| Enhancing species distribution modeling by characterizing predator-prey interactions | Enhancing species distribution modeling by characterizing predator-prey interactions | Article | Biotic interactions
Canada lynx
<em>Lepus americanus</em>
Canada lynx
Niche theory
Predator–prey system
Snowshoe hare
Species distribution modeling
Tropic interaction distribution model |
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Type:Article Subject:Biotic interactions
Canada lynx
<em>Lepus americanus</em>
Canada lynx
Niche theory
Predator–prey system
Snowshoe hare
Species distribution modeling
Tropic interaction distribution model |
Description:Niche theory is a well-established concept integrating a diverse array of environmental variables and multispecies interactions used to describe species geographic distribution. It is now customary to employ species distribution models (SDMs) that use environmental variables in conjunction with species location information to characterize species' niches and map their geographic ranges. The challenge remains, however, to account for the biotic interactions of species with other community members on which they depend. We show here how to connect species spatial distribution and their dependence with other species by modeling spatially explicit predator–prey interactions, which we call a trophic interaction distribution model (TIDM). To develop the principles, we capitalized on data from Canada lynx (Lynx canadensis) reintroduced into Colorado. Spatial location information for lynx obtained from telemetry was used in conjunction with environmental data to construct an SDM. The spatial locations of lynx–snowshoe hare encounters obtained from snow-tracking in conjunction with environmental data were used to construct a TIDM. The environmental conditions associated with lynx locations and lynx–hare encounters identified through both SDM and TIDM revealed an initial transient phase in habitat use that settled into a steady state. Nevertheless, despite the potential for the SDM to broadly encompass all lynx hunting and nonhunting spatial locations, the spatial extents of the SDM and TIDM differed; about 40% of important lynx–snowshoe hare locations identified in the TIDM were not identified in the lynx-only SDM. Our results encourage greater effort to quantify spatial locations of trophic interactions among species in a community and the associated environmental conditions when attempting to construct models aimed at projecting current and future species geographic distributions. [show more]
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| Environmental dynamics and anthropogenic development alter philopatry and space‐use in a North American cervid | Environmental dynamics and anthropogenic development alter philopatry and space‐use in a North American cervid | Article | Animal movement
Energy development
Home range
<em>Odocoileus hemionus</em>
Utilization distribution |
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Type:Article Subject:Animal movement
Energy development
Home range
<em>Odocoileus hemionus</em>
Utilization distribution |
Description: Aim
The space an animal uses over a given time period must provide the resources required for meeting energetic needs, reproducing and avoiding predation. Anthropogenic landscape change in concert with environmental dynamics can strongly structure space-use. Investigating these dynamics can provide critical insight into animal ecology, conservation and management.
Location
The Piceance Basin, Colorado, USA.
Methods
We applied a novel utilization distribution estimation technique based on a continuous-time correlated random walk model to characterize range dynamics of mule deer during winter and summer seasons across multiple years. This approach leverages second-order properties of movement to provide a probabilistic estimate of space-use. We assessed the influence of environmental (cover and forage), individual and anthropogenic factors on interannual variation in range use of individual deer using a hierarchical Bayesian regression framework.
Results
Mule deer demonstrated remarkable spatial philopatry, with a median of 50% overlap (range: 8–78%) in year-to-year utilization distributions. Environmental conditions were the primary driver of both philopatry and range size, with anthropogenic disturbance playing a secondary role.
