviour in autotomized individuals. Here we examined the relationship between stress, regeneration, and exploratory behaviour in Allegheny Mountain dusky salamanders (Desmognathus ochrophaeus) by manipulating corticosterone (CORT) levels via cutaneous patch. First, we measured tail regeneration in salamanders with elevated CORT for 13 weeks after the induction of tail autotomy. Test subjects received a weekly patch to wear for one hour that was saturated with either a low CORT (0.25 mg/ml) or high CORT (0.50 mg/ml) solution. Individuals receiving CORT patches regenerated significantly less of their tail length and volume (versus control), but without exhibiting dose-dependent effects. Second, we used a factorial design to evaluate the effects of autotomy and elevated CORT on exploration within a test arena consisting of low barriers arrayed in concentric rings. Individuals experiencing tail autotomy exhibited significantly less exploratory behaviour indicated by an increased latency to cross first barrier and a decreased number of barriers crossed. Neither elevated CORT (0.50 mg/ml), nor the interaction between elevated CORT and tail autotomy significantly affected salamander activity within the array. Although CORT did not have a direct effect on explorative behaviour, a delay in regeneration attributed to CORT could lead to changes in patterns of movement in autotomized individuals.

Stream salamander persistence influenced by the interaction between exurban housing age and development

Exurban development is the fastest growing form of land use in the United States and already predominates southern New England. These housing developments alter stream ecosystems in a predictable manner described as urban stream syndrome. Yet, many stream salamanders are considered ubiquitous in the region. To determine what stream and watershed features enhance long-term population persistence in an exurban landscape, we compared the occupancy and abundance of two stream salamanders, Eurycea bislineata (northern two-lined salamander) and Desmognathus fuscus (northern dusky salamander), in watersheds that differed in housing density and time since construction. We estimated E. bislineata occupancy at 100% and found strong support for an interaction between the quadratic of average housing development age and housing density in watersheds influencing abundance. Abundance was sensitive to new and high-density housing developments and increased in watersheds that were more than 20 years post-construction when housing density was low. In comparison, D. fuscus occupancy was estimated at 18% and best explained by fine-scale stream features including soil temperature, water conductivity, dissolved oxygen, discharge, and sediment distribution. Notably, estimates of D. fuscus relative abundance within watersheds, including watersheds with low housing densities, were much lower than comparable estimates in the literature. We suggest an adaptive management approach to monitor and manage D. fuscus populations in the region. Future wildlife management decisions in exurban landscapes should consider interactions between housing age and density as well as development legacy effects.

A Survey of Terrestrially Active Salamanders from Two Different Woodlands at the Powdermill Nature Reserve, Pennsylvania

Variation in habitat and microhabitat can affect salamander populations. We systematically surveyed terrestrially active salamanders in an old forest tract and a young forest tract at the Powdermill Nature Reserve in southwestern Pennsylvania during 2009–2011. We examined the effect forest age had on the 2 salamander assemblage structures. While species compositions were similar, assemblage structures were uneven in both the old and young forest sites. Differential use of survey coverboards across species was detected at both sites. This difference in use may be best explained by ground-moisture levels as a function of coverboard distance to water. Counterintuitive findings of low numbers of Desmognathus ochrophaeus (Mountain Dusky Salamander) and Plethodon cinereus (Red-backed Salamander) compared to past studies at these 2 sites appears most likely related to differences in trapping methodology. Patterns of differential use of coverboards and inter-site differences in seasonal activity patterns point to P. glutinosus (Northern Slimy Salamander) as the least restricted species in terms of microhabitat conditions and most seasonally variable in activity.

A Synopsis of the Reptiles and Amphibians of Illinois

This synopsis is presented largely as it was written several years ago. Before a final report on our reptiles and amphibians is prepared, it is sincerely to be desired that examples of every Illinois species may be in the Illinois Laboratory collection for description, and that the local features of the fauna may be brought out by a critical comparison of Illinois specimens with collections from other parts of the United States. Specimens of the following species, and observations upon them, are especially desirable: Cistudo ornata, Chrysemys picta, Pseudemys hieroglyphica, P. concinna, Heterodon simus, Ophibolus rhombomaculatus, Nerodia sipedon var. fasciata, Rana areolata, R. sylvatica, Hyla cinerea, Desmognathus fusca, Spelerpes ruber, Amblystoma jeffersonianum and A. punctatum.

