[Show abstract][Hide abstract] ABSTRACT: Maternal care influences offspring quality and can improve a mother's inclusive fitness. However, improved fitness may only occur when offspring quality (i.e., offspring birth mass) persists throughout life and enhances survival and/or reproductive success. Although maternal body mass, age, and social rank have been shown to influence offspring birth mass, the interdependence among these variables makes identifying causation problematic. We established that fawn birth mass was related to adult body mass for captive male and female white-tailed deer (Odocoileus virginianus), thus maternal care should improve offspring fitness. We then used path analysis to identify which maternal characteristic(s) most influenced fawn birth mass of captive female white-tailed deer. Maternal age, body mass and social rank had varying effects on fawn birth mass. Maternal body mass displayed the strongest direct effect on fawn birth mass, followed by maternal age and social rank. Maternal body mass had a greater effect on social rank than age. The direct path between social rank and fawn birth mass may indicate dominance as an underlying mechanism. Our results suggest that heavier mothers could use dominance to improve access to resources, resulting in increased fitness through production of heavier offspring.
PLoS ONE 08/2015; 10(e0136034). DOI:10.1371/journal.pone.0136034 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ocelots Leopardus pardalis (Linnaeus, 1758) are one of the most common fe-lids in the Neotropics and in the absence of large carnivores, can function as apex predators. Despite occupying numerous habitats across its range, including human-dominated landscapes, there is limited information on how ocelots use fragmented landscapes. We radio-tracked a female ocelot in a fragmented landscape of the Caribbean region of Colombia from November 2010 to January 2011 to estimate home range and habitat use. We obtained 100 locations overall; home range size was 9.64 km 2 using the 95% fixed kernel density estimate. Rivers and roads were the main variables related with the locations and the ocelot selected for natural forests but also used disturbed habitats. Home range size and habitat use was similar to previous studies, but we observed greater use of disturbed habitats. As ocelots become the top predators in many fragmented landscapes of the Neotropics, it is important to understand how they use landscapes and could serve as surrogates for conservation.
[Show abstract][Hide abstract] ABSTRACT: Wildlife incidents with aircraft are of concern in the United States as they pose a risk to human safety and economic losses for the aviation industry. Most previous research on wildlife-aircraft incidents has emphasized birds, bats, and ungulates. We queried the Federal Aviation Administration’s National Wildlife Strike Database from 1990 to 2012 to characterize carnivore incidents with U.S. civil aircraft. We found 1016 carnivore incidents with aircraft representing at least 16 species, with coyotes (n = 404) being the species most frequently struck. California and Texas had the most reported incidents and incidents were most likely to occur at night from August to November. Overall estimated damage to aircraft was US$ 7 million. Coinciding with the increase in air traffic, the rate of carnivore-aircraft incidents increased 13.1% annually from 1990 to 2012 whereas the rate of damaging incidents remained fairly constant. Due to the increase in carnivore-aircraft incidents from 1990 to 2012, we recommend further research on techniques to increase detection of carnivores and implementation and scheduled maintenance of perimeter high fences for exclusion. Additionally, we recommend increasing patrol of runways, especially during peak incident periods (July–November) and at night (2000–0600 h).