Main conclusions
Philopatry in mule deer is suspected to reflect the importance of spatial familiarity (memory) to this species and, therefore, factors driving spatial displacement are of conservation concern. The interaction between range behaviour and dynamics in development disturbance and environmental conditions highlights mechanisms by which anthropogenic environmental change may displace deer from familiar areas and alter their foraging and survival strategies. [show more]
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| Environmental, not individual, factors drive markers of biological aging in black bears | Environmental, not individual, factors drive markers of biological aging in black bears | Article | Biological aging
Landscape variation
Stress
Telomere
<em>Ursus americanus</em> |
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Type:Article Subject:Biological aging
Landscape variation
Stress
Telomere
<em>Ursus americanus</em> |
Description:Aging negatively affects individual survival and reproduction; consequently, characterizing the factors behind aging can enhance our understanding of fitness in wild populations. The drivers of biological age are diverse, but often related to factors like chronological age or sex of the individual. Recently, however, environmental factors have been shown to strongly influence biological age. To explore the relative importance of these influences on biological aging in a free-ranging and long-lived vertebrate, we quantified the length of telomeres—highly conserved DNA sequences that cap the ends of eukaryotic chromosomes and a useful molecular marker of biological age—for black bears sampled throughout Colorado, and measured a variety of environmental variables (habitat productivity, human development, latitude, elevation) and individual characteristics (age, sex, body size, genetic relatedness). Our extensive sampling of bears (n = 245) revealed no relationships between telomere length and any individual characteristics. Instead, we found a broad-scale latitudinal pattern in telomere length, with bears in northern Colorado possessing shorter telomeres. Our results suggest that environmental characteristics overwhelm individual ones in determining biological aging for this large carnivore. [show more]
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Epidemiological differences between sexes affect management
efficacy in simulated chronic wasting disease systems | Epidemiological differences between sexes affect management
efficacy in simulated chronic wasting disease systems | Article | Chronic wasting disease (CWD)
Demography
Disease ecology
Harvest management |
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Type:Article Subject:Chronic wasting disease (CWD)
Demography
Disease ecology
Harvest management |
Description:
- Sex-based differences in physiology, behaviour and demography commonly result in differences in disease prevalence. However, sex differences in prevalence may reflect exposure rather than transmission, which could affect disease control programmes. One potential example is chronic wasting disease (CWD), which has been observed at greater prevalence among male than female deer.
- We used an age- and sex-structured simulation model to explore harvest-based management of CWD under three different transmission scenarios that all generate higher male prevalence: (1) increased male susceptibility, (2) high male-to-male transmission or (3) high female-to-male transmission.
- Both female and male harvests were required to limit CWD epidemics across all transmission scenarios (approximated by R0), though invasion was more likely under high female-to-male transmission.
- In simulations, heavily male-biased harvests controlled CWD epidemics and maintained large host populations under high male-to-male transmission and increased male susceptibility scenarios. However, male-biased harvests were ineffective under high female-to-male transmission. Instead, female-biased harvests were able to limit disease transmission under high female-to-male transmission but incurred a trade-off with smaller population sizes.
- Synthesis and applications. Higher disease prevalence in a sex or age group may be due to higher exposure or susceptibility but does not necessarily indicate if that group is responsible for more disease transmission. We showed that multiple processes can result in the pattern of higher male prevalence, but that population-level management interventions must focus on the sex responsible for disease transmission, not just those that are most exposed.
[show more]
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| Estimating cougar predation rates from GPS location clusters | Estimating cougar predation rates from GPS location clusters | Article | Cougar
Global Positioning System (GPS)
Predation model
Predation rate
Prey composition
Color
Wyoming |
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Type:Article Subject:Cougar
Global Positioning System (GPS)
Predation model
Predation rate
Prey composition
Color
Wyoming |
Description:We examined cougar (Puma concolor) predation from Global Positioning System (GPS) location clusters (≥2 locations within 200 m on the same or consecutive nights) of 11 cougars during September-May, 1999-2001. Location success of GPS averaged 2.4-5.0 of 6 location attempts/night/cougar. We surveyed potential predation sites during summer-fall 2000 and summer 2001 to identify prey composition (n = 74; 3-388 days post predation) and record predation-site variables (n = 97; 3-270 days post predation). We developed a model to estimate probability that a cougar killed a large mammal from data collected at GPS location clusters where the probability of predation increased with number of nights (defined as locations at 2200, 0200, or 0500 hr) of cougar presence within a 200-m radius (P<0.001). Mean estimated cougar predation rates for large mammals were 7.3 days/kill for subadult females (1-2.5 yr; n = 3, 90% CI: 6.3 to 9.9), 7.0 days/kill for adult females (n = 2, 90% CI: 5.8 to 10.8), 5.4 days/kill for family groups (females with young; n = 3, 90% CI: 4.5 to 8.4), 9.5 days/kill for a subadult male (1-2.5 yr; n = 1, 90% CI: 6.9 to 16.4), and 7.8 days/kill for adult males (n = 2, 90% CI: 6.8 to 10.7). We may have slightly overestimated cougar predation rates due to our inability to separate scavenging from predation. We detected 45 deer (Odocoileus spp.), 15 elk (Cervus elaphus), 6 pronghorn (Antilocapra americana), 2 livestock, 1 moose (Alces alces), and 6 small mammals at cougar predation sites. Comparisons between cougar sexes suggested that females selected mule deer and males selected elk (P < 0.001). Cougars averaged 3.0 nights on pronghorn carcasses, 3.4 nights on deer carcasses, and 6.0 nights on elk carcasses. Most cougar predation (81.7%) occurred between 1901-0500 hr and peaked from 2201-0200 hr (31.7%). Applying GPS technology to identify predation rates and prey selection will allow managers to efficiently estimate the ability of an area's prey base to sustain or be affected by cougar predation. [show more]
