Geology Reports⌕ Search

SEARCH · Geology Reports

Results for “Predator”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 559 records · Page 31Linked to original sources
USGS1998

Estimation of invertebrate production from patterns of fish predation in western Lake Superior

We used bioenergetic models for lake herring Coregonus artedi , bloater Coregonus hoyi , and rainbow smelt Osmerus mordax to estimate consumption of zooplankton, Mysis , and Diporeia in western Lake Superior for selected years between 1978 and 1995. Total invertebrate biomass consumed yearly ranged from 2.5 to 38 g/m 2 with nearly 40% consumed between August and October in all years. Copepod zooplankton represented the largest proportion of biomass collectively consumed by the three species (81%), although rainbow smelt consumed almost twice as much Mysis as zooplankton. Growth efficiency was highest for rainbow smelt (3.84–16.64%) and lower for the coregonids (1.91–12.26%). In the absence of quantitative secondary production values, we suggest our estimates of predatory demand provide a conservative range of the minimum invertebrate production in western Lake Superior during the past 20 years.

Transactions of the American Fisheries Society↗
USGS2011

Modeling management scenarios and the effects of an introduced apex predator on a coastal riverine fish community

The flathead catfish Pylodictis olivaris, a carnivorous fish species native to most of the central interior basin of North America, has been introduced into at least 13 U.S. states and 1 Canadian province. Concurrent declines in abundance of native fishes have been reported in aquatic systems where flathead catfish have been introduced. To evaluate the potential impact of this invasive species on the native fish community we developed an ecosystem simulation model (including flathead catfish) based on empirical data collected from a North Carolina coastal river. The model results suggest that flathead catfish suppress native fish community biomass by 5-50% through both predatory and competitive interactions. However, our model suggests these reductions could be mitigated through sustained exploitation of flathead catfish by recreational or commercial fishers at rates equivalent to those for native flathead catfish populations (annual exploitation = 6-25%). These findings demonstrate the potential for using directed harvest of an invasive species to assist in restoring native communities. ?? Copyright by the American Fisheries Society 2007.

Transactions of the American Fisheries Society↗
USGS2016

Demography of an apex predator at the edge of its range: impacts of changing sea ice on polar bears in Hudson Bay

Changes in the abundance and distribution of wildlife populations are common consequences of historic and contemporary climate change. Some Arctic marine mammals, such as the polar bear ( Ursus maritimus ), may be particularly vulnerable to such changes due to the loss of Arctic sea ice. We evaluated the impacts of environmental variation on demographic rates for the Western Hudson Bay (WH), polar bear subpopulation from 1984 to 2011 using live-recapture and dead-recovery data in a Bayesian implementation of multistate capture–recapture models. We found that survival of female polar bears was related to the annual timing of sea ice break-up and formation. Using estimated vital rates (e.g., survival and reproduction) in matrix projection models, we calculated the growth rate of the WH subpopulation and projected population responses under different environmental scenarios while accounting for parametric uncertainty, temporal variation, and demographic stochasticity. Our analysis suggested a long-term decline in the number of bears from 1185 (95% Bayesian credible interval [BCI] = 993–1411) in 1987 to 806 (95% BCI = 653–984) in 2011. In the last 10 yr of the study, the number of bears appeared stable due to temporary stability in sea ice conditions (mean population growth rate for the period 2001–2010 = 1.02, 95% BCI = 0.98–1.06). Looking forward, we estimated long-term growth rates for the WH subpopulation of ~1.02 (95% BCI = 1.00–1.05) and 0.97 (95% BCI = 0.92–1.01) under hypothetical high and low sea ice conditions, respectively. Our findings support previous evidence for a demographic linkage between sea ice conditions and polar bear population dynamics. Furthermore, we present a robust framework for sensitivity analysis with respect to continued climate change (e.g., to inform scenario planning) and for evaluating the combined effects of climate change and management actions on the status of wildlife populations.

Hudson Bay↗
USGS1995

Waterbird predation on fish in western Lake Erie: a bioenergetics model application

To better understand the role of piscivorous waterbirds in the food web of western Lake Erie, we applied a bioenergetics model to determine their total fish consumption, The important nesting species included the Herring Gull (Larus argentatus), Ring-billed Gull (L. delawarensis), Double-crested Cormorant (Phalacrocorax auritus), Great Blue Heron (Ardea herodias), Black-crowned Night-Heron (Nycticorax nycticorax), and Great Egret (Casmerodius albus). The impact of migrant waterbirds, including the Red-breasted Merganser (Mergus serrator), on western Lake Erie fish biomass was also considered in the analysis. According to the modeling results, during the early 1990s, piscivorous waterbirds consumed 13,368 tonnes of fish from western Lake Erie each year. This tonnage was equivalent to 15.2% of the prey fish biomass needed to support the walleye (Stizostedion vitreum) population in western Lake Erie during a single growing season. The model application was useful in quantifying energy flow between birds and fish in a large lake ecosystem.

