Desmognathus Fuscus Research Articles

Carpal variability and asymmetry in limb reduced Western lesser sirens (Siren nettingi).

Trait functionality can act as a constraint on morphological development. Traits that become vestigialized can exhibit unstable developmental patterns such as fluctuating asymmetry (FA) and variation in populations. We use clearing and staining along with morphometric analyzes to compare FA and allometry of limbs in Western lesser sirens (Siren nettingi) to Ouachita dusky salamanders (Desmognathus brimleyorum). Our results describe new carpal phenotypes and carpal asymmetry in our sample of S. nettingi. However, we found no significant evidence of limb length asymmetry in S. nettingi. The degree of relative limb asymmetry correlates inversely with body size in both of our samples. This work provides strong evidence of increased mesopodal variation within a population of S. nettingi. Our work provides a basis for further study of a broader range of morphological traits across salamanders.

Androgen Receptors in the Dermal Glands of Male and Female Ouachita Dusky Salamanders

Synopsis The presence of androgens in female development is an important, yet often overlooked, topic. We tested for the presence of androgen receptors (ARs) in the dermal glands of male and female Desmognathus brimleyorum, a plethodontid salamander. This species engages in a courtship behavior called the tail-straddling walk. During this process, communication between males and females is hypothesized to be facilitated by pheromones secreted from modified granular glands (MGGs) on the dorsal tail base, where the female's chin is positioned. These glands are present not only dorsally but also laterally and ventrally on the tail of both males and females. Using immunohistochemistry with a polyclonal antibody, ARs were located in the MGGs of both sexes. Males had a higher percentage of immunopositive cells per MGG than females. The presence of ARs in both sexes highlights the similarity between MGGs in males and females and suggests androgens play a role in female gland function. Furthermore, our results suggest courtship communication is bidirectional, and females have a more active role, signaling the male, than previously described.

Assortment of Dusky Salamanders along Moisture Gradients in Multispecies Assemblages: Revisiting the Ideas

Assortment of Dusky Salamanders along Moisture Gradients in Multispecies Assemblages: Revisiting the Ideas

Systematic revision of the Spotted and Northern Dusky Salamanders (Plethodontidae: Desmognathus conanti and D. fuscus), with six new species from the eastern United States.

Spotted and Northern Dusky Salamanders (Desmognathus conanti and D. fuscus) have a long and complex taxonomic history. At least 10 other currently recognized species in the genus were either described from populations previously considered D. fuscus, described as or later considered subspecies thereof, or later considered synonyms thereof, before ultimately being recognized as distinct. Recent molecular analyses have also revealed extensive cryptic diversity within both species, which are polyphyletic assemblages of 13 distinct mitochondrial lineages with 5.7-10.3% uncorrected 'p' distances in the COI barcode locus. Based on phylogenomic data and population-clustering analyses considering admixture between lineages, 11 candidate species were circumscribed by recent authors. Those within D. conanti are also ecomorphologically variable, comprising both large, robust, keel-tailed populations, and small, gracile, round-tailed forms. Evaluating their distinctiveness based on genetic, geographic, and morphological evidence, we conclude that six of the candidates represent new species: Desmognathus anicetus sp. nov., D. bairdi sp. nov., D. campi sp. nov., D. catahoula sp. nov., D. lycos sp. nov., and D. tilleyi sp. nov. Consequently, we recognize eight total species from populations formerly associated with the nominal species D. conanti and D. fuscus, the re-delimited concepts of which also contain additional phylogeographic lineage diversity that may represent further distinct species. In addition to existing mitochondrial and nuclear phylogenetic, network, and clustering results, we present preliminary analyses of linear morphometrics to bolster diagnostic specificity based on phenotypic characteristics. These changes stabilize the previously paraphyletic taxonomy of species-level lineages within Desmognathus, though additional cryptic diversity may exist both within the species considered here, and elsewhere in the genus.

In Vitro Investigation of the Antibacterial Activity of Salamander Skin Peptides.