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| Estimating density and detection of bobcats in a fragmented Midwestern landscapes using spatial capture-recapture data from camera traps | Estimating density and detection of bobcats in a fragmented Midwestern landscapes using spatial capture-recapture data from camera traps | Article | Bobcat
Camera trap
Density estimation
Fragmentation
Illinois
<em>Lynx rufus</em>
Spatial capture–recapture model
Trap array |
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Type:Article Subject:Bobcat
Camera trap
Density estimation
Fragmentation
Illinois
<em>Lynx rufus</em>
Spatial capture–recapture model
Trap array |
Description:Camera-trapping data analyzed with spatially explicit capture–recapture (SCR) models can provide a rigorous method for estimating density of small populations of elusive carnivore species. We sought to develop and evaluate the efficacy of SCR models for estimating density of a presumed low-density bobcat (Lynx rufus) population in fragmented landscapes of west-central Illinois, USA. We analyzed camera-trapping data from 49 camera stations in a 1,458-km2 area deployed over a 77-day period from 1 February to 18 April 2017. Mean operational time of cameras was 52 days (range = 32–67 days). We captured 23 uniquely identifiable bobcats 113 times and recaptured these same individuals 90 times; 15 of 23 (65.2%) individuals were recaptured at ≥2 camera traps. Total number of bobcat capture events was 139, of which 26 (18.7%) were discarded from analyses because of poor image quality or capture of only a part of an animal in photographs. Of 113 capture events used in analyses, 106 (93.8%) and 7 (6.2%) were classified as positive and tentative identifications, respectively; agreement on tentative identifications of bobcats was high (71.4%) among 3 observers. We photographed bobcats at 36 of 49 (73.5%) camera stations, of which 34 stations were used in analyses. We estimated bobcat density at 1.40 individuals (range = 1.00–2.02)/100 km 2. Our modeled bobcat density estimates are considerably below previously reported densities (30.5 individuals/100 km 2) within the state, and among the lowest yet recorded for the species. Nevertheless, use of remote cameras and SCR models was a viable technique for reliably estimating bobcat density across west-central Illinois. Our research establishes ecological benchmarks for understanding potential effects of colonization, habitat fragmentation, and exploitation on future assessments of bobcat density using standardized methodologies that can be compared directly over time. Further application of SCR models that quantify specific costs of animal movements (i.e., least-cost path models) while accounting for landscape connectivity has great utility and relevance for conservation and management of bobcat populations across fragmented Midwestern landscapes. [show more]
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| Estimating the abundance of rare and elusive carnivores from photographic-sampling data when the population size is very small | Estimating the abundance of rare and elusive carnivores from photographic-sampling data when the population size is very small | Article | Camera traps
Capture–recapture
Heterogeneous detection
Small population |
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Type:Article Subject:Camera traps
Capture–recapture
Heterogeneous detection
Small population |
Description:Conservation and management agencies require accurate and precise estimates of abundance when considering the status of a species and the need for directed actions. Due to the proliferation of remote sampling cameras, there has been an increase in capture–recapture studies that estimate the abundance of rare and/or elusive species using closed capture–recapture estimators (C–R). However, data from these studies often do not meet necessary statistical assumptions. Common attributes of these data are (1) infrequent detections, (2) a small number of individuals detected, (3) long survey durations, and (4) variability in detection among individuals. We believe there is a need for guidance when analyzing this type of sparse data. We highlight statistical limitations of closed C–R estimators when data are sparse and suggest an alternative approach over the conventional use of the Jackknife estimator. Our approach aims to maximize the probability individuals are detected at least once over the entire sampling period, thus making the modeling of variability in the detection process irrelevant, estimating abundance accurately and precisely. We use simulations to demonstrate when using the unconditional-likelihood M0 (constant detection probability) closed C–R estimator with profile-likelihood confidence intervals provides reliable results even when detection varies by individual. If each individual in the population is detected on average of at least 2.5 times, abundance estimates are accurate and precise. When studies sample the same species at multiple areas or at the same area over time, we suggest sharing detection information across datasets to increase precision when estimating abundance. The approach suggested here should be useful for monitoring small populations of species that are difficult to detect. [show more]
