About

Professor William Hopkins is a faculty member in the Department of Fish and Wildlife Conservation at Virginia Tech, with a focus on physiological ecology and wildlife ecotoxicology. His research addresses pressing questions in both basic and applied science, including the energy costs of physiological and behavioral processes, and how anthropogenic disturbances alter the ability of fish and wildlife to interact appropriately with their environment. His work involves understanding the effects of land use, mercury contamination, coal combustion wastes, and other environmental factors on various species such as hellbenders, wood ducks, freshwater turtles, amphibians, and snakes. Professor Hopkins teaches courses related to vertebrate physiological ecology, global change, and wildlife biology, contributing to the education of students in these fields. His research aims to provide insights into how environmental changes impact wildlife health and behavior, with a particular emphasis on ecotoxicology and the effects of contaminants on reproductive and physiological functions.

Research topics

• Ecology
• Biology
• Zoology
• Animal science
• Medicine
• Demography
• Internal medicine
• Endocrinology

Selected publications

• Parasite Infections Influence Immunological Responses But Not Reproductive Success of Male Hellbender Salamanders (<i>Cryptobranchus alleganiensis</i>)

  Integrative Organismal Biology · 2025-01-01 · 1 citations

  articleOpen accessSenior author

  spp) to the host, with coinfection frequently occurring. We centered our study on adult males throughout their extended 8-month paternal care period because recent research indicates that nest failure caused by lack of paternal care and filial cannibalism is contributing to hellbender population declines. Recognizing the potential for parasites to modulate host physiology and behavior, we explored how infection severity influences paternal health and reproductive success. We assessed white blood cell profiles of adult male hellbenders in response to parasites, coinfection, and seasonal temperature fluctuations, while also investigating whether parasite infection or coinfection was predictive of nest success. We found that hellbenders exhibited seasonal shifts in white blood cell indices; as temperatures increased across seasons (from 5°C to 20°C), the proportion of neutrophils and eosinophils decreased (by 14% and 46%, respectively) in circulation while the proportion of lymphocytes and basophils increased (by 8% and 101%, respectively). Moreover, the proportion of neutrophil precursors increased by 80% under colder temperatures, which signifies seasonal immune cell recruitment. We demonstrated that neutrophils and eosinophils increased while lymphocytes decreased in response to leech infection. However, as leech and trypanosome infection intensity increased together, the proportion of lymphocytes increased while neutrophils and eosinophils decreased, underscoring the complex interactions between coinfection and immune responses of hellbenders that warrant future research. Despite the influence of infection and coinfection on hellbender physiology, we detected no evidence to support the hypothesis that parasites influence the likelihood of nest failure or whole-clutch filial cannibalism. In light of amphibian declines being exacerbated by climate change and disease, our study emphasizes the need to establish hematological reference values that account for physiological adaptations to seasonal fluctuations in temperature and different life history stages and to study the physiological responses of imperiled amphibian species to parasites.

  PublisherOA PDFDOI

• Prebreeding, Courtship, and Mating Behaviors of Wild Eastern Hellbenders (Cryptobranchus alleganiensis alleganiensis)

  Herpetologica · 2024-02-23 · 9 citations

  articleSenior author

  Eastern Hellbenders (Cryptobranchus alleganiensis alleganiensis) are giant, charismatic salamanders of conservation concern. Despite growing interest in their breeding behavior, significant gaps remain in our understanding of hellbender reproduction, particularly the behavior occurring immediately prior to and during breeding because these activities typically occur within the nesting cavity and out of view. In this study, we used custom-built infrared cameras installed underwater in artificial nesting shelters to record prebreeding behaviors, complete mating sequences, and failed mating attempts in 11 shelters. Using these recordings, we describe the basic mating sequence, the presence of potential alternative mating tactics, and two novel behaviors, including possible signal production via wave-based communication and unique egg laying behavior by female hellbenders. These findings add to our understanding of hellbenders' life history as well as informing conservation efforts in both captive and wild environments.

