Magazine article Endangered Species Update

Hypothetical Relationships between the San Joaquin Kit Fox, California Grizzly Bear, and Gray Wolf on the Pre-European California Landscape

Magazine article Endangered Species Update

Hypothetical Relationships between the San Joaquin Kit Fox, California Grizzly Bear, and Gray Wolf on the Pre-European California Landscape

Article excerpt

Abstract

Predator dynamics and other community-level interactions more than 200 years ago within California's Central Valley would likely have been emphatically different with grizzly bears and wolves as an important part of the landscape. With the advent of European settlement of California, the ecosystem was drastically altered. The removal of wolves and grizzly bears from the Central Valley may have had a negative effect on the San Joaquin kit fox. Cascading effects with negative results like the ones described here are likely commonplace when top-down ecosystems are altered by human activities.

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The interspecific interactions between mammalian carnivores are typically limited to interference competition and predation (Cypher and Spencer 1998; Palomares and Caro 1999). These interactions have important implications on carnivore competition (Linnell and Strand 2000). For example, spotted hyenas (Crocuta crocuta) kill golden jackals (Canis aureus) and brown hyenas (Hyaena brunnea) when competing for resources (Palomares and Caro 1999). Spotted hyenas and lions (Panthera leo) limit the density of African wild dogs (Lycaon pictus) through interference competition (Creel and Creel 1996). These types of interspecific interactions are common within communities of North America, Africa, and Europe, although the behavioral factors of these interactions are poorly understood (Palomares and Caro 1999).

Comparatively, interspecific cooperative hunting and other beneficial associations between mammalian carnivores are just as poorly understood (Packer and Ruttan 1988). A notable example includes hunting associations between badgers (Taxidea taxus) and coyotes (Canis latrans; Hawkins 1907, Cahalane 1950). Badgers and coyotes have been observed on many occasions helping each other prey upon ground squirrels (Spermophilus spp.; Kiliaan et al. 1991; Minta et al. 1992). Hunting methods include a double rushing of a squirrel colony, where confused squirrels are easily captured by both the coyote and the badger, and opportunistic capturing of escaping squirrels by the coyote as the badger excavates the burrow, akin to the coyote using the badger as a hunting tool. In the last instance, the benefit to the badger is not immediately obvious. Perhaps having an alert predator in the area provides warning of approaching danger, or squirrels, sensing a coyote outside of the burrow, may choose to remain underground and eventually become prey for the badger. However, coyote-badger associations are most likely phoretic rather than a form of social symbiosis (Kiliaan et al. 1991). Cooperative or opportunistic foraging between badgers and swift foxes (Vulpes velox) have also been recorded (Ausband and Ausband 2006).

Other interspecific associations between mammalian carnivores have been described elsewhere. In one case, a Tibetan fox (V. ferrilata) closely followed the movements of a brown bear (Ursus arctos) that was excavating pikas (Ochotona curzoniae; Harris and Loggers 2004). The fox directly benefited from the bear's activities by capturing pikas disturbed but not captured by the bear. Przewalski (1883) recorded a similar situation whereby four Tibetan foxes were observed searching for rodents near a bear excavating a burrow complex.

At other times fox-bear interactions suggest scavenging behavior on the part of the fox. Red foxes (V. vulpes) have been observed patiently waiting for an opportunity to partake in feeding on carrion when a brown bear was already present at the carcass (Murie 1987). In another instance, a red fox found a bear cache and relocated a portion of it to a new cache nearby. Eventually a brown bear arrived at the original cache and ate a part of it, then followed the fox's scent to the newly hidden cache and ate what was left (Murie 1987). Arctic foxes (V. lagopus) are known to follow polar bears (U. maritimus) on pack ice and wolves (C. lupus) on the mainland to scavenge remains of kills (Chesemore 1968). …

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