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| Estimating the risk of elk-to-livestock brucellosis transmission in Montana | Estimating the risk of elk-to-livestock brucellosis transmission in Montana | Article | Brucella abortus
Cervus canadensis
Cross-species pathogen spillover
Habitat selection
Human-wildlife conflict
Resource selection function
Wildlife disease |
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Type:Article Subject:Brucella abortus
Cervus canadensis
Cross-species pathogen spillover
Habitat selection
Human-wildlife conflict
Resource selection function
Wildlife disease |
Description:Wildlife reservoirs of infectious disease are a major source of human-wildlife conflict because of the risk of potential spillover associated with commingling of wildlife and livestock. In Montana, the presence of brucellosis (Brucella abortus) in free-ranging elk (Cervus canadensis) populations is of significant management concern because of the risk of disease transmission from elk to livestock. To help mitigate potential conflict, we identified how spillover risk changes through space and time using a combination of elk population, disease, and movement data. We developed resource selection functions using telemetry data from 223 female elk to predict the relative probability of female elk occurrence on a daily basis during the 15 February-30 June transmission risk period. We combined these spatiotemporal predictions with elk seroprevalence, demography, and abortion timing data to identify when and where abortions (the primary transmission route of brucellosis) were most likely to occur. Additionally, we integrated these predictions with spatiotemporal data on livestock distribution to estimate the daily risk of livestock encountering brucellosis-induced elk abortions. We estimated that a minimum of ~17,500 adult female elk lived within our study area, which resulted in a conservative estimate of ~525 brucellosis-induced abortions each year. We predicted that approximately half of the transmission events occurred on livestock properties and 98% of those properties were private ranchlands as opposed to state or federal grazing allotments. Our fine-resolution (250-m spatial, 1-day temporal), large-scale (17,732 km2) predictions of potential elk-to-livestock transmission risk provide wildlife and livestock managers with a useful tool to identify higher risk areas in space and time and proactively focus actions in these areas to separate elk and livestock to reduce spillover risk. [show more]
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| Estimation of moose parturition dates in Colorado: incorporating imperfect detections | Estimation of moose parturition dates in Colorado: incorporating imperfect detections | Article | Calf-at-heel
Ground surveys
Detection probability (p)
Parturition
Recruitment |
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Type:Article Subject:Calf-at-heel
Ground surveys
Detection probability (p)
Parturition
Recruitment |
Description:Researchers and managers use productivity surveys to evaluate moose populations for harvest and population management purposes, yet such surveys are prone to bias. We incorporated detection probability estimates (p) into spring and summer ground surveys to reduce the influence of observer bias on the estimation of moose parturition dates in Colorado. In our study, the cumulative parturition probability for moose was 0.50 by May 19, and the probability of parturition exceeded 0.9 by May 27. Timing of moose calf parturition in Colorado appears synchronous with parturition in more northern latitudes. Our results can be used to plan ground surveys in a manner that will reduce bias stemming from unobservable and yet-born calves. [show more]
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| Evaluating noninvasive methods for estimating cestode prevalence in a wild carnivore population | Evaluating noninvasive methods for estimating cestode prevalence in a wild carnivore population | Article | Wolf
Genotyping
Cestode infection |
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Type:Article Subject:Wolf
Genotyping
Cestode infection |
Description:Helminth infections are cryptic and can be difficult to study in wildlife species. Helminth research in wildlife hosts has historically required invasive animal handling and necropsy, while results from noninvasive parasite research, like scat analysis, may not be possible at the helminth species or individual host levels. To increase the utility of noninvasive sampling, individual hosts can be identified by applying molecular methods. This allows for longitudinal sampling of known hosts and can be paired with individual-level covariates. Here we evaluate a combination of methods and existing long-term monitoring data to identify patterns of cestode infections in gray wolves in Yellowstone National Park. Our goals were: (1) Identify the species and apparent prevalence of cestodes infecting Yellowstone wolves; (2) Assess the relationships between wolf biological and social characteristics and cestode infections; (3) Examine how wolf samples were affected by environmental conditions with respect to the success of individual genotyping. We collected over 200 wolf scats from 2018–2020 and conducted laboratory analyses including individual wolf genotyping, sex identification, cestode identification, and fecal glucocorticoid measurements. Wolf genotyping success rate was 45%, which was higher in the winter but decreased with higher precipitation and as more time elapsed between scat deposit and collection. One cestode species was detected in 28% of all fecal samples, and 38% of known individuals. The most common infection was Echinococcus granulosus sensu lato (primarily E. canadensis). Adult wolves had 4x greater odds of having a cestode infection than pups, as well as wolves sampled in the winter. Our methods provide an alternative approach to estimate cestode prevalence and to linking parasites to known individuals in a wild host system, but may be most useful when employed in existing study systems and when field collections are designed to minimize the time between fecal deposition and collection. [show more]
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