  PublisherDOI

• The Influence of Environmental Conditions and Coinfection by Blood-Feeding Parasites on Red Blood Cell Physiology of an Ectothermic Host

  Ecological and Evolutionary Physiology · 2024-07-01 · 4 citations

  articleSenior author

  Vector-borne blood parasites cause myriad sublethal effects and can even be deadly to endotherms, but far less is known about their impacts on ectothermic hosts. Moreover, the pathologies documented in endotherms are generally linked to infection by blood parasites rather than by their vectors. Here, we measured hematocrit, hemoglobin, and relative proportions of immature red blood cells to evaluate the physiological effects of two blood-feeding parasites and coinfection on ectothermic hosts, differentiating among pathological responses, extrinsic factors, and natural variations. We investigated a population of wild eastern hellbender salamanders (Cryptobranchus alleganiensis), which harbor leeches (Placobdella appalachiensis) that transmit blood parasites (Trypanosoma spp.) to their hosts, often resulting in coinfection. We observed seasonal changes in host hematology corresponding to water temperature and demonstrated their ability to modulate hematological parameters in response to acute stress. We reveal seasonal relationships between parasite dynamics and host physiology, in which peak parasitemia occurred when hosts had seasonally high hematocrit and hemoglobin concentrations. We found that coinfected individuals expressed symptoms of anemia, including a regenerative response to depletion of their red blood cells. We also documented a more pronounced pathological response to leech vectors than to the trypanosomes they transmit. Our research underscores the complex interactions between host physiology, multiple parasites, and environmental factors and highlights the pathologies associated with the vector in coinfections. Given the contributions of climate change and disease in the rapid global decline of ectotherms such as amphibians, our study provides timely foundational insights into multiple factors that influence their red blood cell physiology.

  PublisherDOI

• Concurrent threats and extinction risk in a long‐lived, highly fecund vertebrate with parental care

  Ecological Applications · 2024-02-01 · 4 citations

  articleOpen access

  Detecting declines and quantifying extinction risk of long-lived, highly fecund vertebrates, including fishes, reptiles, and amphibians, can be challenging. In addition to the false notion that large clutches always buffer against population declines, the imperiled status of long-lived species can often be masked by extinction debt, wherein adults persist on the landscape for several years after populations cease to be viable. Here we develop a demographic model for the eastern hellbender (Cryptobranchus alleganiensis), an imperiled aquatic salamander with paternal care. We examined the individual and interactive effects of three of the leading threats hypothesized to contribute to the species' demise: habitat loss due to siltation, high rates of nest failure, and excess adult mortality caused by fishing and harvest. We parameterized the model using data on their life history and reproductive ecology to model the fates of individual nests and address multiple sources of density-dependent mortality under both deterministic and stochastic environmental conditions. Our model suggests that high rates of nest failure observed in the field are sufficient to drive hellbender populations toward a geriatric age distribution and eventually to localized extinction but that this process takes decades. Moreover, the combination of limited nest site availability due to siltation, nest failure, and stochastic adult mortality can interact to increase the likelihood and pace of extinction, which was particularly evident under stochastic scenarios. Density dependence in larval survival and recruitment can severely hamper a population's ability to recover from declines. Our model helps to identify tipping points beyond which extinction becomes certain and management interventions become necessary. Our approach can be generalized to understand the interactive effects of various threats to the extinction risk of other long-lived vertebrates. As we face unprecedented rates of environmental change, holistic approaches incorporating multiple concurrent threats and their impacts on different aspects of life history will be necessary to proactively conserve long-lived species.

  PublisherOA PDFDOI

• The habitat quality paradox: loss of riparian forest cover leads to decreased risk of parasitism and improved body condition in an imperiled amphibian

