Werdel Wildlife
Landscape Effects on Carnivore Communities
Abstract
The Great Plains region has undergone extensive conversion of native prairies to agriculture production and energy development since European colonization. Temperate prairies, including remaining prairies within the Great Plains, are considered among Earth’s most imperiled ecosystems. Prairie patches now exist as components of a landscape mosaic proportionately dominated by cultivated agriculture. These contemporary human-modified landscapes may structure species’ distributions, influence community dynamics, and supplant established abiotic range-limiting processes. Understanding the direction and scale of these processes, and how they are affected by landscape composition and configuration, is necessary to enhance conservation efforts. Carnivore communities may be most affected by landscape changes due to negative interactions with humans and their inherent biological traits; however, information regarding landscape-scale effects on the existing suite of carnivores in the Great Plains is lacking. I examined how landscape composition and characteristics influenced site occupancy probabilities and turnover rates by swift foxes (Vulpes velox), the spatial and temporal interactions between swift foxes and coyotes (Canis latrans), and carnivore richness in agro-prairie ecosystems. Additionally, I strategically identified native prairie areas to focus conservation and management of remaining swift fox habitat.
During 2018-2020, I used detection/non-detection data from camera traps at 381 randomly selected sites distributed throughout a landscape mosaic comprising the westernmost 31 counties (7.16 million ha) of Kansas, USA. I subsequently used presence/absence data from these sites across three years to infer species-specific responses to landscape change and carnivore community dynamics. To evaluate effects of landscape composition and configuration on site occupancy probabilities and turnover rates by swift fox, I used a distance-weighted scale of effect of landscape metrics within multi-season occupancy models. Swift foxes were more likely to occur at sites with moderate landcover diversity within 254.47 ha, greater proportion of shortgrass prairie (7.07 ha) and loamy soil types (0.79 ha), and lower proportions of Conservation Reserve Program (CRP) landcover (78.54 ha). Swift foxes were more likely to colonize sites with less diverse landcover, a greater proportion of loamy soil types, and lower proportions of CRP landcover. Swift foxes were insensitive to the proportion of row-crop agriculture surrounding sites (3.14 ha). To evaluate landscape composition effects on swift foxes and coyote (the apex predator in the region) spatiotemporal interactions, I used a Bayesian hierarchical multi-season occupancy model to evaluate spatial interactions, and a coefficient of overlap of temporal activity to assess factors affecting temporal interactions. Mean persistence of swift foxes differed across sites where coyotes were not detected (0.66; SE = 0.001) and where coyotes were detected (0.39; SE=0.001). The coefficient of overlap at sites surrounded by lower proportions of CRP (≥0.10) differed (95% CIs did not overlap) from coefficient of overlap of all other landscape effects. The spatial distribution of swift foxes was positively influenced (Species Interaction Factor [SIF] > 1) by coyote presence through space and time at low proportions of CRP (≤0.04). SIF decreased as proportion of CRP increased; however, Bayesian confidence intervals overlapped SIF = 1, suggesting that swift foxes were spatially distributed independent of coyotes through space and time at greater proportions of CRP (>0.04).
I used a structural equation model to test hypotheses of multiple direct and indirect relationships between landscape composition and configuration and prey availability on carnivore richness. My hypothesized model (X2 = 23.92, df = 24, P = 0.47) explained 27% of the variance of carnivore richness. Agriculture, native prairie, landcover diversity, CRP, water availability, prey occurrence, and sampling effort all had direct positive effects on my measure of carnivore richness, while loamy tableland soil had only an indirect effect. To strategically identify native prairie areas for conservation of swift fox habitat, I created a predicted swift fox occupancy map based on my most-supported, stacked single-season occupancy model. I identified predicted occupancy rate (range = 0.01–0.46) where sensitivity equaled specificity (0.09) within a receiver operating characteristic curve, and reclassified the predicted occupancy map to include only predicted occupancy rates >0.09, and again for a more targeted approach with predicted occupancy rates >0.18. These two maps were intersected with a map of grassland proportions >0.60 to identify areas that were expected to have relatively high occupancy and survival rates by swift fox. Swift foxes were more likely to occur at sites with low levels of landscape diversity (β = -0.411 ± 0.140), greater proportions of native grassland (β = 0.375 ± 0.154) and loamy tableland soils (β = 0.944 ± 0.188), and lower proportions of CRP landcover (β = -1.081 ± 0.360). Identified native grassland conservation areas totaled 84,420.24 ha (mean patch size = 162.66 ha [SE = 29.67]). Conservation areas located on privately owned working lands included 82,703.86 ha, while conservation areas located within the boundaries of federal, state, and non-governmental organizations (NGO) parcels included 1,716.38 ha.
My results provide a unique understanding of how landscape composition and configuration, intraguild competition, and prey availability drive carnivore community dynamics in agro-prairie ecosystems. Additionally, my research elucidated constraints to range expansions for an iconic prairie-obligate carnivore (swift fox) at the edge of their range, while also identifying areas for strategic conservation for their populations.