Given the current and future costs of antibiotic-resistant bacteria to human health and economic productivity, there is an urgent need to develop new antimicrobial compounds. Antimicrobial peptides are a promising alternative to conventional antibiotics and other antimicrobials. Amphibian skin is a rich source of bioactive compounds, but the antibacterial properties of salamander skin peptides have been neglected. Here, we examined the in vitro ability of skin peptides from 9 species of salamander representing 6 salamander families to inhibit the growth of ESKAPE pathogens, which are bacteria that have developed resistance to conventional antibiotics. We also examined whether the skin peptides caused lysis of human red blood cells. Skin peptides from Amphiuma tridactylum had the greatest antimicrobial properties, completely inhibiting the growth of all bacterial strains except for Enterococcus faecium. Likewise, skin peptides from Cryptobranchus alleganiensis completely inhibited the growth of several of the bacterial strains. In contrast, skin peptide mixtures from Ambystoma maculatum, Desmognathus fuscus, Eurycea bislineata, E. longicauda, Necturus beyeri, N. maculosus, and Siren intermedia did not completely inhibit bacterial growth even at the highest concentrations. Finally, none of the skin peptide mixtures caused lysis of human red blood cells. Together, we demonstrate that salamander skin produces peptides with potent antibacterial properties. It remains to elucidate the peptide sequences and their antibacterial mechanisms.

Pregastrular Development of Amphibians: Ontogenetic Diversity and Eco-Devo

Comparative and ecological aspects of the reorganizations of early development in the class Amphibia are analyzed. We used data on the developmental diversity in a number of families belonging to the orders Anura and Caudata, in which many species had lost their connection with the aquatic environment. Model representatives of the class Amphibia (Ambystoma mexicanum, Rana temporaria, and Xenopus laevis) have small eggs (no more than 2.5 mm in diameter). In these species, the slowdown in the rate of cell divisions and the loss of synchrony occur at the midblastula stage. However, phylogenetically basal amphibian species (Ascaphus truei, Cryptobranchus alleganiensis) are characterized by the large (4–6 mm in diameter) yolky eggs and a short series of synchronous blastomere divisions (the synchrony is already lost at the 8-cell stage of cleavage). They do not have a “midblastula transition”, which is characteristic of the above model species. On the other hand, many evolutionarily advanced non-model species of caudate and anuran amphibians (for example, Desmognathus fuscus, Gastrotheca riobambae, Philoria sphagnicolus), as well as the basal species, are characterized by the large, yolk-rich eggs and the early loss of cell division synchrony. Phylogenetic analysis suggests that the cleavage pattern of the most extensively studied amphibians, the Mexican axolotl (Caudata) and the African clawed frog (Anura), represents a homoplasy. The midblastula transition, which is characteristic of these two species, might have evolved convergently in these two orders of amphibians as an embryonic adaptation to development in lentic water.

Salamander Movement Propensity Resists Effects of Supraseasonal Drought

Movement can act as an effective strategy used by amphibians to avoid detrimental environmental conditions, particularly drought. However, due to the unpredictable nature of droughts, evaluating the patterns and consequences of movement has rarely been investigated. In 2007–2008, the southeastern United States experienced a supraseasonal drought that resulted in 110 yr low flow levels among the first-order streams. In this study, 61 months of mark–recapture data collected from one first-order stream were used to examine the effects of drought on the movement frequency distribution, survival, and growth rates of adult Desmognathus fuscus (Northern Dusky Salamander). We hypothesized that salamanders would demonstrate a higher propensity to move during supraseasonal drought conditions and that moving salamanders would experience higher survival and growth rates. We found that salamanders were more likely to move immediately after the drought compared to the pre-drought and drought conditions. Although movement frequency was low during the drought, survival was higher for individuals who moved during drought conditions in comparison to individuals who remained in their original capture location. Although our model did not detect a trend, salamanders experienced slightly higher growth in the post-drought conditions compared to drought and pre-drought conditions. In addition, during the post-drought, salamanders that moved had slightly higher growth rates compared to salamanders who remained in their original capture location. Our results suggest that adult salamanders were potentially displaying an adaptive movement strategy to resist drought conditions by moving away from affected (i.e., dry) areas within the study stream. In addition, movement was likely utilized to access replenished resources in other areas after the severe effects of the drought ended. Therefore, both in-stream and riparian barriers that impede movement may inhibit resilience of stream amphibians during severe droughts.

