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USGS2025

Habitat and predator influences on the spatial ecology of nine-banded armadillos

Mesopredator suppression has implications for community structure, biodiversity, and ecosystem function, but mesopredators with physical defenses may not avoid apex predators. We investigated nine-banded armadillos ( Dasypus novemcinctus ) in southwestern Oklahoma (USA) to evaluate if a species with physical defenses was influenced by a dominant predator, the coyote ( Canis latrans ). We sampled nine-banded armadillos and coyotes with motion-activated cameras. We used single-species and conditional two-species occupancy models to assess the influences of environmental factors and coyotes on nine-banded armadillo occurrence and site-use intensity (i.e., detection). We used camera-based detections to characterize the diel activity of each species and their overlap. Nine-banded armadillo occupancy was greater at sites closer to cover, with lower slopes, and further from water, whereas coyote space use was greater at higher elevations; both species were positively associated with recent burns. Nine-banded armadillo occurrence was not influenced by coyotes, but site-use intensity was suppressed by the presence of coyotes. Nine-banded armadillos (strictly nocturnal) and coyotes (predominantly nocturnal) had a high overlap in summer diel activity. Nine-banded armadillos are ecosystem engineers but are often considered a threat to species of concern and/or a nuisance. Thus, understanding the role of interspecific interactions on nine-banded armadillos has important implications for conservation and management.

Oklahoma↗

USGS2006

Changes in seasonal nearshore zooplankton abundance patterns in Lake Ontario following establishment of the exotic predator Cercopagis pengoi

Cercopagis pengoi, a zooplanktivore first discovered in Lake Ontario in 1998, may reduce availability of prey for planktivorous fish. Cercoapgis pengoi is most abundant in late summer and fall. Therefore, we hypothesized that abundance of small zooplankton (bosminids and cyclopoids) species would decrease at that time. To determine if the establishment of C. pengoi was followed by changes in the zooplankton community, seasonal patterns in nearshore zooplankton collected from May to October 1995–2000 were examined. Early summer density of small zooplankton was similar in all years while late summer and fall densities were significantly lower in 1998–2000 than in 1995–1997. The declines of small zooplankton coincided seasonally with the peak in C. pengoi density. Other possible causes for the observed changes in small zooplankton are less likely. High levels of fish predation should have resulted in smaller zooplankton in 1998–2000 than in 1995–1997 and larger declines in Daphnia than other groups. This was not observed. There was no significant decline in chlorophyll-a concentrations or changes in temperature between 1995–1997 and 1998–2000. Therefore, the declines in density of small zooplankton were most likely the result of C. pengoi predation. The effect of C. pengoi establishment on alewives is increased competition for zooplankton prey but C. pengoi has replaced a portion of the zooplankton biomass and adult alewife diet formerly dominated by Diacyclops thomasi and Bosmina longirostris .

Journal of Great Lakes Research↗

USGS2011

Diet overlap of top-level predators in recent sympatry: bull trout and nonnative lake trout

The establishment of nonnative lake trout Salvelinus namaycush in lakes containing lacustrine–adfluvial bull trout Salvelinus confluentus often results in a precipitous decline in bull trout abundance. The exact mechanism for the decline is unknown, but one hypothesis is related to competitive exclusion for prey resources. We had the rare opportunity to study the diets of bull trout and nonnative lake trout in Swan Lake, Montana during a concomitant study. The presence of nonnative lake trout in Swan Lake is relatively recent and the population is experiencing rapid population growth. The objective of this study was to evaluate the diets of bull trout and lake trout during the early expansion of this nonnative predator. Diets were sampled from 142 bull trout and 327 lake trout during the autumn in 2007 and 2008. Bull trout and lake trout had similar diets, both consumed Mysis diluviana as the primary invertebrate, especially at juvenile stages, and kokanee Oncorhynchus nerka as the primary vertebrate prey, as adults. A diet shift from primarily M. diluviana to fish occurred at similar lengths for both species, 506 mm (476–545 mm, 95% CI) for bull trout and 495 mm (470–518 mm CI) for lake trout. These data indicate high diet overlap between these two morphologically similar top-level predators. Competitive exclusion may be a possible mechanism if the observed overlap remains similar at varying prey densities and availability.

