|Scientific Name:||Urocyon littoralis|
|Species Authority:||(Baird, 1857)|
|Red List Category & Criteria:||Critically Endangered A2be+3e ver 3.1|
|Assessor/s:||Roemer, G.W., Fuller, T.K., List, R. & Wayne, R.K. (IUCN SSC Canid Specilaist Group - Island Fox Working Group)|
|Reviewer/s:||Sillero-Zubiri, C. & Hoffmann, M. (Canid Red List Authority)|
The Island Fox is restricted to six of the California Channel Islands off the coast of southern California, USA. The population has suffered declines of more than 80% in recent years, primarily caused by Golden Eagle predation and possible introduction of canine disease (e.g., canine distemper virus (CDV)). Population decline is expected to continue.
|Range Description:||The current distribution is thought to be a consequence of waif dispersal to the northern Channel Islands during the late Pleistocene, followed by Native American assisted dispersal to the southern Channel Islands (Collins 1982, 1991a, b, 1993; Wayne et al. 1991; Goldstein et al. 1999). The species is now geographically restricted to the six largest of the eight California Channel Islands located off the coast of southern California, USA.|
Native:United States (California)
|Range Map:||Click here to open the map viewer and explore range.|
Island Foxes exhibit substantial variability in abundance, both spatially and temporally. Total island fox numbers have fallen from approximately 6,000 individuals (Roemer et al. 1994) to less than 1,500 in 2002. Four of the six island fox subspecies have experienced precipitous declines in the last four years. Fox populations on both San Miguel and Santa Cruz Islands declined by > 90% between 1995 and 2000. Similar declines also occurred on Santa Rosa and Santa Catalina Islands (Roemer 1999; Timm et al. 2000; Roemer et al. 2001a, 2002; Coonan 2003). Only 28 foxes are left on San Miguel and 45 foxes on Santa Rosa, all are in captivity (Coonan 2002, 2003). The Santa Cruz population has dropped from an estimated 1,312 foxes in 1993 to 133 foxes in 1999 (Roemer 1999; Roemer et al. 2001a). Estimates for 2001 suggest that this population may have declined to as low as 60?80 individuals in the wild (Coonan 2002). A captive breeding facility was initiated on Santa Cruz Island in 2002 when three adult pairs were brought into captivity; one pair had five pups in the spring (Coonan 2002). The subspecies on all three northern Channel Islands are in imminent danger of extinction. Fox populations on San Miguel and Santa Cruz Islands have an estimated 50% chance of persistence over the next decade, are Critically Endangered and in need of immediate conservation action (Roemer 1999; Roemer et al. 2001a, 2002; Coonan 2003). On Santa Catalina, Island Foxes are now rare on the larger eastern portion of the island as a result of a canine distemper outbreak that swept through the population in 1999 (Timm et al. 2000). The San Clemente population could be as low as 410 adult foxes, down from a high of 800?900 foxes. The causes of this decline are not yet clear (Garcelon 1999; Roemer 1999); however, it has been suggested that management actions aimed at protecting the threatened San Clemente loggerhead shrike (Lanius ludovicianus mearnsi) may be a major factor in this decline (Cooper et al. 2001; Schmidt et al. 2002; Roemer and Wayne 2003). The San Nicolas population appears to be at high density (5.6?16.4 foxes/km²) and currently harbours one of the largest populations (estimate = 734 foxes; Roemer et al. 2001b). However, this estimate may be positively biased and the actual population size may be closer to 435 foxes (G. Smith pers. comm.).
All of the current estimates of density and population size in Island Foxes have been conducted using modifications of a capture-recapture approach (Roemer et al. 1994). In its simplest application, population size is determined by multiplying average density among sampling sites times island area. Population estimates could be improved by first determining habitat-specific estimates of density and multiplying these densities times the area covered by the specific habitat (Roemer et al. 1994), an approach amenable to analysis with geographical information systems. However, density estimates made from aggregating home ranges suggest that the use of capture-recapture data may also overestimate density. For example, fox density estimated at Fraser Point, Santa Cruz Island using the capture-recapture approach was 7.0 foxes/km² (Roemer et al. 1994). A simultaneous estimate of density based on the distribution of home ranges for 14 radio-collared foxes with overlapping home ranges was approximately 31% lower (4.8 foxes/km²) (Roemer 1999). Thus the size of island fox populations may be lower than current capture-recapture analyses suggest.
|Habitat and Ecology:||
Island Foxes occur in all habitats on the islands including native perennial and exotic European grassland, coastal sage scrub, maritime desert scrub, Coreopsis scrub, Isocoma scrub, chaparral, oak woodland, pine woodland, riparian and inland and coastal dune.
