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At least 811 records · Page 45Linked to original sources

USGS2026

Small cumulative survival costs of enzootic disease could suppress long-term population size

Fungal pathogens can cause epizootics that result in widespread mortality and rapid population declines in some species. However, even in the absence of high disease-induced mortality, enzootic mycoses could have large-scale impacts on host population dynamics. Here, we examined the effects of ophidiomycosis, an enzootic fungal disease, on a Louisiana snake community over a 3-year period using a multi-state Jolly–Seber model with disease-state misclassification. We did not detect a difference between the average weekly apparent survival probability of uninfected and infected hosts for either Nerodia species or Thamnophis proximus . We also found a strong positive association between snout-to-vent length and weekly apparent survival probability across all species. We found that recruitment of infected hosts was slightly higher than recruitment of uninfected hosts for two of the three species. Population projections suggested divergent trajectories between disease-present and disease-absent scenarios, where disease-absent populations had higher abundance than disease-present populations. Our results highlight that small differences in survival can accumulate over time, as well as the challenges of quantifying population-level impacts of enzootic diseases when survival differences are not readily detected, underscoring the importance of continued long-term monitoring to assess whether ophidiomycosis affects snake population dynamics.

Louisiana↗

USGS2020

Illegal killing of nongame wildlife and recreational shooting in conservation areas

Illegal killing of nongame wildlife is a global yet poorly documented problem. The prevalence and ecological consequences of illegal killing are often underestimated or completely unknown. We review the practice of legal recreational shooting and present data gathered from telemetry, surveys, and observations on its association with illegal killing of wildlife (birds and snakes) within conservation areas in Idaho, USA. In total, 33% of telemetered long‐billed curlews ( Numenius americanus ) and 59% of other bird carcasses found with known cause of death (or 32% of total) were illegally shot. Analysis of spatial distributions of illegal and legal shooting is consistent with birds being shot illegally in the course of otherwise legal recreational shooting, but snakes being intentionally sought out and targeted elsewhere, in locations where they congregate. Preliminary public surveys indicate that most recreational shooters find abhorrent the practice of illegal killing of wildlife. Viewed through this lens, our data may imply only a small fraction of recreational shooters is responsible for this activity. This study highlights a poorly known conservation problem that could have broad implications for some species and populations of wildlife.

Idaho↗

USGS2009

Movements by adult cutthroat trout in a lotic system: Implications for watershed-scale management

Movements by adult cutthroat trout, Oncorhynchus clarkii (Richardson), were assessed from autumn to summer in the Salt River watershed, Wyoming-Idaho, USA by radio telemetry. Adult cutthroat trout were captured during September and October 2005 in the main stem of the Salt River, surgically implanted with radio transmitters, and tracked through to August 2006. Adult cutthroat trout were relatively sedentary and resided primarily in pools from October to March, but their movement rates increased during April. Higher movement rates were observed among tagged fish during May and early June. Among 43 fish residing in the Salt River during April 2006, 44% remained in the river, 37% moved into mountain tributaries and 19% moved into spring streams during the spawning season. Fish did not use segments of mountain tributaries or the upstream Salt River where fish passage was blocked by anthropogenic barriers or the channel was dewatered during summer. Almost all the fish that moved into spring streams used spring streams where pools and gravel-cobble riffles had been constructed by landowners. The results suggest that adult Snake River cutthroat move widely during May and early June to use spawning habitat in mountain tributaries and improved spring streams. Maintaining the ability of adult fish to move into mountain streams with spawning habitat, preserving spawning habitat in accessible mountain tributaries and removing barriers to upstream movements, and re-establishing summer stream flows in mountain tributaries affected by dams appear to be habitat management alternatives to preserve the Snake River cutthroat trout fishery in the Salt River. ?? 2009 Blackwell Publishing Ltd.

