Geology topics

Richard B. Harris

Publications and source records attributed to Richard B. Harris.

7 recordsLinked to original sources

USGS2026

Abundance, trends, and challenges facing mountain goats throughout their North American distribution

Recent declines among some mountain goat ( Oreamnos americanus ) populations have heightened concern about their current status and ability to cope with future challenges. We conducted a range-wide assessment of the status of mountain goats across their distribution to understand the extent and patterns of change in recent years. We queried states, provinces, National Parks, and Indigenous governments with territories and reserves containing local wild populations, requesting updates on estimated mountain goat abundance and trends over time, as well as qualitative assessments of conservation challenges. We supplemented the questionnaires with existing literature (both published and available from agency websites). We subjected a subset of mountain goat population time−series to exploratory meta-analyses, examining covariates associated with rates of change. Respondents identified 203 units within which estimates were documented, a majority of which were raw counts from aircraft; fewer jurisdictions used site-specific sightability models, mark-recapture statistics, or other approaches to account for imperfect detection. Jurisdictions updated unit-specific estimates on average every 4.0 years (SD = 2.9, Min–Max = 1–24 years). Among 152 qualitative estimates of trends of native populations, 3% were reported as having increased substantially, 10% as having increased slightly, 24% as having declined slightly, and 14% as having declined substantially (49% reported either no detectable trend or insufficient data to identify a trend). Among 133 estimates of trends of introduced or pioneering populations, 5% increased substantially, 24% increased slightly, 20% declined slightly, and 11% declined substantially (40% reported no detectable trend). Jurisdiction-wide abundance estimates were lower than those previously published in all jurisdictions except Colorado and Oregon, and in Alaska, where trends were unclear. Intrinsic rates of increase ( r ) were positively associated with the population being introduced or pioneering, negatively associated with heavy snow and, to a lesser extent, with drought, but were not associated with abundance or presence of hunter harvest. Existing evidence suggested that many local populations, especially native populations, have declined, but understanding of specific causes has been constrained by limited monitoring capacity. Greater spatiotemporal monitoring effort and detailed studies would inform appropriate strategies to address threats and future challenges to mountain goats.

Wildlife Society Bulletin↗

USGS2025

Mountain sentinels in a changing world: Review and conservation implications of weather and climate effects on mountain goats (Oreamnos americanus)

Climate change is occurring at an accelerated rate in high-elevation alpine and mountain ecosystems. Cold-adapted, mountain species are at risk due to forecasted change and knowledge is needed to respond to current and future conservation challenges. Mountain goats ( Oreamnos americanus ) are an iconic species of North American mountain cultures and landscapes, and due to specialized adaptations for life in cold, mountainous environments they are particularly sensitive to changes in weather and climate. As sentinels of change in alpine ecosystems, the study of mountain goats offers insight into the ecological effects and conservation challenges associated with climate change in these sensitive and biodiverse environments. Here, we synthesize existing knowledge about how climate change is expected to influence environmental conditions experienced by mountain goats and associated mechanistic changes to behavior, nutritional ecology, demography, health, and interspecific interactions. In many instances, climate change effects are likely to be negative and additive to existing threats (such as human disturbance, hunting, disease, predation) though benefits are expected in some cases. Changes in climate and mountain environments will necessitate re-examination and modification of population monitoring, management, and conservation strategies. Specifically, spatiotemporal (and other) aspects of monitoring and management may need to be adjusted to accommodate emerging and novel conservation challenges. Yet, key data and knowledge gaps remain and should be addressed to advance conservation and decision-making capabilities. For mountain goats and similarly climate-sensitive alpine herbivores, effective conservation will ultimately benefit from collaborations among diverse networks guided by well-planned, strategic visions focused on common ground – namely the resiliency and persistence of culturally and ecologically significant mountain species and the alpine environment they inhabit.

Alaska, Alberta, British Columbia, Idaho, Montana,↗

USGS2024

Warm places, warm years, and warm seasons increase parasitizing of moose by winter ticks

Observed links between parasites, such as ticks, and climate change have aroused concern for human health, wildlife population dynamics, and broader ecosystem effects. The one-host life history of the winter tick ( Dermacentor albipictus ) links each annual cohort to environmental conditions during three specific time periods when they are predictably vulnerable: spring detachment from hosts, summer larval stage, and fall questing for hosts. We used mixed-effects generalized linear models to investigate the drivers of tick loads carried by moose ( Alces alces ) relative to these time periods and across 750 moose, 10 years, and 16 study areas in the western United States. We tested for the effects of biotic factors (moose density, shared winter range, vegetation, migratory behavior) and weather conditions (temperature, snow, humidity) during each seasonal period when ticks are vulnerable and off-host. We found that warm climatic regions, warm seasonal periods across multiple partitions of the annual tick life cycle, and warm years relative to long-term averages each contributed to increased tick loads. We also found important effects of snow and other biotic factors such as host density and vegetation. Tick loads in the western United States were, on average, lower than those where tick-related die-offs in moose populations have occurred recently, but loads carried by some individuals may be sufficient to cause mortality. Lastly, we found interannual variation in tick loads to be most correlated with spring snowpack, suggesting this environmental component may have the highest potential to induce change in tick load dynamics in the immediate future of this region.

