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Sciurini

Sciurini is a tribe that includes about forty species of squirrels,[2] mostly from the Americas. It includes five living genera—the American dwarf squirrels, Microsciurus; the Bornean Rheithrosciurus; the widespread American and Eurasian tree squirrels of the genus Sciurus, which includes some of the best known squirrel species; the Central American Syntheosciurus; and the American red squirrels, Tamiasciurus. Like other arboreal squirrels, they are sometimes referred to as tree squirrels.[3]

Taxonomy[edit]

The name "Sciurini" was first employed by Hermann Burmeister in 1854, who used it for the entire squirrel family.[4] In his influential 1945 classification of mammals, George Gaylord Simpson included four genera of squirrels in Sciurini, which he recognized as one of eight tribes within the subfamily Sciurinae (including all squirrels except the flying squirrels): Sciurus, Syntheosciurus, Microsciurus, and Sciurillus. He also classified Rheithrosciurus as "?Sciurini incertae sedis" (of uncertain placement).[5] This grouping derives from Reginald Innes Pocock, who united these squirrels in 1923 as the subfamily Sciurinae.[6]

In 1959, Joseph Curtis Moore published a review of the interrelationships of the squirrels. His definition of Sciurini was similar to Simpson's, but he no longer considered Rheithrosciurus to be incertae sedis. He noted that the members of Sciurini were united only by the possession of a special type of baculum (penis bone).[7] He also divided the tribe into subtribes, producing the following classification:[8]

In their 1997 update to Simpson's classification, McKenna and Bell retained a similar definition for Sciurini, but also included several extinct genera, as follows:[10]

Sciuridae

Sciurillus



Ratufa


  

Callosciurinae



Xerinae


Sciurinae

Pteromyini


Sciurini

Tamiasciurus



Sciurus[fn 1]






Phylogeny of the squirrels.[12]

In the early 2000s, several studies were published using DNA sequences to study the interrelationships of squirrels. Two, published in 2003 and 2004 and both based on several different genes, produced largely concordant results, concluding that Sciurillus is not related to other Sciurini, but rather forms one of the most distinctive lineages of all squirrels; that Tamiasciurus is the closest relative to the other Sciurini; and that the group of Tamiasciurus and the other Sciurini is most closely related to the flying squirrels.[12] The authors of the 2004 study formalized these results into a revised classification of squirrels. They removed Sciurillus from Sciurini, placed Tamiasciurus in it, and classified Sciurini with the flying squirrels (tribe Pteromyini) in a subfamily Sciurinae.[13] Their classification was adopted in the 2005 third edition of Mammal Species of the World[2] and remains current.

The same studies also provided insights into the interrelationships of genera within Sciurini. Microsciurus, Syntheosciurus, and Rheithrosciurus all appear among the various species of Sciurus included, making the latter genus paraphyletic; additionally, the two species of Microsciurus included in Mercer and Roth's 2003 study did not cluster with each other.[12] A morphological study of Central American Sciurini also found that Microsciurus and Syntheosciurus are part of the Sciurus radiation, and suggested that Syntheosciurus be lumped into Sciurus while further work is needed on Microsciurus.[14] In a 2008 monograph on Brazilian rodents, Bonvicino and others considered Guerlinguetus and Urosciurus, conventionally placed in Sciurus, as separate genera.[15]

Fossil history[edit]

Douglassciurus, a fossil from the late Eocene (about 36 million years ago) of Wyoming, Montana, and Saskatchewan, is so similar to living Sciurus that the latter has been considered a living fossil.[16] but some exclude this animal from the squirrel family because of several primitive characters.[17] Emry and Korth, who re-described the animal in 1996, classified it within Sciurini[1] and speculated that other squirrels may have evolved from animals similar to Sciurini squirrels.[18] The Oligocene to early Miocene North American genera Protosciurus and Miosciurus are classified in Sciurini and may have given rise to the earliest known member of Sciurus, S. olsoni from the early late Miocene (about 10 million years ago) of Nevada. In Europe, Sciurus first appears early in the Pliocene. The 2005 discovery of S. olsoni provided evidence that the origin of the Sciurini lies in North America.[19]

A Miocene squirrel from France and Spain, Freudenthalia, has been tentatively placed in Sciurini.[20] Plesiosciurus from the Miocene of China has been interpreted as a member of Sciurini, but is unlikely to belong to the tribe.[21]

See also[edit]

Footnotes[edit]

  1. ^ Syntheosciurus, Rheithrosciurus, and Microsciurus appear among the species of Sciurus.[12]

References[edit]

  1. ^ a b Emry and Korth, 1996, p. 775
  2. ^ a b c Thorington and Hoffmann, 2005, p. 754
  3. ^ Thorington and Ferrell, 2006, p. 18
  4. ^ Burmeister, 1854, p. 145; McKenna and Bell, 1997, p. 122
  5. ^ Simpson, 1945, p. 78
  6. ^ Moore, 1959, p. 177
  7. ^ Moore, 1959, pp. 177–178
  8. ^ Moore, 1959, pp. 177–180
  9. ^ Thorington and Hoffmann, 2005, p. 758
  10. ^ a b McKenna and Bell, 1997, p. 122
  11. ^ Emry and Korth, 2001
  12. ^ a b c d Mercer and Roth, 2003; Steppan et al., 2004
  13. ^ Steppan et al., 2004, p. 715
  14. ^ Villalobos and Cervantes-Reza, 2007
  15. ^ Bonvicino et al., 2008, pp. 15–16, 18
  16. ^ Mercer and Roth, 2003, p. 1569; Emry and Korth, 1996, p. 775
  17. ^ Thorington and Ferrell, 2006, p. 23
  18. ^ Emry and Korth, 1996, p. 778
  19. ^ Emry et al., 2005, p. 235
  20. ^ Cuenca Bescós, 1988, p. 92; Aguilar, 2002, p. 388
  21. ^ Emry et al., 2005, p. 228

