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At least 37 records · Page 2Linked to original sources
USGS2018

Population ecology of Roosevelt elk: Conservation and management in Redwood National and State Parks. Butch Weckerly. 2017. University of Nevada Press, Reno, Nevada, USA. 224 pp. $54.95 hardback. ISBN 978- 1943859504.

Long-term research on large ungulate populations typically conjures perceptions of extensive (and expensive) animal capture and telemetry work, and subsequent advanced modeling of resource selection and population dynamics that inform management decisions. In contrast, studies lacking a telemetry component are often limited to animal behavior or natural history. Although compelling from a standpoint of advancing understanding of ecological and evolutionary processes, results from the latter can be unfairly labeled as esoteric because they are not easily transferable to resource managers or may not provide exceptional interest to a general public drawn to these charismatic megafuana. Such dichotomies are not predetermined, however, because study conditions exist where dedicated academic researchers on tight budgets can achieve results relevant to ecology and management.

Journal of Wildlife Management↗
USGS2013

Population ecology of polar bears in Davis Strait, Canada and Greenland

Until recently, the sea ice habitat of polar bears was understood to be variable, but environmental variability was considered to be cyclic or random, rather than progressive. Harvested populations were believed to be at levels where density effects were considered not significant. However, because we now understand that polar bear demography can also be influenced by progressive change in the environment, and some populations have increased to greater densities than historically lower numbers, a broader suite of factors should be considered in demographic studies and management. We analyzed 35 years of capture and harvest data from the polar bear ( Ursus maritimus ) subpopulation in Davis Strait, including data from a new study (2005–2007), to quantify its current demography. We estimated the population size in 2007 to be 2,158 ± 180 (SE), a likely increase from the 1970s. We detected variation in survival, reproductive rates, and age-structure of polar bears from geographic sub-regions. Survival and reproduction of bears in southern Davis Strait was greater than in the north and tied to a concurrent dramatic increase in breeding harp seals ( Pagophilus groenlandicus ) in Labrador. The most supported survival models contained geographic and temporal variables. Harp seal abundance was significantly related to polar bear survival. Our estimates of declining harvest recovery rate, and increasing total survival, suggest that the rate of harvest declined over time. Low recruitment rates, average adult survival rates, and high population density, in an environment of high prey density, but deteriorating and variable ice conditions, currently characterize the Davis Strait polar bears. Low reproductive rates may reflect negative effects of greater densities or worsening ice conditions.

Davis Strait↗
USGS2015

Population ecology of the gulf ribbed mussel across a salinity gradient: recruitment, growth and density

Benthic intertidal bivalves play an essential role in estuarine ecosystems by contributing to habitat provision, water filtration, and promoting productivity. As such, changes that impact population distributions and persistence of local bivalve populations may have large ecosystem level consequences. Recruitment, growth, mortality, population size structure and density of the gulf coast ribbed mussel, Geukensia granosissima , were examined across a salinity gradient in southeastern Louisiana. Data were collected along 100-m transects at interior and edge marsh plots located at duplicate sites in upper (salinity ~4 psu), central (salinity ~8 psu) and lower (salinity ~15 psu) Barataria Bay, Louisiana, U.S.A. Growth, mortality and recruitment were measured in established plots from April through November 2012. Mussel densities were greatest within the middle bay (salinity ~8) regardless of flooding regime, but strongly associated with highest stem densities of Juncus roemerianus vegetation. Mussel recruitment, growth, size and survival were significantly higher at mid and high salinity marsh edge sites as compared to all interior marsh and low salinity sites. The observed patterns of density, growth and mortality in Barataria Bay may reflect detrital food resource availability, host vegetation community distribution along the salinity gradient, salinity tolerance of the mussel, and reduced predation at higher salinity edge sites.

Louisiana↗
USGS1971

Population ecology of the great blue heron with special reference to western Oregon

Great Blue Heron (Ardea herodias) begin nesting in western Oregon about 1 month earlier than reported from the Philadelphia region and about 2 months earlier than reported from Southern Alberta. The number of young fledged per nesting pair in Oregon was 2.04 in 1970 which was nearly identical to the 1.91 believed necessary to maintain a stable population in the northern United States. The level of p,p'DDE reported from two eggs in Oregon was within the same range as that reported from 40 eggs in Alberta. Although some thin-shelled eggs were being laid in Alberta, the observed production was believed sufficient for maintaining a stable population. Production rates reported from a heronry in central California suggested that the population there was also remaining fairly stable.