Fisheries Management and Ecology↗

USGS2009

Using time-dependent models to investigate body condition and growth rate of the giant gartersnake

Identifying links between phenotypic attributes and fitness is a primary goal of reproductive ecology. Differences in within-year patterns of body condition between sexes of gartersnakes in relation to reproduction and growth are not fully understood. We conducted an 11-year field study of body condition and growth rate of the giant gartersnake Thamnophis gigas across 13 study areas in the Central Valley of California, USA. We developed a priori mixed effects models of body condition index (BCI), which included covariates of time, sex and snout-vent length and reported the best-approximating models using an information theoretic approach. Also, we developed models of growth rate index (GRI) using covariates of sex and periods based on reproductive behavior. The largest difference in BCI between sexes, as predicted by a non-linear (cubic) time model, occurred during the mating period when female body condition (0.014??0.001 se) was substantially greater than males (-0.027??0.002 se). Males likely allocated energy to search for mates, while females likely stored energy for embryonic development. We also provided evidence that males use more body energy reserves than females during hibernation, perhaps because of different body temperatures between sexes. We found GRI of male snakes was substantially lower during the mating period than during a non-mating period, which indicated that a trade-off existed between searching for mates and growth. These findings contribute to our understanding of snake ecology in a Mediterranean climate. ?? 2009 The Zoological Society of London.

Journal of Zoology↗

USGS2008

Middle to late cenozoic geology, hydrography, and fish evolution in the American Southwest

An evaluation of the poorly understood Cenozoic hydrologic history of the American Southwest using combined geological and biological data yields new insights with implications for tectonic evolution. The Mesozoic Cordilleran orogen next to the continental margin of southwestern North America probably formed the continental divide. Mountain building migrated eastward to cause uplift of the Rocky Mountains during the Late Cretaceous to early Tertiary Laramide orogeny. Closed drainage basins that developed between the two mountain belts trapped lake waters containing fish of Atlantic affinity. Oligocene-Miocene tectonic extension fragmented the western mountain belt and created abundant closed basins that gradually filled with sediments and became conduits for dispersal of fishes of both Pacific and Atlantic affinity. Abrupt arrival of the modern Colorado River to the Mojave-Sonora Desert region at ca. 5 Ma provided a new conduit for fish dispersal. Great dissimilarities in modern fish fauna, including differences in their mitochondrial deoxyribonucleic acid (DNA), indicate that late Miocene runoff from the Colorado Plateau did not flow down the Platte or Rio Grande, or through the Lake Bonneville Basin. Fossil fishes from the upper Miocene part of the Bidahochi Formation on the Colorado Plateau have characteristics that reflect a habitat of large, swift-moving waters, and they are closely related to fossil fishes associated with the Snake and Sacramento Rivers. This evidence suggests that influx of fishes from the ancestral Snake River involved a major drainage, not merely small headwater transfers. ?? 2008 The Geological Society of America.

Conference Paper↗

USGS2015

The Yellowstone “hot spot” track results from migrating basin-range extension

Whether the volcanism of the Columbia River Plateau, eastern Snake River Plain, and Yellowstone (western U.S.) is related to a mantle plume or to plate tectonic processes is a long-standing controversy. There are many geological mismatches with the basic plume model as well as logical flaws, such as citing data postulated to require a deep-mantle origin in support of an “upper-mantle plume” model. USArray has recently yielded abundant new seismological results, but despite this, seismic analyses have still not resolved the disparity of opinion. This suggests that seismology may be unable to resolve the plume question for Yellowstone, and perhaps elsewhere. USArray data have inspired many new models that relate western U.S. volcanism to shallow mantle convection associated with subduction zone processes. Many of these models assume that the principal requirement for surface volcanism is melt in the mantle and that the lithosphere is essentially passive. In this paper we propose a pure plate model in which melt is commonplace in the mantle, and its inherent buoyancy is not what causes surface eruptions. Instead, it is extension of the lithosphere that permits melt to escape to the surface and eruptions to occur—the mere presence of underlying melt is not a sufficient condition. The time-progressive chain of rhyolitic calderas in the eastern Snake River Plain–Yellowstone zone that has formed since basin-range extension began at ca. 17 Ma results from laterally migrating lithospheric extension and thinning that has permitted basaltic magma to rise from the upper mantle and melt the lower crust. We propose that this migration formed part of the systematic eastward migration of the axis of most intense basin-range extension. The bimodal rhyolite-basalt volcanism followed migration of the locus of most rapid extension, not vice versa. This model does not depend on seismology to test it but instead on surface geological observations.

