Island gray fox
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Island gray fox ( Urocyon littoralis ) |
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| Urocyon littoralis | ||||||||||||
| ( Baird , 1857) |
The island gray fox or California island gray fox ( Urocyon littoralis ) is a species of gray fox . It only lives on six of the eight Channel Islands off the coast of California , making it an endemic species.
In North America , the island gray fox is the smallest of the native fox species. Worldwide only the fennec is smaller than this species.
features
height and weight
The island gray fox is much smaller than the mainland gray fox ; its size roughly corresponds to that of a house cat . The shoulder height is about 30 to 33 centimeters and the head body length about 48 to 50 centimeters, plus a tail length of 29 centimeters. In contrast, the mainland gray fox has a head body length of up to 68 centimeters and a tail length of up to 44 centimeters.
The island gray foxes weigh between 1.3 and 2.8 kilograms, with the male always being larger and heavier than the female. Of the six different subspecies, the largest lives on Santa Catalina , the smallest subspecies on Santa Cruz Island .
hide
The fur on the fox's back is gray; the sides of the body are rust-red. The lower abdomen, head and the lower half of the face, on the other hand, are colored white. The tip of the tail is black. In contrast to the gray fox, the coat is generally darker.
The hair change occurs in the months from August to November. Until they change their hair for the first time, the pups' fur is woolier and darker in color than that of the adult island gray foxes.
distribution
The range of the island gray fox is now limited to the six largest of the eight Channel Islands off the coast of California .
Way of life
Despite their relatively small size, the California Channel Islands contain a number of different habitats . These include oak and pine forests in the temperate climate zone , grass steppes and dune areas as well as shrub zones made up of sage species. The foxes used each of these habitats. However, they avoid open terrain on the islands, where they have been subject to heavy hunting by the golden eagle since the 1990s .
The foxes communicate with each other using sounds, visual signals and olfactory marks. They mark their territorial boundaries with urine and excrement, for example.
Island gray foxes show little fear of humans and are relatively easy to tame . This low shyness, which often occurs in island species, is due to the fact that they have had no contact with humans for a long time and thus do not perceive them as a threat.
nutrition
Their diet consists of fruits, insects , birds , eggs , crabs and small mammals. In their foraging, they usually rummage around the islands alone. The foxes are mostly diurnal, and their activity pattern varies depending on the season. During the winter months they also look for food at night. However, they are most actively foraging for food at dawn and dusk. One of the unusual characteristics of the island gray foxes is their predilection for climbing trees when foraging. They share this trait with the mainland gray fox .
Reproduction and Life Expectancy
Island gray foxes usually form monogamous pairs. From January, when the satchel season begins, the couples can often be observed together. The gestation period is between 33 and 50 days, so the puppies are born between late February and mid-March.
The female dog gives birth to between one and five puppies per litter in a den. The normal litter size consists of two to three puppies. The mother will suckle the puppies for seven to nine weeks. The puppies leave the den in early summer. The young foxes are sexually mature at the age of 10 months. The females usually mate before the end of their first year of life.
In the wild, island gray foxes reach an age of four to six years. They can live up to eight years in captivity.
Systematics and evolution
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Phylogenetic systematics of dogs
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The first scientific description of the island gray fox comes from Spencer Fullerton Baird from the year 1857. Baird described the species as Vulpes littoralis and assigned them to the genus Vulpes . The first description was based on an individual from San Miguel Island .
Today, the island gray fox and the gray fox form the genus Urocyon . On the basis of morphological and molecular biological data, both were categorized together as a sister group of all recent dogs, while in classical systematics they are usually assigned to the real foxes (Vulpini). This position as the sister group of all dogs was confirmed in 2012, whereby the ancestors of the gray foxes probably split off from those of all other dogs about 16.5 million years ago, but the separation into the two species known today only about a million years ago.