Although fox density varies by habitat, there is no clear habitat-specific pattern. When fox populations were dense, foxes could be trapped or observed in almost any of the island habitats, except for those that were highly degraded owing to human disturbance or overgrazing by introduced herbivores. More recently, foxes have become scarce owing to precipitous population declines. On the northern Channel Islands where the declines are principally a consequence of hyperpredation by Golden Eagles (Aquila chrysaetos) (Roemer et al. 2001a, 2002), foxes are more numerous in habitats with dense cover, including chaparral and introduced stands of fennel (Foeniculum vulgare) (G. Roemer, pers. obs.).
The current primary threats to the species include Golden Eagle predation on the northern Channel Islands (Roemer 1999; Roemer et al. 2001a, 2002) and the possible introduction of canine diseases, especially CDV, to all populations (Garcelon et al. 1992; Roemer 1999; Timm et al. 2000). All populations are small, several critically so, and are threatened by demographic stochasticity and environmental variability. The small populations are especially vulnerable to any catastrophic mortality source, be it predation, canine disease, or environmental extremes (Roemer et al. 2000).
Recently, there has also been a management conflict between island foxes and the San Clemente Island loggerhead shrike (Roemer and Wayne 2003). Island Foxes were euthanized on San Clemente Island in 1998 as part of a programme to protect nesting shrikes (Elliot and Popper 1999; Cooper et al. 2001). Although euthanasia of foxes has stopped, a number of foxes are now retained in captivity each year, during the nesting and fledging stage of the shrike, and subsequently released back into the environment. The impact to fox reproduction and the potential disruption of the social system are unknown, but may be significant. These actions may have contributed to a 60% decline in the fox population on San Clemente Island (Cooper et al. 2001; Schmidt et al. 2002; Roemer and Wayne 2003). Considering the precipitous declines in foxes on four of six islands and the continued decline in the San Clemente population, this current management practice needs further scrutiny.
Not included in CITES Appendices.
The species was formerly a category II candidate for federal listing, but is not currently listed by the U.S. Fish and Wildlife Service (USFWS) as threatened or endangered under the Federal Endangered Species Act. The species is listed by the state of California as a threatened species (California Department of Fish and Game 1987). The current legal status has not been sufficient to prevent recent catastrophic population declines. In June 2000, the USFWS was petitioned to list the populations on the three northern Channel Islands and Santa Catalina Island as endangered (Suckling and Garcelon 2000). The USFWS recently proposed to list these four subspecies as endangered (USDI 2001).
The three subspecies on the northern Channel Islands occur within the Channel Islands National Park. Approximately two-thirds of Santa Cruz Island is owned by The Nature Conservancy (TNC), and managed as the Santa Cruz Island Preserve. The Preserve is within the boundaries of the Channel Islands National Park, and the TNC and NPS (National Parks Service), co-manage natural resources together under a cooperative agreement. Approximately 87% of Santa Catalina Island is owned by the Santa Catalina Island Conservancy, a non-profit conservation organization, and both San Clemente and San Nicolas Islands are owned and managed by the U.S. Navy.
Based upon recommendations from an ad hoc recovery team, the Island Fox Conservation Working Group, the National Park Service (NPS) began initiating emergency actions in 1999, with the objectives being to remove the primary mortality factor currently affecting Island Foxes (Golden Eagle predation), and to recover populations to viable levels via captive breeding. Between November 1999 and June 2002, 22 eagles were removed from Santa Cruz Island and relocated to north-eastern California. In 1999, the NPS established an Island Fox captive breeding facility on San Miguel Island, added a second facility on Santa Rosa in 2000 and a third on Santa Cruz Island in 2002 (Coonan 2002, 2003; Coonan and Rutz 2000, 2002). Fourteen foxes were originally brought into captivity on San Miguel; current captive population is now 28. There are currently 45 foxes in captivity on Santa Rosa, and 12 adult foxes in the Santa Cruz facility that produced a single litter of five pups (Coonan 2002, 2003).