The effect of predator kairomones on caudal regeneration by Allegheny Mountain Dusky Salamanders (Desmognathus ochrophaeus)

Many prey use autotomy as an antipredator mechanism. Rapid regeneration of autotomized appendages is beneficial because forfeited tissues may serve as organs for energy storage, accessories for locomotion, or indicators of social status. We monitored levels of caudal regeneration by Allegheny Mountain Dusky Salamanders (Desmognathus ochrophaeus Cope, 1859) exposed to kairomones from predatory Eastern Garter Snakes (Thamnophis sirtalis (Linnaeus, 1758)). After the induction of autotomy, salamanders were exposed to one of three treatment regimens: blank (water), or acute (30 min per week) or chronic (constant) exposure to predator kairomones during a 12-week study period. Overall, the mean volume of regenerated tissue, as a percentage of the original tail volume, was highest for individuals exposed to the blank versus predator kairomones. When the combined effects of time elapsed since the induction of caudal autotomy and the different treatment regimens were considered, we found that the mean volume of regenerated tissue was significantly greater for control salamanders beginning 8 weeks after autotomy. The mechanism contributing to the differential rates of regeneration among individuals in our treatment groups is unknown, but previous work suggests that elevated stress related to predation threat can have detrimental effects on wound healing and growth in amphibians.

Palatability and Predator Avoidance Behavior of Salamanders in Response to the Virginia Opossum (Didelphis Virginiana)

Our understanding of mammalian predation on salamanders is primarily restricted to small carnivorous species (i.e., shrews). We conducted a series of investigations to determine whether the Virginia opossum (Didelphis virginiana) is a predator of various salamander species [Desmognathus fuscus, Plethodon dorsalis, and Notophthalmus viridescens (adult and eft)] from the eastern United States. All species, including toxic newt efts, were palatable to opossums. These results suggest opossums could be an active predator of salamanders. In a second study, each terrestrial salamander species exhibited avoidance responses to kairomones from opossums indicating that despite a significant risk of mortality each salamander has evolved mechanisms to minimize predation risk. Combined with overlapping habitat preferences, foraging behavior that places them in contact, and a dietary preference for animal matter, these data suggest opossums may be an important predator on terrestrial salamanders.

Histological Variation in Plethodontid Digital Surfaces [University of Findlay

Despite numerous investigations into the morphology and function of toe pads in many species, most notably anurans and geckonids, there is relatively little knowledge on salamander digit morphology. To date, toe morphology in salamanders has been limited to Desmognathus fuscus, Ambystoma maculatum, Bolitoglossa sp., and Aneides aeneus. The limited studies to date have shown variation inter- and intra-specifically but have not investigated numerous taxa within a given family which may provide deeper insights into the causes of variation (phylogenetic vs ecological pressures). Therefore, to test hypotheses concerning the presence of variation in the ventral digital surface of plethodontid salamanders, we plan to use various microscopy methodologies to view the ventral surface of the digital tips of three species from three different genera within the Plethodontidae: Desmognathus, Eurycea, and Plethodon. Toe pads will be characterized grossly using scanning electron microscopy, histologically using light microscopy, and ultrastructurally using transmission electron microscopy. Preliminary results suggest that all three species investigated display enlarged surfaces. Surface morphology (assessed via scanning electron microscopy) varies between species at a gross level concerning the shape and overall orientation of the enlarged surface. Surface morphologies include a well-developed circular pad (D. fuscus), a well-developed oval pad (P. cinereus), and a poorly developed circular pad (E. cirrigera). Furthermore, surface morphology appears to vary at the cellular level as well, with Desmognathus having polygonal squamous cells with microprojections and Eurycea having polygonal cells with nanopillars in a honeycomb arrangement. These differences may be attributed to differences in habitat preference as the three species tested include a terrestrial, semi-aquatic, and aquatic dwelling species. However, further investigation including light microscopy and enhanced scanning electron microscopy are needed. Further understanding of the morphological variation will aid in our understanding of ecomorphology and understanding of morphological evolution in amphibians.

Variations in Tissue Mercury Contents in Three Species of Adult Salamanders in Streams in Western Maryland.

