出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/11/14 16:24:10」(JST)
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| プレーリードッグ | ||||||||||||||||||||||||||||||
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オグロプレーリードッグ
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| Cynomys Rafinesque, 1817 | ||||||||||||||||||||||||||||||
| 和名 | ||||||||||||||||||||||||||||||
| プレーリードッグ | ||||||||||||||||||||||||||||||
| 英名 | ||||||||||||||||||||||||||||||
| prairie dog | ||||||||||||||||||||||||||||||
| 種 | ||||||||||||||||||||||||||||||
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プレーリードッグ (prairie dog) は、ネズミ目（齧歯類）リス科プレーリードッグ属の動物の総称。すべてが北米原産で、北米の草原地帯（プレーリー）に穴を掘って巣穴をつくり、群れで生活する。体長30-40cmほどで、毛色はおおむね淡い茶色。草食で、ムラサキウマゴヤシ（アルファルファ）、イネ科の植物を好む。プレリードッグとも呼ばれる。
雄1匹に対し、雌数匹という一夫多妻制で、コテリーと呼ばれる家族を形成する。なわばり意識が強く、他のコテリーの雄が進入してきた場合、互いにお尻の臭腺から臭いを出し威嚇し合う。なわばり争いでは敵対する雄を生き埋めにすることもある。稀に、埋められた穴の反対側から生還する個体もいる。また、口と口でキスをしたり、抱き合ったりすることで挨拶を交す。
巣穴は地中深く複雑になっており、出入り口も複数存在する。巣穴内の平均気温は年間を通し、15 °C前後といわれている。巣穴周辺の草がプレーリードッグの身長より高く育つと、プレーリードッグは視界確保のためにそれらを刈り取るため、草原が荒れることはない。刈り取ったあとにはやわらかく栄養価の高い草が伸びてくるため、コテリー周辺にはそれを求める動物が集まる。逆にプレーリードッグのいなくなった草原は荒れ、砂漠化が進む。
巣穴周辺には、巣を掘った際の土が積み上げられており、バッファロー等の土浴びの場として多くの動物が利用している。巣穴の入口周辺に土を盛り上げたマウントと呼ばれる見張り台を造り、歩哨のように立って見張りをする習性がある。コヨーテ、タカなどの天敵が近づくと、「キャンキャン」というイヌのような鳴き声を発して仲間に警告することから、プレーリードッグ（草原のイヌ）という名がついた。この鳴き声は情報量が多く、1秒程度の鳴き声に「接近する生物の種類（人間、タカなど）」「色」「大きさ」「だいたいの形」「脅威の程度」などの情報が入っていることが確認されている。なお、巣穴や見張りのシステムを利用して外敵から身を守るウサギなども数多く見出されている。
主にカロリーが低く繊維質の多いイネ科の牧草を食べ、付着した土や虫なども同時に食べることでミネラルの補給をする。同じ牧草でもマメ科のアルファルファは、カルシウムが多くカロリーも高いのでプレーリードッグの食物としては適さない。カルシウムが多い食物は尿管結石を作りやすいので注意が必要である。種子をはじめとしたカロリーの高い食物は嗜好性が高く、よく食べるが健康上は好ましくない。野生では降水の少ない地域に生息するため、水はあまり飲まずに食物から水分を摂取する。ただし、飼育環境ではその限りではない。
その姿の可愛らしさから日本では人気があり、一時期ペットとして輸入されていたが、ペスト、野兎病などの感染症を媒介するおそれがあり、2003年3月から輸入は禁止されている（現在、日本国内で販売されている個体は、輸入禁止以前の個体から国内で繁殖されたものである）。ただし、これらの感染症に対してプレーリードッグは弱く、感染してから発症、死亡に至るまで長くとも数週間である。そのため、感染源から隔離されている状態で、その期間以上健常な個体からは感染の危険はない。そのため、2008年8月に米FDAにて輸出禁止を解除する方針が示された。ただし、日本国内への輸入に関しては未だ禁止の状態である。
アメリカなどでは、牧草地において家畜が巣穴で足を折るなどした事故や、入植者たちの畑を荒らしたことなどから害獣扱いされてきた。また、町外れに作られた野球場が巣穴でぼろぼろになったなどの話が各地に残る。そのため、アメリカなどでは駆除対象として扱われる種もある。大規模な駆除の多くは毒物により行われ、現在でも毒ガスが用いられることがある[要出典]。駆除によりプレーリードッグを捕食してきたクロアシイタチが絶滅寸前に追い込まれ、現在レッドリストへ登録されている。生きたまま駆除する場合には、巣穴にホースを差し込んでプレーリードッグを吸い出す掃除機のような機械が開発されている。その機械の影響で、手足を失ったり、死亡する個体も多い。また最近では草原の生態系の重要な一部を成す存在として保護が進んでいる地域もあるが、そもそも崩れたバランスの中での保護のあり方に模索が続いている。
オグロプレーリードッグの2000年代の個体数は1842万頭であり、やや減少傾向にある[1]。
| ウィキメディア・コモンズには、プレーリードッグに関連するメディアおよびカテゴリがあります。 |
| ウィキスピーシーズにプレーリードッグに関する情報があります。 |
| この項目は、動物に関連した書きかけの項目です。この項目を加筆・訂正などしてくださる協力者を求めています（Portal:生き物と自然／プロジェクト:生物）。 |
| Prairie dogs Temporal range: Late Pliocene-Holocene |
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| Black-tailed prairie dog at the Smithsonian National Zoo Park in Washington, D.C. | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Rodentia |
| Family: | Sciuridae |
| Tribe: | Marmotini |
| Genus: | Cynomys Rafinesque, 1817 |
| Species | |
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Cynomys gunnisoni |