Size and Cycle in Dusky Salamanders

The equal fitness paradigm (EFP) is a life-history model in which the currency of fitness is usable energy rather than individuals, and the principal trade-off is between survival, evaluated as generation time, and productivity, evaluated as growth and reproductive rates. In the current study I examined variation in generation time, age at first reproduction, productivity, and mortality in salamanders of the genus Desmognathus within the framework of the EFP. Desmognathus salamanders are restricted to eastern North America, with a center of distribution in the southern Appalachian Mountains. The data sources of the present report are published studies of life histories and demographics of five species of Desmognathus that include the smallest and largest members of the genus. The analysis showed that Desmognathus salamanders have greater ages at first reproduction, lengthier generation times, lower productivities, and lower mortality rates than are predicted by the scaling functions of the EFP for vertebrates of equivalent sizes. The differences among species in these parameters are correlated with variation in adult body size and the association between body size and habitat utilization in the genus, wherein the largest species are aquatic in mountain streams and the smallest are terrestrial in mesic forests. Streamside species of intermediate size exploit a broader range of habitats and are more widely distributed than the stream- and forest-dwelling forms. It is likely that the streamside mode of life in Desmognathus represents an adaptation promoting dispersal. Adaptive radiation in the genus is expressed in extreme life-history and body-size diversification mediated through variation in age at first reproduction and generation time.

Systematics of the Ocoee Salamander (Plethodontidae: Desmognathus ocoee), with description of two new species from the southern Blue Ridge Mountains.

The "mountain" dusky is a charismatic ecomorph of Dusky Salamander (Desmognathus): smaller (~20-50mm SVL), more terrestrial and montane woodland species, typically with round tails and extremely variable, often colorful patterns. Originally considered a single species (D. ochrophaeus), populations across the Appalachians are now divided into D. abditus, D. carolinensis, D. ochrophaeus, D. ocoee, and D. orestes, which do not form a clade but are instead scattered across the phylogeny of Desmognathus. A Coastal Plain species with a mountain dusky phenotype (D. apalachicolae) is also nested within a lineage related to D. ocoee. Within the current concept of D. ocoee, there are up to 8 genetically distinct geographic lineages which display significantly different but substantially overlapping morphologies. Recent studies have suggested that as many as six species could reasonably be delimited based on genetic data. We evaluate the strength of that evidence here and find support for five species in the D. apalachicolae + D. ocoee group. The first is D. apalachicolae in essentially its originally described form from the Coastal Plain. The second and third are D. adatsihi sp. nov. and D. balsameus sp. nov., endemic to the Great Smoky/Plott Balsam and Great Balsam Mountains, respectively. The fourth corresponds to the resurrected D. perlapsus for populations from the Alarka and Cowee Mountains in North Carolina, through the Chattahoochee River drainage to the Fall Line in the Piedmont of Georgia and Alabama. The fifth is D. ocoee, here restricted to populations in the Nantahala and Unicoi Mountains and southernmost Blue Ridge escarpment, along with previously recognized populations from the Cumberland Escarpment and Cumberland Plateau of south-central Tennessee and northeastern Alabama. This taxon concept of D. ocoee includes three deeply divergent geographic genetic segments that hybridize across two contact zones, while D. apalachicolae may be nested within some southern Blue Ridge populations of D. ocoee. The resurrected form of D. perlapsus also exhibits some admixture with the newly restricted D. ocoee. While this taxonomic arrangement is robust and stably derived from mitochondrial, morphological, and nuclear data, more sophisticated future analyses sampling additional populations and loci to estimate relationships may reach more subtle conclusions regarding the identity of some lineages within D. ocoee.

