Wild Snake Research Articles

Snake scales record environmental metal(loid) contamination.

Wetland snakes, as top predators, are becoming globally recognised as bioindicators of wetland contamination. Livers are the traditional test organ for contaminant exposure in organisms, but research is moving towards a preference for non-lethal tissue sampling. Snake scales can be used as an indicator of exposure, as many metals bind to the keratin. We used laser ablation with inductively coupled plasma-atomic emission spectroscopy and mass spectrometry (LA-ICP-MS) to quantify the concentrations of 19 metals and metalloids (collectively referred to 'metals' hereafter) in Western tiger snake (Notechis scutatus occidentalis) scales from four wetlands along an urban gradient, and compared them to concentrations measured in captive tiger snake scales. We conducted repeat measures to determine the concentration accuracy of each metal using LA-ICP-MS. Concentrations in wild Western tiger snake scales were significantly higher than in reference tiger snake scales for most metals analysed, suggesting accumulation from environmental exposure. We compared the scale concentrations to sediment concentrations of sampled wetlands, and found inter-site differences between mean concentrations of metals in scales parallel patterns recorded from sediment. Four metals (Mn, As, Se, Sb) had strong positive correlations with liver tissue contents suggesting scale concentrations can be used to infer internal concentrations. By screening for a larger suite of metals than we could using traditional digestive methods, we identified additional metals (Ti, V, Sr, Cs, Tl, Th, U) that may be accumulating to levels of concern in tiger snakes in Perth, Western Australia. This research has progressed the use of LA-ICP-MS for quantifying a suite of metals available in snake scales, and highlights the significance of using wetland snake scales as a non-lethal indicator of environmental contamination.

Species Identification of Shed Snake Skins by Scanning Electron Microscopy, with Verification of Intraspecific Variations and Phylogenetic Comparative Analyses of Microdermatoglyphics

Shed skins of snakes have practical applications and can provide information on biodiversity. We examined shed skins or scales stripped from 53 native species of snakes from Taiwan and adjacent islands and 13 foreign species, verified the intraspecific variation of microstructures on the scales, conducted phylogenetic comparative analyses of microdermatoglyphics, and developed a guide and key to identify shed skins by scanning electron microscopy. We examined several microstructural characteristics of scales including the form and dimensions of oberhautchen cells, denticulations, microridges, nanopits, and nanochannels. Furthermore, we noted scale shape and presence or absence of rounded tubercles on the scales. The microstructures of apical (and central) regions of scales were similar to each other, but different from those on basal and lateral margins, the keel, or apical pits. The microdermatoglyphics on cranial scales (cephalic shields) differed from those on scales from other regions of the body. Those from the dorsal and dorsolateral surfaces of the body, and the dorsal surface of the tail were similar, as were those on scales from the ventral surfaces of the body and tail. For adults or juveniles, there was no significant ontogenetic variation in many microdermatoglyphic characteristics. By conducting phylogenetic mapping, we found that symmetrical (dorsal) scales without apical pit organs or rounded tubercles, keelless and rounded scales, flat microdermatoglyphic patterns (without longitudinal microridges), (sub)lamellate oberhautchen cells, cell borders without denticulations or with tiny and keelless denticulations, and relatively small nanopits at denticulation joints or covering cells, are likely to be plesiomorphic character states. We also examined character evolution models based on the microdermatoglyphics and their phylogenetic signals, conducted phylogenetic generalized least-squares regressions to examine the correlations among snake habitat type and the morphological traits on scales, and confirmed a hypothesis that the evolution of scale microstructures is dominated by both phylogenetic and functional (ecological) constraints. This study also indicates that scale microstructure can be used to identify snakeskin products, roadkill specimens and fragmented samples, scale remnants in predator feces, and wild snake sloughs.

Micro-geographic shift between negligible and actuarial senescence in a wild snake.