Montana↗

USGS1999

Fish losses to double-crested cormorant predation in Eastern Lake Ontario, 1992-97

We examined 4,848 regurgitated digestive pellets of double-crested cormorants ( Phalacrocorax auritus ) over a 6-year period (1992–97) to estimate annual predation on sport and other fishes in the eastern basin of Lake Ontario. We found more than 51,000 fish of 28 species. Using a model that incorporates annual colony nest counts; fledgling production rates; adult, immature, and young-of-year residence times (seasonal); estimates of mean number of fish per pellet and mean fish size; and a fecal pathway correction factor (4.0 percent), we estimate total annual number of fish consumed by cormorants in the eastern basin of Lake Ontario to range from 37 million to 128 million fish for 1993–97. This fish loss equates to an estimated 0.93 million to 3.21 million kg (mean 2.07 million kg) of fish consumed per year, principally alewife ( Alosa pseudoharengus , 42.3 percent) and yellow perch ( Perca flavescens , 18.4 percent). Forage fish (alewife, cyprinids, trout-perch [ Percopsis omiscomaycus ], and other minor components) accounted for 65 percent of the diet, and panfish contributed 34 percent of the diet for the 5-year period. Game fish were minor components of the diet, in view of an average estimated annual consumption of 900,000 smallmouth bass ( Micropterus dolomieui , 1.1 percent) and 168,000 salmonines (mostly lake trout, Salvelinus namaycush , 0.2 percent). Cormorant predation on lake trout fingerlings stocked in May 1993 and June 1994 was estimated through the use of coded wire tag recoveries from pellets collected on Little Galloo Island 1 and 4 days after stocking events. We estimated losses of 13.6 percent and 8.8 percent, respectively, of the fish stocked for the two events, an average of 11.2 percent. Such losses may be reduced through alteration of existing stocking practices.

Lake Ontario;Little Galloo Island↗

USGS1991

Wolf predation risk associated with white-tailed deer movements

The survival of 159 yearling and adult deer (Odocoileus virginianus) was monitored by telemetry during 282 spring and 219 fall individual migrations to winter deeryards in northeastern Minnesota. A disproportionate number of deer were killed by wolves (Canis lupus) during fall migration relative to the short time they spent migrating, but not during spring migration. Predation was also significantly greater for male and female yearlings and adult females outside deeryards during winter. Survival of 79 yearlings dispersing from natal ranges was high (1.00). It appears that changing climatic conditions combined with unfamiliar terrain and undetermined factors predispose migratory deer to wolf predation during fall. These findings support an earlier hypothesis that winter yarding is an antipredator strategy.

Canadian Journal of Zoology↗

USGS2003

Pesticide-laced predator baits: considerations for prosecution and sentencing

The illegal use of pesticide-laced baits for predator control is a wildlife crime that is underreported, inadequately documented, and insufficiently punished. The crime occurs when some ranchers, farmers, and hunting groups illegally lace baits with pesticides to control avian and mammalian predators. The activity has poisoned birds protected by the Endangered Species Act, Migratory Bird Treaty Act, and the Bald and Golden Eagle Protection Act. However, because of difficulties in discovering, reporting, and confirming the baitings and the wildlife kills, the crimes often appear inconsequential. The limited knowledge of these crimes in the public, regulatory, and judicial arenas distorts their importance .for some prosecutors and judges. The United States pesticide regulatory system has positioned federal and state prosecutors and judges in a critical role for protecting wildlife from the illegal practice of lacing baits with pesticides. In this article, the authors provide an overview of the crime and describe the ways in which the crime is investigated. They then present investigative and experimental evidence on the extent of the illegal practice and the magnitude of the kills in order to elucidate their importance with respect to prosecution and sentencing. The authors conclude by recommending that sufficient resources be made available, public awareness and education increased, and persistent prosecution occur in order to improve the effectiveness of all federal wildlife enforcement.

