Multistage time-to-event models improve survival inference by partitioning mortality processes of tracked organisms.

Advances in tagging technologies are expanding opportunities to estimate survival of fish and wildlife populations. Yet, capture and handling effects could impact survival outcomes and bias inference about natural mortality processes. We developed a multistage time-to-event model that can partition the survival process into sequential phases that reflect the tagged animal experience, including handling and release mortality, post-release recovery mortality, and subsequently, natural mortality.

Species and physiographic factors drive Indian cucumber root and Canada mayflower plant chemistry: Implications for white-tailed deer forage quality.

Nutrition is fundamental to white-tailed deer (Odocoileus virginianus) management given its relationship to habitat carrying capacity and population productivity. Ecological Sites (ESs) are a United States federal landscape management unit of specific land potential due to unique soils, topography, climate, parent material, and perhaps deer forage nutritional value. We present results of a study that extends the use of ESs to inform white-tailed deer management by evaluating indicator plant chemistry in two spring forb species, Indian cucumber root (Medeola virginiana) and Canada mayflower (Maianthemum canadense), across the northcentral Appalachians.

Caution is warranted when using animal space-use and movement to infer behavioral states.

Background: Identifying the behavioral state for wild animals that can't be directly observed is of growing interest to the ecological community. Advances in telemetry technology and statistical methodologies allow researchers to use space-use and movement metrics to infer the underlying, latent, behavioral state of an animal without direct observations. For example, researchers studying ungulate ecology have started using these methods to quantify behaviors related to mating strategies.

Threading the needle: How humans influence predator-prey spatiotemporal interactions in a multiple-predator system.

Perceived predation risk and the resulting antipredator behaviour varies across space, time and predator identity. Communities with multiple predators that interact and differ in their use of space, time of activity and hunting mode create a complex landscape for prey to avoid predation. Anthropogenic presence and disturbance have the potential to shift interactions among predators and prey and the where and when encounters occur.

Risky movements? Natal dispersal does not decrease survival of a large herbivore.

Natal dispersal is assumed to be a particularly risky movement behavior as individuals transfer, often long distances, from birth site to site of potential first reproduction. Though, because this behavior persists in populations, it is assumed that dispersal increases the fitness of individuals despite the potential for increased risk of mortality. The extent of dispersal risk, however, has rarely been tested, especially for large mammals.

Survival is negatively associated with glucocorticoids in a wild ungulate neonate.

It is unknown how ungulate physiological responses to environmental perturbation influence overall population demographics. Moreover, neonatal physiological responses remain poorly studied despite the importance of neonatal survival to population growth. Glucocorticoid (GC) hormones potentially facilitate critical physiological and behavioral responses to environmental perturbations.

Assessment of spatial genetic structure to identify populations at risk for infection of an emerging epizootic disease.

Understanding the geographic extent and connectivity of wildlife populations can provide important insights into the management of disease outbreaks but defining patterns of population structure is difficult for widely distributed species. Landscape genetic analyses are powerful methods for identifying cryptic structure and movement patterns that may be associated with spatial epizootic patterns in such cases.We characterized patterns of population substructure and connectivity using microsatellite genotypes from 2,222 white-tailed deer () in the Mid-Atlantic region of the United States, a region where chronic wasting disease was first detected in 2009.

Soil chemistry, and not short-term (1-2 year) deer exclusion, explains understory plant occupancy in forests affected by acid deposition.

The loss of species diversity and plant community structure throughout the temperate deciduous forests of North America have often been attributed to overbrowsing by white-tailed deer (). Slow species recovery following removal from browsing, or reduction in deer density, has been termed a legacy effect of past deer herbivory. However, vegetation legacy effects have also coincided with changes to soil chemistry throughout the north-eastern USA.

Heterogeneity of a landscape influences size of home range in a North American cervid.

In the northeastern United States, chronic wasting disease has recently been detected in white-tailed deer (Odocoileus virginianus) populations, and understanding the relationship between landscape configuration and home range may improve disease surveillance and containment efforts. The objectives of our study were to compare size of home range for deer occupying a continuum of forested landscapes and to investigate relationships between size of home range and measures of landscape configuration. We used a movement-based kernel density estimator to estimate home range at five spatial scales among deer across study areas.

