Barren ground caribou (Rangifer tarandus groenlandicus) herds experience significant fluctuations in abundance through time. A proposed hypothesis for these fluctuations involves the overgrazing of ...vegetation on herd summer ranges at high herd densities resulting in a reduction in available forage. Semi-domesticated reindeer (Rangifer tarandus) herds in Scandinavia negatively affect vegetation productivity at high herd densities and exclosure experiments have indicated that overgrazing may also affect barren ground caribou herds. However, overgrazing of summer range vegetation has yet to be tested at the landscape level or related to herd densities for barren ground caribou herds. Accordingly, the question examined in this study was — does barren ground caribou herd density have an effect on summer range vegetation productivity? To answer this question, summer home ranges for four herds in the Northwest Territories and Nunavut, Canada, were delineated using caribou telemetry data. Yearly overall productivity and vegetation seasonality (the change between the maximum and minimum productivity throughout the year) metrics were calculated by year using Moderate Resolution Imaging Spectroradiometer and Advanced Very High Resolution Radiometer data and related to herd densities. Overall vegetation productivity was negatively related to herd density, indicating that some summer range degradation may have occurred at high densities. Conversely, and contrary to our expectations, vegetation seasonality was positively related to herd density. The Bathurst herd, which experienced densities more than three times those of the other herds examined, had the least negative association with overall productivity. Given the negative relationship detected between each herd's densities and overall vegetation productivity, it is likely that some summer range degradation occurred as herd densities increased. Considering the results of the Bathurst herd however, it is difficult to conclude that overgrazing has been a major factor governing herd abundance in the herds examined here. This study demonstrated the utility of archived remotely sensed productivity data and how productivity indices can be useful tools for providing information on large mammal grazing impacts.
•Barren ground caribou herd sizes change through time, possibly due to overgrazing.•Recent processing of AVHRR data offers productivity data back to 1987 in Canada.•We assessed change in climate corrected vegetation productivity against herd size.•We detected a negative relationship between vegetation productivity and herd size.•We demonstrate that RS data allows for broad scale assessments of grazing impacts.
Understanding species–habitat relationships is critical for wildlife management, providing information on habitat requirements, distribution, and potential land use impacts. In this paper, we ...examined occurrence and abundance–habitat relationships for moose (Alces alces), a species of economic and ecological importance, across its range in southern and central Ontario. We (1) evaluated and tested competing hypotheses for predicting moose distribution and abundance, and (2) examined the ability of remotely derived environmental indicators to characterize and extrapolate moose habitat throughout the Ontario moose range. To do so, remotely sensed environmental indicators – including vegetation productivity calculated using the Dynamic Habitat Index (DHI), land cover, topography, snow cover, and natural and anthropogenic disturbances – were used to estimate moose occurrence and abundance derived from moose aerial survey data. A 2-step Hurdle model was used to accommodate for zero-inflated data, separately modeling moose occurrence and abundance in a common model framework. Our results indicate that remotely sensed indicators are able to estimate moose occurrence with a moderate degree of certainty; however, these environmental indicators did not successfully estimate moose abundance. The approach outlined in this paper provides a useful framework for hypothesis testing of remote sensing environmental drivers at broad scales, as well as for estimating moose occurrence at the regional level.
•We examined occurrence and abundance–habitat relationships for moose.•We assessed if remotely-derived environmental indicators can help predictions.•Moose distribution was more accurately estimated than moose abundance.•Presence of conifers and snow cover were the most significant indicators.•Linking remote sensing to hypothesis helped model development and assessment.
Changing climates are altering wildlife habitats and wildlife behavior in complex ways. Here, we examine how changing spring snow cover dynamics and early season forage availability are altering ...grizzly bear (Ursus arctos) behavior postden emergence. Telemetry data were used to identify spring activity dates for 48 individuals in the Yellowhead region of Alberta, Canada. Spring activity date was related to snow cover dynamics using a daily percent snow cover dataset. Snow melt end date, melt rate, and melt consistency explained 45% of the variation in spring activity date. We applied this activity date model across the entire Yellowhead region from 2000 to 2016 using simulated grizzly bear home ranges. Predicted spring activity date was then compared with a daily spring forage availability date dataset, resulting in “wait time” estimates for four key early season forage species. Temporal changes in both spring activity date and early season forage “wait times” were assessed using non‐parametric regression. Grizzly bear activity date was found to have either remained constant (95%) or become earlier (5%) across the study area; virtually no areas with significantly later spring activity dates were detected. Similarly, the majority of “wait times” did not change (85%); however, the majority of significant changes in “wait times” for the four early season forage species indicated that “wait times” were lessening where changes were detected. Our results show that spring activity date is largely dictated by snow melt characteristics and that changing snow melt conditions may result in earlier spring activity. However, early season food stress conditions are likely to remain unchanged or improve as vegetation phenology also becomes earlier. Our findings extend the recent work examining animal movement in response to changing phenology from migratory birds and ungulates to an apex predator, further demonstrating the potential effects of changing climates on wildlife species.