While it has long been known that species have contrasted life expectancy (pace of mortality) and generation time (pace of reproduction), recent studies have also uncovered that the shape of adult age trajectories of mortality and reproduction can vary remarkably among species along a continuum of senescence ranging from strong deterioration (senescence), insignificant deterioration (negligible senescence) to improvement with advancing age (negative senescence). As for many long-lived ectotherms with asymptotic growth and increasing reproductive output with age, snakes are good candidates for negligible senescence to occur. Yet, intraspecific variation in the pace and shape of actuarial and reproductive senescence across wild populations of these species remains to be explored. Here, we used 37years of mark-recapture data in two nearby habitats inside a meadow viper Vipera ursinii population to quantify life expectancies, generation times and the shape of actuarial and reproductive senescence. Female vipers maintained stable reproductive performances at old ages, even when accounting for the predicted increase of fertility with body size, providing evidence for negligible reproductive senescence in both habitats. Males had a higher adult mortality and a shorter life expectancy on average than females and actuarial senescence shifted from negligible senescence in the optimal habitat to strong senescence in the sub-optimal habitat. Overall, these results demonstrate that micro-geographic environmental variation can generate qualitative shifts in actuarial senescence patterns. This highlights that taking into account the within-species plasticity of age-dependent trajectories could prove useful in better understanding what determines the evolution of life-history age trajectories.

Forty-four years of global trade in CITES-listed snakes: Trends and implications for conservation and public health

Trade in venomous and non-venomous snakes can negatively impact wild snake populations and may drive snakebite risk for people. However, we often lack sufficient trade data to identify where the potential risks for snake population decline and snakebite are highest. Currently, the legal, international trade of 164 snake species is regulated by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). We analyzed CITES-listed snake trade from 1975 to 2018 using the recently released shipment-level CITES Trade Database to identify spatiotemporal trends of snake trade and generate insights regarding snake conservation and potential public health risks from snakebite. Commercially purposed pythons dominated the global snake trade, comprising 38.8% of all traded snakes. Live snakes were mainly exported by Ghana, Indonesia, Togo, and Benin, and imported by China and the USA. Venomous snake trade comprised 10.8% of all traded snakes, and over 75% of wild-sourced venomous snakes came from Indonesia. Although traded snakes in recent years are increasingly comprised of captive-bred animals, the majority of snakes are still wild-sourced (> 60% between 2015 and 2017), including IUCN-listed species, with potentially detrimental impacts on conservation status. Further, the CITES Trade Database reveals geographic regions where venomous snakes are sourced from the wild, posing potential risks to snake catchers, traders, and pet owners. The database also documents the movement of non-native snake species through trade, with implications for conservation of native species. This study represents the first global analysis focused specifically on CITES-listed snake trade using the CITES Trade Database.

Smolt Transportation Influences Straying of Wild and Hatchery Snake River Steelhead into the John Day River

AbstractBarge transportation of steelhead Oncorhynchus mykiss smolts through the Snake and Columbia rivers can increase the probability of straying by returning adults at the individual scale. However, the effect of barge transportation on a major population group has not been evaluated. We estimated the proportion of hatchery‐origin steelhead spawners present in the John Day River from 2004 to 2018 via observation of adults on spawning ground surveys and in traps. Despite no hatchery releases within the John Day River, up to 42% of the observed spawners in nature were of hatchery origin. The proportion of hatchery‐origin spawners in the John Day River was best explained by the number of smolts that were barge transported from the Snake River 2–3 years prior to spawning and natural‐origin spawner abundance. At an individual scale, barged hatchery steelhead from the Snake River, when compared with hatchery and wild steelhead that were allowed to migrate in‐river as smolts, were 73 times more likely to be detected in the John Day River during their adult return migration. Barged hatchery and barged wild steelhead exhibited no difference in the probability of adult detection in the John Day River. Our study demonstrates how a salmonid recovery effort in one portion of the Columbia River basin had an unintended and potentially adverse impact on non‐target populations. To minimize stray spawners (both hatchery and wild) in the John Day River, transportation of Snake River steelhead smolts should replicate spawning years 2013–2018 (i.e., the 2010–2016 smolt cohorts), with transportation not beginning until May 1 and with the total number of transported hatchery smolts maintained at a level no greater than 2.3 million annually.

