Prairie dogs
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Prairie dogs in the Zurich Zoo |
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| Rafinesque , 1817 |
Prairie dogs ( Cynomys ) are a North American genus of ground squirrels . They are related to the marmots and the ground squirrel .
features
The plump body, short legs, and short tail give the prairie dogs a vaguely marmot-like appearance. Prairie dogs have a head body length of 30–35 cm and a weight of 800–1400 g. Males are on average slightly larger and 10% heavier than females.
The fur is gray-brown in color and a bit darker on the top than on the underside. Black-tailed and Mexican Prairie Dogs have black-tipped tails, while White-tailed, Gunnison, and Utah Prairie Dogs have white-tipped tails. In addition, the species are very difficult to distinguish. The shape and size of the molars and the type of vocalizations are among the few characteristics that can be used to distinguish the species.
Way of life
Prairie dogs live on the prairies of North America . The habitat must have short or medium-length grass and dry soil.
As diurnal animals , prairie dogs stay in their self-dug burrows at night. The tunnels are about 10 to 15 cm wide and can reach a maximum length of 34 m. They lead to nest chambers, which have an extension of about 40 cm, are laid out with grass and 1 to 5 m below the surface of the earth. The earth dug when digging is piled up around the entrances so that no water can run into them in the event of flooding. A prairie dog den usually only has one or two entrances, in rare cases up to six.
The white-tailed prairie dog hibernates for six months . The black-tailed prairie dog, on the other hand, is active all year round and comes outside even when it is snowy. Prairie dogs feed on plants , especially grasses . The plants in the vicinity of the burrow are kept short, which allows the prairie dogs a broad overview.
Life in Colonies
Four of the five prairie dog species live in complex colonies with a high degree of social organization. The only exception is the white-tailed prairie dog, whose colonies are more like those of many ground squirrels . They are smaller and less organized. Usually only one female and her young live in a burrow; other members of the colony have their own burrows. The social bonds between group members are low.
The following information describes the social life of the black-tailed prairie dog. Much should also apply to the Mexican, Gunnison and Utah prairie dogs. These species are less well researched, but have similarly complex, albeit smaller, colonies.
The colonies of the black-tailed prairie dog are divided into individual family groups. An association usually consists of a full-grown male, three or four females and a large number of young and juvenile animals of both sexes. It can contain up to 26 individuals in total. In some cases more than one male can belong to an association. These are usually pairs of brothers.
Females born in a union stay there, so all females in a group are related to one another. Males, on the other hand, have to leave the association before they reach the age of two. You then try to take control of another association. In order to avoid inbreeding , the adult males also change their association annually; if they fail to do so, the females ultimately refuse to mate with them.
The individual associations together form a colony made up of hundreds of animals. Often these colonies are referred to as "prairie dog towns". In the 19th century, Texas is said to have had a prairie dog town that covered an area of 65,000 km² and consisted of 400 million people. The largest prairie dog town today is located in the northwest of the Mexican state Chihuahua , covers 350 km² and has more than 1 million inhabitants. There is no social interaction between the associations in a city; on the contrary, each association defends its borders against its neighbors.
A joint rearing of the young does not take place. Each female only takes care of her own young and becomes extremely aggressive during gestation and lactation. Mutual attacks often occur within the colony, with the females trying to kill and eat the young of other dams. In this way, almost 40% of all young animals in a colony die. No comparable behavior is known from any other mammal. The advantage is obviously that the offspring of the strongest mothers ultimately survive. Males behave peaceably towards all the young in their colony and try to defend them.
Mating takes place between January and April, depending on the species and geographical latitude. It is being carried out under construction. The willingness to mate can be seen in certain behaviors: Both partners lick their genitals, they use the same burrow, and the males collect nesting material that they put into this burrow. Young animals are born after a gestation period of 35 days. There can be up to eight cubs in a litter, who are 7 cm tall and 15 g weight at birth and are naked and blind. The fur forms at three weeks of age, the eyes open after six weeks. The young are suckled for 40 to 50 days, then they leave their den for the first time. As soon as they are independent enough to go outside and look for food, the young are in danger of being killed by other mothers. Lifespan can be over eight years in captivity but is usually shorter in the wild.
Systematics
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Phylogenetic systematics of the Marmotini according to Herron et al. 2004
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The prairie dogs are a genus of squirrels , where they are assigned to the ground squirrels (Xerinae) and therein the real ground squirrels (Xerini). The first scientific description of the genus was made by Constantine S. Rafinesque-Schmaltz in 1817.
The prairie dogs were confirmed as a monophyletic group in a molecular biological study in 2004 and identified as a sister group of the entire Marmotini with the exception of the genus Xerospermophilus originally assigned to the ground squirrel . The Franklin ground squirrel ( Poliocitellus franklinii ) is the common sister species of this taxon formed from the two groups .
Five species are known from the prairie dog genus :
- Gunnison's Prairie Dog ( Cynomys gunnisoni ), Utah , Colorado , Arizona , New Mexico
- White-tailed prairie dog ( Cynomys leucurus ), Wyoming , Colorado
- Black-tailed prairie dog ( Cynomys ludovicianus ), prairies from Saskatchewan to the central United States to Chihuahua
- Mexican prairie dog ( Cynomys mexicanus ), Coahuila , San Luis Potosí
- Utah Prairie Dog ( Cynomys parvidens ), Utah
The first two of these species are often grouped together in a subgenus Cynomys , the last three in Leucocrossuromys .
etymology
Prairie dogs are named for their habitat and for their warning call, which is similar to a dog's bark. The name was not used until 1774 at the earliest , according to the Online Etymology Dictionary . The reports of the Lewis and Clark expedition state that it reached "a village of animals, which the French call prairie dogs" in September 1804.
