Population Biology Commons^™

Of Changing Climate And Habitat: Range-Wide Individual Growth And Local Patterns Of Phenology And Landscape Use In A Threatened Pit-Viper, James Helferich

Theses and Dissertations

Over the 21st century, climate change and wetland habitat loss will pose major threats to the Eastern Massasauga (Sistrurus catenatus), a federally threatened and Great Lakes region endemic rattlesnake. I collected capture-recapture data from sites across the range and modeled the effect of climatic variables on growth rate and asymptotic size. I found that high snow residence time was associated with larger asymptotic sizes but slower growth, while high spring precipitation increased growth rate. I then projected future growth and size under different carbon emission scenarios. Given the threat posed by successional encroachment of woody vegetation, I used spatially explicit …

Fall Field Report, August–November 2023, W. Ross Silcock

Nebraska Bird Review

As in the last few fall seasons, late departure dates continue to increase in number. This is often attributed to a warming climate but may also result from increased observer activity and usage of eBird. Late dates are probably the most important aspect of this report, most prominent the record late fall dates for Ruby-throated Hummingbird, Sanderling, Bank Swallow, and Cassin’s Sparrow. Although these species are taxonomically diverse, there were species group concentrations of late dates, notably among shorebirds. Examples were Marbled Godwit for which the four latest reports this fall were four of the latest six fall dates on …

Index To Volume 91

Nebraska Bird Review

Adams: Pam 11; Paul 11
Aden, Debbie 55
Allard, Savannah 29
Allen, Edward 10
Allison, Betty 30
Alpheus, A. 154
Altman, Dakota 21, 30
Andersen: Bennett 30; Brett 30, 52, 142; D. E. 83
Anderson: Bob 139, 147; Chris 7; Janet 29; Will 68
Angkaew, Rongron 6
Ani, Groove-billed 127, 131
Anich: Charlie 99; Nick 99; Paula 99
Arends, Jim 30
Armstrong, Wyatt 121
Askerooth, Kristine 29
Atkins, Kate 16
Atwell, Erik 55, 58, 99, 100, 102, 112
Audubon, M. 82
Augustine, Jackie 63
Austin, Mary 7
Avocet, American 19, 53, 86, 100, 132, 158

. . .

Zach, Joel …

Yellow-Throated Warbler In Scotts Bluff County, Nebraska, Mark A. Brogie, Bill F. Huser, Jerry Probst

Nebraska Bird Review

Yellow-throated Warbler (Setophaga dominica) is a rare to uncommon migrant in eastern and central Nebraska. It is possibly a regular breeder locally at sites containing sycamores in several southeastern Nebraska counties bordering the Missouri River. There are few Nebraska reports after July, with more reports November–January than August–October. This species has three previous documented Nebraska Panhandle records, all from May.

1. One photographed 26 May 2009, at Crescent Lake NWR, Garden Co.

2. One seen and “well described” 06 May 1931, at Antioch, Sheridan Co.

3. A specimen taken 20 May 1917, at Oshkosh, Garden Co., was once …

The Nebraska Bird Review (December 2023) 91(4), Whole Issue

Nebraska Bird Review

Fall Field Report, August–November 2023, by W. Ross Silcock

NOU Founding Ornithologist, Hypnotist, Physician: Isador Trostler, by Rick Wright

Yellow-throated Warbler in Scotts Bluff County, Nebraska, by Mark A. Brogie, Bill F. Huser, and Jerry Probst

Holdrege Fall Field Days, Sept. 22–24, 2023

Index to Volume 91

Subscription and Organization Information

Nou Founding Ornithologist, Hypnotist, Physician: Isador Trostler, Rick Wright

Nebraska Bird Review

Eminent radiologist Benjamin H. Orndoff, eulogizing an esteemed colleague some months after his death, noted that Isador Simon Trostler (1869–1957) “as a lad . . . became interested in ornithology and herpetology, sending accounts of his observations and explorations to natural history magazines up to the late [18]90s.” Understandably more interested in Trostler’s role as a “pioneer in radiology,” Orndoff had no more to say about the natural history pursuits of one of Nebraska’s most notable early ornithologists, one of the founders 125 years ago of the Nebraska Ornithologists’ Union.