Condor↗
USGS1992

Cannibalism and predation on black bears by grizzly bears in the Yellowstone ecosystem, 1975-1990

We documented one instance of an adult male grizzly bear preying upon a black bear and four instances where circumstantial evidence suggested that grizzly bears (two cubs-of-the-year, one yearling female that was injured, and one adult male) had been preyed upon by conspecifics. We also examined feces of grizzly bears for bear remains. Remains of bears tended to be more common in spring feces and did not differ in frequency between early and late years of the study. Our observations generally support existing hypotheses concerning cannibalism among bears.

Idaho;Montana;Wyoming↗
USGS1951

An aquarium experiment on the American eel as a predator on larval lampreys

The parasitic sea lamprey, Petromyzon marinus , has in recent years spread throughout Lakes Huron and Michigan and is now firmly established in these waters (Applegate, 1949, Mich. Cons., 18 (4): 13-15). Coincident with their spread, the abundance of lake trout, Salvelinus namaycush , has declined in both lakes (Hile, 1949, Trans. Amer. Fish. Soc., 76 (1946): 121-147) and the lake trout as well as other species of fishes are showing an increase in scarring from lamprey attacks. For Lake Michigan the analysis of fishermen's questionnaires gave an increase in percentage by weight of lamprey-scarred lake trout from 31 percent in 1947 to 41 percent in 1948. The sea lamprey is now spreading through Lake Superior, the last of the Great Lakes containing a large population of lake trout.

Copeia↗
USGS2000

Predation on Corynorhinus townsendii by Rattus rattus

Corynorhinus townsendii (Townsend's big- eared bat) is a rare and declining species. Ex- tensive surveys for the coastal subspecies, C. t. townsendii, in California indicate that only 50% of historic maternity colonies are occu- pied currently (Pierson and Rainey, 1996). Three of the largest maternity colonies occur in Marin Co. Two of these have been moni- tored with evening exit counts on a regular basis since their discovery (1987-Randall House; 1990-Jerrys) through 1996. From 1987 through 1993, the Randall House colony slowly increased from 123 to 215 bats as the colony was afforded greater protection from disturbance once the bats were discovered. Since 1990, both colonies have been com- posed of ca. 200 adult bats in the spring, and ca. 300 adults and young through the summer and early fall.

Southwestern Naturalist↗
USGS1964

Management of predator populations with antifertility agents

The search for methods, other than lethal techniques, for controlling predatory animals causing economic losses to the livestock industry prompted investigation of antifertility agents to suppress reproduction. Diethylstilbestrol was selected for initial trials because of its demonstrated antifertility effect on rabbits, mink ( Mustela vison ), dogs, and cattle. In penned tests with stilbestrol, pregnancy was terminated in six coyotes ( C anis latrans ) fed a single 100-mg oral dose dissolved in tallow. A subsequent field trial was conducted in New Mexico on 20 townships, March 5-15, 1963. Five thousand (100 mg stilbestrol in ½ ounce of tallow) drop baits were placed wherever coyote sign was found. After a delay of 3 weeks to allow the drug to take effect, a collection of female tracts from the treated area and a reference area 25 miles away was made to measure and compare reproductive success. Of the 20 females in reproductive condition recovered from the treated area, only 4 had viable embryos, while reproduction was blocked in 16 specimens by failure of implantation or resorption of embryos. All of the 13 females in reproductive condition from the reference area would have produced pups as evidenced by viable embryos. Future tests are scheduled to determine effects on other species and to confirm results on coyotes under a variety of field conditions.