Allocation of Salamandra auriculata Holbrook, 1838, with a new species of swamp-dwelling dusky salamander (Plethodontidae: Desmognathus) from the Atlantic Coastal Plain

Most swamp-dwelling dusky salamanders of the genus Desmognathus from the Coastal Plain were long treated as a single species (Desmognathus auriculatus) ranging from east Texas to southeastern Virginia. This taxon concept was based on the name Salamandra auriculata Holbrook, 1838 with type locality Riceboro, Liberty County, Georgia and a type series that could not be located by later authors. Recent workers have been unable to locate or verify swamp-dwelling populations from east Texas and western Louisiana, which appear to be extirpated and may not have represented a distinct taxon from co-occurring lineages of D. conanti. Recent molecular phylogenies have supported at least four distinct species-level taxa within D. auriculatus. Populations from the Gulf Coastal Plain in eastern Louisiana, Mississippi, and southwestern Alabama were recently described as D. valentinei Means, Lamb, and Bernardo, 2017 and D. pascagoula Pyron, O'Connell, Lamb, and Beamer, 2022. This leaves two remaining species-level lineages with uncertain taxonomy and nomenclature: D. auriculatus A (Alabama, Florida, and Georgia), and D. auriculatus B/C (Georgia, South Carolina, and North Carolina), both of which occur near the type locality. We recently located a specimen at the Muséum national d'Histoire naturelle in Paris (MNHN 0.4675) that we concluded is one of Holbrook's syntypes and designated it as the lectotype, but without allocation. Here, we use linear morphometrics to confidently allocate it to D. auriculatus A, bolstered by examination of three historical topotypic collections. This requires a new name for D. auriculatus B/C, which we describe as D. valtos sp. nov. (suggested common name: Carolina Swamp Dusky Salamander) from Otter Creek, Craven County, North Carolina. Other related and sympatric species of Desmognathus remain to be described from the Atlantic Coastal Plain and adjacent Piedmont of the southeastern United States.

The taxonomic and nomenclatural status of the nomina Salamandra fusca Green, 1818 and Salamandra quadramaculata Holbrook, 1840 (Amphibia, Urodela)

We address here a few nomenclatural problems concerning some salamander nomina of the plethodontid genus Desmognathus Baird, 1850: the identification of the scriptores (first users) of aponyms (subsequent spellings) in cases of primary homonymy; the validity of airesies (first reviser actions) in special cases; and the validity of neotype designations. Accordingly, we validate Pyron & Beamer’s (2020) invalid designation of a neotype for Salamandra nigra Green, 1818, and we provide a synonymic and aponymic list for Desmognathus fuscus (Green, 1818).

A new, narrowly endemic species of swamp-dwelling dusky salamander (Plethodontidae: Desmognathus) from the Gulf Coastal Plain of Mississippi and Alabama.

We describe a new, narrowly endemic species of swamp-dwelling dusky salamander (Plethodontidae: Desmognathus pascagoula sp. nov.) from the Gulf Coastal Plain of southeastern Mississippi and southwestern Alabama based on linear morphometrics, mitochondrial DNA, and single nucleotide polymorphisms from 881 loci produced using genotype-by-sequencing. Some populations of the new species were historically referred to as D. auriculatus, a polyphyletic assemblage of at least three species in the Atlantic and Gulf Coastal Plain from Texas to North Carolina. Populations of D. auriculatus from the Gulf Coastal Plain in Louisiana and Mississippi were recently described as D. valentinei. The new species includes populations that were tentatively referred to D. valentinei, but we find it is morphologically, genetically, and geographically distinct. It is smaller, has a more defined dorsal color pattern, more irregular whitish portholes in up to three rows on the lateral surfaces of the body and tail, and a brighter orange or yellowish orange postocular stripe. At present, the new species is known from only six extant populations in the lower Pascagoula, Escatawpa, and Mobile drainages. The latter represents a distinct phylogeographic lineage. We also refer a historical collection from the northeastern side of the Mobile-Tensaw River Delta to this species, suggesting a much broader range in the past. We suspect that more populations remain to be discovered in the area, and their potential species-level distinctiveness should be tested further. This discovery increases knowledge of the biodiversity in the southeastern United States Coastal Plain, a candidate region meeting the global criteria for a biodiversity hotspot, and underscores the amount of cryptic diversity likely remaining to be discovered and described in Nearctic salamanders.