Conversely, we birders have known little or nothing of Trostler’s …

Holdrege Fall Field Days, Janis Paseka

Nebraska Bird Review

The 2023 NOU Fall Field Days were held in Holdrege on September 22–24, with approximately 45 in attendance. The programs were held at the Rodeway Inn. The meeting was planned by Robin Harding, Jan Johnson, and Ruthie Stearns. Field trips were led by Robin Harding, Paul Dunbar, and William Flack to numerous locations including Johnson Lake SRA, Elwood Reservoir WMA, the eagle viewing site on the Phelps County Canal in northern Gosper Co., the Platte River bridge south of Overton, Cottonwood WPA, Harlan Co. Reservoir, the Alma water treatment plant, Funk WPA, Nature's Mosaic Recreation Area, and Sacramento-Wilcox WPA.

The …

Rapid Evolution Of A(H5n1) Influenza Viruses After Intercontinental Spread To North America, Ahmed Kandeil, Christopher Patton, Jeremy C. Jones, Trushar Jeevan, Walter N. Harrington, Sanja Trifkovic, Jon P. Seiler, Thomas Fabrizio, Karlie Woodard, Jasmine C. Turner, Jeri Carol Crumpton, Lance Miller, Adam Rubrum, Jennifer Debeauchamp, Charles J. Russell, Elena A. Govorkova, Peter Vogel, Mia Kim-Torchetti, Yohannes Berhane, David Stallknecht, Rebecca Poulson, Lisa Kercher, Richard J. Webby

United States Department of Agriculture Wildlife Services: Staff Publications

Highly pathogenic avian influenza A(H5N1) viruses of clade 2.3.4.4b underwent an explosive geographic expansion in 2021 among wild birds and domestic poultry across Asia, Europe, and Africa. By the end of 2021, 2.3.4.4b viruses were detected in North America, signifying further intercontinental spread. Here we show that the western movement of clade 2.3.4.4b was quickly followed by reassortment with viruses circulating in wild birds in North America, resulting in the acquisition of different combinations of ribonucleoprotein genes. These reassortant A(H5N1) viruses are genotypically and phenotypically diverse, with many causing severe disease with dramatic neurologic involvement in mammals. The proclivity of …

Impacts Of Disturbance And Nutrient Addition On Coastal Dune Arthropod Communities, Kayla Beitzel

Honors Theses

Coastal dune ecosystems are globally distributed ecosystems that occur from the tropics to the poles and serve as the first line of defense during storms. They are critical habitats for a variety of organisms and also play a critical role in stabilizing coastal habitats. These systems face increased pressure via urban development, recreational expansion, and sea-level rise (Newman et al. 2023; Webster et al. 2005). Insects are vital consumers in coastal ecosystems and act as regulators of plant growth. Low-diversity ecosystems, like coastal dune systems, often contain a higher abundance of low-diverse insect consumers (Ripple et al. 2021), which can …

Accelerated Evolution Of Sars-Cov-2 In Free-Ranging White-Tailed Deer, Dillon S. Mcbride, Sofya K. Garushyants, John Franks, Andrew F. Magee, Steven H. Overend, Devra Huey, Amanda M. Williams, Seth A. Faith, Ahmed Kandeil, Sanja Trifkovic, Lance Miller, Trushar Jeevan, Anami Patel, Jacqueline M. Nolting, Michael J. Tonkovich, J. Tyler Genders, Andrew J. Montoney, Kevin Kasnyik, Timothy J. Linder, Sarah N. Bevins, Julianna B. Lenoch, Jeffrey C. Chandler, Thomas J. Deliberto, Eugene V. Koonin, Marc A. Suchard, Philippe Lemey, Richard J. Webby, Martha I. Nelson, Andrew S. Bowman

United States Department of Agriculture Wildlife Services: Staff Publications

The zoonotic origin of the COVID-19 pandemic virus highlights the need to fill the vast gaps in our knowledge of SARS-CoV-2 ecology and evolution in non-human hosts. Here, we detected that SARS-CoV-2 was introduced from humans into white-tailed deer more than 30 times in Ohio, USA during November 2021-March 2022. Subsequently, deer-to-deer transmission persisted for 2–8 months, disseminating across hundreds of kilometers. Newly developed Bayesian phylogenetic methods quantified how SARS-CoV-2 evolution is not only three-times faster in white-tailed deer compared to the rate observed in humans but also driven by different mutational biases and selection pressures. The long-term effect of …

Analysis Of Mitochondrial Dna Sequence Data Demonstrates That Monophyly Of Myotis Occultus Is Complicated By Greater Sampling Of Myotis Lucifugus, Jeffrey M. Lorch, Daniel R. Taylor, Antoinette J. Piaggio

