Island fox spatial ecology and implications for management of disease

Abstract

Disease, predation, and genetic isolation resulted in 4 of 6 island fox (Urocyon littoralis) subspecies being listed as endangered in 2004. Potential for disease outbreaks continues to pose a major threat to the persistence of these isolated, endemic populations. We examined how roads influence the spatial ecology of San Clemente Island foxes (U. l. clementae), particularly in regard to spread of disease, to provide management recommendations for preventing or minimizing a disease outbreak on San Clemente Island, California, USA. Home range areas (truex¯ = 0.75 km2) and core areas (truex¯ = 0.19 km2) of foxes on San Clemente Island were 0.36–1.23 and 2.17 times larger, respectively, than estimates from Santa Cruz Island foxes (U. l. santacruzae). Home ranges and core areas were 78% larger and 73% larger, respectively, for foxes near roads than for foxes away from roads. Home ranges were also largest when foxes were not caring for offspring (i.e., seasons of pup‐independence and breeding). We did not detect any dispersal movements, but foxes living near roads moved 33% farther in 2‐hours periods than foxes not living near roads. Foxes near roads move faster, range more widely, and could more rapidly spread a pathogen throughout the island; therefore, roads might serve as transmission corridors. We recommend reducing this risk by increasing widths of vaccination firewalls (areas where vaccination is used to induce a disease‐resistant or immune population of foxes), ensuring these areas deliberately intersect roads, and vaccinating a higher proportion of foxes living near roads. Disease risk models incorporating these strategies could inform the lowest risk scenarios. © 2018 The Wildlife Society.

Vaccination and monitoring strategies for epidemic prevention and detection in the Channel Island fox (Urocyon littoralis)

“…Similarly, if pathogens are most likely to invade into low-density regions, vaccinating randomly throughout the area may be more effective. Previous studies have suggested that vaccination programs should also consider landscape features when designing deployment strategies: using natural barriers to enhance vaccination firewalls [73] and accounting for habitat corridors and roads that promote host movement [11,74]. Firewall vaccination would likely be most beneficial in situations where host populations living in and around key landscape features (such as narrow habitat corridors) could be saturated with vaccinations in order to more effectively reduced the number of hosts infected early in the epidemic and the risk of infection crossing the firewall.…”

Where and when to vaccinate? Interdisciplinary design and evaluation of the 2018 Tanzanian anti-rabies campaign

“…For instance, investigations of the biogeography associated with rabies could detect factors that promote epidemic spread as well as barriers that prevent dissemination (Smith et al, 2002). Recent studies conducted with wildlife species have identified where vaccinations against rabies are more likely to be beneficial (Resnik et al, 2018). Because delayed interventions tend to be less effective and costlier, estimating when is the optimal (or critical response) time to intervene also requires geographical data (Rivas et al, 2003).…”