Swift Fox | Pheasant | White-tailed Deer |
---|---|---|
Coyote | Burrowing Owl | Bobcat |
Bobcat | Striped Skunk | Raccoons |
Long-tailed Weasel | ||
Coyote | ||
Coyote | Striped Skunk | |
Bobcat | Mule Deer | Raccoons |
Turkey Vulture | Bobcat | Black-tailed Jackrabbit |
Turkey Vulture | Badger | Kangaroo Rat |
Coyote | Mule Deer | Badger |
Badgers | Mule Deer | Striped Skunk |
Black-tailed Jackrabbit | Long-tailed Weasel | Badger |
Striped Skunk | Coyote | |
Mule Deer | ||
Raccoons | Black-tailed Jackrabbit | Striped Skunk |
Black-tailed Jackrabbit | Mule Deer | Thirteen-lined Ground Squirrel |
Coyote | Coyote | Virginia Opossum |
Coyote | Mule Deer | White-tailed Deer |
Badger | Badger | Coyote |
White-tailed Deer | Coyote | Badger |
Bobcat | Coyote | Bobcat |
Coyote | Coyotes | White-tailed Deer |
Coyote | Coyotes | Badger |
Mule Deer | Striped Skunk | Mule Deer |
Mule Deer | Field Truck | Turkey Vulture |
Swift Fox | Pronghorn | |
Swift Fox | Black-tailed Prairie Dog | Coyote |
Badger | Coyote | Coyote |
Coyote | Research Team | Coyote |
Striped Skunk | Badger | Badger |
Badger | Flooded Site | Badger |
Coyote | Mule Deer | Coyote |
Badger | Bobcat | Coyote |
White-tailed Deer | Cow/Calf | Turkey |
Coyote | Pheasant | Pheasant |
Pronghorn | Pronghorn | Raccoon |
Bobcat | Bobcat | |
Black-tailed Prairie Dog | Bobcat | White-tailed Deer |
Coyote | Raccoon | |
Turkey | Bobcat | |
Virginia Opossum | Pronghorn | |
Striped Skunk | Coyote | |
Coyote | Coyote | Coyote |
Swift Fox | Swift Fox | Swift Fox |
Swift Fox | Swift Fox |
Deadwood Bighorn Sheep Translocation
Abstract
From 2015-2017, we evaluated a newly established bighorn sheep (Ovis canadensis) herd in the Deadwood Region of the Black Hills, South Dakota. Our objectives were to 1a) determine annual survival rates, 1b) determine cause-specific mortality, 1c) estimate population size, 2a) assess genetic diversity, 2b) assess disease prevalence, 3) evaluate movement patterns post-release, 4a) evaluate 3rd-order habitat selection, and 4b) estimate herbaceous biomass at foraging sites post-release of translocated bighorn sheep. In February 2015, we captured and translocated 26 bighorn sheep from the Luscar Mine near Hinton, Alberta, Canada to the Deadwood Region of the Black Hills, South Dakota. Overall annual bighorn sheep survival rates were 64.4% (95% CI=0.48-0.77). Confirmed pneumonia accounted for 57.9% (n=11) of all cause-specific mortalities, while no predation was documented during the study. We estimated the population size at the end of the study period was 24 bighorn sheep (λ=0.92). Observed and expected heterozygosity were 0.71 (SE=0.06) and 0.64 (SE=0.05), respectively. The Mycoplasma ovipneumoniae pathogen found within the Deadwood bighorn sheep herd was of a strain type previously undocumented in the Black Hills. Dispersal among individual bighorn sheep occurred year 1, while establishment of home-ranges occurred year 2. We used 95% Brownian Bridge Movement Models for year 2, which resulted in a mean home-range size of 5.29 km2. Forested habitat was actively avoided (ŵ=0.30), while barren (ŵ=16.93), shrubland (ŵ=1.28), and grassland (ŵ=1.65) habitats were selected. Foraging sites were typically located in areas with little overstory tree canopy cover (mean= 8.41%, SE=1.85), short distance to escape terrain (mean= 24.00 m, SE=3.21), and little woody debris (mean= 0.25 kg/ha, SE=0.07). Herbaceous biomass ranged from 302.07 kg/ha to 2,487.43 kg/ha. Our results indicate that the Deadwood Region of the Black Hills, South Dakota had sufficient forage and habitat capabilities to support a healthy population of bighorn sheep. Translocations to this region can be successful, however, pneumonia, caused by the Mycoplasma ovipneumoniae pathogen, was the greatest limiting factor to population growth within the Deadwood bighorn sheep herd.
Small Mammal Abundance and Diversity
Abstract
In the last 150 years prairie dog populations have declined by 90-98%. They historically occupied millions of hectares of land, but due to encroachment by human populations, and extermination, their range is disappearing. Gunnison’s prairie dog (Cynomys gunnisoni) range is generally considered the southwest or Four Corners region of the United States. This species was selected to be reintroduced within the Sevilleta National Wildlife Refuge in 2010. Their reintroduction within the refuge gives researchers the opportunity to study the affects of C. gunnisoni upon the ecosystem. Much of the research done on the relationship between small mammals and prairie dogs has been with the black-tailed prairie dog (Cynomys ludovicianus). Small mammals, in habitats that include prairie dogs, utilize prairie dog burrows for shelter: some cannot dig their own burrows in the hard ground, while others simply exploit them because of their presence (Ceballos et al. 1998). The burrows also provide escape from predators and provide denning opportunities. Small mammal species richness, diversity, and abundance have been shown to be higher in areas with prairie dogs when compared to similar habitats without prairie dogs (Ceballos et al. 1998). Certain species of small mammals are also more apt to live in areas of short grass and bare ground, such as pocket mice (Perognathus spp.) and kangaroo rats (Dipodomys spp.) (Bock and Bock 2006). Small mammal species richness, diversity, and abundance is expected to be higher due to the presence of prarie dogs. However, the relationship between small mammals and C. gunnisoni has not been well documented. I evaluated how small mammal species have responded to the presence of C. gunnisoni by measuring small mammal species diversity and relative abundance between control sites and reintroduction sites. Small mammal richness and diversity was similar among treatment and control sites. Small mammal abundance was higher (P=0.32) in treatment than control sites. Although the results were not statistically significant, the overall trend of higher abundance on treatment sites was noteworthy.