Environmental Lawyer↗

USGS2008

Impact of the newly arrived seed-predating beetle Specularius impressithorax (Coleoptera: Chrysomelidae: Bruchinae) in Hawai'i

Prior to 2001, seed predation was virtually absent in the endemic Wiliwili Erythrina sandwicensis (Fabaceae: Degener), dominant tree species of lower-elevation Hawaiian dryland forests. The African bruchine chrysomelid Specularius impressithorax (Pic) (Coleoptera: Chrysomelidae: Bruchinae) was first detected in Hawai'i in 2001 and became established on all main islands within the next two years. The mode of entry for this invasive Erythrina seed predator into Hawai'i is unknown, but likely occurred with the importation of trinket jewelry from Africa containing characteristically brightly-colored Erythrina seeds. The initial establishment of this insect likely occurred on a non-native host, the widely cultivated coral tree E. variegata. Within three years of its first record, S. impressithorax accounted for 77.4% mean seed crop loss in 12 populations of Wiliwili on six main Hawaiian islands. Specularius impressithorax, dispersed through international commerce and established via E. variegata, has become a threat to a unique Hawaiian forest type and may threaten other Erythrina, especially New World representatives.

Pacific Conservation Biology↗

USGS2015

Peregrine falcon predation of endangered Laysan teal and Laysan Finches on remote Hawaiian atolls

We report the first records of Peregrine falcon ( Falco peregrinus ) predation on endangered Laysan teal (or duck; Anas laysanensis ) and predation on endangered Laysan finches ( Telespiza cantans ). At Midway Atoll, vagrant Peregrine falcons killed ≥4% of a newly translocated Laysan teal population in 2006 and ≥2% in 2008. On Laysan Island during 2008–2009, remains of >76 Laysan finches (<1% of the population) were found at peregrine perches. On Midway Atoll, all depredated Laysan teal and other seabirds were recovered at kill sites on tarmac (runways). If the frequency or duration of vagrant raptors visitation increases at small atolls, this could pose a mortality risk to consider, especially during proposed translocations of endangered species. Vegetation restoration of abandoned runways near wetlands at Midway Atoll would provide cover and may help reduce mortality of endangered species due to vagrant raptors.

Laysan Island, Midway atoll↗

USGS1988

Predation of Karluk River sockeye salmon by coho salmon and char

The number of sockeye salmon, Oncorhynchus nerka , in Alaska's Karluk River (Fig. 1) declined from millions to thousands during the early part of the present century. Rounsefell (1958) discussed alternative explanations for the decline including a general loss offertility ofthe system as the number of salmon carcasses declined, competition, overfishing, subtle changes in climate, and predation; he concluded that the combined effect of predation and fishing was the most probable explanation. Later, Van Cleave and Bevan (1973) suggested that the weir constructed in the river each year to facilitate counting the fish as they entered the system was the most probable cause ofthe decline. Itprevented free movement of both adults and juveniles in the river. All of these hypotheses remain as potential explanations for the decline