Idaho, Montana, Wyoming↗

USGS1998

The role of introduced species in the degradation of island ecosystems: A case history of Guam

The accidental introduction of the brown treesnake ( Boiga irregularis ) on Guam around 1950 induced a cascade of extirpations that may be unprecedented among historical extinction events in taxonomic scope and severity. Birds, bats, and reptiles were affected, and by 1990 most forested areas on Guam retained only three native vertebrates, all of which were small lizards. Of the hypotheses to account for the severity of this extinction event, we find some support for the importance of lack of coevolution between introduced predator and prey, availability of alternate prey, extraordinary predatory capabilities of the snake, and vulnerabilities of the Guam ecosystem. In addition, there were important interactions among these factors, especially the presence of introduced prey (possessing coevolutionary experience) that were thus able to maintain their populations and provide alternate prey to the introduced predator while it was driving the native prey species to extinction. This complex of vulnerabilities is common on oceanic islands.

Annual Review of Ecology and Systematics↗

USGS2026

Case report: Observations on expulsions from 20 years of radiotransmitter implantation in adult Burmese pythons

Background Radiotelemetry as a research tool has advanced our understanding of snake behavior and ecology. However, surgical transmitter implantation can lead to health complications for study animals, including expulsion, which may also interfere with research objectives. Two implantation methods include intramuscular and coelomic placements, and we evaluate expulsion rates of transmitters using these methods in Burmese pythons ( Python bivittatus ) in southern Florida. Results From 2005 to 2024, we implanted 305 transmitters in 142 adult Burmese pythons, primarily using intramuscular implantation ( n = 221), then transitioning to include coelomic placement ( n = 84). There were no observations of transmitter-related mortality. Overall, 98.7% of transmitters were retained, with a 1.3% expulsion rate ( n = 4 transmitters). Expelled transmitters were only observed in intramuscularly implanted transmitters from 4 of 13 gravid females. Conclusions We observed no mortality related to transmitter implantation and few instances of transmitter expulsion, indicating that both intramuscular and coelomic implantation techniques are effective for monitoring adult pythons in the wild. However, there is some risk that females may expel transmitters when gravid, and this risk may be reduced when implanting transmitters intracoelomically. Our findings may be useful for studies of other large-bodied snake populations worldwide where radiotransmitter implantation is appropriate and logistically feasible.

Florida↗

USGS2022

Cumulative effects of piscivorous colonial waterbirds on juvenile salmonids: A multi predator-prey species evaluation

We investigated the cumulative effects of predation by piscivorous colonial waterbirds on the survival of multiple salmonid ( Oncorhynchus spp.) populations listed under the U.S. Endangered Species Act (ESA) and determined what proportion of all sources of fish mortality (1 –survival) were due to birds in the Columbia River basin, USA. Anadromous juvenile salmonids (smolts) were exposed to predation by Caspian terns ( Hydroprogne caspia ), double-crested cormorants ( Nannopterum auritum ), California gulls ( Larus californicus ), and ring-billed gulls ( L . delawarensis ), birds known to consume both live and dead fish. Avian consumption and survival probabilities (proportion of available fish consumed or alive) were estimated for steelhead trout ( O . mykiss ), yearling Chinook salmon ( O . tshawytscha ), sub-yearling Chinook salmon, and sockeye salmon ( O . nerka ) during out-migration from the lower Snake River to the Pacific Ocean during an 11-year study period (2008–2018). Results indicated that probabilities of avian consumption varied greatly across salmonid populations, bird species, colony location, river reach, and year. Cumulative consumption probabilities (consumption by birds from all colonies combined) were consistently the highest for steelhead, with annual estimates ranging from 0.22 (95% credible interval = 0.20–0.26) to 0.51 (0.43–0.60) of available smolts. The cumulative effects of avian consumption were significantly lower for yearling and sub-yearling Chinook salmon, with consumption probabilities ranging annually from 0.04 (0.02–0.07) to 0.10 (0.07–0.15) and from 0.06 (0.3–0.09) to 0.15 (0.10–0.23), respectively. Avian consumption probabilities for sockeye salmon smolts was generally higher than for Chinook salmon smolts, but lower than for steelhead smolts, ranging annually from 0.08 (0.03–0.22) to 0.25 (0.14–0.44). Although annual consumption probabilities for birds from certain colonies were more than 0.20 of available smolts, probabilities from other colonies were less than 0.01 of available smolts, indicating that not all colonies of birds posed a substantial risk to smolt mortality. Consumption probabilities were lowest for small colonies and for colonies located a considerable distance from the Snake and Columbia rivers. Total mortality attributed to avian consumption was relatively small for Chinook salmon (less than 10%) but was the single greatest source of mortality for steelhead (greater than 50%) in all years evaluated. Results suggest that the potential benefits to salmonid populations of managing birds to reduce smolt mortality would vary widely depending on the salmonid population, the species of bird, and the size and location of the breeding colony.