Canadian Field-Naturalist↗
USGS1975

The screech owl: Its life history and population ecology in northern Ohio

The screech owl ( Otus asio ) is native to North America and breeds throughout the United States and in portions of Canada and Mexico. It is a small owl, 20 cm (8 in) in length from the tip of the bill to the tip of the tail, with a wing span of 56 cm (22 in); it has yellow eyes and prominent ear tufts (see Frontispiece). Although the species is common throughout much of North America, it has not been studied intensively, particularly over a long period. The published literature is concerned mostly with food habits, color phase, taxonomy, and miscellaneous observations. Breeding biology and population dynamics have received little attention. This report presents the basic life history and population information about screech owls in northern Ohio over a 30-yr period. The owls studied were nesting in boxes (Fig. 1) established for wood ducks ( Aix sponsa ) along rivers, creeks, and marshes in a four-county area (Ottawa, Sandusky, Wood, and Lucas Counties) near Lake Erie (Fig. 2). No special trapping techniques were required as the screech owls readily used these nesting boxes and could be easily captured while in them. More than 3,000 owls were captured and banded; 500 were recaptured after the initial banding, some 10 or 15 times. This process provided a large quanity of basic information for this report.

Ohio↗
USGS1987

Population ecology of the mallard VIII: Winter distribution patterns and survival rates of winter-banded mallards

In the present report we address questions about winter distribution patterns and survival rates of North American mallards Anas platyrhynchos . Inferences are based on analyses of banding and recovery data from both winter and preseason banding period. The primary wintering range of the mallard was dividded into 45 minor reference areas and 15 major reference areas which were used to summarize winter banding data. Descriptive tables and figures on the recovery distributions of winter-banded mallards are presented. Using winter recoveries of preseason-banded mallards, we found apparent differences between recovery distribution of young versus adult birds from the same breeding ground reference areas. However, we found no sex-specific differences in winter recovery distribution patterns. Winter recovery distributions of preseason-banded birds also provided evidence that mallards exhibited some degree of year-to-year variation in wintering ground location. The age- and sex-specificity of such variation was tested using winter recoveries of winter-banded birds, and results indicated that subadult (first year) birds were less likely to return to the same wintering grounds the following year than adults. Winter recovery distributions of preseason-banded mallards during 1950-58 differed from distributions in 1966-76. These differences could have resulted from either true distributional shifts or geographic changes in hunting pressure. Survival and recovery rates were estimated from winter banding data. We found no evidence of differences in survival or recovery rates between subadult and adult mallards. Thus, the substantial difference between survival rates of preseason-banded young and adult mallards must result almost entirely from higher mortality of young birds during the approximate period, August-January. Male mallards showed higher survival than females, corroborating inferences based on preseason data. Tests with winter banding and band recovery data indicated some degree of year-to-year variation in both survival and recovery rates, a result again consistent with inference from preseason data. Some evidence indication geographic variation in survival rates; however, there were no consistent directional differences between survival rates of mallards from adjacent northern versus southern areas, or eastern versus western areas. In some comparisons, Central Flyway mallards exhibited slightly higher survival rates than mallards from other flyways. Weighted mean estimates of continental survival rates were computed for the period 1960-77 from both winter banding data and preseason banding of adults. Resulting estimates differed significantly for males, but not for females, and the magnitude of the difference between point estimates was relatively small, even for males. The direction of the difference between these estimates was predicted correctly from previous work on the effects of heterogeneous survival an d recovery rates on band recovery model estimates. The similarity of survival estimates from these two independent data sets supports the believe that biases in these estimates are relatively small.

Resource Publication↗
USGS1977

Population ecology of the mallard: IV. A review of duck hunting regulations, activity, and success, with special reference to the mallard