Transportation Research Part D Transport and Environment 05/2015; 36. DOI:10.1016/j.trd.2014.12.001 · 1.29 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: American black bears (Ursus americanus) occur on numerous islands within the Apostle Islands National Lakeshore in Lake Superior, Wisconsin, USA, and provide an opportunity to better understand patterns in abundance and genetic structure among island populations. In 2002 and 2010, we derived genotypes from DNA obtained from hair samples collected at hair traps to estimate population abundance on Stockton (40.7 km2), Sand (11.9 km2), and Oak (20.6 km2; 2010 only) islands. We used Huggins closed-population mark–recapture models to estimate island-specific abundance and density. We used Program STRUCTURE and parentage analysis to examine inter-island population structure, migration patterns, and relatedness. In 2010, we estimated abundance on Stockton, Sand, and Oak islands to be 13.1 (95% CI = 12.4–13.8), 10.1 (95% CI = 9.3–11.0), and 18.1 (95% CI = 17.3–19.0) bears, with a density of 0.32, 0.85, and 0.88 bears/km2, respectively. Whereas abundance on Sand Island increased 60% since 2002 (N = 6.3, 95% CI = 4.0–8.6), abundance on Stockton declined 50% (N = 26.3, 95% CI = 24.7–27.9), including an 83% decline in detected females. Density on Oak Island was the highest reported in Wisconsin, although we identified 13 individuals as likely mates or offspring of a single male. We identified 4 genetic groups, corresponding to Stockton, Sand, Oak, and Mainland ancestry. No individuals on Stockton or Sand islands were assigned ancestry from another island, whereas one male on Oak Island was assigned Stockton ancestry. We detected individuals of predominately Mainland ancestry on all but Hermit Island, suggesting a high rate of immigration from the mainland. We suggest these islands can support high bear densities, but may undergo rapid shifts in sex-specific abundance. Genetic connectivity appears maintained by male-mediated gene flow, but a small number of wide-ranging females may sustain inter-island population viability.
[Show abstract][Hide abstract] ABSTRACT: To access a free e-print version of this article, please visit this link:
Capsule-- Interpretation of nest survival estimates may be improved by incorporating the search method used to locate nests as a covariate.
Aims-- To compare annual survival estimates for Dickcissel Spiza americana nests and determine if incorporating search method (structured, opportunistic, or behavioural searches) improved model fit.
Methods-- Dickcissel nests were located using structured, opportunistic, or behavioural searches over three years (2011–2013) in Mississippi, USA. Models were used to estimate daily survival rates (DSRs) and to analyse factors influencing nest survival.
Results-- DSRs for Dickcissels were best explained by quadratic date, nest age, age found, and year, but incorporating search method improved model fit. Daily survival was 1.51 times greater for nests located using opportunistic search methods relative to structured searches, but was not significantly different between structured and behavioural searches.
Conclusions-- Survival estimates varied by search method, specifically between structured searches and opportunistically located nests. This might have arisen because heterogeneity in nest placement or parental behaviour may influence the sample of nests located with a given search method. Researchers may be able to account for this potential source of bias by including search method as a model covariate when using standard survey designs or modelling approaches.
Bird Study 04/2015; 62(2). DOI:10.1080/00063657.2015.1010140 · 1.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The distribution of animals is influenced by numerous factors including spatial distribution and temporal availability of resources. We tested the spatial resource variability hypothesis (increasing landscape heterogeneity results in increasing amount of space use) and the temporal resource variability hypothesis (temporal variation in resources reduces amount of space use) using location data from radiomarked American black bears Ursus americanus in Missouri and Arkansas, USA. We used 95% utilization distributions (UDs) to define individual seasonal space use and constructed 22 models using covariates that described composition, spatial arrangement and diversity of land cover types (an index of heterogeneity or patchiness); seasonal hard mast production; and seasonal use of land cover to test our hypotheses using linear modeling and small-sample Akaike information criterion (AICc) model selection approaches. The AICc best performing model supported the spatial resource variability hypothesis and included Shannon diversity index [95% confidence limit (CL) of coefficient = 1.56–2.42] and sex (male; 95% CL of coefficient = 0.05–0.49) as covariates that explained variation in transformed values of UD size. Predicted and observed values during model evaluation were highly correlated (r = 0.90). As land cover heterogeneity increased, UD size increased, likely a consequence of bears responding to greater patchiness to maintain sufficient resources. Further, the Shannon diversity index was greater for males than females , suggesting larger bodied males used larger areas to meet their higher energetic costs due to landscape fragmentation. Studies of resource hypotheses in solitary species should consider intraspecific allometric relationships such as sexual size dimorphism as has been addressed using group size in social species.