Oregon, Washington↗

USGS1996

Feeding response by northern squawfish to a hatchery release of juvenile salmonids in the Clearwater River, Idaho

We collected gut contents from northern squawfish Ptychocheilus oregonensis captured in the Clearwater River, Idaho, 0–6 km from its confluence with the Snake River, following the release of 1.1 million yearling chinook salmon Oncorhynchus tshawytscha from the Dworshak National Fish Hatchery. Before the hatchery release, northern squawfish gut contents (by weight) in the study area were 38% crayfish Pacifastacus spp., 26% insects, 19% nonsalmonid fish, and 16% wheat kernels Triticum spp. Juvenile salmonids constituted 54% of gut contents about 24 h after the hatchery release, 78% after 5 d, and 86% after 7 d. The mean number of salmonids per gut (1.2) after release was higher than typically seen in guts from northern squawfish collected in mid-reservoir areas away from hydroelectric dams on the Snake and Columbia rivers. Length-frequency distributions of juvenile salmonids eaten and those captured in a scoop trap 4 km upstream of the study area indicated that northern squawfish were selectively feeding on the smaller individuals. We attribute the high rates of predation in the study area to the artificially high density of juvenile salmonids resulting from the hatchery release and to the physical characteristics of the study area in which the river changed from free flowing to impounded. Our results suggest that northern squawfish can quickly exploit hatchery releases of juvenile salmonids away from release sites in the Columbia River basin.

Idaho↗

USGS2002

Are traditional methods of determining nest predators and nest fates reliable? An experiment with Wood Thrushes ( Hylocichla mustelina ) using miniature video cameras

We used miniature infrared video cameras to monitor Wood Thrush ( Hylocichla mustelina ) nests during 1998–2000. We documented nest predators and examined whether evidence at nests can be used to predict predator identities and nest fates. Fifty-six nests were monitored; 26 failed, with 3 abandoned and 23 depredated. We predicted predator class (avian, mammalian, snake) prior to review of video footage and were incorrect 57% of the time. Birds and mammals were underrepresented whereas snakes were over-represented in our predictions. We documented ≥9 nest-predator species, with the southern flying squirrel ( Glaucomys volans ) taking the most nests ( n = 8). During 2000, we predicted fate (fledge or fail) of 27 nests; 23 were classified correctly. Traditional methods of monitoring nests appear to be effective for classifying success or failure of nests, but ineffective at classifying nest predators.

The Auk↗

USGS2020

Giant Gartersnakes (Thamnophis gigas) exploit abundant non-native prey while maintaining their appetite for native anurans

The introductions of nonnative species can cause great change in the trophic dynamics of native species. Giant Gartersnakes, endemic predators in the Central Valley of California, are listed as threatened because of the conversion of their once vast wetland habitat to agriculture. Further contributing to this snake's changing ecology is the introduction of many nonnative prey species, resulting in a diet that is almost completely composed of nonnative species. In order to determine whether these snakes actively select their prey or simply consume what is abundant, we examined prey selection by adult Giant Gartersnakes in the context of what prey was available to each individual. Giant Gartersnakes selected a native anuran over nonnative anuran and fish species despite these nonnatives dominating the available species composition. These results contribute to understanding the mechanisms underlying Giant Gartersnake diets in the contemporary landscape and can lead to improved management of prey communities for Giant Gartersnakes and other native predators.