Candidate-species delimitation in Desmognathus salamanders reveals gene flow across lineage boundaries, confounding phylogenetic estimation and clarifying hybrid zones.

Dusky Salamanders (genus Desmognathus) currently comprise only 22 described, extant species. However, recent mitochondrial and nuclear estimates indicate the presence of up to 49 candidate species based on ecogeographic sampling. Previous studies also suggest a complex history of hybridization between these lineages. Studies in other groups suggest that disregarding admixture may affect both phylogenetic inference and clustering‐based species delimitation. With a dataset comprising 233 Anchored Hybrid Enrichment (AHE) loci sequenced for 896 Desmognathus specimens from all 49 candidate species, we test three hypotheses regarding (i) species‐level diversity, (ii) hybridization and admixture, and (iii) misleading phylogenetic inference. Using phylogenetic and population‐clustering analyses considering gene flow, we find support for at least 47 candidate species in the phylogenomic dataset, some of which are newly characterized here while others represent combinations of previously named lineages that are collapsed in the current dataset. Within these, we observe significant phylogeographic structure, with up to 64 total geographic genetic lineages, many of which hybridize either narrowly at contact zones or extensively across ecological gradients. We find strong support for both recent admixture between terminal lineages and ancient hybridization across internal branches. This signal appears to distort concatenated phylogenetic inference, wherein more heavily admixed terminal specimens occupy apparently artifactual early‐diverging topological positions, occasionally to the extent of forming false clades of intermediate hybrids. Additional geographic and genetic sampling and more robust computational approaches will be needed to clarify taxonomy, and to reconstruct a network topology to display evolutionary relationships in a manner that is consistent with their complex history of reticulation.

Increased growth rates of stream salamanders following forest harvesting.

Timber harvesting can influence headwater streams by altering stream productivity, with cascading effects on the food web and predators within, including stream salamanders. Although studies have examined shifts in salamander occupancy or abundance following timber harvest, few examine sublethal effects such as changes in growth and demography. To examine the effect of upland harvesting on growth of the stream‐associated Ouachita dusky salamander (Desmognathus brimleyorum), we used capture–mark–recapture over three years at three headwater streams embedded in intensely managed pine forests in west‐central Arkansas. The pine stands surrounding two of the streams were harvested, with retention of a 14‐ and 21‐m‐wide forested stream buffer on each side of the stream, whereas the third stream was an unharvested control. At the two treatment sites, measurements of newly metamorphosed salamanders were on average 4.0 and 5.7 mm larger post‐harvest compared with pre‐harvest. We next assessed the influence of timber harvest on growth of post‐metamorphic salamanders with a hierarchical von Bertalanffy growth model that included an effect of harvest on growth rate. Using measurements from 839 individual D. brimleyorum recaptured between 1 and 6 times (total captures, n = 1229), we found growth rates to be 40% higher post‐harvest. Our study is among the first to examine responses of individual stream salamanders to timber harvesting, and we discuss mechanisms that may be responsible for observed shifts in growth. Our results suggest timber harvest that includes retention of a riparian buffer (i.e., streamside management zone) may have short‐term positive effects on juvenile stream salamander growth, potentially offsetting negative sublethal effects associated with harvest.