We estimated grizzly bear den emergence dates and forage availability dates in spring across the Yellowhead region of Alberta from 2000 to 2016. We examined changes in wait times from 2000 to 2016 across the landscape. We show that while individual den emergence dates are either unchanged or becoming earlier, wait times either remain unchanged or are decreasing.
Aim
To quantify changes in vegetation productivity over the past three decades across five barren ground caribou (Rangifer tarandus groenlandicus) herd ranges and assess how these changes are ...influencing caribou movement rates.
Location
Northwest Territories and Nunavut, Canada.
Methods
As an indicator of vegetation productivity, the enhanced vegetation index (EVI) was calculated on newly developed cloud‐free, gap‐free, Landsat surface reflectance image composites representing 1984–2012. Changes in EVI were assessed on a pixel basis using Theil‐Sen's nonparametric regression and compared across herd ranges and land cover types using generalized least squares regression. Animal movement velocity was calculated from caribou telemetry data and generalized additive mixed models were used to link movement rates with vegetation productivity during the post‐calving phase of the year (July and August).
Results
Vegetation productivity increased across the five caribou herd ranges examined. The largest productivity increase occurred over the ranges of the most western herds, with the largest observed changes in grassland or shrub habitats. Caribou tended to move more slowly through tundra habitats with elevated levels of productivity to a point, while grasslands movement rates decreased linearly with increasing productivity. Movement velocities peaked at intermediate productivity levels in shrub habitats.
Main conclusions
Over the three decades of collected data, barren ground caribou habitats have become more productive, which is consistent with other studies that have documented increases in Arctic vegetation productivity. The more western herds, whose ranges are also closest to the Arctic Ocean, experienced the largest increases in productivity. Finally, we demonstrate that barren ground caribou movement patterns will likely change as a result of changing vegetation productivity in complex manners depending on herd, habitat type and the magnitude of change in vegetation productivity.
AIM: Systematic conservation planning often involves the application of a regionalization scheme, which is assumed to delineate distinct ecological communities of target species. Commonly, such ...schemes are constructed using environmental surrogates; however, their effectiveness with regard to community delineation has been questioned in previous studies. Here, we aim to assess multiple environmental regionalization schemes' ability to delineate avian communities and to evaluate these schemes against a regionalization scheme built using species data directly. LOCATION: British Columbia, Canada. METHODS: We employed a beta diversity metric using community data from the BC Breeding Bird Atlas in multiple analysis of similarity (ANOSIM) tests, to assess the ability of a number of environmental regionalization schemes to delineate species turnover. We also developed a new species‐based scheme using kriged local beta diversity values and a thematic resolution optimized through ANOSIM testing, which was then evaluated against the previously tested schemes. RESULTS: All regionalization schemes delineated significant patterns in community structure, with the Bird Conservation Regions performing most similarly to the species‐based regionalization. Regionalizations that required regions to be spatially contiguous outperformed non‐contiguous regionalizations. Increasing thematic resolution (the number of regions within a regionalization) improved a regionalization's overall performance; however, regional redundancy also increased. MAIN CONCLUSIONS: We argue that environmental regionalizations can function as effective alternatives to species‐based regionalizations, particularly in areas with poor availability of species data. Also, we conclude that spatially contiguous regionalizations are superior to non‐contiguous ones for delineating distinct communities. Lastly, we demonstrate how thematic resolution represents a trade‐off between overall regionalization performance and regional redundancy, and how differing thematic resolutions can be employed depending upon the goals of the user.
At high herbivore density, herbivory can reduce forage abundance, potentially contributing to habitat degradation and driving changes in herbivore population size or range use, in accordance with the ...exploitation ecosystem hypothesis. The migratory Rivière-George caribou herd (RGH,
Rangifer tarandus
) of the Quebec-Labrador Peninsula (Canada) has experienced a large decline in population size since the population peaked in the early 1990s, with similarly large changes in seasonal range use. Demographic changes are suspected to have influenced forage abundance and caribou range use through density-dependent interactions between caribou and their habitat. We used the Normalized Difference Vegetation Index (NDVI) to examine relationships between RGH caribou density and range productivity from 1991 to 2011. A modelling approach was used to control for the response of climate and to isolate the influence of caribou herbivory on primary productivity. Significant negative relationships were identified between caribou density and primary productivity, after controlling for climatic variation, for the global RGH calving grounds (
r
2
= 0.54–0.55) and summer range (
r
2
= 0.42–0.51), but not for the “core” ranges, where caribou density was highest. Positive temporal trends in primary productivity appeared to reflect the decline in RGH population size, suggesting vegetation recovery following reductions in caribou abundance. Climate warming (of up to + 1.5 °C per decade) was most responsible for the strong positive trends in primary productivity observed over the 1991–2011 period, but decreases in RGH herbivory likely also contributed to the increases in range productivity. Forage access likely improved over the study period, which may have influenced RGH range use and habitat selection.