The island fox comes evolutionarily from the living on the North American mainland gray fox from. The small body size is a result of the island dwarfing . In the 1970s, the island gray fox was occasionally classified as a subspecies of the mainland gray fox. Due to the morphological and genetic differences to this fox species, the island fox is now generally regarded as an independent species.
Today a total of six subspecies of the island gray fox are distinguished. Each of these subspecies is native to one of California's six Channel Islands:
- Urocyon littoralis littoralis, which lives on the only 37.7 square kilometers large island of San Miguel
- Urocyon littoralis santarosae, which is native to the 213.6 square kilometer island of Santa Rosa
- Urocyon littoralis santacruzae, which lives on the 245.4 square kilometer Santa Cruz Island
- Urocyon littoralis catalinae, which is only found on Santa Catalina
- Urocyon littoralis clementae, which lives on the island of San Clemente
- Urocyon littoralis dickeyi, which is native to San Nicolas.
However, each subspecies has its own genetic and phenotypic characteristics that clearly distinguish it from the other subspecies. For example, each subspecies has a different number of caudal vertebrae.
Evolutionary history
The dwarfing of the island gray fox is an adaptation to the limited resources that are available on the islands.
It is believed that the foxes arrived on the three northern islands of San Miguel, Santa Cruz and Santa Rosa about 10,400 to 16,000 years ago. These three islands were apparently easy to reach from the mainland during the last ice age : During the ice age the sea level sank, so that the three islands of San Miguel, Santa Cruz and Santa Rosa formed a land mass and were only separated from the mainland by a small channel. The island gray foxes apparently only reached the islands of San Nicolas, Santa Catalina and San Clemente further away from the mainland. Many authors believe that Chumash Indians, who viewed the foxes as sacred animals, brought them to the islands as pets.
This assessment is also supported by fossils and the genetic distance to the gray fox on the mainland. Island gray foxes have apparently lived on San Clemente for 3,400 to 4,300 years, and on San Nicolas for around 2,200 years. The subspecies of the Santa Catalina foxes is probably the most recently developed subspecies, with estimates of when the foxes have been on this island differing widely. Depending on the author, the island population is believed to have been on Santa Catalina for 800 to 3,800 years.
The California Channel Islands include two other islands, on which, however, no fox populations have been able to develop. Anacapa Island has no reliable sources of fresh water, and Santa Barbara Island is too small to meet a fox's nutritional needs.
Inventory development
The population of the island gray fox is low. The fox species is therefore threatened like any other species with a small number of individuals due to natural demographic fluctuations and rapid environmental changes. Such a species is particularly endangered when extreme environmental changes, sudden epidemics and a sharp increase in predatory animals occur. In the island gray fox, each of these threatening factors has occurred in a very short time.
Decline in the population since 1994
In the early 1990s, there was a sharp decline in the island gray fox population. On the island of San Miguel, the population fell from 450 adults in 1994 to only 15 in 1999. Similar dramatic declines in the population were also found for the island of Santa Cruz, where the population fell from 2,000 adults to 135 in the same period . On Santa Rosa, where 1,500 animals were counted in 1994, only 14 adults lived in 2000.
In 2002 there were no more wild foxes on San Miguel and Santa Rosa. The number of individuals in these subspecies had increased to 28 (San Miguel) or 45 animals. However, these were kept in captivity and bred. Foxes have been bred in captivity on Santa Cruz since 2002, after the number of foxes living in the wild was estimated at only 60 to 80 individuals. The number of foxes living on San Clemente and San Nicolas is estimated to be just over four hundred each. How many foxes live on Santa Catalina is unknown as this island is privately owned.
Golden eagles as the cause of the population decline
Based on observations and telemetric examinations, it was found that the colonization of the Californian Channel Islands by the American golden eagle was the main cause of the sharp population decline. The island gray fox is ideal prey for the golden eagle due to its small size.