The purpose of this study was to improve our understanding of the relationship between mercury in three species of adult salamanders and relatively pristine first-order streams in western Maryland. We measured the tissue mercury content of 106 northern two-lined salamanders (Eurycea bislineata bislineata), 111 northern dusky (Desmognathus fuscus), and 107 Allegheny mountain dusky (Desmognathus ocrophaeus) salamanders collected during three sampling periods. Averaged over our entire data set, northern two-lined salamanders had significantly greater tissue mercury contents (29.57 ± 1.32ngg-1) than northern dusky (20.95 ± 0.78ngg-1) and Allegheny mountain dusky salamanders (22.84 ± 1.23ngg-1). This may be due in part to the longer larval period of the northern two-lined salamanders (24-36 vs. 0-10months). A longer larval period suggests that the northern two-lined larvae were consuming a fully aquatic diet for a longer time period, which is likely to be higher in mercury compared with a more terrestrial diet. The tissue mercury content in northern two-lined and northern dusky salamanders were strongly correlated with the average total mercury, methyl mercury, and dissolved organic carbon concentrations in stream water. In contrast, the tissue mercury content of the more terrestrial salamander, the Allegheny mountain dusky, was not correlated with stream water chemistry. This suggest that the mercury in the terrestrial prey consumed by the Allegheny mountain dusky salamanders is not directly linked to the mercury in stream water. Our results also suggest that the aquatic salamanders could be important bioindicators of mercury contamination of small streams.

Making the best of a bad situation: differential predator avoidance in a diminutive woodland salamander

Predator avoidance behaviour has been observed in many species and can strongly affect trophic interactions. Animals frequently adjust their response to predators in proportion to risk; however, when they are exposed to chronic predation risk, some animals reduce their antipredator responses in favour of resource acquisition. Animals that are subjected to predation pressure from multiple predator species may have to respond to different spatial and temporal distributions of risk; how they balance these risks will affect their choice of habitat or microhabitat patches. One species that is exposed to a wide range of predators is the pygmy salamander, Desmognathus wrighti. These miniaturized terrestrial plethodontids spend their entire life on the forest floor where they are exposed to a diversity of predators. We examined pygmy salamanders' ability to avoid potential predators based on the presence of substrate-borne chemical cues. The predator species included ground beetles (Carabidae: Pterostichus), Jordan's salamanders, Plethodon jordani, and ring-necked snakes, Diadophis punctatus. The ring-necked snake is a trophic specialist feeding on salamanders while the beetles and Jordan's salamanders are generalist predators. The pygmy salamanders were also exposed to chemical alarm cues from a congeneric salamander (Desmognathus fuscus) and odours from two unfamiliar species: corn snakes (Pantherophis gutattus) and herbivorous desert tortoises (Gopherus agassizii). We used a hierarchical Bayesian beta regression with a repeated measures design to model proportion of time spent in each treatment. Compared to controls, pygmy salamanders exhibited strong aversion to fed ring-necked snakes, a moderate avoidance of unfamiliar odours and a slight attraction to scents from the two common generalist predators. Our results suggest that pygmy salamanders accept modest risk from common generalist predators but avoid less common, specialist predators and unfamiliar species.

Influence of riparian buffers and habitat characteristics on salamander assemblages in headwater streams within managed forests

Streamside management zones (SMZs), buffers of forest retained along streams when adjacent areas are harvested, are a primary tool for maintaining ecological functions in managed forests. However, few studies have examined the influence of SMZs on salamanders, and none have examined variation in salamander occupancy, species richness, and abundance across a gradient of SMZ widths at a large spatial scale. Further, because previous studies had limited ability to detect responses of uncommon species, little is known about interspecific variation in salamander responses or whether SMZs serve as refuges for terrestrial species during harvesting. To evaluate the role of SMZs in maintaining salamander species, we conducted four replicate surveys at 102 headwater stream sites, spanning a gradient of SMZ widths and adjacent forest stand ages, within the Ouachita Mountains, Arkansas, USA. We used a hierarchical Bayesian community occupancy model to estimate salamander species richness and species-specific occupancy responses to SMZ and overstory characteristics, while accounting for variation in occupancy and detection attributable to site and sampling covariates. Additionally, we used Bayesian binomial mixture models to examine the influence of SMZ width and surrounding stand age on abundance of two stream-associated salamanders [Ouachita dusky salamander (Desmognathus brimleyorum) and many-ribbed salamander (Eurycea multiplicata)] and three terrestrial salamanders [red-backed salamander (Plethodon serratus), slimy salamander (P. glutinosus complex), and Caddo Mountain salamander (P. caddoensis)]. Occupancy, species richness, and abundance increased with increasing SMZ width, but the strength of responses varied among species. Occupancy of uncommon species was highest at sites with wide SMZs, likely because of the need for specific habitat elements (e.g., wetlands, rocky talus). Richness was lowest in SMZs dominated by pine overstory, and lowest in mid-aged stands, consistent with a lagged decrease in richness within SMZs following harvest. Finally, we documented patterns of abundance consistent with the evacuation hypothesis, indicating that salamanders may leave recently harvested areas seeking more suitable habitat and microclimate within SMZs. Collectively, results indicate that SMZs in intensively managed forests can support robust salamander communities, provided managers continue to retain wide SMZs at some key sites across the landscape (i.e., ≥55 m on each side of the stream), a value larger than current Forestry BMP guidelines.

