A Survey of California Deer Herds, Their Ranges and Management Problems

Severinghaus, C. W.; Longhurst, William M.; Leopold, Aldo; Dasmann, Raymond F.

doi:10.2307/3797124

Cited by 12 publications

(2 citation statements)

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“…Perhaps more importantly, population densities of potential antagonists, the herbivorous ungulates, have long been exceptional on Catalina (Table 4). Ungulate densities on the island in the past two centuries have generally been in the many tens to hundreds of individuals per km 2 , compared to mainland (statewide) densities of deer of 4-9/km 2 [76,89], with concentrations of more than 20/km 2 in relatively small areas [90,91]. Much smaller numbers of bighorn sheep (Ovis canadensis) remain on the mainland [92], but their population and that of the regionally extirpated pronghorn (Antilocapra americana [93]) were undoubtedly greater in prior centuries (no estimates exist).…”

Section: Mainland Versus Island Mammal Abundancementioning

confidence: 99%

“…Current densities of these animals on Catalina substantially exceed those of the mainland. Although we do not know historic densities of ungulates on the mainland, they were unlikely to have approached those in the past two centuries on Catalina, which have substantially denuded the vegetation and at times exceeded carrying capacity [76,84,[122][123][124].…”

Section: Possible Causes Of Increased Defensivenessmentioning

confidence: 99%

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Paradoxical Exception to Island Tameness: Increased Defensiveness in an Insular Population of Rattlesnakes

Hayes,

Person,

Fox

et al. 2024

Toxins

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Island tameness results largely from a lack of natural predators. Because some insular rattlesnake populations lack functional rattles, presumably the consequence of relaxed selection from reduced predation, we hypothesized that on Santa Catalina Island, California, USA, populations of the southern Pacific rattlesnake (Crotalus helleri), which possesses functional rattles, would exhibit a decrement in defensive behavior relative to their mainland counterparts. Contrary to our prediction, rattlesnakes from the island not only lacked tameness compared to mainland snakes, but instead exhibited measurably greater levels of defensiveness. Island snakes attempted to bite 4.7 times more frequently as we endeavored to secure them by hand, and required 2.1-fold more time to be pinned and captured. When induced to bite a beaker after being grasped, the island snakes also delivered 2.1-fold greater quantities of venom when controlling for body size. The additional venom resulted from 2.1-fold larger pulses of venom ejected from the fangs. We found no effects of duration in captivity (2–36 months), which suggests an absence of long-term habituation of antipredator behaviors. Breeding bird surveys and Christmas bird counts indicated reduced population densities of avian predators on Catalina compared to the mainland. However, historical estimates confirmed that populations of foxes and introduced mammalian predators (cats and pigs) and antagonists (herbivorous ungulates) substantially exceeded those on the mainland in recent centuries, and therefore best explain the paradoxically exaggerated defensive behaviors exhibited by Catalina’s rattlesnakes. These findings augment our understanding of anthropogenic effects on the behaviors of island animals and underscore how these effects can negatively affect human safety.

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