According to biologists, golden eagles have only been using the Channel Islands as a hunting ground since the 1990s. The first nest of golden eagles was not even discovered until 1999 on Santa Cruz Island. The islands have become attractive as a hunting ground for these eagles for two reasons. Feral domestic animals such as cats, pigs, sheep and goats are now at home on these islands and, together with the island gray fox, offer the eagles sufficient prey. At the same time, the stocks of bald eagles originally living here have declined sharply since the 1960s due to DDT contamination. The presence of bald eagles had prevented golden eagles from settling on the island, mainly because of the rivalry for nesting sites. The food competition between the two types of eagle is low, however, since bald eagles mainly live on fish.
Other causes of the decline in stocks
In addition to the increasing hunting by golden eagles, diseases and parasites introduced to the islands have also decimated the fox population. Due to their long isolation , the island gray foxes have not developed resistance to the parasites and diseases typical of canine species on the mainland. For example, an outbreak of rabies on the island of Santa Catalina in 1998 killed 90 percent of the remaining population. Habitat destruction caused by humans also contributes to the decline. The domestic animals, introduced by humans and now feral, make the islands not only attractive as hunting grounds for golden eagles, but also change the habitat of the islands so much that the foxes' food sources are endangered. The bison , which were released by a film team in the 1920s when they were filming a western on the island of Santa Catalina, also contributed to such a habitat change . In addition, the island gray foxes are in direct food competition with feral domestic cats .
Protective measures
Animal rights activists have been fighting to place four of the six subspecies under protection since 2000. In 2004 they were successful with this venture. Four of the subspecies have been legally protected as threatened species in the United States since 2004, and efforts are being made to increase the numbers and stabilize the Channel Islands ecosystem so that the species can continue to exist. The subspecies that are native to Santa Cruz, Santa Rosa, San Miguel and Santa Catalina are now protected. The IUCN listed the island gray foxes as an animal species with only a low degree of endangerment until 2004 and then changed the degree of endangerment to (after "extinct") the highest threat level critically endangered .
A number of measures have been taken to protect the island gray fox. The protective measures include the shooting of the domestic pigs on Santa Cruz and Catilina, which endangered the foxes' food sources and which attracted the golden eagle. The National Park Administration of the Channel Islands National Park has categorically prohibited the introduction of pets in order to rule out disease transmission. In addition, a breeding program has been established on San Miguel, Santa Rosa and Santa Cruz, for which the foxes are caught and bred in captivity. It is planned that the previously successful offspring will be released back into the wild. The threat posed by the golden eagle is currently preventing the release of the captive bred animals.
A key measure for the recovery of the island's gray foxes is the expulsion of the golden eagle from the Channel Islands. They are captured and released on the mainland. At the same time, attempts are being made to protect or increase the population of the bald eagle so that it displaces the golden eagle in the habitat of the Channel Islands. Both programs are very resource-intensive and therefore cost-intensive and therefore run the risk of being suspended again.
The protective measures proved to be successful. The population, which had shrunk to around 100 foxes on Santa Cruz, was 2150 animals in 2015. The United States Fish and Wildlife Service announced that it would remove three subspecies of the island gray fox from the list of endangered animals.
Island gray fox as a threat to a subspecies of the Louisiana strangler
A population of the critically endangered San Clemente shrike ( Lanius ludovicianus mearnsi ), a subspecies of the Louisiana shrike , lives on the island of San Clemente . This species of bird belongs to the range of prey of the island gray fox. The protection measures in favor of this bird species until the year 2000 included the capture and killing of island gray foxes by the United States Navy based on this island . Since conservationists have drawn attention to the grave threat to the island gray fox, the Navy has taken other measures to conserve the population of this shrike species. The new protective measures include trapping and imprisoning the foxes during the shrike's breeding season and installing electric fences around the shrike's breeding grounds. The IUCN points out, however, that the effect of the trapping campaigns on the reproductive behavior of the foxes may well have contributed to the fact that the number of individuals on this island has also decreased by 60 percent since the 1990s, and therefore calls for a review of this procedure.
supporting documents
- ↑ a b Urocyon littoralis in the IUCN Red List of Threatened Species 2012.2. Posted by: GW Roemer, TK Fuller, R. List, RK Wayne (IUCN SSC Canid Specialist Group - Island Fox Working Group), 2008. Retrieved April 28, 2013.