Defensive behaviors and brain regional activation changes in rats confronting a snake

In the present study, we examined behavioral and brain regional activation changes of rats). To a nonmammalian predator, a wild rattler snake (Crotalus durissus terrificus). Accordingly, during snake threat, rat subjects showed a striking and highly significant behavioral response of freezing, stretch attend, and, especially, spatial avoidance of this threat. The brain regional activation patterns for these rats were in broad outline similar to those of rats encountering other predator threats, showing Fos activation of sites in the amygdala, hypothalamus, and periaqueductal gray matter. In the amygdala, only the lateral nucleus showed significant activation, although the medial nucleus, highly responsive to olfaction, also showed higher activation. Importantly, the hypothalamus, in particular, was somewhat different, with significant Fos increases in the anterior and central parts of the ventromedial hypothalamic nucleus (VMH), in contrast to patterns of enhanced Fos expression in the dorsomedial VMH to cat predators, and in the ventrolateral VMH to an attacking conspecific. In addition, the juxtodorsalmedial region of the lateral hypothalamus showed enhanced Fos activation, where inputs from the septo-hippocampal system may suggest the potential involvement of hippocampal boundary cells in the very strong spatial avoidance of the snake and the area it occupied. Notably, these two hypothalamic paths appear to merge into the dorsomedial part of the dorsal premammillary nucleus and dorsomedial and lateral parts of the periaqueductal gray, all of which present significant increases in Fos expression and are likely to be critical for the expression of defensive behaviors in responses to the snake threat.

An emerging fungal pathogen is associated with increased resting metabolic rate and total evaporative water loss rate in a winter‐active snake

Abstract Energy allocation trade‐offs associated with mounting metabolically costly immune responses may serve as sublethal mechanisms by which pathogens reduce host fitness. The emergence of cutaneous fungal pathogens, which invade the skin of their host and have the potential to disturb energy and water balance, highlight the importance of host physiology in determining individual‐ and population‐level effects of disease. Snake fungal disease (SFD, ophidiomycosis), caused by the fungal pathogen Ophidiomyces ophiodiicola (Oo), is an emerging disease afflicting wild snake populations throughout eastern North America. Emaciation and dehydration are phenotypic correlates of SFD, but it is unknown if such declines in host condition occur via effects of Oo infection on host physiology (i.e. increased rates of metabolism and evaporative water loss respectively). We used flow‐through respirometry to assess the energetic and hydric consequences of natural Oo infection in winter‐active pygmy rattlesnakes Sistrurus miliarius. We measured resting metabolic rate (CO2 production rate) and total evaporative water loss rate of winter‐acclimatized S. miliarius as a function of SFD status and acute temperature (17, 25 and 32°C). We also used regression models characterizing individual variation in the thermal‐sensitivity of resting metabolic rate to predict the theoretical effects of behavioural fever on daily resting CO2 production by free‐ranging S. miliarius with SFD in winter. Natural infection by Oo was associated with significant increases in resting metabolic rate (30%–45%) and total evaporative water loss rate (30%–40%) across all measurement temperatures. Under simulated scenarios of behavioural fever, Oo infection was predicted to increase daily resting CO2 production rate by 58%–102%. Our results are consistent with the hypothesis that the immune response to Oo infection is energetically costly and may contribute to declining host condition. Our modelling efforts combining the cumulative effects of increased immune activity and increased body temperature on metabolism represent a novel approach in quantifying the total daily energetic cost of infection in ectothermic vertebrates undergoing behavioural fever. A free Plain Language Summary can be found within the Supporting Information of this article.

Hissing like a snake: bird hisses are similar to snake hisses and prompt similar anxiety behavior in a mammalian model