Journal of Zoology 04/2015; 296:200-207. DOI:10.1111/jzo.12234 · 1.95 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Sport hunting has reportedly multiple benefits to economies and local communities; however, few of these benefits have been quantified. As part of their lease agreements with the Zambia Wildlife Authority, sport hunting operators in Zambia are required to provide annually to local communities free of charge i.e., provision a percentage of the meat obtained through sport hunting. We characterized provisioning of game meat to rural communities by the sport hunting industry in Zambia for three game management areas (GMAs) during 2004-2011. Rural communities located within GMAs where sport hunting occurred received on average > 6,000 kgs per GMA of fresh game meat annually from hunting operators. To assess hunting industry compliance, we also compared the amount of meat expected as per the lease agreements versus observed amounts of meat provisioned from three GMAs during 2007-2009. In seven of eight annual comparisons of these GMAs, provisioning of meat exceeded what was required in the lease agreements. Provisioning occurred throughout the hunting season and peaked during the end of the dry season (September-October) coincident with when rural Zambians are most likely to encounter food shortages. We extrapolated our results across all GMAs and estimated 129,771 kgs of fresh game meat provisioned annually by the sport hunting industry to rural communities in Zambia at an approximate value for the meat alone of >US$600,000 exclusive of distribution costs. During the hunting moratorium (2013-2014), this supply of meat has halted, likely adversely affecting rural communities previously reliant on this food source. Proposed alternatives to sport hunting should consider protein provisioning in addition to other benefits (e.g., employment, community pledges, anti-poaching funds) that rural Zambian communities receive from the sport hunting industry.
PLoS ONE 02/2015; 10(2):e0117237. DOI:10.1371/journal.pone.0117237 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Responses of biodiversity to changes in both land cover and climate are recognized [ 1 ] but still poorly understood [ 2 ]. This poses significant challenges for spatial planning as species could shift, contract, expand, or maintain their range inside or outside protected areas [ 2–4 ]. We examine this problem in Borneo, a global biodiversity hotspot [ 5 ], using spatial prioritization analyses that maximize species conservation under multiple environmental-change forecasts. Climate projections indicate that 11%–36% of Bornean mammal species will lose ≥30% of their habitat by 2080, and suitable ecological conditions will shift upslope for 23%–46%. Deforestation exacerbates this process, increasing the proportion of species facing comparable habitat loss to 30%–49%, a 2-fold increase on historical trends. Accommodating these distributional changes will require conserving land outside existing protected areas, but this may be less than anticipated from models incorporating deforestation alone because some species will colonize high-elevation reserves. Our results demonstrate the increasing importance of upland reserves and that relatively small additions (16,000–28,000 km2) to the current conservation estate could provide substantial benefits to biodiversity facing changes to land cover and climate. On Borneo, much of this land is under forestry jurisdiction, warranting targeted conservation partnerships to safeguard biodiversity in an era of global change.
Current Biology 02/2015; 25(3):372–378. DOI:10.1016/j.cub.2014.11.067 · 9.92 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Understanding species distributions and population responses to environmental parameters is important for addressing landscape-level species conservation. We assessed American black bear (Ursus americanus) resource selection based on spatial distribution of a recolonizing population in Mississippi, USA. Given the philopatric behavior of female bears and the risk-disturbance hypothesis, we predicted that bears recolonizing Mississippi would occupy areas close to their source population but avoid areas near roads and with greater human population density. Using location data from radio-collared black bears, landscape metrics, and spatial autoregressive modeling, we estimated annual population-level space use. Our results confirm that black bears recolonizing Mississippi occupy habitats proximate to source populations and avoid areas near roads as probability of bear use was greater in areas closer to source breeding populations and areas farther from roads. Land cover type, elevation, and human density did not influence black bear occurrence at the spatial resolution examined. The lack of avoidance to areas inhabited by humans was likely a consequence of overall low human density, legal protection afforded this species, and that proximity to source population likely has a greater effect on recolonization than avoidance of humans.