Moving in the Anthropocene: Global reductions in terrestrial mammalian movements.

Animal movement is fundamental for ecosystem functioning and species survival, yet the effects of the anthropogenic footprint on animal movements have not been estimated across species. Using a unique GPS-tracking database of 803 individuals across 57 species, we found that movements of mammals in areas with a comparatively high human footprint were on average one-half to one-third the extent of their movements in areas with a low human footprint. We attribute this reduction to behavioral changes of individual animals and to the exclusion of species with long-range movements from areas with higher human impact.

Population and genetic outcomes 20 years after reintroducing bobcats (Lynx rufus) to Cumberland Island, Georgia USA.

In 1988-1989, 32 bobcats Lynx rufus were reintroduced to Cumberland Island (CUIS), Georgia, USA, from which they had previously been extirpated. They were monitored intensively for 3 years immediately post-reintroduction, but no estimation of the size or genetic diversity of the population had been conducted in over 20 years since reintroduction. We returned to CUIS in 2012 to estimate abundance and effective population size of the present-day population, as well as to quantify genetic diversity and inbreeding.

Habitat availability is a more plausible explanation than insecticide acute toxicity for U.S. grassland bird species declines.

Grassland bird species have experienced substantial declines in North America. These declines have been largely attributed to habitat loss and degradation, especially from agricultural practices and intensification (the habitat-availability hypothesis). A recent analysis of North American Breeding Bird Survey (BBS) "grassland breeding" bird trends reported the surprising conclusion that insecticide acute toxicity was a better correlate of grassland bird declines in North America from 1980-2003 (the insecticide-acute-toxicity hypothesis) than was habitat loss through agricultural intensification.

Accounting for tagging-to-harvest mortality in a Brownie tag-recovery model by incorporating radio-telemetry data.

The Brownie tag-recovery model is useful for estimating harvest rates but assumes all tagged individuals survive to the first hunting season; otherwise, mortality between time of tagging and the hunting season will cause the Brownie estimator to be negatively biased. Alternatively, fitting animals with radio transmitters can be used to accurately estimate harvest rate but may be more costly. We developed a joint model to estimate harvest and annual survival rates that combines known-fate data from animals fitted with transmitters to estimate the probability of surviving the period from capture to the first hunting season, and data from reward-tagged animals in a Brownie tag-recovery model.

Occupancy patterns of regionally declining grassland sparrow populations in a forested Pennsylvania landscape.

Organisms can be affected by processes in the surrounding landscape outside the boundary of habitat areas and by local vegetation characteristics. There is substantial interest in understanding how these processes affect populations of grassland birds, which have experienced substantial population declines. Much of our knowledge regarding patterns of occupancy and density stem from prairie systems, whereas relatively little is known regarding how occurrence and abundance of grassland birds vary in reclaimed surface mine grasslands.

Bayesian analysis of wildlife age-at-harvest data.

State and federal natural resource management agencies often collect age-structured harvest data. These data represent finite realizations of stochastic demographic and sampling processes and have long been used by biologists to infer population trends. However, different sources of data have been combined in ad hoc ways and these methods usually failed to incorporate sampling error.

Adjusting age and stage distributions for misclassification errors.

Ecologists often use samples from the age or stage structure of a population to make inferences about population-level processes and to parameterize matrix models. Typically, researchers make a simplifying assumption that age and stage classes are determined without error, when in fact some level of misclassification often can be expected. If unaccounted for, misclassification will lead to overly optimistic levels of precision and can cause biased estimates of age or stage structure.

Controlling for anthropogenically induced atmospheric variation in stable carbon isotope studies.

Increased use of stable isotope analysis to examine food-web dynamics, migration, transfer of nutrients, and behavior will likely result in expansion of stable isotope studies investigating human-induced global changes. Recent elevation of atmospheric CO2 concentration, related primarily to fossil fuel combustion, has reduced atmospheric CO2 delta13C (13C/12C), and this change in isotopic baseline has, in turn, reduced plant and animal tissue delta13C of terrestrial and aquatic organisms. Such depletion in CO2 delta13C and its effects on tissue delta13C may introduce bias into delta13C investigations, and if this variation is not controlled, may confound interpretation of results obtained from tissue samples collected over a temporal span.