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Prairie dogs (genus Cynomys) are herbivorous burrowing rodents native to the grasslands of North America. The five species are: black-tailed, white-tailed, Gunnison's, Utah, and Mexican prairie dogs. They are a type of ground squirrel, found in the United States, Canada and Mexico. In Mexico, prairie dogs are found primarily in the northern states, which lie at the southern end of the Great Plains: northeastern Sonora, north and northeastern Chihuahua, northern Coahuila, northern Nuevo León, and northern Tamaulipas. In the United States, they range primarily to the west of the Mississippi River, though they have also been introduced in a few eastern locales. Despite the name, they are not canines.
Prairie dogs are named for their habitat and warning call, which sounds similar to a dog's bark.[1] The name was in use at least as early as 1774.[2] The 1804 journals of the Lewis and Clark Expedition note that in September 1804, they "discovered a Village of an animal the French Call the Prairie Dog".[3] Its genus, Cynomys, derives from the Greek for "dog mouse".
The black-tailed prairie dog (Cynomys ludovicianus) was first described by Lewis and Clark in 1804.[3] Lewis described it in more detail in 1806, calling it the "barking squirrel".[4]
On average, these stout-bodied rodents will grow to be between 30 and 40 cm (12 and 16 in) long, including the short tail, and weigh between 0.5 and 1.5 kilograms (1 and 3 lb). Sexual dimorphism in body mass in the prairie dog varies 105 to 136% between the sexes.[5] Among the species, black-tailed prairie dogs tend to be the least sexually dimorphic, and white-tailed prairie dogs tend to be the most sexually dimorphic. Sexual dimorphism peaks during weaning, when the females lose weight and the males start eating more, and is at its lowest when the females are pregnant, which is also when the males are tired from breeding.
Prairie dogs are chiefly herbivorous, though they eat some insects. They feed primarily on grasses and small seeds. In the fall, they eat broadleaf forbs. In the winter, lactating and pregnant females supplement their diets with snow for extra water.[6] They also will eat roots, seeds, fruit, and buds. Grasses of various species are eaten. Black-tailed prairie dogs in South Dakota eat western bluegrass, blue grama, buffalo grass, six weeks fescue, and tumblegrass,[6] while Gunnison’s prairie dogs eat rabbit brush, tumbleweeds, dandelions, saltbush, and cacti in addition to buffalo grass and blue grama. White-tailed prairie dogs have been observed to kill ground squirrels, a competing herbivore.[7][8]
Prairie dogs live mainly at altitudes ranging from 2,000 to 10,000 ft above sea level.[9] The areas where they live can get as warm as 38 °C (100 °F) in the summer and as cold as −37 °C (−35 °F) in the winter.[9] As prairie dogs live in areas prone to environmental threats, including hailstorms, blizzards, and floods, as well as drought and prairie fires, burrows provide important protection. Burrows help prairie dogs control their body temperature (Thermoregulation) as they are 5–10 °C during the winter and 15–25 °C in the summer. Prairie dog tunnel systems channel rainwater into the water table which prevents runoff and erosion, and can also change the composition of the soil in a region by reversing soil compaction that can result from cattle grazing.