European Journal of Wildlife Research 01/2015; DOI:10.1007/s10344-015-0933-5 · 1.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Anthropogenic disturbance is an important factor influencing biological invasions. The European hare (Lepus europaeus) and wild boar (Sus scrofa) are invasive species known to cause substantial environmental damage, and were introduced to Argentina during the early 1900s. We compared the relative importance of anthropogenic and environmental factors in hare and boar occurrence in Nahuel Huapi National Park, Argentina, and assessed the hypothesis that invasion can occur regardless of anthropogenic disturbance. Also, we assessed whether hare and boar occupancy offered support for the disturbance hypothesis, which states that invasive species are facilitated by anthropogenic disturbance. We deployed 80 cameras from February to May 2012 and January to April 2013 and at each site measured three environmental (land cover, horizontal cover, and percentage herbaceous vegetation) and three anthropogenic (distance to nearest human settlement, distance to nearest road, and average daily number of people) variables. We used likelihood-based occupancy modeling to estimate site occurrence and detectability. We obtained 480 independent detections of hares and 134 of boars in 1680 camera days. Environmental factors had a greater effect on hare occupancy than anthropogenic disturbances, and hare occupancy was greater in more open areas and closer to human settlements, supporting both hypotheses. Boar occurrence was equally influenced by anthropogenic and environmental factors, and offered mixed support for both hypotheses; boars were present only in humid land covers, and occupancy was lesser closer to settlements but greater closer to roads. Species responses to anthropogenic and environmental factors can vary based on life history traits and role in human society. Identifying the effect of environmental factors and human disturbances on species is fundamental for allocating limited resources in management and conservation.
[Show abstract][Hide abstract] ABSTRACT: Spatial capture-recapture (SCR) models have advanced our ability to estimate population density for wide ranging animals by explicitly incorporating individual movement. Though these models are more robust to various spatial sampling designs, few studies have empirically tested different large-scale trap configurations using SCR models. We investigated how extent of trap coverage and trap spacing affects precision and accuracy of SCR parameters, implementing models using the R package secr. We tested two trapping scenarios, one spatially extensive and one intensive, using black bear (Ursus americanus) DNA data from hair snare arrays in south-central Missouri, USA. We also examined the influence that adding a second, lower barbed-wire strand to snares had on quantity and spatial distribution of detections. We simulated trapping data to test bias in density estimates of each configuration under a range of density and detection parameter values. Field data showed that using multiple arrays with intensive snare coverage produced more detections of more individuals than extensive coverage. Consequently, density and detection parameters were more precise for the intensive design. Density was estimated as 1.7 bears per 100 km2 and was 5.5 times greater than that under extensive sampling. Abundance was 279 (95% CI = 193-406) bears in the 16,812 km2 study area. Excluding detections from the lower strand resulted in the loss of 35 detections, 14 unique bears, and the largest recorded movement between snares. All simulations showed low bias for density under both configurations. Results demonstrated that in low density populations with non-uniform distribution of population density, optimizing the tradeoff among snare spacing, coverage, and sample size is of critical importance to estimating parameters with high precision and accuracy. With limited resources, allocating available traps to multiple arrays with intensive trap spacing increased the amount of information needed to inform parameters with high precision.
PLoS ONE 10/2014; 9(10):e111257. DOI:10.1371/journal.pone.0111257 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Individual variation and fitness are cornerstones of evolution by natural selection. The niche variation hypothesis (NVH) posits that when interspecific competition is relaxed, intraspecific competition should drive niche expansion by selection favoring use of novel resources and that among-individual variation should confer a selective advantage. Population-level niche expansion could be achieved by all individuals using all available resources, or by each individual using a unique combination of resources, thereby increasing among-individual dietary niche variation. Although individual variation can lead to species-level evolutionary and ecological change, observed variation does not ensure a beneficial outcome. We used carbon and nitrogen stable isotope analysis of claw keratin and a Bayesian stable isotope mixing model to estimate the summer (July–September) assimilated diet of individual female black Ursus americanus and brown U. arctos bears. We quantified variation in dietary niche in both populations, and assessed diet relative to percentage body fat. We hypothesized that if the NVH held, percentage body fat would be similar for individuals of the same species across much of the dietary range of observed proportional salmon contributions to individual bear diets. Although we found greater differences in dietary niches between than within species, we observed greater among-individual dietary variation in the brown bear population. Moreover, we found that within each species individual female bears achieved similar ranges of percentage body fat at various levels of salmon in the diet. Our results provide support for the NVH. Linking individual dietary niches to measures of physiological condition related to fitness can offer new insights into eco-evolutionary processes related to food resource use.
