There is growing recognition of the important roles played by predators in regulating ecosystems and sustaining biodiversity. Much attention has focused on the consequences of predator-regulation of herbivore populations, and associated trophic cascades. However apex predators may also control smaller 'mesopredators' through intraguild interactions. Removal of apex predators can result in changes to intraguild interactions and outbreaks of mesopredators ('mesopredator release'), leading in turn to increased predation on smaller prey. Here we provide a review and synthesis of studies of predator interactions, mesopredator release and their impacts on biodiversity. Mesopredator suppression by apex predators is widespread geographically and taxonomically. Apex predators suppress mesopredators both by killing them, or instilling fear, which motivates changes in behaviour and habitat use that limit mesopredator distribution and abundance. Changes in the abundance of apex predators may have disproportionate (up to fourfold) effects on mesopredator abundance. Outcomes of interactions between predators may however vary with resource availability, habitat complexity and the complexity of predator communities. There is potential for the restoration of apex predators to have benefits for biodiversity conservation through moderation of the impacts of mesopredators on their prey, but this requires a whole-ecosystem view to avoid unforeseen negative effects. 'Nothing has changed since I began. My eye has permitted no change. I am going to keep things like this.' From 'Hawk Roosting', by Ted Hughes.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1461-0248.2009.01347.x

Predator interactions, mesopredator release and biodiversity conservation

Animal movement is fundamental for ecosystem functioning and species survival, yet the effects of the anthropogenic footprint on animal movements have not been estimated across species. Using a unique GPS-tracking database of 803 individuals across 57 species, we found that movements of mammals in areas with a comparatively high human footprint were on average one-half to one-third the extent of their movements in areas with a low human footprint. We attribute this reduction to behavioral changes of individual animals and to the exclusion of species with long-range movements from areas with higher human impact. Global loss of vagility alters a key ecological trait of animals that affects not only population persistence but also ecosystem processes such as predator-prey interactions, nutrient cycling, and disease transmission.

/pdf/moving-in-the-anthropocene-global-reductions-in-terrestrial-34qvh08h50.pdf

Moving in the Anthropocene : global reductions in terrestrial mammalian movements

Interspecific killing is a key determinant of the abundances and distributions of carnivores, their prey, and nonprey community members. Similarity of body size has been proposed to lead competitors to seek similar prey, which increases the likelihood of interference encounters, including lethal ones. We explored the influence of body size, diet, predatory habits, and taxonomic relatedness on interspecific killing. The frequency of attacks depends on differences in body size: at small and large differences, attacks are less likely to occur; at intermediate differences, killing interactions are frequent and related to diet overlap. Further, the importance of interspecific killing as a mortality factor in the victim population increases with an increase in body size differences between killers and victims. Carnivores highly adapted to kill vertebrate prey are more prone to killing interactions, usually with animals of similar predatory habits. Family-level taxonomy influences killing interactions; carnivores tend to interact more with species in the same family than with species in different families. We conclude that although resource exploitation (diet), predatory habits, and taxonomy are influential in predisposing carnivores to attack each other, relative body size of the participants is overwhelmingly important. We discuss the implications of interspecific killing for body size and the dynamics of geographic ranges.

https://www.jstor.org/stable/10.1086/501033

Diet, morphology, and interspecific killing in carnivora.

Parental investment and sexual selection in dart-poison frogs (genus Dendrobates).

Alien predators can have catastrophic effects on ecosystems and are thought to be much more harmful to biodiversity than their native counterparts. However, trophic cascade theory and the mesopredator release hypothesis predict that the removal of top predators will result in the reorganization of trophic webs and loss of biodiversity. Using field data collected throughout arid Australia, we provide evidence that removal of an alien top-predator, the dingo, has cascading effects through lower trophic levels. Dingo removal was linked to increased activity of herbivores and an invasive mesopredator, the red fox (Vulpes vulpes), and to the loss of grass cover and native species of small mammals. Using species distribution data, we predict that reintroducing or maintaining dingo populations would produce a net benefit for the conservation of threatened native mammals across greater than 2.42 x 10(6) km(2) of Australia. Our study provides evidence that an alien top predator can assume a keystone role and be beneficial for biodiversity conservation, and also that mammalian carnivores more generally can generate strong trophic cascades in terrestrial ecosystems.

/pdf/keystone-effects-of-an-alien-top-predator-stem-extinctions-2w30tkhayt.pdf

Keystone effects of an alien top-predator stem extinctions of native mammals.