United States Department of Agriculture Wildlife Services: Staff Publications

Abstract

The validity of Myotis occultus as a species unique from Myotis lucifugus has been a source of debate. Most recently, many authorities treat M. occultus as a distinct species, at least in part because a previous study showed that M. occultus and M. l. carissima (the subspecies that occurs in closest geographic proximity to M. occultus) form separate monophyletic clades based on sequences of two mitochondrial genes (cytochrome-b [cytb] and cytochrome oxidase subunit II [COII]). We re-evaluated the phylogenetic relationship between M. occultus and M. lucifugus based on mitochondrial sequences …

Unlocking The Mysteries Of Opportunism: Neuroendocrine Insights From An Aseasonal Breeder (Taeniopygia Guttata), Jessica A. Moodie

Graduate Theses and Dissertations (2019 - present)

The regulation of reproductive physiology in animals is mediated by the Hypothalamus-Pituitary-Gonad (HPG) axis. In seasonal breeders, a conserved reciprocal switching of deiodinase enzymes alters thyroid hormone signaling, which controls HPG activity. This study tested the hypothesis that neural regulation of the HPG axis as described in seasonal systems is conserved and repurposed to respond to other cues in aseasonal species. Using water deprivation and nest restriction in the opportunistic Zebra Finch, we were able to create a breeding group and non-breeding group, confirmed by egg laying and changes in ovarian anatomy. Breeding females had clear follicular hierarchy, increased ovary …

Pathogenicity In Chickens And Turkeys Of A 2021 United States H5n1 Highly Pathogenic Avian Influenza Clade 2.3.4.4b Wild Bird Virus Compared To Two Previous H5n8 Clade 2.3.4.4 Viruses, Mary J. Pantin-Jackwood, Erica Spackman, Christina Leyson, Sungsu Youk, Scott A. Lee, Linda M. Moon, Mia K. Torchetti, Mary L. Killian, Julianna B. Lenoch, Darrell R. Kapczynski, David E. Swayne, David L. Suarez

United States Department of Agriculture Wildlife Services: Staff Publications

Highly pathogenic avian influenza viruses (HPAIVs) of subtype H5 of the Gs/GD/96 lineage remain a major threat to poultry due to endemicity in wild birds. H5N1 HPAIVs from this lineage were detected in 2021 in the United States (US) and since then have infected many wild and domestic birds. We evaluated the pathobiology of an early US H5N1 HPAIV (clade 2.3.4.4b, 2021) and two H5N8 HPAIVs from previous outbreaks in the US (clade 2.3.4.4c, 2014) and Europe (clade 2.3.4.4b, 2016) in chickens and turkeys. Differences in clinical signs, mean death times (MDTs), and virus transmissibility were found between chickens and …

Raccoon Spatial Ecology In The Rural Southeastern United States, Jacob E. Hill, Madison L. Miller, James L. Helton, Richard B. Chipman, Amy Gilbert, University Of Georgia, Guha Dharmarajan, Olin E. Rhodes Jr.

United States Department of Agriculture Wildlife Services: Staff Publications

The movement ecology of raccoons varies widely across habitats with important implications for the management of zoonotic diseases such as rabies. However, the spatial ecology of raccoons remains poorly understood in many regions of the United States, particularly in the southeast. To better understand the spatial ecology of raccoons in the southeastern United States, we investigated the role of sex, season, and habitat on monthly raccoon home range and core area sizes in three common rural habitats (bottomland hardwood, upland pine, and riparian forest) in South Carolina, USA. From 2018–2022, we obtained 264 monthly home ranges from 46 raccoons. Mean …

Raccoon Spatial Ecology In The Rural Southeastern United States, Jacob E. Hill, Madison L. Miller, James L. Helton, Richard B. Chipman, Amy T. Gilbert, James C. Beasley, Guha Dharmarajan, Olin E. Rhodes Jr.