The scientific name Cynomys means "dog mouse" in Greek , which refers to the mouse-like way of life.
Humans and prairie dogs
Although prairie dogs were never rare, according to consistent reports they experienced an almost explosive increase in numbers at the end of the 19th century. White settlers decimated the natural enemies of the prairie dogs and introduced domestic cattle , who ensured that the vegetation was kept short, which made the habitat particularly favorable for prairie dogs. By 1900 there were believed to have been approximately 5 billion black-tailed prairie dogs on U.S. territory, which were increasingly viewed as a serious threat to agriculture as they attacked fields of grain and vegetables. At the beginning of the 20th century, the US government organized an extermination campaign: food mixed with strychnine was laid out on a massive scale, causing populations everywhere to collapse. In Texas alone, 99.8% of the prairie dogs living there were killed within a few years; in other states the numbers were comparable. Today the black-tailed prairie dog is considered to be at low risk. With an end to poisoning and the protective measures that followed, the US species are now quite common again. The Utah Prairie Dog, which was considered endangered until 1996, has since been listed in the IUCN Red List as “dependent on protective measures” following an effective protection program . The Mexican Prairie Dog, on the other hand, is endangered as it is still exposed to persecution and poisoning and its natural habitat is being destroyed by the spread of agriculture.
Some Indian peoples used to eat prairie dogs. Today they are sometimes used as laboratory animals and are enjoying increasing popularity as pets, although they can hardly be kept appropriately . The prairie dog cities are popular tourist destinations in the US west.
Meriwether Lewis , who explored the North American West together with William Clark on behalf of President Thomas Jefferson , called the prairie dog "Barking Squirrel". He was trying to dig up a prairie dog alive as a gift for the president. Since this did not succeed because of the depth of the construction, he had the cave flooded and was able to catch a prairie dog. The prairie dog then lived in the White House for some time.
The importance of prairie dogs as vectors of disease has mostly been exaggerated to provide rationale for the eradication campaigns. Still, prairie dogs are possible carriers of the plague in some regions of the southwestern United States . In 2003 there was a high-profile monkeypox epidemic in the United States that was actually spread by prairie dogs. The culprits here were African giant hamster rats who had run away from pet shops and had transmitted the infection to the prairie dogs.
Others
The extensive persecution of the prairie dogs has also led to the almost complete extermination of the black-footed pelvis, 90% of which feed on these animals. The polecats became extinct in the wild in the 1980s and only survived thanks to a breeding program. Other enemies of the prairie dogs include coyotes , silver badgers , rattlesnakes and birds of prey .
While long as the ground squirrel for the sister group held the prairie dogs, ground squirrels only the sub-genre seems truly Spermophilus Schwestertaxon to be the prairie dogs.
Prairie dogs play a key role in the prairie habitat: Through their underground construction activities, they not only offer other prairie inhabitants such as owls and snakes protection and breeding opportunities, they also loosen the soil that has been compressed by bison and fertilize it by introducing grass into the subsoil. In winter the lower corridors of the buildings are full of water and store it for a long time; This means that many plants can thrive even in summer with little rain and thus provide food for many animals.
For Gunnison's prairie dog ( Cynomys gunnisoni ) it has been proven that these animals have unusually highly differentiated communication skills. Accordingly, they each utter different warning calls when a falcon , a domestic dog , a coyote or a person approaches. Furthermore, the warning calls when small people approach differ from those when tall people approach. Finally, it was possible to prove in an experiment that - with otherwise the same external appearance - a person with a green T-shirt approaching is warned by different calls than when a person is seen in a blue T-shirt.
literature
- John L. Hoogland: The Black-Tailed Prairie Dog. Social Life of a Burrowing Mammal. University of Chicago Press, Chicago IL 1995, ISBN 0-226-35118-1 .
- Ronald M. Nowak: Walker's Mammals of the World. 2 volumes. 6th edition. Johns Hopkins University Press, Baltimore MD et al. 1999, ISBN 0-8018-5789-9 .
- Christian Ehrlich: Prairie dogs. Biology, husbandry, breeding. NTV, Münster 2004, ISBN 3-931587-97-5 .
- John L. Hoogland (Ed.): Conservation of the Black-Tailed Prairie Dog. Saving North America's Western Grasslands. Island Press, Washington DC et al. 2006, ISBN 1-55963-498-7 .
Individual evidence
- ^ A b Matthew D. Herron, Todd A. Castoe, Christopher L. Parkinson: Sciurid phylogeny and the paraphyly of holarctic ground squirrels (Spermophilus). Molecular Phylogenetics and Evolution 31, 2004; Pp. 1015-1030. ( doi : 10.1016 / j.ympev.2003.09.015 , full text , PMID 15120398 )
- ^ Online Etymology Dictionary, prairie .
- ^ Journals of the Lewis and Clark expedition, "7th September Friday 1804. a verry Cold morning" ( Memento from February 1, 2009 in the Internet Archive )
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↑ CN Slobodchikoff, Andrea Paseka, Jennifer L. Verdolin: Prairie dog alarm calls encode labels about predator colors. In: Animal Cognition. Vol. 12, No. 3, 2009, ISSN 1435-9448 , pp. 435-439, doi : 10.1007 / s10071-008-0203-y .
newscientist.com of May 13, 2009 (identical to New Scientist No. 2707 of May 9, 2009): Prairie dogs issue warnings in glorious technicolor.
Web links
- Prairie dog ( Memento from August 24, 2014 in the Internet Archive )
- Prairie Dog Community (German)