An Evaluation of Immersive and Handling Methods for Collecting Salamander Skin Peptides

Amphibian skin secretions are a rich source of antimicrobial peptides that have long interested both the biomedical and herpetological research communities. While anuran skin peptides are well studied, little is known about skin peptides in salamanders, in part because methods for collecting them are poorly developed. In anurans, pharmacological agents are commonly used to stimulate skin peptide responses, thus increasing the amount of peptide collected. It was unclear whether similar methods would work for salamanders. We conducted a series of experiments to test the effects of immersion in pharmaceutical agents (norepinephrine hydrochloride [NE]; acetylcholine chloride [Ach]), handling, and the interaction of both on peptide collection from the skin of Red-Spotted Newts (Notophthalmus viridescens) and Allegheny Mountain Dusky Salamanders (Desmognathus ochrophaeus). Our results suggest that vigorous handling, but not immersion in NE or Ach, is a better method for collecting salamander skin peptides. Despite the widespread use of pharmaceuticals to collect anuran skin peptides, we found little evidence that NE or Ach induces peptide release in salamanders. In fact, we show that inclusion of NE in collection solutions interferes with peptide quantification in protein assays.

Leaf litter and rock bag surveys allow for detection and DNA barcoding characterization of diet composition of dusky salamanders

Salamanders are vital components of many aquatic ecosystems food webs and are often found in diverse habitats, including both urban and semi-rural environments. The northern dusky salamander, Desmognathus fuscus is a common salamander found throughout the southeastern United States and is an important predator of aquatic macroinvertebrates. However, very little is known about either diet or suitable survey techniques for this species in human altered habitats, which may vary based on level of urbanization (e.g., are either spring-fed, derived from ponds, modified ditches, etc.). Therefore, we used multiple survey methods (leaf litter bags, novel rock bags, and quadrat sampling) to quantify relative abundance of D. fuscus on Wingate University's campus, in Wingate, North Carolina. We also collected and identified aquatic invertebrates from bag sampling and diet items obtained from gastric lavage of adult salamanders from quadrat sampling. Leaf litter bags contained the highest relative abundance of salamanders (47) compared to rock bags (14), with quadrat sampling yielding primarily adult salamanders. We noted a significant difference among our two sites sampled in salamander relative abundance (Man-Whitney U test = 67.5, p < 0.001), possibly due to reduced water quality, canopy cover, or less available habitat. Aquatic worms represented the most frequent potential food item sampled from both bag types (61.9%), followed by Diptera nymphs (13.7%). Potential food items from leaf and rock bags as well as gastric lavage samples collected from Desmognathus were further identified using DNA barcoding. These food items included a variety of both aquatic and terrestrial invertebrates (annelid worms, springtails, chironomids, carpenter ants, shore flies, wasps, and wood lice). These results indicate urban salamanders may forage both in the stream and in the riparian zone or advantageously consume insects which fall into the stream. This study adds to our body of knowledge on the ecology of salamanders in urban stream environments.

Environmental DNA as a detection and quantitative tool for stream‐dwelling salamanders: A comparison with the traditional active search method

AbstractAs amphibians are showing significant signs of decline, adequate information and understanding of target species are essential for taking appropriate conservation measures. In recent years, environmental DNA has seen notable growth as a monitoring tool and testing this emergent method with various species has become an important step toward a better understanding of its benefits and limits for studying specific taxa. This study focused on using species‐specific qPCR assays developed in our research group to test the eDNA method for three stream‐dwelling salamander species of the Plethodontidae family: the Spring salamander (Gyrinophilus porphyriticus), the Northern dusky salamander (Desmognathus fuscus), and the Northern two‐lined salamander (Eurycea bislineata). The traditional active search method and the eDNA method were compared for both their ability to detect species as well as to provide a quantitative assessment of populations in 24 headwater streams in Québec, eastern Canada. For all three species, eDNA was detected in every stream where the target species was observed during the active search method. Moreover, eDNA was detected in nine streams where the target species was not identified with the active search. A marginally significant association was found between eDNA concentration and salamander density for D. fuscus only. All species showed high variability for eDNA concentration between qPCR technical replicates and between samples of a given stream. The results of this study lead us to conclude that eDNA can be an excellent method for detection of stream‐dwelling salamanders. Given the inconsistent quantitative aspect of eDNA with the studied species, the future of these stream‐dwelling salamander monitoring most likely lies in the combined use of both eDNA and active search methods. Hence, active search could continue to offer useful small‐scale detection and reliable quantitative data while eDNA could be implemented as an efficient and promising tool for large‐scale detection.