The distribution of swift foxes (Vulpes velox) in the western Great Plains has been dramatically reduced since historical times. Because coyotes (Canis latrans) have been identified as the main cause of mortality in swift fox populations, we studied the impacts of coyotes on swift foxes in northwestern Texas, USA. We radiomarked and monitored 88 swift foxes and 29 coyotes at 2 study sites from 1998 to 2000. On site 1, coyotes had relatively high abundance (41 ± 6.8 scats/2 km) and survival (0.90), whereas swift foxes had low survival (0.47), low density (0.24-0.31 foxes/km 2 ), and low recruitment (0.25 young/adult), and killings by coyotes (n = 8) were the major cause of death. On site 2, coyotes had relatively low abundance (19 ± 4.9 scats/2 km) and survival (0.54) due to greater human persecution, whereas swift foxes had relatively high survival (0.69), high density (0.68-0.77 foxes/km 2 ), and high recruitment (1.3 young/adult), and few (n = 2) were killed by coyotes. Our initial results -. suggested that swift foxes benefited from lower coyote numbers. To test this hypothesis, we removed 227 coyotes on site 1 during the final year of our study. Subsequently, coyote abundance decreased (18 ± = 4.5 tcats/2 km), whereas swift foxes had increased survival (0.63), increased density (0.68 foxes/km 2 ), arid increased recruitment (1.2 young/adult), and few (n = 3) were killed by coyotes. All parameters remained consistent on site 2. Our results indicate that coyotes can suppress swift fox populations, and that reductions in coyote numbers can change a swift fox population from a sink to a source.

https://www.jstor.org/stable/pdfplus/3802773.pdf

Impacts of coyotes on swift foxes in Northwestern Texas

Habitat loss might be one of the primary reasons for the decline of the swift fox (Vulpes velox) in the western Great Plains of North America. From 1998 to 2001, we monitored 42 swift foxes in a landscape interspersed with native short-grass prairies, nonnative grasslands enrolled in the Conservation Reserve Program, irrigated agricultural fields, and dryland agricultural fields. Survival estimates ranged from 0.52 to 0.66 for both adults and juveniles, and the primary causes of death were vehicle collisions (42% deaths) and coyote (Canis latrans) predation (33%). Annual home-range size was similar for males and females (10.8 and 10.5 km 2 , respectively). Within the study area, swift foxes selected only shortgrass prairies and had lower-than-expected use or complete avoidance of all other habitat types. Our results indicate swift foxes are more specialized in habitat selection than other North American canids; thus, protection of native short-grass prairies might be necessary for their long-term existence.

https://bioone.org/journals/journal-of-mammalogy/volume-84/issue-3/BJK-033/HABITAT-USE-HOME-RANGES-AND-SURVIVAL-OF-SWIFT-FOXES-IN/10.1644/BJK-033.pdf

Habitat Use, Home Ranges, and Survival of Swift Foxes in a Fragmented Landscape: Conservation Implications

http://web.mnstate.edu/stockram/sdarticle%20swift%20fox%20mating%20systems.pdf

Variation in mating system and group structure in two populations of swift foxes, Vulpes velox

From 1999 to 2001 we monitored 12 coyotes (Canis latrans) in northwestern Texas to determine their home ranges and habitat use in a landscape interspersed with native prairie, farmland and Conservation Reserve Program (CRP) fields. Annual home range size was 10.1 km2 for residents and 84.5 km2 for transients. We determined habitat use at two spatial scales: within home ranges and within study area. Habitat use patterns were similar at both scales, as residents selected for native prairie and transients selected for CRP fields. Habitat use between residents and transients differed in both seasons, with residents selecting more native prairie, less farmland and less CRP (summer only) than transients. Habitat at natal den sites also differed from expected for residents, as most dens (8 of 10) were located in CRP fields. The CRP fields contained the only tall permanent vegetation on our study sites and appeared to provide important foraging habitat for transient coyotes, and denning habitat for resid...

Home Range and Habitat Use of Coyotes in an Area of Native Prairie, Farmland and CRP Fields

Activity of Swift Foxes ( Vulpes velox ) at den sites was studied in northwestern Texas during pup rearing seasons in 2000 and 2001 to determine role of males in parental care. Twenty-four percent of radio-collared females with a potential to breed successfully raised pups to eight weeks of age. We intensively monitored presence and absence of male and female Swift Foxes at two den sites each year. Females were present >2.6 times more at den sites than males during the pup rearing season. Female and male Swift Foxes largely stayed at dens during diurnal hours and were active away from dens during nocturnal and crepuscular hours. Females and males spent 12.4% and 3.0% more time at dens before pups emerged, than after pups emerged, respectively. Following depredation of one male parent, the female spent 29% less time at the den site. Decrease in time spent at the den by the female following loss of her mate suggested that loss of one parent might severely impact recruitment of Swift Foxes. Our observations indicated that intense Coyote ( Canis latrans ) depredation may severely impact pup-rearing success as well as the parental care within Swift Fox family groups.

/pdf/den-site-activity-patterns-of-adult-male-and-female-swift-2gcvdpb0fn.pdf

Patrick R. Lemons

Papers

Impacts of coyotes on swift foxes in Northwestern Texas

Habitat Use, Home Ranges, and Survival of Swift Foxes in a Fragmented Landscape: Conservation Implications

Variation in mating system and group structure in two populations of swift foxes, Vulpes velox

Home Range and Habitat Use of Coyotes in an Area of Native Prairie, Farmland and CRP Fields

Den Site Activity Patterns of Adult Male and Female Swift Foxes, Vulpes velox , in Northwestern Texas