United States Department of Agriculture Wildlife Services: Staff Publications

The movement ecology of raccoons varies widely across habitats with important implications for the management of zoonotic diseases such as rabies. However, the spatial ecology of raccoons remains poorly understood in many regions of the United States, particularly in the southeast. To better understand the spatial ecology of raccoons in the southeastern US, we investigated the role of sex, season, and habitat on monthly raccoon home range and core area sizes in three common rural habitats (bottomland hardwood, upland pine, and riparian forest) in South Carolina, USA. From 2018–2022, we obtained 264 monthly home ranges from 46 raccoons. Mean monthly …

Gene Variants In Bola-Dmb, Decr1, Fasn And Srebf1 Associated With Conceptus Death On Day 16 Of Pregnancy In Holstein Cows [Abstract], Carolina L. Gonzalez-Berrios, Courtney Bowden, Pablo J. Pinedo, Jeanette V. Bishop, Hana Van Campen, Thomas R. R. Hansen, Milton G. Thomas

United States Department of Agriculture Wildlife Services: Staff Publications

Investigating the influences of single nucleotide polymorphisms (SNP) associated with conceptus death (CD) on day 16 of pregnancy could distinguish cows who have inferior value for fertility traits. We hypothesized that CD is associated with SNP genotypes that disrupt maternal recognition and lead to early pregnancy loss. RNA sequences from Holstein cow pregnancies (n = 15) with normal conceptuses (Norm) or CD were subjected to SNP discovery via Qiagen CLC Genomics Workbench. Selected SNP were based on previous fertility studies, differentially expressed genes within pregnancy development analyses and proximity to SNP associated with fertility traits in the Cattle QTL …

Skin Lipids Alone Enable Conspecific Tracking In An Invasive Reptile, The Argentine Black And White Tegu Lizard (Salvator Merianae), M. Rockwell Parker, Eric A. Tillman, Lauren A. Nazarian, Megan L. Barlowe, Julianna M. Lincoln, Bryan M. Kluever

United States Department of Agriculture Wildlife Services: Staff Publications

Locating potential mates in non-native habitats is one of the most important challenges faced by invasive vertebrate species. The Argentine black and white tegu lizard (Salvator merianae) is a major invasive reptile species in the contiguous United States and is rapidly expanding its range across Florida and the Southeast, in part due to inadequate management strategies and tools. Because a wide array of reptiles, especially squamates (snakes and lizards), have been well-studied for their reliance on chemical cues to locate conspecifics, our project aimed to isolate chemical cues from tegus and assess the ability of adult males and …

Limited Accumulation And Persistence Of An Influenza A Virus In Tadpole Snails (Physa Spp.), Paul T. Oesterle, J. Jeffrey Root, Darcy S.O. Mora, Heather Schneider, Alan B. Franklin, Kathryn P. Huyvaert

United States Department of Agriculture Wildlife Services: Staff Publications

Waterfowl infected with avian influenza A viruses (IAVs) shed infectious virus into aquatic environments, providing a mechanism for transmission among waterfowl, while also exposing the entire aquatic ecosystem to the virus. Aquatic invertebrates such as freshwater snails are likely exposed to IAVs in the water column and sediment. Freshwater snails comprise a significant portion of some waterfowl species’ diets, so this trophic interaction may serve as a novel route of IAV transmission. In these experiments, tadpole snails (Physa spp.) were exposed to a low-pathogenicity IAV (H3N8) to determine whether snails can accumulate the virus and, if so, how long virus …

H5n1 Highly Pathogenic Avian Influenza Clade 2.3.4.4b In Wild And Domestic Birds: Introductions Into The United States And Reassortments, December 2021–April 2022, Sungsu Youk, Mia Kim Torchetti, Kristina Lantz, Julianna B. Lenoch, Mary Lea Killian, Christina Leyson, Sarah N. Bevins, Krista Dilione, Hon S. Ip, David E. Stallknecht, Rebecca L. Poulson, David L. Suarez, David E. Swayne, Mary J. Pantin-Jackwood

United States Department of Agriculture Wildlife Services: Staff Publications

Highly pathogenic avian influenza viruses (HPAIVs) of the A/goose/Guangdong/1/1996 lineage H5 clade 2.3.4.4b continue to have a devastating effect on domestic and wild birds. Full genome sequence analyses using 1369 H5N1 HPAIVs detected in the United States (U.S.) in wild birds, commercial poultry, and backyard flocks from December 2021 to April 2022, showed three phylogenetically distinct H5N1 virus introductions in the U.S. by wild birds. Unreassorted Eurasian genotypes A1 and A2 entered the Northeast Atlantic states, whereas a genetically distinct A3 genotype was detected in Alaska. The A1 genotype spread westward via wild bird migration and reassorted with North American …

South Coast Offshore Crustacean Resource Of Western Australia Harvest Strategy, Department Of Primary Industries And Regional Development, Western Australia