Interspecific Variation in Reproductive Effort in Two Assemblages of Dusky Salamanders

Abstract Body-size variation in desmognathan salamanders in the southern Appalachian Mountains is coupled with trade-offs among life-history traits that affect growth, survival, and reproduction. Reproductive effort is an important trait that is often measured as the gonadosomatic index (GSI), defined as clutch mass relative to total body mass. I measured GSI as brood mass relative to maternal body mass in two assemblages of Desmognathus in the Cowee and Nantahala mountains of southwestern North Carolina. I also re-evaluated the size–fecundity relationship in the Nantahala Mountain assemblage on the basis of newer data. In addition, I examined the potential trade-off between number and size of offspring in several species in both assemblages. Among species, GSI decreased slightly with increasing body size; the trend is considered a probable effect of decreasing metabolic rate with body size rather than a trade-off with one or another life-history trait. Although both propagule size and number increased wi...

The Lack of Nasolacrimal Ducts in Plethodontid Salamanders?

Nasolacrimal ducts are a terrestrial vertebrate adaptation and appear to have co-evolved with orbital glands. Although plethodontid salamanders possess orbital glands, a recent study concluded that plethodontid salamanders lack nasolacrimal ducts. Functionally, the absence of nasolacrimal ducts closes the route for orbital gland secretion passage into the nasal and vomeronasal organ cavities. Orbital glands have been implicated in enhancement of vomeronasal function so loss could have important implications for communication. Multiple older studies depict or discuss nasolacrimal ducts in plethodontid salamanders. Interestingly, the only consensus between recent and older literature is that Desmognathus lacks nasolacrimal ducts. To determine if plethodontid salamanders truly lack nasolacrimal ducts, we sectioned plethodontid salamander heads for general histological examination of species from the majority of the plethodontid tribes. From our representative sample, we found only two species that completely lacked nasolacrimal ducts (Desmognathus fuscus and Eurycea tynerensis) and one species that possessed nasolacrimal ducts that ended blindly before reaching the nasal cavities (E. spelaea). Bayesian ancestral state reconstruction resulted in the presence of nasolacrimal ducts on the branch leading to Plethodontidae and both subfamilies within Plethodontidae, with two independent losses in Desmognathus and Eurycea. Anat Rec, 301:765-775, 2018. © 2017 Wiley Periodicals, Inc.

Effect of chronic low body temperature on feeding and gut passage in a plethodontid salamander

Although feeding in some plethodontid salamander species, such as Dusky Salamanders (Desmognathus, family Plethodontidae), occurs at short-term (acute) low temperature below 5°C, it is unknown whether feeding, digestion, and gut passage continue to occur during periods of long-term (chronic) low temperature. We performed a controlled laboratory experiment to examine the effect of several chronic low environmental temperatures on both feeding and gut passage in semiaquatic Spotted Dusky Salamanders (D. conanti). We quantified salamander feeding and defecation for different experimental groups maintained for many weeks at a constant temperature of 4, 7, 10, or 13°C. Although feeding frequency, number of prey items consumed per feeding, and defecation frequency were significantly less for individuals at 4°C than for individuals at 10 or 13°C, salamanders continued to feed, defecate, and maintain body mass for 12 weeks at 4°C. The ratio of the number of fecal pellets produced to the number of prey items consumed each week by individuals did not significantly decrease at 4°C, which indicates gut passage was sustained at this temperature. Because both time between feeding and time between defecation were similarly affected by prolonged low temperature, the significant decrease in feeding frequency at 4°C may depend, in part, on a decrease in digestive function and an extended time for gut passage at low temperature. We conclude that most individuals of D. conanti can feed, digest, and maintain body mass for several months at constant low temperature down to 4°C. Our results support a growing body of data that indicate some plethodontid salamanders may acquire energy at environmental temperatures only a few degrees above freezing.