[Show abstract][Hide abstract] ABSTRACT: Wildlife incidents with aircraft cost the United States (U.S.) civil aviation industry >US$1.4 billion in estimated damages and loss of revenue from 1990 to 2009. Although terrestrial mammals represented only 2.3 % of wildlife incidents, damage to aircraft occurred in 59 % of mammal incidents. We examined mammal incidents (excluding bats) at all airports in the Federal Aviation Administration (FAA) National Wildlife Strike Database from 1990 to 2010 to characterize these incidents by airport type: Part-139 certified (certificated) and general aviation (GA). We also calculated relative hazard scores for species most frequently involved in incidents. We found certificated airports had more than twice as many incidents as GA airports. Incidents were most frequent in October (n = 215 of 1,764 total) at certificated airports and November (n = 111 of 741 total) at GA airports. Most (63.2 %) incidents at all airports (n = 1,523) occurred at night but the greatest incident rate occurred at dusk (177.3 incidents/hr). More incidents with damage (n = 1,594) occurred at GA airports (38.6 %) than certificated airports (19.0 %). Artiodactyla (even-toed ungulates) incidents incurred greatest (92.4 %) damage costs (n = 326; US$51.8 million) overall and mule deer (Odocoileus hemionus) was the most hazardous species. Overall, relative hazard score increased with increasing log body mass. Frequency of incidents was influenced by species relative seasonal abundance and behavior. We recommend airport wildlife officials evaluate the risks mammal species pose to aircraft based on the hazard information we provide and consider prioritizing management strategies that emphasize reducing their occurrence on airport property.
[Show abstract][Hide abstract] ABSTRACT: Radiotelemetry and unmarked occupancy modeling have been used to estimate animal population growth, but have not been compared for ungulates. We compared white-tailed deer (Odocoileus virginianus) population growth estimates from radiomarked individuals and occupancy modeling of unmarked individuals and evaluated advantages and disadvantages of each method. Estimates of population growth were obtained using remote camera (N = 54/year) detection/non-detection occupancy surveys of unmarked deer and from survival and recruitment data of radiomarked adult females (N = 87) and neonate fawns (N = 127) in a predominantly forested region of the Upper Peninsula of Michigan, USA, 2009–2011. We hypothesized that occupancy models and radiotelemetry data would have similar population growth trends because both methods sampled the same temporally closed population. Percent changes in camera trap data generally reflected finite population growth (λ) of radiomarked deer which increased (λ = 1.10 ± 0.01) from 2009 to 2010, but decreased (λ = 0.87 ± 0.02) from 2010 to 2011. Also, unmarked adult female abundance and fawn:adult female ratios generally reflected trends in radiomarked deer survival and recruitment. Royle–Nichols occupancy model abundance estimates had wide confidence intervals, which may preclude using this method from accurately estimating deer population growth. Radiotelemetry provided more precise population growth estimates, while allowing collection of vital rates and location data. However, the Royle–Nichols occupancy model may be preferred to radiotelemetry because it reflected yearly variation in population growth with reduced labor and no invasive marking. Researchers should consider the objectives and logistics of their study when choosing a specific method.
Population Ecology 07/2014; 56(3). DOI:10.1007/s10144-014-0432-7 · 1.70 Impact Factor