Batesian mimicry refers to a harmless species protecting itself from predators by mimicking a harmful species. A case of acoustic Batesian mimicry has been proposed in the naturalist literature: it is suspected that birds called like a snake when disturbed in their cavities to deter mammalian predators or repel competitors. To evaluate this hypothesis, we first test the assumption that the hissing sound produced by adult females of a wild cavity-nesting species – the blue tit (Cyanistes caeruleus) – is acoustically similar to the hisses of three wild sympatric snake species. Then, we tested one prediction of this hypothesis which is that the receiver of the signal should react similarly to the snake and bird hisses. To do so, we used, hiss-naïve individuals, without any past experience with predators: the house mouse (Mus musculus domesticus), representing a model of a possible nest competitor. We quantified mouse responses to blue tit and snake hisses and two non-hiss sounds (other blue tit vocalizations and human voices). Our results show that snake hisses and blue tit hisses are structurally more similar to each other than to other blue tit vocalizations and that both hisses provoke comparable levels of anxiety behavior in mice. Taken together, these results are compatible with the hypothesis that blue tits have evolved to mimic the sound of snakes, i.e., the Batesian mimicry hypothesis. We also note however that our results also agree with another hypothesis, suggesting that mechanisms underlying the production and perception of hisses are conserved across vertebrates. Further research is needed to disentangle these two hypotheses. Mimicry is a fascinating illustration of the principles of evolution in communication. In the case of Batesian mimicry, species evolve to resemble other species as a mean of deterring harmful receivers. While visual mimicry has been thoroughly investigated across a wide range of species, vocal mimicry remains less studied. In the present study, we compared the acoustic similarity of the hissing sound produced by female blue tits, a cavity-nesting species, to the hisses of three snake species. Then, we exposed mice, a model of a possible cavity competitor, to bird and snake hisses. We showed that snake and blue tit hisses are acoustically similar and provoke comparable anxiety behaviors in mice. These results are compatible with the hypothesis that blue tits utilize an innate fear response to hisses in mammals, a result that may explain why blue tit hisses have been linked to increased survival by other authors. Furthermore, the results also suggest a conserved function of, and response to, hiss vocalizations across vertebrates.

Bioaccumulation characteristics of PBDEs and alternative brominated flame retardants in a wild frog-eating snake

While a large body of studies have examined polybrominated diphenyl ethers (PBDEs) and alternative brominated flame retardants (ABFRs) in wildlife, information on the bioaccumulation of these contaminants in reptiles in general, and snakes in particular, are scarce. We investigated the bioaccumulation characteristics of PBDEs and several ABFRs including decabromodiphenyl ethane (DBDPE), 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE), hexabromobenzene (HBB) and pentabromotoluene (PBT) in a frog-eating snake, the striped keelback snake (Amphiesma stolata), from an e-waste recycling site in South China. The concentrations of ∑PBDEs and ∑ABFRs in the snakes ranged 53–5200 and 3.1–87 ng/g lipid weight, respectively; with higher levels in males than females. Additionally, the concentrations of BDE-28, -47, and −66 were positively correlated with snake size (snout-vent length and body mass), while negative correlations were found for most of the higher brominated PBDE congeners and HBB, PBT and BTBPE. The biomagnification factors (BMFs) estimated in the snake/frog relationship indicated a mild to moderate biomagnification of BDE-28, -47, −66, −100, −153 and −154 (with mean BMFs of 1.1–5.3), while a lack of magnification for the other PBDE congeners and all the ABFRs. This is the first report on the sex- and size-related accumulation and biomagnification potentials of PBDEs and ABFRs in snakes.

Patterns of Iteroparity in Wild Snake River Steelhead

AbstractSome anadromous salmonids are iteroparous (repeat spawners); however, postspawn individuals are often not considered in management plans because of the lack of long‐term studies of this life history. The balance of factors affecting survival between spawns and fecundity of repeat spawners should determine the percentage of iteroparous individuals in a population. Steelhead Oncorhynchus mykiss are capable of iteroparity, but Snake River populations in the interior Columbia River basin in the Pacific Northwest have the lowest iteroparity rates. Managers are interested in augmenting the incidence of iteroparity as a conservation measure. However, there is little information about repeat‐spawning steelhead to guide and evaluate management. In this study, we elucidated patterns and characteristics of repeat‐spawning steelhead in the Snake River basin. Repeat spawners were overwhelmingly female and were found in all 10 stocks. Most iteroparous fish first spawned after 1 year in the ocean (51.4%) and skipped a year between spawns (55.4%). Growth between spawns declined for longer, older steelhead. Survival from the first spawning migration to postspawn emigration increased during the study. However, survival in the Columbia River estuary and Pacific Ocean declined such that overall survival to second spawn varied little. Small females were most likely to survive to a second spawning migration. We hypothesized that iteroparity in Snake River steelhead was constrained by the energetic costs of the spawning migration (distance, elevation, timing, dam passage) combined with a lack of timely postspawn recovery. Hence, survival to second spawning migration is low for Snake River steelhead and most postspawn steelhead needed a full year to recover. Management programs intended to augment the incidence of iteroparity should account for (1) factors that increase stress and metabolic demand on spawning and postspawn fish and (2) factors that increase the time it takes for emigrating kelts to effectively refuel and recover.