Design tradeoffs in long‐term research for stream salamanders

ABSTRACTLong‐term research programs can benefit from early and periodic evaluation of their ability to meet stated objectives. In particular, consideration of the spatial allocation of effort is key. We sampled 4 species of stream salamanders intensively for 2 years (2010–2011) in the Chesapeake and Ohio Canal National Historical Park, Maryland, USA to evaluate alternative distributions of sampling locations within stream networks, and then evaluated via simulation the ability of multiple survey designs to detect declines in occupancy and to estimate dynamic parameters (colonization, extinction) over 5 years for 2 species. We expected that fine‐scale microhabitat variables (e.g., cobble, detritus) would be the strongest determinants of occupancy for each of the 4 species; however, we found greater support for all species for models including variables describing position within the stream network, stream size, or stream microhabitat. A monitoring design focused on headwater sections had greater power to detect changes in occupancy and the dynamic parameters in each of 3 scenarios for the dusky salamander (Desmognathus fuscus) and red salamander (Pseudotriton ruber). Results for transect length were more variable, but across all species and scenarios, 25‐m transects are most suitable as a balance between maximizing detection probability and describing colonization and extinction. These results inform sampling design and provide a general framework for setting appropriate goals, effort, and duration in the initial planning stages of research programs on stream salamanders in the eastern United States. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

Sexual Isolation between Two Sympatric Desmognathus in the Gulf Coastal Plain

A substantial body of work exists examining courtship in lungless salamanders (family Plethodontidae), but there are many species and population pairs that have not been tested for sexual isolation. Spotted (Desmognathus conanti sensu lato [SL]) and Southern Dusky Salamanders (D. aff. auriculatus) occur sympatrically within drainages in South Mississippi. I crossed individuals from three populations of D. aff. auriculatus (n = 6 individuals) and seven populations of D. conanti (SL) (n = 10) occurring in the Pascagoula and Pearl River basins. I alternated homospecific (n = 23) and heterospecific (n = 23) trials across nights in the spring and summer of 2014 and 2015, and I used GoPro™ HERO3 cameras and time-lapse photography to record the behaviors of a random subset of these pairs, as well as to determine the stage of courtship reached. Seventeen of the 23 homospecific trials resulted in spermatophore deposition and 14 in insemination. None of the 23 heterospecific trials (D. aff. auriculatus ♂ x D. conan...

Effects of size, caudal autotomy, and predator kairomones on the foraging behavior of Allegheny Mountain dusky salamanders (Desmognathus ochrophaeus)

Prey must balance the conflicting demands of foraging and defensive behavior. Foraging under the threat of predation may be further complicated among species that engage in caudal autotomy, the loss of a portion of the tail at preformed breakage planes, because the tail may serve as an important energy storage organ and contribute to motility, culminating in a trade-off between foraging and predator avoidance. As a result of the advantages conferred by the presence of a tail, individuals that have recently undergone autotomy may be more motivated to forage despite elevated levels of threat indicated by predator kairomones. We used a full factorial design to evaluate the combined effects of body size, exposure to predator kairomones, and experience with autotomy on the latency to strike at Drosophila prey, number of strikes, and prey captured per strike by Allegheny Mountain dusky salamanders (Desmognathus ochrophaeus). In our study, caudal autotomy was the only significant main effect and influenced both the latency to attack prey and the number of strikes attempted. In terms of latency to attack prey, there was a significant interaction between body size and autotomy such that “small” salamanders (≤3.2 cm SVL) without tails delayed their foraging behavior. In terms of the number of strikes toward prey, there was a significant interaction between autotomy and exposure to predator kairomones such that individuals with intact tails exhibited a greater number of strikes, with the exception of the “large” (>3.2 cm SVL) salamanders, which performed fewer strikes when exposed to the snake kairomones. There was no significant effect on foraging efficiency, although the trend in the data suggests that autotomized individuals forage more efficiently. This study was designed to evaluate the confluence of factors related to size, caudal autotomy, and exposure to stimuli from predators and hints at the magnitude of caudal autotomy on antipredator decision-making. Our data suggest that despite the importance of tail tissue for energy storage, locomotion, and mating, salamanders without tails are cautious when foraging under elevated risk.