Alaska↗

USGS1982

Predation on seabirds by red foxes at Shaiak Island, Alaska

Two Red Foxes (Vulpes fulva ) that invaded Shaiak Island before the 1976 nesting season had a marked impact on the nesting success of five of seven species of seabirds breeding on the island that year. Common Eiders ( Somateria mollissima ), Glaucous-winged Gulls ( Larus glaucescens ), and Common Murres ( Uria aalge ), that nest in areas accessible to foxes, did not raise any young to fledging. Double-crested Cormorants ( Phalacrocorax auritus ) were only slightly more successful; 13 (4.3%) of 300 pairs raised one or more young to fledging. Evidence suggested that 21 (35.6%) of 62 pairs of Tufted Puffins (Lunda cirrhata ) lost eggs or chicks to foxes, and foxes killed at least 13 (8.3%) of 156 adult puffins on ten sample plots. Conversely, Black-Legged Kittiwakes ( Rissa tridactyl a) and Pelagic Cormorants ( Phalacrocorax pelagicus ), which nested primarily on cliffs inaccessible to foxes, lost very few nests. There was no apparent change in general nest site selections by seabirds the following year, when foxes were no longer present. Any avoidance by birds of areas vulnerable to fox predation would probably be discernible only after several years of continuous predation.

Alaska↗

USGS2016

Diadophis Puntatus Puntatus (Southern Ring-neck Snake) Predation

DIADOPHIS PUNCTATUS PUNCTATUS (Southern Ring-necked Snake). PREDATION. Here I present the first record of Buteo lineatus (Red-shouldered Hawk) predator on a Diadophis p. punctatus. At ca. 1100h on l2 February2 013,I observed a B. lineatus eating a katydid in Corkscrew Swamp Sanctuary (26.2730'N, 81.6079"W;WGS 84), Collier Co., Florida, USA. The hawk was in a Pond Cypress tree on the edge of a small prairie bordered on one side by a cypress swamp and by pine woodland on the other. Immediately upon consuming the katydid, the hawk flew to the ground ca. 1.5 m from an elevated boardwalk to grab an adult D. punctatus. It then flew with the snake in its talons to a branch 3 m high ca. l0 m from the boardwalk. The hawk stretched and otherwise manipulated the struggling snake (Fig.1) before consuming the still moving snake. Although snakes are a well-known component of B. lineatus diet (Clark1 987A. Field Guide to the Hawks of North America. Houghton Mifflin Co. Boston, Massachusetts 198 pp.), I found only one literature reference to Red-shouldered Hawks eating Ring-neck Snakes (Fisher 1893.Hawks and Owls of the United States in their Relation to Agriculture. U.S. Dept. Agric., Div Ornith. Mamm. Bull. 3). That specimen was from Canton, New York (taken 26 Oct IBBB) and would be a D. p. edwardisii (Northern Ring-necked Snake), while the snake reported on here is a Diadophis p. punctatus (USNM Herp Image 2847a -c). Based on evidence presented by Fontanella et al. (2008. Mol. Phylogenet Evol.46:1049-1070), D. p. edwardisii and D. p. punctatus are likely different species.

Florida↗

USGS1999

Sand lance: A review of biology and predator relations and annotated bibliography

Six species of sand lance ( Ammodytes ) in temperate and boreal regions are currently recognized. Sand lance can occupy a wide range of environmental conditions, but all appear to be dormant predominantly in winter, and one species is in summer also. They lack a swim bladder and spend much of their time buried in specific substrates. Copepods are the primary food. Spawning usually occurs in fall or winter (although some species also spawn in spring), eggs are demersal, and larvae may hatch at times of low food abundance. Sand lance usually occur in schools and are regarded as a relatively high-quality forage fish. Sand lance constitute a major prey for at least some populations of over 100 species of consumer, including 40 species of birds, 12 species of marine mammals, 45 species of fishes, and some invertebrates. Variation in the availability of sand lance (and other forage fishes) can have major effects on the breeding success and survival of their predators. Commercial fishing and other pressures on sand lance populations potentially have ramifying effects on many species of wildlife. The bibliography contains over 1,700 references on the family Ammodytidae, with an emphasis on the genus Ammodytes . Keywords are provided for each reference and have been further organized into taxonomic, geographic, subject, and predator indexes.