Evidence of Vertical Transmission of the Snake Fungal Pathogen Ophidiomyces ophiodiicola

Snake fungal disease (ophidiomycosis) is an emerging infection of snakes caused by Ophidiomyces ophiodiicola. Little is known about mechanisms of this pathogen's transmission and its implications for conservation of wild snake populations. We report four cases with evidence of vertical transmission of O. ophiodiicola from dam to offspring.

Snake Fungal Disease in Colubridae Snakes in Connecticut, USA in 2015 and 2017.

Snake fungal disease (SFD), caused by the fungus Ophidiomyces ophiodiicola, is an emerging threat to wild snake populations in the US. Data regarding its distribution, prevalence, and population-level impacts are sparse, and more information is needed to better manage SFD in the wild. In this study, we captured 38 wild snakes of five species in Connecticut in the summers of 2015 and 2017. Skin lesions were biopsied and evaluated histologically for fungal dermatitis. At least one individual from each species was positive for SFD, and 48% of snakes sampled in 2015 and 39% of snakes sampled in 2017 were positive for SFD. A Dekay's brownsnake (Storeria dekayi dekayi) with SFD lesions, captured in the summer of 2017, extended the host range of the disease. Thus, SFD was present in wild Connecticut snakes in 2015 and 2017, which demonstrated a wide-spread distribution throughout the state.

Next-generation sequencing analysis reveals high bacterial diversity in wild venomous and non-venomous snakes from India.

BackgroundThe oral cavities of snakes are replete with various types of bacterial flora. Culture-dependent studies suggest that some of the bacterial species are responsible for secondary bacterial infection associated with snakebite. A complete profile of the ophidian oral bacterial community has been unreported until now. Therefore, in the present study, we determined the complete bacterial compositions in the oral cavity of some snakes from India.MethodsTotal DNA was isolated from oral swabs collected from three wild snake species (Indian Cobra, King Cobra and Indian Python). Next, the DNA was subjected to PCR amplification of microbial 16S rRNA gene using V3-region-specific primers. The amplicons were used for preparation of DNA libraries that were sequenced on an Illumina MiSeq platform.ResultsThe cluster-based taxonomy analysis revealed that Proteobacteria and Actinobacteria were the most predominant phyla present in the oral cavities of snakes. This result indicates that snakes show more similarities to birds than mammals as to their oral bacterial communities. Furthermore, our study reports all the unique and common bacterial species (total: 147) found among the oral microbes of snakes studied, while the majority of commonly abundant species were pathogens or opportunistic pathogens to humans. A wide difference in ophidian oral bacterial flora suggests variation by individual, species and geographical region.ConclusionThe present study would provide a foundation for further research on snakes to recognize the potential drugs/antibiotics for the different infectious diseases.

Field Diagnostics and Seasonality of Ophidiomyces ophiodiicola in Wild Snake Populations

Snake fungal disease (SFD) is an emerging disease caused by the fungal pathogen, Ophidiomyces ophiodiicola. Clinical signs of SFD include dermal lesions, including regional and local edema, crusts, and ulcers. Snake fungal disease is widespread in the Eastern United States, yet there are limited data on how clinical signs of SFD compare with laboratory diagnostics. We compared two sampling methods for O. ophiodiicola, scale clip collection and swabbing, to evaluate whether collection method impacted the results of polymerase chain reaction (PCR). In addition, we evaluated the use of clinical signs to predict the presence of O. ophiodiicola across seasons, snake habitat affiliation (aquatic or terrestrial) and study sites. We found no significant difference in PCR results between sampling methods. Clinical signs were a strong predictor of O. ophiodiicola presence in spring and summer seasons. Snakes occupying terrestrial environments had a lower overall probability of testing positive for O. ophiodiicola compared to snakes occupying aquatic environments. Although our study indicates that both clinical signs of SFD and prevalence of O. ophiodiicola vary seasonally and based on habitat preferences of the host, our analysis suggests that clinical signs can serve as a reliable indicator of O. ophiodiicola presence, especially during spring and summer.