Prairie dog burrows are 5–10 m (16–33 ft) long and 2–3 m (6.6–9.8 ft) below the ground.[10] The entrance holes are generally 10–30 cm (3.9–11.8 in) in diameter.[10] Prairie dog burrows can have up to six entrances. Sometimes the entrances are simply flat holes in the ground, while at other times they are surrounded by mounds of soil either left as piles or hard packed.[10] Some mounds, known as dome craters, can be as high as 0.2–0.3 m (7.9–11.8 in) high. Other mounds, known as rim craters, can be as high as 1 m.[10] Dome craters and rim craters serve as observation posts used by the animals to watch for predators. They also protect the burrows from flooding. The holes also possibly provide ventilation as the air enters through the dome crater and leaves through the rim crater, causing a breeze though the burrow.[10] Prairie dog burrows contain chambers to provide certain functions. They have nursery chambers for their young, chambers for night, and chambers for the winter. They also contain air chambers that may function to protect the burrow from flooding[9] and a listening post for predators. When hiding from predators, prairie dogs use less-deep chambers that are usually a meter below the surface.[10] Nursery chambers tend to be deeper, being two to three meters below the surface.[10]
Highly social, prairie dogs live in large colonies or "towns", and collections of prairie dog families that can span hundreds of acres. The prairie dog family groups are the most basic units of its society.[10] Members of a family group inhabit the same territory.[5] Family groups of black-tailed and Mexican prairie dogs are called "coteries", while "clans" are used to describe family groups of white-tailed, Gunnison’s, and Utah prairie dogs.[5] Although these two family groups are similar, coteries tend to be more closely knit than clans.[11] Members of a family group interact through oral contact or "kissing" and grooming one another.[9][10] They do not perform these behaviors with prairie dogs from other family groups.[10]
A prairie dog town may contain 15–26 family groups.[10] There may also be subgroups within a town, called "wards", which are separated by a physical barrier. Family groups exist within these wards. Most prairie dog family groups are made up of one adult breeding male, two to three adult females and one to two male offspring and one to two female offspring. Females remain in their natal groups for life and are thus the source of stability in the groups.[10] Males leave their natal groups when they mature to find another family group to defend and breed in. Some family groups contain more breeding females than one male can control, so have more than one breeding adult male in them. Among these multiple-male groups, some may contain males that have friendly relationships, but the majority contain males that have largely antagonistic relationships. In the former, the males tend to be related, while in the latter, they tend to not be related. Two to three groups of females may be controlled by one male. However, among these female groups, there are no friendly relations.[10]
The average prairie dog territory takes up 0.05–1.01 hectares. Territories have well-established borders that coincide with physical barriers such as rocks and trees.[10] The resident male of a territory defends it and antagonistic behavior will occur between two males of different families to defend their territories. These interactions may happen 20 times per day and last five minutes. When two prairie dogs encounter each other at the edges of their territories, they will start staring, make bluff charges, flare their tails, chatter their teeth, and sniff each other's perianal scent glands. When fighting, prairie dogs will bite, kick and ram each other.[10] If their competitor is around their size or smaller, the females will participate in fighting. Otherwise, if a competitor is sighted, the females signal for the resident male.
Prairie dog copulation occurs in the burrows, and this reduces the risk of interruption by a competing male. They are also at less risk of predation. Behaviors that signal that a female is in estrus include underground consorting, self-licking of genitals, dust-bathing, and late entrances into the burrow at night.[12] The licking of genitals may protect against sexually transmitted diseases and genital infections,[12] while dust-bathing may protect against fleas and other parasites. Prairie dogs also have a mating call which consists of a set of 2 to 25 barks with a 3- to 15-second pause between each one.[12] Females may try to increase their reproduction success by mating with males outside their family groups. When copulation is over, the male is no longer interested in the female sexually, but will prevent other males from mating with her by inserting copulatory plugs.[12]
For black-tailed prairie dogs, the resident male of the family group fathers all the offspring.[13] Multiple paternity in litters seems to be more common in Utah and Gunnison’s prairie dogs.[11] Mother prairie dogs do most of the care for the young. In addition to nursing the young, the mother also defends the nursery chamber and collects grass for the nest. Males play their part by defending the territories and maintaining the burrows.[10] The young spend their first six weeks below the ground being nursed.[9] They are then weaned and begin to surface from the burrow. By five months, they are fully grown.[9] The subject of cooperative breeding in prairie dogs has been debated among biologists. Some argue prairie dogs will defend and feed young that are not theirs,[14] and it seems young will sleep in a nursery chamber with other mothers; since most nursing occurs at night, this may be a case of communal nursing.[10] In the case of the latter, others suggest communal nursing occurs only when mothers mistake another female's young for their own. Infanticide is known to occur in prairie dogs. Males which take over a family group will kill the offspring of the previous male.[10] This causes the mother to go into estrus sooner.[10] However, most infanticide is done by close relatives.[10] Lactating females will kill the offspring of a related female both to decrease competition for the female’s offspring and for increased foraging area due to a decrease in territorial defense by the victimized mother. Supporters of the theory that prairie dogs are communal breeders state that another reason for this type of infanticide is so that the female can get a possible helper. With their own offspring gone, the victimized mother may help raise the young of other females.