Fisheries Management Papers

Harvest strategies for aquatic resources in Western Australia (WA) that are managed by the Department of Primary Industries and Regional Development (DPIRD, the Department) are formal documents that ensures decision-making processes are consistent with the principles of Ecologically Sustainable Development (ESD; Fletcher 2002) and Ecosystem Based Fisheries Management (EBFM; Fletcher et al. 2012). The objectives of ESD are reflected in the objects of the Fish Resources Management Act 1994 (FRMA) and the Aquatic Resources Management Act 2016 (ARMA), which is anticipated replace the FRMA once enacted. At this point, the Fish Resources Management Regulations 1995 (FRMR) is also anticipated to …

Observations On A 40-Year January Bird Census In Boone County, Nebraska, 1978–2017, Wayne Mollhoff

Zea E-Books Collection

For 40 years Wayne Mollhoff conducted a personal bird census every January. He explains: "After having run several Breeding Bird Survey routes, and participated in several Christmas Bird Counts, I became curious to see what might be found on a winter count under the more tightly controlled parameters of a census, as contrasted with Christmas counts done with variable numbers of observers."

The count was set up similarly to the USGS Breeding Bird Survey routes with 50 stops, one-half mile (800 meters) apart, all birds counted for 3 minutes, with birds counted at one stop not counted again at following …

Summer Field Report, June–July 2023, W. Ross Silcock

Nebraska Bird Review

There were no new species for Nebraska. This was also a lean season for records of species with few Nebraska records. Probably most significant were continuing Common Ravens in two Sioux Co locations, and possibly the first summer records of Baird’s Sparrow, a recording of the latter currently under NOURC review.

Within-state breeders nesting at new locations. There were several instances of nesting reported away from known breeding areas. These include documented records of first nesting Black-necked Stilts in Cherry Co, Least Terns off river at Offutt Base Lake in Sarpy Co, Mississippi Kite in Adams Co, Yellow-throated Vireo in …

The Nebraska Bird Review (September 2023) 91(3), Whole Issue

Nebraska Bird Review

Summer Field Report, June–July 2023, by W. Ross Silcock

2023 Limpkin at Crystal Cove Park, Dakota County, NE, by Bill Huser

2022 (34th) Report of the NOU Records Committee, by Mark A. Brogie

Subscription and Organization Information

2022 (34th) Report Of The Nou Records Committee, Mark A. Brogie

Nebraska Bird Review

The functions and methods of the Nebraska Ornithologists’ Union Records Committee (NOURC) are described in its bylaws (NOURC 2010). The committee’s purpose is to provide a procedure for documenting unusual bird sightings and to establish a list of all documented birds for Nebraska. Species for which the NOURC seeks documentation (NOURC Review List) can be found at the NOU website www.NOUbirds.org. Starting in 2020, the NOURC decided to deal mainly with those species deemed as Accidental on the “Official List of the Birds of Nebraska.” Casual species and out-of-range species are now summarized in the “Seasonal Reports” of the …

2023 Limpkin At Crystal Cove Park, Dakota County, Ne, Bill Huser

Nebraska Bird Review

On the morning of October 7, 2023, I observed Nebraska’s second Limpkin (Aramus guarauna) at Crystal Cove Park in South Sioux City, and the bird was subsequently seen by several other observers throughout that afternoon. Photo and video records were obtained (https://ebird.org/checklist/S151656716). The summer and fall of 2023 brought fourteen sightings to Iowa, though it is impossible to determine how many birds were involved (eBird, 2023). One of those sightings occurred in the northwestern part of the state at Bacon Creek Park in Sioux City when a single Limpkin was independently reported by two observers on …

Antiviral Susceptibility Of Clade 2.3.4.4b Highly Pathogenic Avian Influenza A(H5n1) Viruses Isolated From Birds And Mammals In The United States, 2022, Ha T. Nguyen, Anton Chesnokov, Juan De La Cruz, Philippe Noriel Q. Pascua, Vasiliy P. Mishin, Yunho Jang, Joyce Jones, Han Di, Andrei A. Ivashchenko, Mary Lea Killian, Mia K. Torchetti, Kristina Lantz, David E. Wentworth, Charles T. Davis, Alexandre V. Ivachtchenko, Larisa V. Gubareva