The NPS has prepared an Island Fox recovery plan for the northern Channel Islands (Coonan 2001) and an island-wide restoration plan for Santa Cruz Island (USDI 2002). The measures taken thus far on the northern Channel Islands (golden eagle removal and captive breeding) will form the basis for long-term recovery for the subspecies on the northern Channel Islands. In addition, the reintroduction of Bald Eagles (Haliaeetus leucocephalus), the eradication of feral pigs, and the removal of exotic plants have been recommended and are being implemented (Roemer et al. 2001a; USDI 2002). Demographic modelling indicates that recovery to viable population levels could take up to a decade (Roemer et al. 2000).
On Santa Catalina Island, The Santa Catalina Island Conservancy has taken a series of measures to mitigate the effects of canine distemper virus on that subspecies. Close to 150 foxes from the west end have been field-vaccinated for CDV and both translocation and captive breeding programmes have been established to aid in recolonizing the eastern portion of the island (Timm et al. 2000, 2002).
Although the Island Fox Conservation Working Group recognized the need for a species-wide recovery plan, there is currently no formal vehicle to accomplish such a planning effort, because the species is not listed under the Federal Endangered Species Act. Nonetheless, the Working Group recognized that the following actions need to be implemented in order to insure recovery of island fox populations to viable levels (Coonan 2002, 2003):
Complete removal of Golden Eagles from northern Channel Islands.
? Implement monitoring/response program for future golden eagles.
? Remove feral pigs from Santa Cruz Island.
? Reintroduce bald eagles to the northern Channel Islands.
? Eliminate canine distemper as a mortality factor on Santa Catalina Island.
? Vaccinate wild foxes against canine distemper virus, as needed.
? Monitor populations for diseases causing morbidity and mortality through necropsy and faecal and blood testing.
? Enforce no-dog policy on islands, and vaccinate working dogs.
? Educate the public about potential disease transmission from domestic dogs.
? Establish and maintain captive breeding facilities on San Miguel, Santa Rosa, Santa Cruz and Santa Catalina Islands.
? Supplement wild populations with captive-reared foxes.
? Implement annual population monitoring of each subspecies/population.
? Halt management actions to protect the San Clemente loggerhead shrike that are adversely affecting the San Clemente island fox.
? Develop adaptive management programme.
Island Foxes currently are kept in captivity on four islands. The National Park Service's captive breeding programme maintains facilities on San Miguel, Santa Rosa and Santa Cruz Islands, in which there are currently 28, 45 and 17 island foxes, respectively. The Santa Catalina Island Conservancy and the Institute for Wildlife Studies have established a captive breeding facility on that island, and there are currently 12 adult pairs of foxes there (Timm et al. 2002). Small numbers (1?4) of San Clemente Island foxes are kept in a total of four zoos on the mainland with a variable number of foxes held in captivity each year on that island (Cooper et al. 2001).
Gaps in knowledge
It is known that wild Island Fox pairs are unrelated and that extra-pair copulations occur (Roemer et al. 2001b), but little is known about how foxes select mates and whether mate choice could play a role in improving the currently low reproduction characterizing captive foxes (Coonan and Rutz 2002). Controlled mate-choice experiments are needed.
It has been suggested that intense predation by Golden Eagles could have altered Island Fox activity patterns and selected for greater nocturnal activity in those foxes that have survived predation (Roemer et al. 2002). The survival of the remaining wild Island Foxes on Santa Cruz Island is being monitored, but there has been no attempt to document daily activity levels (Dennis et al. 2001). The pattern of daily activity of wild Santa Cruz Island Foxes needs to be assessed, and compared to the activity of captive and captive-reared foxes that are released into the wild. If captive-reared foxes are more active during diurnal and crepuscular periods than their wild counterparts, it is probable that captive-reared foxes reintroduced into the wild will suffer higher mortality owing to Golden Eagle predation.
There has been only a single study that has examined dispersal in Island Foxes (Roemer et al. 2001b) and the number of dispersal events recorded was small (n=8). Additional information on Island Fox dispersal patterns on different islands and during periods of high and low density are needed.
|Citation:||Roemer, G.W., Fuller, T.K., List, R. & Wayne, R.K. (IUCN SSC Canid Specilaist Group - Island Fox Working Group) 2008. Urocyon littoralis. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 20 May 2013.|
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