Ecosphere↗

USGS2017

Pneumonia in bighorn sheep: Risk and resilience

Infectious disease was an important driver of historic declines and extirpations of bighorn sheep (Ovis canadensis) in North America and continues to impede population restoration and management. Domestic sheep have long been linked to pneumonia outbreaks in bighorn sheep and this association has now been confirmed in 13 captive commingling experiments. However, ecological and etiological complexities still hinder our understanding and control of the disease. We provide an overview of the current state of knowledge about the biology and management of respiratory disease in bighorn sheep and propose strategies for moving forward. Epizootic pneumonia in bighorn sheep is polymicrobial. Mycoplasma ovipneumoniae, a bacterium host-specific to Caprinae and commonly carried by healthy domestic sheep and goats appears to be a necessary primary agent. All-age epizootics following introduction of M. ovipneumoniae along with other pathogens into bighorn sheep populations are usually severe (median mortality 47%) but fatality rates vary widely, from 15 – 100%. Disease severity may be influenced by the strain of M. ovipneumoniae, by secondary bacterial and viral pathogens, and by factors affecting transmission and host immunity. Once introduced, M. ovipneumoniae can persist in bighorn sheep populations for decades. Carrier dams transmit the pathogen to their susceptible lambs, triggering fatal pneumonia outbreaks in nursery groups, which limits recruitment and slows or prevents population recovery. The result is that demographic costs of pathogen persistence often outweigh the impacts of the initial invasion and die-off. There is currently no effective vaccine or antibiotic for domestic or wild sheep and to date, no management actions have been successful in reducing morbidity, mortality, or disease spread once pathogen invasion has occurred. Molecular-based strain typing suggests that spillover of M. ovipneumoniae into bighorn sheep populations from domestic small ruminants is ongoing, and that consequences of pathogen invasion are amplified by movements of infected bighorn sheep. Therefore, current disease management strategies focus on reducing risk of spillover from reservoir populations of domestic small ruminants and on limiting transmission among bighorn sheep. A broad array of approaches has been tried and more are needed to prevent pathogen introduction, induce disease fadeout in persistently infected populations, and promote population resilience across the diverse landscapes bighorn sheep inhabit. A comprehensive examination of disease dynamics across populations could help elucidate how disease fades out naturally and if population resilience can be increased in the face of infection. Cross-jurisdictional adaptive management experiments and transdisciplinary collaboration, including partnerships with members of the domestic sheep and goat community, are needed to facilitate innovation and speed progress towards sustainable solutions for managing pneumonia to protect and restore bighorn sheep populations.

California, Idaho, Nevada, Oregon, Utah, Washingto↗

USGS2014

Re-evaluation of Yellowstone grizzly bear population dynamics not supported by empirical data: response to Doak & Cutler

Doak and Cutler critiqued methods used by the Interagency Grizzly Bear Study Team (IGBST) to estimate grizzly bear population size and trend in the Greater Yellowstone Ecosystem. Here, we focus on the premise, implementation, and interpretation of simulations they used to support their arguments. They argued that population increases documented by IGBST based on females with cubs-of-the-year were an artifact of increased search effort. However, we demonstrate their simulations were neither reflective of the true observation process nor did their results provide statistical support for their conclusion. They further argued that survival and reproductive senescence should be incorporated into population projections, but we demonstrate their choice of extreme mortality risk beyond age 20 and incompatible baseline fecundity led to erroneous conclusions. The conclusions of Doak and Cutler are unsubstantiated when placed within the context of a thorough understanding of the data, study system, and previous research findings and publications.

Conservation Letters↗

USGS2010

The impact of conservation on the status of the world's vertebrates

Using data for 25,780 species categorized on the International Union for Conservation of Nature Red List, we present an assessment of the status of the world's vertebrates. One-fifth of species are classified as Threatened, and we show that this figure is increasing: On average, 52 species of mammals, birds, and amphibians move one category closer to extinction each year. However, this overall pattern conceals the impact of conservation successes, and we show that the rate of deterioration would have been at least one-fifth again as much in the absence of these. Nonetheless, current conservation efforts remain insufficient to offset the main drivers of biodiversity loss in these groups: agricultural expansion, logging, overexploitation, and invasive alien species.

Science↗

USGS2006

Temporal, spatial, and environmental influences on the demographics of grizzly bears in the Greater Yellowstone Ecosystem

During the past 2 decades, the grizzly bear ( Ursus arctos ) population in the Greater Yellowstone Ecosystem (GYE) has increased in numbers and expanded in range. Understanding temporal, environmental, and spatial variables responsible for this change is useful in evaluating what likely influenced grizzly bear demographics in the GYE and where future management efforts might benefit conservation and management. We used recent data from radio-marked bears to estimate reproduction (1983–2002) and survival (1983–2001); these we combined into models to evaluate demographic vigor (lambda [λ]). We explored the influence of an array of individual, temporal, and spatial covariates on demographic vigor.

Idaho, Montana, Wyoming↗