Herpetologica↗

USGS2013

Quantifiable long-term monitoring on parks and nature preserves

Herpetofauna have declined globally, and monitoring is a useful approach to document local and long-term changes. However, monitoring efforts often fail to account for detectability or follow standardized protocols. We performed a case study at Hemlock Bluffs Nature Preserve in Cary, NC to model occupancy of focal species and demonstrate a replicable long-term protocol useful to parks and nature preserves. From March 2010 to 2011, we documented occupancy of Ambystoma opacum (Marbled Salamander), Plethodon cinereus (Red-backed Salamander), Carphophis amoenus (Eastern Worm Snake), and Diadophis punctatus (Ringneck Snake) at coverboard sites and estimated breeding female Ambystoma maculatum (Spotted Salamander) abundance via dependent double-observer egg-mass counts in ephemeral pools. Temperature influenced detection of both Marbled and Red-backed Salamanders. Based on egg-mass data, we estimated Spotted Salamander abundance to be between 21 and 44 breeding females. We detected 43 of 53 previously documented herpetofauna species. Our approach demonstrates a monitoring protocol that accounts for factors that influence species detection and is replicable by parks or nature preserves with limited resources.

North Carolina↗

USGS2016

Prospects and limitations of citizen science in invasive species management: A case study with Burmese pythons in Everglades National Park

Citizen-science programs have the potential to contribute to the management of invasive species, including Python molurus bivittatus (Burmese Python) in Florida. We characterized citizen-science–generated Burmese Python information from Everglades National Park (ENP) to explore how citizen science may be useful in this effort. As an initial step, we compiled and summarized records of Burmese Python observations and removals collected by both professional and citizen scientists in ENP during 2000–2014 and found many patterns of possible significance, including changes in annual observations and in demographic composition after a cold event. These patterns are difficult to confidently interpret because the records lack search-effort information, however, and differences among years may result from differences in search effort. We began collecting search-effort information in 2014 by leveraging an ongoing citizen-science program in ENP. Program participation was generally low, with most authorized participants in 2014 not searching for the snakes at all. We discuss the possible explanations for low participation, especially how the low likelihood of observing pythons weakens incentives to search. The monthly rate of Burmese Python observations for 2014 averaged ~1 observation for every 8 h of searching, but during several months, the rate was 1 python per >40 h of searching. These low observation-rates are a natural outcome of the snakes’ low detectability—few Burmese Pythons are likely to be observed even if many are present. The general inaccessibility of the southern Florida landscape also severely limits the effectiveness of using visual searches to find and remove pythons for the purposes of population control. Instead, and despite the difficulties in incentivizing voluntary participation, the value of citizen-science efforts in the management of the Burmese Python population is in collecting search-effort information.

Southeastern Naturalist↗

USGS2009

Behavioral response of the coachwhip (Masticophis flagellum) to habitat fragment size and isolation in an urban landscape

Habitat fragmentation is a significant threat to biodiversity worldwide. Habitat loss and the isolation of habitat fragments disrupt biological communities, accelerate the extinction of populations, and often lead to the alteration of behavioral patterns typical of individuals in large, contiguous natural areas. We used radio-telemetry to study the space-use behavior of the Coachwhip, a larger-bodied, wide-ranging snake species threatened by habitat fragmentation, in fragmented and contiguous areas of coastal southern California. We tracked 24 individuals at three sites over two years. Movement patterns of Coachwhips changed in habitat fragments. As area available to the snakes was reduced, individuals faced increased crowding, had smaller home-range sizes, tolerated greater home-range overlap, and showed more concentrated movement activity and convoluted movement pathways. The behavioral response shown by Coachwhips suggests, on a regional level, area-effects alone cannot explain observed extinctions on habitat fragments but, instead, suggests changes in habitat configuration are more likely to explain the decline of this species. Ultimately, if “edge-exposure” is a common cause of decline, then isolated fragments, appropriately buffered to reduce emigration and edge effects, may support viable populations of fragmentation-sensitive species.