United States Department of Agriculture Wildlife Services: Staff Publications

Clade 2.3.4.4b highly pathogenic avian influenza (HPAI) A(H5N1) viruses that are responsible for devastating outbreaks in birds and mammals pose a potential threat to public health. Here, we evaluated their susceptibility to influenza antivirals. Of 1,015 sequences of HPAI A(H5N1) viruses collected in the United States during 2022, eight viruses (∼0.8%) had a molecular marker of drug resistance to an FDA-approved antiviral: three adamantane-resistant (M2-V27A), four oseltamivir-resistant (NA-H275Y), and one baloxavir-resistant (PA-I38T). Additionally, 31 viruses contained mutations that may reduce susceptibility to inhibitors of neuraminidase (NA) (n = 20) or cap-dependent endonuclease (CEN) (n = 11). A panel of 22 …

Go Big Or Go Home: Divergence In Morphology And Behavior Between Island And Islet Populations Of The San Cristóbal Lava Lizard (Microlophus Bivittatus), Emilio J. Mancero

Masters Theses

Rapid divergence in body size is a well-documented phenomenon among island species, associated with macroevolutionary processes of diversification and adaptive radiation. The effect of insularity in determining larger body size as an optimal phenotype is primarily attributed to lower predation and greater intraspecific competition on islands. Our study examined interpopulation variation in morphology, social behavior and predator avoidance in Galápagos lava lizards endemic to San Cristóbal island (Microlophus bivittatus), and the nearby islet Isla Lobos. Islet populations have fewer competitors than those on the island, where native and introduced predators are abundant. We simulated interactions with predators and …

The Devil You Know And The Devil You Don’T: Current Status And Challenges Of Bovine Tuberculosis Eradication In The United States, Daniel J. O'Brien, Tyler C. Thacker, Liliana C.M. Salvador, Anthony G. Duffiney, Suelee Robbe‑Austerman, Mark S. Camacho, Jason E. Lombard, Mitchell V. Palmer

United States Department of Agriculture Wildlife Services: Staff Publications

Having entered into its second century, the eradication program for bovine tuberculosis (bTB, caused by Mycobacterium bovis) in the United States of America occupies a position both enviable and daunting. Excepting four counties in Michigan comprising only 6109 km2 (0.06% of US land area) classified as Modified Accredited, as of April 2022 the entire country was considered Accredited Free of bTB by the US Department of Agriculture for cattle and bison. On the surface, the now well-described circumstances of endemic bTB in Michigan, where white-tailed deer (Odocoileus virginianus) serve as a free-ranging wildlife maintenance host, may appear to be …

Leveraging Eco-Evolutionary Models For Gene Drive Risk Assessment, Matthew A. Combs, Andrew J. Golnar, Justin M. Overcash, Alun L. Lloyd, Keith R. Hayes, David A. O'Brochta, Kim M. Pepin

United States Department of Agriculture Wildlife Services: Staff Publications

Engineered gene drives create potential for both widespread benefits and irreversible harms to ecosystems. CRISPR-based systems of allelic conversion have rapidly accelerated gene drive research across diverse taxa, putting field trials and their necessary risk assessments on the horizon. Dynamic processbased models provide flexible quantitative platforms to predict gene drive outcomes in the context of system-specific ecological and evolutionary features. Here, we synthesize gene drive dynamic modeling studies to highlight research trends, knowledge gaps, and emergent principles, organized around their genetic, demographic, spatial, environmental, and implementation features. We identify the phenomena that most significantly influence model predictions, discuss limitations of …

Western Pearlshell (Margaritifera Falcata) Extirpation In The Smith River, Montana, With A Possible Link To Warming Water Temperatures, David M. Stagliano

Western North American Naturalist

Western pearlshell (Margaritifera falcata) populations are in decline across the species’ range in western North America. In 2008, Montana categorized the western pearlshell as an imperiled species of concern (S2) based on reduced detections at historically occupied sites and few viable populations. Between 2004 and 2014, we surveyed 24 Smith River reaches (61 total sites in the watershed) for the presence of western pearlshell populations. Despite historical and anecdotal descriptions of abundant western pearlshell in the Smith River, intensive structured surveys between 2004 and 2007 documented only 4 sections with low-density, nonviable western pearlshell populations (<10 individuals, large size classes [average total length = 70 mm], with no signs of recruitment). In 2014, we revisited these occupied sites to repeat surveys (expending significantly more search time) and observed no live individuals. This was surprising given that, although those populations would certainly die out without recruitment, older individuals can oftentimes persist for decades. Therefore, we consider the western pearlshell mussel extirpated from the Smith River watershed. We reviewed long-term USGS gage discharge and temperature data near the western pearlshell populations to evaluate the potential causal factors for, and timing of, the extirpation. From 3 July to 3 August 2007, water temperatures were at or above the thermal stress levels of the western pearlshell (>25 °C, …