Research Paper↗

USGS2015

Golden Eagle predation of an adult turkey vulture

The Golden Eagle (Aquila chrysaetos) is a large, apex predator that occurs at low densities, has a long life span, experiences delayed maturity, has low reproductive rates, and has no natural predators (Watson 1997, Kochert et al. 2002). Golden Eagles are sensitive to anthropogenic driven landscape changes in land cover and land use (Hunt 2002, Kochert and Steenhof 2002). Landscape level alterations, such as encroachment of woody vegetation in eagle foraging areas, may result in decreased abundance of suitable prey or interfere with the eagle’s ability to see or capture prey. Currently, there is substantial concern for Golden Eagle conservation due to widespread anthropogenic changes to landscapes across much of the species distribution (U.S. Fish and Wildlife Service 2013). In particular, the rapid expansion of wind energy development has led to heightened concerns for Golden Eagle conservation, as the species is susceptible to mortality through collision with turbines (Hunt 2002, U.S. Fish and Wildlife Service 2013). This has resulted in a recent increase in research to develop a better understanding of the species’ ecology.

Bulletin of the Texas Ornithological Society↗

USGS2020

Acris blanchardi (Blanchard's Cricket Frog), Predation

Invertebrates are well-known predators of amphibians with many documented cases of spiders preying upon anurans (reviewed in Toledo 2005. Herpetol. Rev. 36:395–400). Wolf spiders are known to feed on a variety of frogs, including those in the genus Acris (Blackburn et al. 2002. Herpetol. Rev. 33:299). Although typically terrestrial, wolf spiders have been found feeding on arboreal frogs ca. 1 m above the ground (Aucone and Card 2002. Herpetol. Rev. 33:48). To our knowledge, no records exist of a wolf spider feeding on a terrestrial frog at an elevated height. At 0113 h on 30 April 2019, we observed an adult female wolf spider (Tigrosa georgicola: Lycosidae) feeding on an adult Acris blanchardi ca. 1.5 m high on the trunk of a small tree at the edge of a pond in Sherburne Wildlife Management Area, St. Martin Parish, Louisiana, USA (30.424°N, 91.663°W; WGS 84; Fig. 1). The spider was positioned facing the ground and the partially digested frog was hanging from its mouthparts. The spider likely captured the frog on the ground near the edge of the water and retreated up the tree with its meal (Fig. 1B). Movement of spiders with prey from an initial point of capture is documented in wolf spiders (Aucone and Card 2002, op. cit.) and other large terrestrial spiders (Maffei et al. 2010. Herpetol. Notes 3:167–170). This behavior may minimize the vulnerability of the spider to predators. We thank Zack Lemann, Curator of Animal Collections at the Audubon Butterfly Garden and Insectarium, for spider identification.

Louisiana↗

USGS2024

Predator disturbance contributed to Common Murre Uria aalge breeding failures in Cook Inlet, Alaska following the 2014–2016 Pacific marine heatwave

The 2014-2016 Pacific marine heatwave caused unprecedented die-offs and multi-year reproductive failures for Common Murres Uria aalge along the west coast of North America. Lingering impacts, such as declines in colony attendance and productivity, have persisted at some colonies following the heatwave and are attributed largely to changes in prey availability and quality. Here, we present evidence of an additional, top-down mechanism contributing to Common Murre breeding failures on Gull Island (Alaska): disturbance of nesting birds by aerial predators and associated egg depredation. We collected time-lapse images over five murre breeding seasons (2016-2020) on Gull Island to document the frequency, duration, and intensity of disturbances caused by aerial predators, as well as to quantify disturbance-associated egg depredation. To identify seasonal and inter-annual variability of disturbances, we calculated a daily disturbance index and compared years using generalized additive models. In all years, Bald Eagles Haliaeetus leucocephalus were the primary cause of disturbance, which led to periods of prolonged colony abandonment by murres and facilitated high levels of murre egg depredation by Glaucous-winged Gulls Larus glaucescens and Herring Gulls L. argentatus . We found that the seasonality of disturbance was an important factor in determining egg depredation rates. In years when disturbance levels were high and persisted later in the season, the colony experienced complete breeding failures due to disturbance-associated egg depredation. Our study revealed that the response of nesting murres to a strong environmental perturbation, such as the Pacific marine heatwave, can be complex and involve multiple stressors from both bottom-up and top-down factors.