Stream Salamanders are Relatively Tolerant of Salty Streams.

The application of road salt as a deicing agent is common, but investigations of potential negative effects of salt runoff on stream salamanders have been limited. Additionally, modern stormwater management practices should influence the delivery of salt ions to streams. We used data loggers in streams draining watersheds with and without stormwater management ponds and acute 96-h LC50 tests to investigate exposure of, and road salt toxicity among, two widespread salamanders in the Eastern USA, northern dusky salamanders (Desmognathus fuscus) and northern two-lined salamanders (Eurycea bislineata). In streams below stormwater ponds, base levels of conductivity were elevated throughout the year and elevated Cl- levels led to more frequent acute and chronic exceedances of U.S. Environmental Protection Agency ambient water quality criteria for Cl- when compared to streams draining watersheds with no stormwater management ponds. However, five of the six streams studied had exceedance frequencies suggesting Cl- associated with road salt application represented a persistent threat to aquatic life. Larval stream salamanders were relatively tolerant of salt, not exhibiting any lethal effects over a 96-h period until chloride levels exceeded 5000mg/L for both species, and concentrations in streams rarely exceeded these levels and only for very short periods of time. Our results suggest road salts are not having acute lethal effects on salamanders in the streams we studied, but exceedance of U.S. Environmental Protection Agency ambient water quality standards for Cl- suggest the potential for sublethal and indirect effects of Cl- on salamander populations that require further study.

Combined Effects of Experimentally Elevated CORT and Predation Threat on Exploratory and Foraging Behavior of Desmognathus ochrophaeus

Amphibian responses to stress are generally mediated through glucocorticoids produced by the hypothalamic–pituitary–interrenal axis. Chronic elevation of glucocorticoids can result in delayed wound healing and growth, but less is known about its influence on behavioral responses to predators. We examined the effect of acute and chronic CORT elevation on exploratory and foraging behaviors of Allegheny Mountain Dusky Salamanders (Desmognathus ochrophaeus) exposed to kairomones from a predatory snake. We established ‘No CORT,' ‘Acute CORT,' and ‘Chronic CORT’ conditions during an 18-d preparation phase by varying salamander exposure to an exogenous source of CORT (0.51 mg/mL) delivered via cutaneous patch. During the trial phase, we conducted assays to evaluate exploratory and foraging behavior of salamanders from the different CORT groups when exposed to snake kairomones or control. Exploratory behavior was examined within a circular arena with a series of surmountable concentric barriers, and foraging behavior was observed within Petri dishes containing Drosophila prey. Salamanders experiencing both Chronic CORT and snake kairomones exhibited the least exploratory behavior, escaped the array with the lowest frequency, climbed the fewest barriers, and delayed their movement. However, foraging behavior (latency to strike at prey, number of strikes, number of prey captured) was not affected by exposure to CORT or snake kairomone. Our findings suggest that artificially elevated CORT can modify some behavioral responses to predator kairomones, but only when individuals experience multiple CORT applications in the period preceding the trials.

Maximum likelihood inference for the band-read error model for capture-recapture data with misidentification

Misidentification of animals is a common problem for many capture-recapture experiments. Considerably misleading inference may be obtained when traditional models are used for capture-recapture data with misidentification. In this paper, we investigate the so-called band-read error model for modeling misidentification, assuming that it is possible to identify one marked individual as another on each capture occasion. Currently, fitting this model relies primarily on a Bayesian Markov chain Monte Carlo approach, while maximum likelihood is difficult because there is not a computationally efficient likelihood function available. The Bayesian method is exact but requires considerable computation time. We propose an approximate model for modeling misidentification and then develop a fast maximum-likelihood approach for the approximate model using likelihood constructed by the saddlepoint approximation method. We demonstrate the promising performance of our proposed method by simulation and by comparisons with the Bayesian inference under the original model. We apply the method to analyze capture-recapture data from a population of Northern Dusky Salamanders (Desmognathus fuscus) collected in North Carolina, USA.