Analysis of Reptarenavirus genomes indicates different selective forces acting on the S and L segments and recent expansion of common genotypes

Reptarenaviruses, a genus of snake-infecting viruses belonging to the family Arenaviridae, have bi-segmented genomes. The long (L) segment encodes the Z and L (RNA polymerase) proteins, whereas the short (S) segment codes for the glycoprotein precursor (GPC) and for the nucleoprotein (NP). Presently, reptarenaviruses have only been described in captive snakes. In these animals, mixed infections are common and most infected reptiles harbor multiple S and/or L segment genotypes. Within single animals, L segments are more genetically diverse than S segments and one S segment genotype (S6) was detected in the majority of snakes. Whether the unbalanced L to S segment ratio is due to stochastic events, to distinct replication/packaging efficiencies, or to differential selective pressure is presently unknown. We addressed these open questions by analyzing the ancient and recent evolutionary history of reptarenavirus genomes. Results indicated that purifying selection shaped the bulk of reptarenavirus coding sequences, although selective constraint was stronger for NP and L compared to GPC. During the divergence of reptarenavirus genomes, episodic positive selection contributed to the evolution of the viral polymerase, an observation that parallels those on mammarenaviruses. Population genetics analyses indicated that the most common S and L segment genotypes (including S6) display markedly negative Tajima's D values, but not low nucleotide diversity, suggesting recent population expansion. In conclusion, our data indicate that the selective pressures were stronger for the L segment than for the S segment, at least during reptarenavirus genotype divergence. More recently, the population sizes of some L and S segment genotypes expanded, suggesting that they out-competed the other genotypes, which show D values consistent with constant or decreasing population size. Competition among segments may have driven the disappearance of some S segment genotypes from wild and/or captive snake populations, eventually leading to the observed L to S imbalance.

Stress bij in het wild en in gevangenschap levende slangen: kwantificatie, gevolgen en het belang van management

Net zoals bij andere diersoorten hebben stress en verminderd welzijn een negatief effect op de mentale status, gezondheid en op het gedrag van zowel in het wild als in gevangenschap levende slangen. Naast antropogene verstoring zijn de beschikbaarheid van voedsel en schuilplaatsen, de aanwezigheid van predatoren en omgevingscondities, zoals seizoenale en klimatologische veranderingen, de belangrijkste factoren die stress en welzijn van wilde slangenpopulaties beïnvloeden. Bij in gevangenschap levende slangen is een ongeschikt management de meest prominente reden van chronische stress en verminderd welzijn. Chronische stress kan bepaald worden door gedragswijzigingen van de slang, maar een gestandaardiseerde kwantificatiemethode om (chronische) stresslevels accurater te bepalen, ontbreekt. Een biomerker die gebruikt kan worden, is het gehalte aan corticosterone in bloedplasma, feces en vervellingshuid.

Tracking Outcomes of Snake Fungal Disease in Free-ranging Pygmy Rattlesnakes ( Sistrurus miliarius).

Snake fungal disease (SFD) is caused by the fungus Ophidiomyces ophiodiicola and its documentation in wild snake populations has risen sharply in the past decade. Little is known regarding the fate of individual, free-ranging snakes afflicted with SFD. We monitored an afflicted population of pygmy rattlesnakes ( Sistrurus miliarius) at Lake Woodruff National Wildlife Refuge in Central Florida, US for 2 yr. The severity of SFD in individual snakes was unrelated to the probability of their recapture later in the study, and half of the snakes diagnosed as severely infected at the onset of the study were recaptured later with no clinical signs of SFD. The clinical progress of 12 serially recaptured individuals also showed that individuals cleared the infection and fluctuated between no or low and severe clinical signs over the 2-yr study.