California↗

USGS2017

Grassland bird productivity in warm season grass fields in southwest Wisconsin

Surrogate grasslands established through federal set-aside programs, such as U.S. Department of Agriculture's Conservation Reserve Program (CRP), provide important habitat for grassland birds. Warm season grass CRP fields as a group have the potential for providing a continuum of habitat structure for breeding birds, depending on how the fields are managed and their floristic composition. We studied the nesting activity of four obligate grassland bird species, Bobolink ( Dolichonyx oryzivorus ), Eastern Meadowlark ( Sturnella magna ), Grasshopper Sparrow ( Ammodramus savannarum ), and Henslow's Sparrow ( A. henslowii ), in relation to vegetative composition and fire management in warm season CRP fields in southwest Wisconsin during 2009–2011. Intraspecific variation in apparent nest density was related to the number of years since the field was burned. Apparent Grasshopper Sparrow nest density was highest in the breeding season immediately following spring burns, apparent Henslow's Sparrow nest density was highest 1 y post burn, and apparent Bobolink and Eastern Meadowlark nest densities were higher in post fire years one to three. Grasshopper Sparrow nest density was highest on sites with more diverse vegetation, specifically prairie forbs, and on sites with shorter less dense vegetation. Bobolink, Eastern Meadowlark, and Henslow's Sparrow apparent nest densities were higher on sites with deeper litter; litter was the vegetative component that was most affected by spring burns. Overall nest success was 0.487 for Bobolink (22 d nesting period), 0.478 for Eastern Meadowlark (25 d nesting period), 0.507 for Grasshopper Sparrow (22 d nesting period), and 0.151 for Henslow's Sparrow (21 d nesting period). The major nest predators were grassland-associated species: thirteen-lined ground squirrel ( Ictidomys tridecemlineatus ), striped skunk ( Mephitis mephitis ), milk snake ( Lampropeltis triangulum ), American badger ( Taxidea taxus ), and western fox snake ( Elaphe vulpina ). Overall depredation rate was not affected by the number of years since the site had been burned. The diversity of vegetation on warm season CRP fields created by management using fire provides a continuum of structure for obligate grassland birds to use for breeding and habitat for a diversity of nest predators.

Wisconsin↗

USGS2010

Reptilian prey of the sonora mud turtle (Kinosternon sonoriense) with comments on saurophagy and ophiophagy in North American Turtles

We detected evidence of predation by the Sonora mud turtle (Kinosternon sonoriense) on the Arizona alligator lizard (Elgaria kingii nobilis) and the ground snake (Sonora semiannulata) at Montezuma Well, Yavapai County, Arizona. Lizards have not been reported in the diet of K. sonoriense, and saurophagy is rare in turtles of the United States, having been reported previously in only two other species:, the false map turtle (Graptemys pseudogeographica) and the eastern box turtle (Terrapene carolina). While the diet of K. sonoriense includes snakes, ours is the first record of S. semiannulata as food of this turtle. Ophiophagy also is rare in turtles of the United States with records for only five other species of turtles. Given the opportunistic diets of many North American turtles, including K. sonoriense, the scarcity of published records of saurophagy and ophiophagy likely represents a shortage of observations, not rarity of occurrence.

Southwestern Naturalist↗

USGS2002

Kilometer-scale rapid transport of naphthalene sulfonate tracer in the unsaturated zone at the Idaho National Engineering and Environmental Laboratory

To investigate possible long-range flow paths through the interbedded basalts and sediments of a 200-m-thick unsaturated zone, we applied a chemical tracer to seasonally filled infiltration ponds on the Snake River Plain in Idaho. This site is near the Subsurface Disposal Area for radioactive and other hazardous waste at the Idaho National Engineering and Environmental Laboratory. Within 4 mo, we detected tracer in one of 13 sampled aquifer wells, and in eight of 11 sampled perched-water wells as far as 1.3 km away. These detections show that (i) low-permeability layers in the unsaturated zone divert some flow horizontally, but do not prevent rapid transport to the aquifer; (ii) horizontal convective transport rates within the unsaturated zone may exceed 14 m d −1 , perhaps through essentially saturated basalt fractures, tension cracks, lava tubes, or rubble zones; and (iii) some perched water beneath the Subsurface Disposal Area derives from episodic surface water more than 1 km away. Such rapid and far-reaching flow may be common throughout the Snake River Plain, and possibly occurs in other locations that have a geologically complex unsaturated zone and comparable sources of infiltrating water.

Idaho↗