•We propose a method for mapping tourism likelihood using social networks and maxent.•All included social networks generated better-than-random likelihood distributions.•Human access was a highly ...important covariate for most models.•Links between grizzly bear telemetry and recreation likelihood were outlined.•This approach could improve mapping of recreation over management areas.
Understanding biodiversity pressures associated with recreation and tourism is a major challenge for conservation planning and landscape management. While estimates of landscape use are often collected using mechanisms such as park entry fees and traffic density estimates, these data do not provide substantial detail about the spatial location or intensity of recreation and tourism across biodiversity management areas. To better predict patterns of recreation and tourism likelihood to support conservation planning, we used social network data from Facebook(™), Flickr(™), Google(™), Strava(™), and Wikilocs(™) along with a suite of remote-sensing-derived environmental covariates in a maximum entropy (MaxEnt) presence-only modelling framework. Social network samples were compiled and processed to reduce sampling bias and spatial autocorrelation. Road access, climate data, and remote sensing covariates describing vegetation greenness, disturbance, topography, and moisture were used as predictor variables in the MaxEnt modelling framework. Our focus site was a grizzly bear (Ursus arctos) management area in west-central Alberta, Canada. Individual models were developed for each social network dataset, as well as a combined model including all the samples . Mean cross-validated AUC, partial ROC, and true skill statistics (TSS) were used to evaluate model accuracy. Results indicated that the covariates proposed were able to best model Strava and Wikilocs activity (TSS = 0.69 and 0.50, respectively), while samples from Flickr or the combination of all social networks were least accurate (TSS = 0.32). The “access” covariate was most important for MaxEnt training gain across a number of social network models, highlighting the importance of access for recreation and tourism likelihood. The summer heat moisture index and normalized burn ratio were also useful spatial covariates in many predictions. Recreation and tourism likelihood maps were combined with grizzly bear telemetry data to examine how recreation and tourism may affect grizzly bear behaviour. All social network models found a similar influence on grizzly bear behaviour, with increasing recreation and tourism use resulting in decreased foraging behaviour and increased rapid movement, suggesting that the models developed here are useful tools for predicting grizzly bear behaviour and planning conservation strategies for the species.
At high herbivore density, herbivory can reduce forage abundance, potentially contributing to habitat degradation and driving changes in herbivore population size or range use, in accordance with the ...exploitation ecosystem hypothesis. The migratory Rivière-George caribou herd (RGH, Rangifer tarandus) of the Quebec-Labrador Peninsula (Canada) has experienced a large decline in population size since the population peaked in the early 1990s, with similarly large changes in seasonal range use. Demographic changes are suspected to have influenced forage abundance and caribou range use through density-dependent interactions between caribou and their habitat. We used the Normalized Difference Vegetation Index (NDVI) to examine relationships between RGH caribou density and range productivity from 1991 to 2011. A modelling approach was used to control for the response of climate and to isolate the influence of caribou herbivory on primary productivity. Significant negative relationships were identified between caribou density and primary productivity, after controlling for climatic variation, for the global RGH calving grounds (r.sup.2 = 0.54-0.55) and summer range (r.sup.2 = 0.42-0.51), but not for the "core" ranges, where caribou density was highest. Positive temporal trends in primary productivity appeared to reflect the decline in RGH population size, suggesting vegetation recovery following reductions in caribou abundance. Climate warming (of up to + 1.5 °C per decade) was most responsible for the strong positive trends in primary productivity observed over the 1991-2011 period, but decreases in RGH herbivory likely also contributed to the increases in range productivity. Forage access likely improved over the study period, which may have influenced RGH range use and habitat selection.
Aim: To quantify changes in vegetation productivity over the past three decades across five barren ground caribou (Rangifer tarandus groenlandicus) herd ranges and assess how these changes are ...influencing caribou movement rates. Location: Northwest Territories and Nunavut, Canada. Methods: As an indicator of vegetation productivity, the enhanced vegetation index (EVI) was calculated on newly developed cloud-free, gap-free, Landsat surface reflectance image composites representing 1984–2012. Changes in EVI were assessed on a pixel basis using Theil-Sen's nonparametric regression and compared across herd ranges and land cover types using generalized least squares regression. Animal movement velocity was calculated from caribou telemetry data and generalized additive mixed models were used to link movement rates with vegetation productivity during the post-calving phase of the year (July and August). Results: Vegetation productivity increased across the five caribou herd ranges examined. The largest productivity increase occurred over the ranges of the most western herds, with the largest observed changes in grassland or shrub habitats. Caribou tended to move more slowly through tundra habitats with elevated levels of productivity to a point, while grasslands movement rates decreased linearly with increasing productivity. Movement velocities peaked at intermediate productivity levels in shrub habitats. Main conclusions: Over the three decades of collected data, barren ground caribou habitats have become more productive, which is consistent with other studies that have documented increases in Arctic vegetation productivity. The more western herds, whose ranges are also closest to the Arctic Ocean, experienced the largest increases in productivity. Finally, we demonstrate that barren ground caribou movement patterns will likely change as a result of changing vegetation productivity in complex manners depending on herd, habitat type and the magnitude of change in vegetation productivity.
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