- ↑ a b Kerstin Lindblad-Toh et al .: Genome sequence, comparative analysis and haplotype structure of the domestic dog. Nature 438, December 2005; Page 803–819. ( Abstract ).
- ↑ a b c Don E. Wilson & DeeAnn M. Reeder (eds.): Urocyon littoralis ( Memento of March 7, 2016 in the Internet Archive ) in Mammal Species of the World. A Taxonomic and Geographic Reference (3rd ed).
- ^ A b Claybourne M. Moore, Paul W. Collins: Urocyon littoralis (Carnivora: Canidae) . In: Mammalian Species . tape 498 , 1995, pp. 1–7 ( full text [PDF; 907 kB ]). Full text ( Memento from April 30, 2015 in the Internet Archive )
- ↑ Katrin Nyakatura, Olaf RP Bininda-Emonds: Updating the evolutionary history of Carnivora (Mammalia): a new species-level supertree complete with divergence time estimates. BMC Biology 10, 2012. doi: 10.1186 / 1741-7007-10-12
- ↑ Christina Boser: Endangered Island Foxes Break Record for Fast Recovery. In: The Nature Conservancy. Retrieved December 23, 2018 .
literature
- Claybourne M. Moore, Paul W. Collins: Urocyon littoralis (Carnivora: Canidae) . In: Mammalian Species . tape 498 , 1995, pp. 1–7 ( full text [PDF; 907 kB ]).
- RK Wayne, et al. a .: A morphological and genetic study of the Island fox, "Urocyon littoralis". in: evolution. Lawrence Can 45, 1991, 1849-1868. ISSN 0014-3820
- PW Collins: Interaction between Island Foxes ("Urocyon littoralis") and Indians on islands off the coast of southern California. I Morphologic and archeological evidence of human assisted dispersal. in: Journal of Ethnobiology. Ariz, Flagstaff 1991-11, 51-82. ISSN 0278-0771
- DA Gilbert, et al. a .: Genetic fingerprinting reflects population differentiation in the California Channel Island fox. in: Nature . London 344.1991, 764-767. ISSN 0028-0836
- CM Morris, PW Collins: Urocyon littoralis. in: Mammalian Species . Washington DC 489. 1995, 1-7. ISSN 0076-3519
- GW Roemer, u. a .: Feral pigs facilitate hyperpredation by golden eagles and indirectly cause the decline of the island fox. In: Animal Conservation. Univ. Press, Cambridge 4. 2001, 307-318. ISSN 1367-9430
- GW Roemer, u. a .: Golden eagles, feral pigs, and insular carnivores: How exotic species turn native predators into prey. In PNAS 99, 2, 791–796, doi: 10.1073 / pnas.012422499 (full text)
- SG Kohlmann, among others: Island fox recovery efforts on Santa Catalina Island, California, October 2001 – October 2002. Annual Report. Ecological Restoration Department, Santa Catalina Island Conservancy, Avalon Cal 2003.
- TJ Coonan, et al .: Island fox recovery program 2003. Annual Report. National Park Service, Channel Islands 2004.
Web links
- Center for biological diversity
- Animal welfare petition
- Channel Islands National Park's Island Fox Home Page
- Catalina Island Conservancy: Catalina Island Fox
- Endangered and Threatened Wildlife and Plants; Proposed Designation of Critical Habitat for the San Miguel Island Fox, Santa Rosa Island Fox, Santa Cruz Island Fox, and Santa Catalina Island Fox. US Environmental Protection Agency 2004.
- Urocyon littoralis inthe IUCN 2012 Red List of Threatened Species . Posted by: GW Roemer, TK Fuller, R. List, RK Wayne (IUCN SSC Canid Specialist Group - Island Fox Working Group), 2008. Retrieved April 28, 2013.