Journal of Wildlife Management↗
USGS1976

White-tailed deer migration and its role in wolf predation

Seventeen white-tailed deer ( Odocoileus virginianus ) were radio-tagged in winter yards and tracked for up to 17 months each (881 locations) from January 1973 through August 1974 in the central Superior National Forest of NE Minnesota following a drastic decline in deer numbers. Ten vyolves ( Canis lupus ) from 7 packs in the same area were radiotracked before and/or during the same period (703 locations). Deer had winter ranges averaging 26.4 ha. Spring migration took place from 26 March to 23 April and was related to loss of snow cover. Deer generally migrated ENE in straight-line distances of 10.0 to 38.0 km to summer ranges. Two fawns did not migrate. Arrival on summer ranges was between 19 April and 18 May, and summer ranges varied from 48.1 to 410.4 ha. Migration back to the same winter yards took place in early December, coincident with snow accumulation and low temperatures. Social grouping appeared strongest during migration and winter yarding. Survival of the radio-tagged deer was studied through 1 May 1975. Four deer were killed by wolves, one was poached, and one drowned. Mean age of the captured deer was 5.4 years and estimated minimum survival after capture was 2.6 years, giving an estimated total minimum survival of 8.0 years. This unusually high survival rate appeared to be related to the fact that both winter and summer ranges of these deer were situated along wolf-pack territory edges rather than in centers. In addition, most summer ranges of the radio-tagged deer were along major waterways where the deer could escape wolves.

Journal of Wildlife Management↗
USGS2019

Predation strategies of larval clownfish capturing evasive copepod prey

Fish larvae depend on finding and capturing enough prey for rapid growth during the planktonic phase. The diet of many fish larvae is dominated by copepods, small crustaceans that are highly sensitive to hydrodynamic disturbances and possess strong escape responses. We examined how fish larvae with immature jaws, musculature and fins capture such evasive prey. The kinematics of feeding attempts by larval clownfish Amphiprion ocellaris on 3 developmental stages of copepod Bestiolina similis were investigated using high-speed videography. A stealthy approach brought the fish larva within ~1 mm of the copepod; shortest distances were observed in early larvae (1 to 5 d post-hatch [dph]) attacking immature copepods. Peak speeds during strikes increased with fish age and copepod developmental stage (150 to 250 mm s -1 ), with time to capture <8 ms on average. Most successful captures (70%) were of copepods that failed to initiate an escape response during the strike. If a copepod initiated an escape, capture success decreased to ~50% for nauplii and copepodites and 25% for adults. Adult copepods were more likely to attempt an escape response than copepodites or nauplii. Prey stage and the interaction between strike distance and speed were the parameters that best fit a logistic regression model to the observed captures and escapes. The successful switch to larger and more evasive copepod prey by A. ocellaris larvae did not occur until 7 dph and coincided with ontogenetic changes (post-flexion) and a predatory strategy that included shorter approach phases and greater strike speeds.

Marine Ecology Progress Series↗
USGS2022

To catch a (marsh) predator: Modified trapping methods for breeding and wintering Northern Harriers (Circus hudsonius)

Although there are a variety of methods available for trapping raptors, some species, such as Northern Harriers ( Circus hudsonius ), are not easily captured with standard methods. We tested several existing trapping methods and modified two of them based on Northern Harrier ecology and behavior across seasons in a study population in California. No previously successful methods described in the literature were effective for our study population. Two modified methods were most effective for trapping Northern Harriers: (1) placing two dho-gazas around the nest in a V-shape and flushing the adult female into the nets during the breeding season, and (2) using remote-triggered bow nets baited with waterbird carcasses in winter. Dho-gazas at the nest worked well during the early nestling-rearing stage, when nestlings were younger than 2 wk old and adult females were most attentive. This method was not suitable during the incubation stage because Northern Harriers are prone to nest abandonment. In the winter, Northern Harriers are known to scavenge, yet this aspect of their behavioral ecology has previously been rarely exploited for trapping purposes. These two methods allow for selective Northern Harrier trapping across seasons and provide modified options for research on this understudied and declining species in North America.

California↗
USGS2018

Exotic predators may threaten another island ecosystem: A comprehensive assessment of python and boa reports from the Florida Keys

Summarizing historical records of potentially invasive species increases understanding of propagule pressure, spatiotemporal trends, and establishment risk of these species. We compiled records of non-native pythons and boas from the Florida Keys, cross-referenced them to eliminate duplicates, and categorized each record’s credibility. We report on 159 observations of six python and boa species in the Florida Keys over the past 17 years. Burmese pythons (Python bivittatus), boa constrictors (Boa constrictor), and ball pythons (Python regius) are the most frequently reported species, but credible records of three additional species were also reported. Among the most notable records, we report on three hatchling and multiple reproductive Burmese pythons captured on North Key Largo since 2016, indicating that the species is now established on that island. The expanding mainland Burmese python population and ongoing python and boa introductions via pet and cargo pathways are likely to keep propagule pressure high in coming years. Both effective public outreach to solicit reporting of sightings and effective early detection and rapid response networks may help to prevent further establishment and associated ecological impacts of python and boa species in the Florida Keys.

Florida↗