Alaska↗

USGS2024

An invasive predator substantially alters energy flux without changing food web functional state or stability

Understanding how invasive species affect the stability and function of ecosystems is critical for conserving ecosystems. Here, we quantified the effect of an actively suppressed invasive species on the Yellowstone Lake, U.S.A. ecosystem using a food-web energetics approach. 2. We compared energy flux, functional state, and stability of four food web states: a pre-invasion network, and three post-invasion networks undergoing active invasive species suppression: initial invasion; expansion; decline. 3. Invasion caused > 25% change (±) in energy flux for most consumers, and total flux increased twofold post-invasion. Flux to the species of conservation concern, Yellowstone cutthroat trout ( Oncorhynchus virginalis bouvieri ), was 2.8-times less post-invasion vs pre-invasion while invasive lake trout ( Salvelinus namaycush ) flux was up to 17.3-times higher compared to the initial invasion network. The dominant functional state and food web stability did not change post-invasion, likely due to introduction of a generalist predator and the stabilizing effect of suppression. 4. Lake trout invasion in Yellowstone Lake caused large changes to energy flux, shifting dominant fluxes away from the species of conservation concern, despite not changing functional state or stability. We demonstrate that changes in energy flux may signal invasions in ecosystems, but functional state or stability may not necessarily reflect the magnitude of invasion influences. 5. Implications for conservation: For invaded fish communities, a better understanding of how the invasive species controls the food web beyond just the direct influence on prey results can be achieved by investigating energy flux, functional state, and food-web stability. Furthermore, evaluating the effect of suppression beyond the invasive species can demonstrate the far-reaching value of suppression management actions for conservation.

Wyoming↗

USGS2025

Non-native prey availability and over-compensatory density dependence drive population dynamics of a native fish predator

Understanding the factors that regulate population dynamics is crucial for conserving imperiled species. Bull trout ( Salvelinus confluentus ), a piscivorous salmonid and one of North America's most threatened cold-water species, has declined significantly due to habitat loss, overfishing, invasive species, and climate change. While recovery efforts have primarily targeted these threats, the role of prey availability in influencing bull trout population dynamics under multiple stressors remains poorly understood. Using a stage-based integrated population model, we quantified the effects of non-native prey availability (kokanee; Oncorhynchus nerka ), angling pressure, climatic variation, and density-dependent processes on bull trout population dynamics in Lake Koocanusa, a transboundary reservoir and river system (United States and Canada), over a 40-year period (1980–2023). Our results show that bull trout populations are regulated by density-dependent processes, including over-compensation in sub-adult recruitment and reduced adult survival at high densities. Increased kokanee biomass and restricted harvest significantly enhanced bull trout survival and abundance, whereas reduced water availability had a limited negative effect on sub-adult production. Model simulations indicate that as kokanee biomass availability increases, the number of bull trout that can be sustainably harvested also increases. In fact, a modest annual fishery (300 individuals) can be sustained, especially under moderate to high kokanee biomass conditions. These results underscore the importance of prey availability, including non-native species, in supporting bull trout populations. Effective management of threatened apex fish predators like bull trout requires addressing the complex interplay between environmental threats, prey dynamics, and density-dependent mechanisms across all life stages.

British Columbia, Montana↗

USGS2022

Face-off: Novel depredation and nest defense behaviors between an invasive and a native predator in the Greater Everglades Ecosystem, Florida, USA

We describe several photo-documented novel interactions between intraguild predators in southern Florida—the native bobcat ( Lynx rufus ) and the invasive Burmese python ( Python bivittatus ). Over several days we documented a bobcat's depredation of an unguarded python nest and subsequent python nest defense behavior following the return of both animals to the nest. This is the first documentation of any animal in Florida preying on python eggs, and the first evidence or description of such antagonistic interactions at a python nest.

Florida↗