This, the fourth in a series of reports on the mallard, ( Anas platyrhynchos ), deals at length with the harvest of mallards by waterfowl hunters. Long-term summaries of duck hunting regulations (1948- 1974), Migratory Bird Hunting Stamp sales (1934-1974), Hunter Questionnaire (1952-1974), Duck Wing Collection (1960-1974), and Hunter Performance (1965-1972) Survey data for the United States are presented and discussed. Similar data from Canada are also summarized. Mallard harvest figures for 1961-1974 are presented by Mallard Harvest Area, of which 100 are defined for the United States and 14 for Canada, as well as by State or Province and flyway. During the 23-year period beginning in 1952, an average of 1.6 million adult and 0.2 million junior waterfowl hunters accumulated almost 12.3 million hunter-days of recreation and a harvest of 11.2 million ducks each year. Hunter reports indicate that mallards made up about 43% (5.5 million annually) of the ducks taken before 1960, when mallard regulations were less restrictive; the Duck Wing Survey indicates that mallards have made up 33% of the harvest (3.6 million annually) since 1960. The age and sex compositions and the chronological distribution of the mallard harvest are examined in detail. Among the patterns noted are peak harvests during the first few days of the season in many States, alternately increasing and decreasing annual age ratios, and sex ratios that suggest differential migration of adult drakes and hunter selectivity for males. It is estimated that almost 19% of the ducks shot down are not retrieved. Relationships between duck hunting regulations and hunter behavior are examined briefly. Hunter compliance with mallard bag limits, hunter selectivity of mallards by sex, and, to a lesser extent, the size of the unretrieved kill are all sensitive to the particular bag limit regulations in effect. Survey data are also examined for relationships between harvest and various hunting regulations: starting time and day of the week for opening day, opening date, season length, split seasons, daily shooting hours, and daily bag limits. Tables are presented relating changes in duck and mallard harvests to season length and bag limit, and examples of what effects changes in other regulations have on harvest are also given. The evaluation of bag limit regulations, one of the most important tools used in managing harvest, is carried a step further with the development of a procedure for calculating expected hunter success under a wide variety of bag limit regulations. This method appears promising for evaluating point-limit as well as fixed-limit regulations. In addition, it may provide useful measurements of the degree of hunter selectivity induced by various types of bag limit regulations, an increasingly important aspect of harvest management. Finally, this study clearly demonstrates that the effects of a particular regulation can differ dramatically from area to area, so it is usually necessary to evaluate each proposal on a State-by-State basis.

Resource Publication↗
USGS2018

United States bat species of concern: A synthesis

In 1994 the federal government designated 24 species or subspecies of bats in the United States (U.S.) and its territories as Category 2 candidates for listing as Endangered or Threatened under the U.S. Endangered Species Act. Category 2 was eliminated in 1996, but taxa previously receiving this designation were informally considered “species of concern”. Various state and federal agencies and conservation organizations assigned bat species of concern to more formal conservation categories. Some of the original 24 taxa designated as Category 2 candidates in 1994 were later listed as Endangered, whereas others were subject to refinements in knowledge of their taxonomy and distribution. The remaining 20 species of bats have the subjects of increased research efforts over the past two decades, and are the focus of this review. Two species occur in the U.S. Territories. All of the 18 mainland species ranges include areas west of the Mississippi River (15 are found primarily in western states), and 13 occur in California (72% of the 18 mainland species). In this review, we provide a comprehensive summary of the literature pertinent to the conservation designations, systematics, distribution, habitats, relative abundance, foraging, diet, roosting ecology, population ecology, and management of each of these 20 species. The species of concern are distributed among four families of bats. The Samoan flying fox (Pteropus samoensis) belong to the old-world family Pteropodidae. The California leaf-nosed bat (Macrotus californicus), red fruit bat (Stenoderma rufum), and Mexican long-tongued bat (Choeronycteris mexicana) are members of the new-world family Phyllostomidae. Three species belong to the cosmopolitan family Molossidae: the greater bonneted bat (Eumops perotis californicus), Underwood’s bonneted bat (Eumops underwoodi), and the big free-tailed bat (Nyctinomops macrotis). Most bat species of concern are in the globally distributed family Vespertilionidae: Townsend’s big-eared bat (Corynorhinus townsendii), Rafinesque’s big-eared bat (C. rafinesquii), spotted bat (Euderma maculatum), Allen’s big-eared bat (Idionycteris phyllotis), southeastern myotis (M. austroriparius), western small-footed myotis (Myotis ciliolabrum), long-eared myotis (M. evotis), eastern small-footed myotis (M. leibii), Arizona myotis (M. occultus), fringed myotis (M. thysanodes), cave myotis (M. velifer), long-legged myotis (M. volans), and Yuma myotis (M. yumanensis). An impressive amount of knowledge has accumulated about these species since their informal designation as species of concern, but this knowledge is unevenly distributed. Comparatively little research has been conducted on the Samoan flying fox and the red fruit bat over the past decade in tropical territories, nor on the Mexican long-tongued bat and Underwood’s mastiff bat in the southwestern U.S. Within temperate regions of the U.S., habitat use of two eastern species that roost in hollow trees or caves (southeastern myotis and Rafinesque’s big-eared bat) has been the focus of much research, as have aspects of the biology of cave-roosting and tree-roosting western species, particularly where information about management of forests, caves and abandoned mines can be used to benefit bat conservation. Comparatively less information has accrued about species that roost in rock crevices and high on cliff faces. Other major gaps in information are also identified. We anticipate that this review will help guide future research and conservation efforts directed at the bat species of concern.