Life History Diversity of Snake River Steelhead Populations between and within Management Categories

AbstractGrouping populations for management may overlook the fine‐scale diversity underpinning the stability and resilience of meta‐populations and fisheries. A bimodal timing distribution of summer‐run steelhead Oncorhynchus mykiss (anadromous Rainbow Trout) historically was observed at Bonneville Dam (BON), the first barrier to upstream migration in the Columbia River basin. Early mode fish (A‐run) tended to be younger and smaller (<78 cm) than later fish (B‐run). While A‐run fish spawn throughout the Columbia River basin, B‐run fish spawn primarily in the Snake River basin. Managers used indices of these modes to make fishery decisions, and later these criteria were adopted for conservation. It is still unclear how life history and body size differences among wild Snake River populations are related to the categories at BON. We examined population parameters characterizing the two categories (date of passage at BON, length) and parameters directly affecting population dynamics (age composition, sex ratio). The life history portfolio of Snake River steelhead is quite diverse. There was broad overlap among populations in several respects, forming a gradient in life history characteristics rather than a dichotomous break. All populations produced adults <78 cm and adults returning after August 25. Median lengths of putative B‐run populations were close to the criterion that was supposed to be a defining characteristic. In contrast, few A‐run populations produced many adults ≥78 cm. Mean percentage of two‐ocean fish was 52.1% for A‐run populations and 82.0% for B‐run populations. Mean age at spawn was greater in populations producing older smolts. Sex ratio was female biased, and older populations had greater percentages of females. Although the run‐type dichotomy was useful for management of fisheries in the past, it is not useful for conservation. A combination of genetic stock identification at main‐stem dams and population‐specific monitoring in natal streams provides a unified framework for the assessment of fisheries management and conservation objectives.Received March 2, 2016; accepted November 9, 2016 Published online March 10, 2017

Environmental and physiological correlates of the severity of clinical signs of snake fungal disease in a population of pigmy rattlesnakes, Sistrurus miliarius.

In the past decade, snake fungal disease (SFD) has been identified as an emerging threat to snake populations throughout the eastern USA. Snake fungal disease is caused by the fungus Ophidiomyces ophiodiicola. Little is known regarding the environmental or physiological variables that affect host vulnerability and O. ophiodiicola virulence in wild snake populations. Understanding the intrinsic and extrinsic factors that correlate with infection severity is a key first step in understanding host-pathogen dynamics. Host vulnerability may vary seasonally as a result of thermal conditions or energetic trade-offs, and pathogen growth rates or dispersal may be tied to seasonal trends in climate. To determine whether season, environmental temperature or energetic trade-offs associated with life-history stage influence an individual's susceptibility to infection, we monitored the severity of clinical signs of SFD, surface air temperature, reproductive status, body condition and serum complement activity (plasma bactericidal ability) in free-ranging pigmy rattlesnakes, Sistrurus miliarius, over the course of 18months. Seasonal increases in the severity of clinical signs of SFD were correlated negatively with monthly air surface temperature and the mean body condition of the population. Bactericidal ability varied seasonally, but pigmy rattlesnakes suffering from active SFD infections did not exhibit deficits in innate immune function. Infected snakes were in significantly lower body condition when compared with the general population, but seasonal patterns in the mean body condition of the population were not driven by seasonal patterns of infection severity. Our results highlight the potential importance of the thermal environment and energetic status in determining infection severity and outcomes and the need for managers and researchers to consider seasonality of symptom presentation when the goal is to identify the prevalence or incidence of SFD in populations.

Snake charming and the exploitation of snakes in Morocco

AbstractTraditional activities that potentially threaten biodiversity represent a challenge to conservationists as they try to reconcile the cultural dimensions of such activities. Quantifying the impact of traditional activities on biodiversity is always helpful for decision making in conservation. In the case of snake charming in Morocco, the practice was introduced there 500 years ago by the religious order the Aissawas, and is now an attraction in the country's growing tourism industry. As a consequence wild snake populations may be threatened by overexploitation. The focal species for snake charming, the Egyptian cobra Naja haje, is undergoing both range and population declines. We estimated the level of exploitation of snakes based on field surveys and questionnaires administered to Aissawas during 2003–2014, and compared our results with those of a study conducted 25 years previously. Aissawas use four venomous and four non-venomous species for snake charming and we estimate they harvest a minimum of 4,500 individuals annually, mostly venomous snakes. For exhibition purposes they selectively remove the largest specimens from the wild (i.e. those that could have the highest reproductive output). Compared to the previous data, we detected (1) a reduction in the number of species collected, (2) an increased distance to collecting fields, and (3) an increase in the market price for snakes, after correction for accumulated inflation, signifying a higher demand for these animals.