  Conservation Physiology · 2024-01-01 · 3 citations

  articleOpen accessSenior author

  ), but their potential to interact in nature remains largely unexplored. We investigated associations between forest cover, parasitic infection and physiology of hellbenders to test the hypotheses that physiological condition responds to infection and/or habitat degradation. We sampled 17 stream reaches in southwest Virginia, USA, on a year-round basis from 2013 to 2016 and recorded 841 captures of 405 unique hellbenders. At each capture we documented prevalence of two blood-associated parasites (a leech and trypanosome) and quantified up to three physiological condition indices (body condition, hematocrit, white blood cell [WBC] differentials). We used generalized linear mixed models to describe spatiotemporal variation in parasitic infection and each condition index. In general, living in the most heavily forested stream reaches, where hellbender density was highest, was associated with the greatest risk of parasitism, elevated neutrophil-to-lymphocyte (N:L) ratios and eosinophils, slightly lower hematocrit and lower mean body condition in hellbenders. All condition indices fluctuated temporally in a manner consistent with seasonal variation in hellbender metabolic demands and breeding phenology and were associated with land use during at least part of the year. Paradoxically, relatively low levels of forest cover appeared to confer a potential advantage to individuals in the form of release from parasites and improved body condition. Despite improved body condition, individuals from less forested areas failed to exhibit fluctuating body condition in response to spawning, which was typical in hellbenders from more forested habitats. We postulate this lack of fluctuation could be due to reduced conspecific competition or reproductive investment and/or high rates of filial cannibalism in response to declining forest cover.

  PublisherOA PDFDOI

• The effect of engagement in private lands research on landowner conservation knowledge, attitudes, awareness, and behavioral intentions

  Human Dimensions of Wildlife · 2024-07-17

  article

  Landowners and scientists often interact during conservation research projects on private lands, creating the opportunity for impactful outreach efforts. However, this potential has received little attention in the literature. This is particularly true for situations where landowners interact with researchers, but do not actively participate in data collection (a "traditional research" model that contrasts to participatory science projects). In this paper, we explore and compare the effects that engaging landowners in traditional versus participatory science research has on landowner conservation knowledge, attitudes, awareness, and behavioral intentions. We find similar effects across both treatment groups, with involvement leading to greater knowledge, increased awareness, more positive attitudes, and/or more behavioral intentions regarding conservation among participants. However, landowners reported limited tangible behavior change during our study. Our results suggest that engaging with landowners during private lands research may be valuable to conservation, but further research is needed on how to optimize these interactions.

  PublisherDOI

• Filial Cannibalism Leads to Chronic Nest Failure of Eastern Hellbender Salamanders (<i>Cryptobranchus alleganiensis</i>)

  The American Naturalist · 2023 · 24 citations

  1st authorCorresponding
  • Ecology
  • Biology
  • Zoology

  ) that has experienced precipitous population declines with unknown causes. We used underwater artificial nesting shelters deployed across a gradient of upstream forest cover to assess the fates of 182 nests at 10 sites over 8 years. We found strong evidence that nest failure rates increased at sites with low riparian forest cover in the upstream catchment. At several sites, reproductive failure was 100%, mainly due to cannibalism by the caring male. The high incidence of filial cannibalism at degraded sites was not explained by evolutionary hypotheses for filial cannibalism based on poor adult body condition or low reproductive value of small clutches. Instead, larger clutches at degraded sites were most vulnerable to cannibalism. We hypothesize that high frequencies of filial cannibalism of large clutches in areas with low forest cover could be related to changes in water chemistry or siltation that influence parental physiology or that reduce the viability of eggs. Importantly, our results identify chronic nest failure as a possible mechanism contributing to population declines and observed geriatric age structure in this imperiled species.

  PublisherDOI

• Concurrent threats and extinction risk in a long-lived, highly fecund vertebrate with parental care