Proceedings of the California Academy of Sciences,↗
USGS2019

Using incidental mark-encounter data to improve survival estimation

Obtaining robust survival estimates is critical, but sample size limitations often result in imprecise estimates or the failure to obtain estimates for population subgroups. Concurrently, data are often recorded on incidental reencounters of marked individuals, but these incidental data are often unused in survival analyses. We evaluated the utility of supplementing a traditional survival dataset with incidental data on marked individuals that were collected ad hoc. We used a continuous time‐to‐event exponential survival model to leverage the matching information contained in both datasets and assessed differences in survival among adult and juvenile and resident and translocated Mojave desert tortoises ( Gopherus agassizii ). Incorporation of the incidental mark‐encounter data improved precision of all annual survival point estimates, with a 3.4%–37.5% reduction in the spread of the 95% Bayesian credible intervals. We were able to estimate annual survival for three subgroup combinations that were previously inestimable. Point estimates between the radiotelemetry and combined datasets were within |0.029| percentage points of each other, suggesting minimal to no bias induced by the incidental data. Annual survival rates were high (>0.89) for resident adult and juvenile tortoises in both study sites and for translocated adults in the southern site. Annual survival rates for translocated juveniles at both sites and translocated adults in the northern site were between 0.73 and 0.76. At both sites, translocated adults and juveniles had significantly lower survival than resident adults. High mortality in the northern site was driven primarily by a single pulse in mortalities. Using exponential survival models to leverage matching information across traditional survival studies and incidental data on marked individuals may serve as a useful tool to improve the precision and estimability of survival rates. This can improve the efficacy of understanding basic population ecology and population monitoring for imperiled species.

Nevada↗
USGS2009

Modeling individual animal histories with multistate capture–recapture models

Many fields of science begin with a phase of exploration and description, followed by investigations of the processes that account for observed patterns. The science of ecology is no exception, and recent decades have seen a focus on understanding key processes underlying the dynamics of ecological systems. In population ecology, emphasis has shifted from the state variable of population size to the demographic processes responsible for changes in this state variable: birth, death, immigration, and emigration. In evolutionary ecology, some of these same demographic processes, rates of birth and death, are also the determinants of fitness. In animal population ecology, the estimation of state variables and their associated vital rates is especially problematic because of the difficulties in sampling such populations and detecting individual animals. Indeed, early capture–recapture models were developed for the purpose of estimating population size, given the reality that all animals are not caught or detected at any sampling occasion. More recently, capture–recapture models for open populations were developed to draw inferences about survival in the face of these same sampling problems. The focus of this paper is on multi‐state mark–recapture models (MSMR), which first appeared in the 1970s but have undergone substantial development in the last 15 years. These models were developed to deal explicitly with biological variation, in that animals in different “states” (classes defined by location, physiology, behavior, reproductive status, etc.) may have different probabilities of survival and detection. Animal transitions between states are also stochastic and themselves of interest. These general models have proven to be extremely useful and provide a way of thinking about a remarkably wide range of important ecological processes. These methods are now at a stage of refinement and sophistication where they can readily be used by biologists to tackle a wide range of important issues in ecology. In this paper, we draw together information on the state of the art in multistate mark–recapture methods, explaining the models and illustrating their use. We provide a modeling philosophy and a series of general principles on how to conduct analyses. We cover key issues and features, and we anticipate the ways in which we expect the models to develop in the years ahead.

Advances in Ecological Research↗
USGS2020

Climate dipoles as continental drivers of plant and animal populations

Ecological processes, such as migration and phenology, are strongly influenced by climate variability. Studying these processes often relies on associating observations of animals and plants with climate variability indices, such as the El Niño–Southern Oscillation. A characteristic of climate indices is the simultaneous emergence of opposite extremes of temperature and precipitation across continental scales, known as climate dipoles. The role of climate dipoles in shaping ecological and evolutionary processes has been largely overlooked. We review emerging evidence that climate dipoles can entrain species dynamics, and offer a framework for identifying ecological dipoles using broad-scale biological data. Given future changes in climatic and atmospheric processes, climate and ecological dipoles will likely shift in their intensity, distribution, and timing.

Trends in Ecology and Evolution↗