The prairie dog is well adapted to predators. Using its dichromatic color vision, it can detect predators from a great distance; it then alerts other prairie dogs of the danger with a special, high-pitched call. Constantine Slobodchikoff and others assert that prairie dogs use a sophisticated system of vocal communication to describe specific predators.[15] According to them, prairie dog calls contain specific information as to what the predator is, how big it is and how fast it is approaching. These have been described as a form of grammar. According to Slobodchikoff, these calls, with their individuality in response to a specific predator, imply that prairie dogs have highly developed cognitive abilities.[15] He also writes that prairie dogs have calls for things that are not predators to them. This is cited as evidence that the animals have a very descriptive language and have calls for any potential threat.[15]
Alarm response behavior varies according to the type of predator announced. If the alarm indicates a hawk diving toward the colony, all the prairie dogs in its flight path dive into their holes, while those outside the flight path stand and watch. If the alarm is for a human, all members of the colony immediately rush inside the burrows. For coyotes, the prairie dogs move to the entrance of a burrow and stand outside the entrance, observing the coyote, while those prairie dogs that were inside the burrows will come out to stand and watch as well. For domestic dogs, the response is to observe, standing in place where they were when the alarm was sounded, again with the underground prairie dogs emerging to watch.[15]
There is debate over whether the alarm calling of prairie dogs is selfish or altruistic. It is possible that prairie dogs alert others to the presence of a predator so they can protect themselves. However, it is also possible that the calls are meant to cause confusion and panic in the groups and cause the others to be more conspicuous to the predator than the caller. Studies of black-tailed prairie dogs suggest that alarm-calling is a form of kin selection, as a prairie dog’s call alerts both offspring and nondescended kin, such as cousins, nephews and nieces.[10] Prairie dogs with kin close by called more often than those that did not have kin nearby. In addition, the caller may be trying to make itself more noticeable to the predator.[10] Predators, though, seem to have difficulty determining which prairie dog is making the call due to its "ventriloquistic" nature.[10]
Perhaps the most striking of prairie dog communications is the territorial call or "jump-yip" display of the black-tailed prairie dog.[16] A black-tailed prairie dog will stretch the length of its body vertically and throw its forefeet into the air while making a call. A jump-yip from one prairie dog causes others nearby to do the same.[17]
Ecologists consider this rodent to be a keystone species. They are an important prey species, being the primary diet in prairie species such as the black-footed ferret, swift fox, golden eagle, American badger, and ferruginous hawk. Other species, such as the mountain plover and the burrowing owl, also rely on prairie dog burrows for nesting areas. Even grazing species, such as plains bison, pronghorn, and mule deer have shown a proclivity for grazing on the same land used by prairie dogs.[18]
Nevertheless, prairie dogs are often identified as pests and exterminated from agricultural properties because they are capable of damaging crops, as they clear the immediate area around their burrows of most vegetation.[19]
As a result, prairie dog habitat has been affected by direct removal by farmers, as well as the more obvious encroachment of urban development, which has greatly reduced their populations. The removal of prairie dogs "causes undesirable spread of brush", the costs of which to livestock range may outweigh the benefits of removal.[20] Black-tailed prairie dogs comprise the largest remaining community.[citation needed] In spite of human encroachment, prairie dogs have adapted, continuing to dig burrows in open areas of western cities.[21]
One common concern which led to the widespread extermination of prairie dog colonies was that their digging activities could injure horses[22] by fracturing their limbs. However, according to writer Fred Durso, Jr., of E Magazine, "after years of asking ranchers this question, we have found not one example."[23] Another concern is their susceptibility to bubonic plague.[24] As of July 2016[update] the U.S. Fish and Wildlife Service plans to distribute an oral vaccine it had developed by unmanned aircraft or drones.[25]
Until 2003, primarily black-tailed prairie dogs were collected from the wild for the exotic pet trade in Canada, the United States, Japan, and Europe. They were removed from their underground burrows each spring, as young pups, with a large vacuum device.[26] They can be difficult to breed in captivity,[27] but breed well in zoos. Removing them from the wild was a far more common method of supplying the market demand.[citation needed]