  bioRxiv (Cold Spring Harbor Laboratory) · 2023-12-09 · 2 citations

  preprintOpen access

  ABSTRACT Detecting declines and quantifying extinction risk of long-lived, highly fecund vertebrates including fishes, reptiles, and amphibians, can be challenging. In addition to the false notion that large clutches always buffer against population declines, the imperiled status of long-lived species can often be masked by extinction debt, wherein adults persist on the landscape for several years after populations cease to be viable. Here we develop a demographic model for the Eastern Hellbender ( Cryptobranchus alleganiensis ), an imperiled aquatic salamander with paternal care. We examined the individual and interactive effects of three of the leading threats hypothesized to contribute to the species’ demise: habitat loss due to siltation, high rates of nest failure, and excess adult mortality caused by fishing and harvest. We parameterized the model using data on their life history and reproductive ecology to model the fates of individual nests and address multiple sources of density-dependent mortality under both deterministic and stochastic environmental conditions. Our model suggests that high rates of nest failure observed in the field are sufficient to drive hellbender populations towards a geriatric age distribution and eventually to localized extinction, but that this process takes decades. Moreover, the combination of limited nest site availability due to siltation, nest failure, and stochastic adult mortality can interact to increase the likelihood and pace of extinction, which was particularly evident under stochastic scenarios. Density-dependence in larval survival and recruitment can severely hamper a population’s ability to recover from declines. Our model helps to identify tipping points beyond which extinction becomes certain and management interventions become necessary. Our approach can be generalized to understand the interactive effects of various threats to the extinction risk of other long-lived vertebrates. As we face unprecedented rates of environmental change, holistic approaches incorporating multiple concurrent threats and their impacts on different aspects of life history will be necessary to proactively conserve long-lived species.

  PublisherOA PDFDOI

• Experimental warming and drying act independently on developmental responses for two amphibian species

  Freshwater Biology · 2023-07-31 · 7 citations

  articleOpen access

  Abstract Climate change is affecting freshwater habitats worldwide through multiple, interacting pressures that influence the survival, distribution, and persistence of freshwater organisms. Temporary freshwater habitats, or those that dry seasonally, can exhibit wide‐ranging variability in temperature and drying regimes. Aquatic organisms with complex life cycles (e.g., aquatic and terrestrial life stages) often rely on temporary freshwaters to complete their life cycles and have specific adaptations to cope with these dynamic environments. However, climate change is altering the temperature and drying regime of many temporary freshwater habitats worldwide, often resulting in warmer habitats available for shorter durations of time. The ways in which climate‐mediated changes to temporary freshwaters affect development and life history of aquatic organisms, particularly those with complex life cycles, remains poorly understood. We investigated larval development, growth, survival, and relationships among them for two amphibian species, wood frogs ( Lithobates sylvaticus ) and spring peepers ( Pseudacris crucifer ), in response to warming and drying in a mesocosm experiment. Over 13 weeks in the spring and summer of 2019, we manipulated temperature and water levels in 48 outdoor pond mesocosms to produce four treatments: control (ambient conditions), drying alone, warming alone, and drying + warming. We predicted reduced survival, body size, and time to metamorphosis for both species in response to warming and drying, with the effect being stronger on wood frogs due to their more specialised habitat use and shorter breeding period. Warming treatments were on average 2°C higher than controls, and drying treatments decreased water depth by 2.5 cm each week. We found that warming temperature shortened larval time to metamorphosis, and drying decreased body size at metamorphosis. Surprisingly, we also found that, across all treatment groups, individuals with early metamorphosis tended to be larger in size and from mesocosms with generally higher survival. Our study indicates that warming and drying may act independently on different developmental responses for amphibians. Our results echo recent calls for a better understanding of the nuanced, often unpredictable, relationships among climate‐mediated environmental pressures and the developmental traits they influence, particularly for organisms with complex life cycles that depend upon dynamic habitat for growth and survival. Understanding these relationships and the mechanisms that drive them will be key to predicting the response of freshwater organisms to climate change.

  PublisherOA PDFDOI

• Parenting in the city: effects of urbanization on incubation behaviour and egg temperature in great tits, Parus major

  Animal Behaviour · 2022-10-12 · 14 citations

  article
  PublisherDOI

Recent grants

• Intrinsic and Extrinsic Factors Modulating the Shift from Paternal Care to Filial Cannibalism

  NSF · $836k · 2018–2025

Frequent coauthors

• Sarah E. DuRant

  University of Arkansas at Fayetteville

  56 shared

• John H. Roe

  University of North Carolina at Pembroke

  41 shared

• Brian P. Jackson

  Dartmouth College

  40 shared

• Justin D. Congdon

  35 shared

• Joel W. Snodgrass

  Virginia Tech

  25 shared

• Jason M. Unrine

  University of Kentucky

  23 shared

• Christopher L. Rowe

  20 shared

• Brandon Staub

  University of Pittsburgh Medical Center

  16 shared

Labs

• Fish and Wildlife ConservationPI