They can be difficult pets to care for, requiring regular attention and a very specific diet of grasses and hay. Each year, they go into a period called rut that can last for several months, in which their personalities can drastically change, often becoming defensive or even aggressive. Despite their needs, prairie dogs are very social animals and come to seem as though they treat humans as members of their colony, answering barks and chirps, and even coming when called by name.[citation needed]
In mid-2003, due to cross-contamination at a Madison, Wisconsin-area pet swap from an unquarantined Gambian pouched rat imported from Ghana, several prairie dogs in captivity acquired monkeypox, and subsequently a few humans were also infected. This led the CDC and FDA to issue a joint order banning the sale, trade, and transport within the United States of prairie dogs (with a few exceptions).[28] The disease was never introduced to any wild populations. The European Union also banned importation of prairie dogs in response.[29] While largely seen by exotic pet owners[who?] and vendors[who?] as unfair, the monkeypox scare was not the only zoonosis incident associated with prairie dogs.[citation needed]
All Cynomys species are classed as a "prohibited new organism" under New Zealand's Hazardous Substances and New Organisms Act 1996, preventing it from being imported into the country.[30]
Prairie dogs are also very susceptible to bubonic plague, and many wild colonies have been wiped out by it.[31][32][33][34] Also, in 2002, a large group of prairie dogs in captivity in Texas were found to have contracted tularemia.[35] The prairie dog ban is frequently cited by the CDC as a successful response to the threat of zoonosis.[citation needed]
Prairie dogs that were in captivity at the time of the ban in 2003 were allowed to be kept under a grandfather clause, but were not to be bought, traded, or sold, and transport was permitted only to and from a veterinarian under quarantine procedures.[citation needed]
On 8 September 2008, the FDA and CDC rescinded the ban, making it once again legal to capture, sell, and transport prairie dogs.[36] Although the federal ban has been lifted, several states still have in place their own ban on prairie dogs.[citation needed]
The European Union did not take action on the ban to import from the U.S. animals captured in the wild, which remains valid. Major European Prairie Dog Associations, such as AICDP[who?], remain against import from the United States, due to the high death rate of wild captures [37][38] Several zoos in Europe have stable prairie dog colonies that generate enough supernumerary pups to saturate the EU internal demand, and several associations help owners to give adoption to captivity-born animals[citation needed].
Prairie dogs in captivity may live up to ten years.[citation needed]
In companies that use large numbers of cubicles in a common space, employees sometimes use the term "prairie dogging" to refer to the action of several people simultaneously looking over the walls of their cubicles in response to a noise or other distraction. This action is thought to resemble the startled response of a group of prairie dogs.[41]
| Wikimedia Commons has media related to Cynomys |
Living species of tribe Marmotini (ground squirrels)
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| Ammospermophilus (antelope squirrels) |
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| Callospermophilus (golden-mantled ground squirrels) |
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| Cynomys (prairie dogs) |
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| Eutamias |
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| Ictidomys (little ground squirrels) |
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| Marmota (marmots) |
Subgenus Marmota: Gray marmot (M. baibacina)
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| Neotamias (western chipmunks) |
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| Notocitellus |
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| Otospermophilus (rock squirrels) |
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| Poliocitellus |
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| Sciurotamias (Asian rock squirrels) |
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| Spermophilus sensu stricto (Old World ground squirrels) |
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| Tamias |
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| Urocitellus (Holarctic ground squirrels) |
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| Xerospermophilus (pygmy ground squirrels) |
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Category
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| Taxon identifiers |
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| Authority control |
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| リンク元 | 「Spermophilus」「chipmunk」「squirrel」「Sciuridae」 |
| 関連記事 | 「do」「dog」 |