Literature cited[edit]

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Tree squirrel

Tree squirrels include over a hundred species found on all continents except Antarctica, and are the members of the squirrel family most commonly referred to as "squirrels".[1] They do not form a single natural, or monophyletic, group, but instead are related to the various other animals in the squirrel family, including ground squirrels, flying squirrels, marmots, and chipmunks. The most well-known genus is Sciurus, which includes the eastern gray squirrel of North America, introduced to Great Britain, the red squirrel of Eurasia, and the fox squirrel, among many others.

Contents

Classification

Guy G. Musser, one of the world's leading experts on rodents, and the Archbold Curator Emeritus of Mammalogy at the American Museum of Natural History in New York City, clarifies the usage of "squirrel" and related terms:

The squirrel family includes ground squirrels, chipmunks, marmots, prairie dogs, and flying squirrels, but to most people squirrel refers to the 122 species of tree squirrels, which belong to 22 genera of the subfamily Sciurinae.[1]

Current taxonomy, based on genetic data, splits the tree squirrels into several subfamilies. The following genera of the squirrel family are classified as tree squirrels:[1][2]

Relationship with humans

Squirrels are generally clever and persistent animals. In residential neighborhoods, they are notorious for eating out of bird feeders, digging in planting pots and flower beds to pull out bulbs which they chew on or to either bury or recover seeds and nuts and for inhabiting sheltered areas including attics and basements. Squirrels use their keen sense of smell to locate buried nuts and can dig extensive holes in the process. Birds, especially crows, often watch a squirrel bury a nut, then dig it up as soon as the squirrel leaves. Although expert climbers, and primarily arboreal, squirrels also thrive in urban environments, where they get used to humans. Their intelligence makes them suitable as pets.

As pests

Squirrels are sometimes considered pests because of their propensity to chew on various edible and inedible objects. This characteristic trait aids in maintaining sharp teeth, and because their teeth grow continuously, prevents over-growth. Homeowners in areas with a heavy squirrel population must keep attics and basements carefully sealed to prevent property damage caused by nesting squirrels. A squirrel nest is called a "drey". Some homeowners resort to more interesting ways of dealing with this problem, such as collecting and planting fur from pets such as domestic cats and dogs in attics. This fur will indicate to nesting squirrels that a potential predator roams and will encourage evacuation. Fake owls and scarecrows are generally ignored by the animals, and the best way to prevent chewing on an object is to coat it with something to make it undesirable: for instance a soft cloth or chili pepper paste or powder. Squirrel trapping is also practised to remove them from residential areas. However, otherwise squirrels are safe neighbors that pose almost zero risk of transmitting rabies.[3]

This iron bird feeder is advertised as being "squirrel proof and bear resistant"

Squirrels are often the cause of power outages. They can readily climb a power pole and crawl across a power line. The animals will climb onto transformers or capacitors looking for food. If they touch a high voltage conductor and a grounded portion of the device at the same time, they are then electrocuted and cause a short circuit that shuts down equipment. Squirrels have brought down the high-tech NASDAQ stock market twice and were responsible for a spate of power outages at the University of Alabama.[4] To sharpen their teeth they will often chew on tree branches or even the occasional live power line. Rubber plates (squirrel guards) are sometimes used to prevent access to these facilities.

Squirrels are blamed for economic losses to homeowners, nut growers, forest managers in addition to damage to electric transmission lines. These losses include direct damage to property, repairs, lost revenue and public relations. While dollar costs of these losses are sometimes calculated for isolated incidents, there is no tracking system to determine the total extent of the losses.[5]

Squirrels are also responsible for burrowing into sensitive earthworks such as dams and levees, causing a loss of structural integrity which requires diligent maintenance and prevention. Squirrel burrowing activity has sometimes resulted in catastrophic failures of these structures.[6]

As pets

Squirrels can be trained to be hand-fed. Because they are able to cache surplus food, they take as much food as is available. Squirrels living in parks and campuses in cities have learned that humans are typically a ready source of food. Urban squirrels have learned to get a lot of food from generous humans. A commonly given food is peanuts, but recent studies show that raw peanuts contain a trypsin inhibitor that prevents the absorption of protein in the intestines. Therefore offering peanuts that have been roasted is the better option.[7] However, wildlife rehabilitators in the field have noted that neither raw nor roasted peanuts nor sunflower seeds are healthy for squirrels, because they are deficient in several essential nutrients. This type of deficiency has been found to cause Metabolic Bone Disease, a somewhat common ailment found in malnourished squirrels.[8][9]

Squirrels are occasionally kept as household pets, provided they are selected young enough and are hand raised in a proper fashion. They can be taught to do tricks, and are said to be as intelligent as dogs in their ability to learn behaviors. Pet squirrels are usually kept without cages, but a large cage and a balanced diet with good variety will keep a pet squirrel healthy and happy. The pet owner must beware of "spring fever" at which time a female pet squirrel will become very defensive of her cage, considering it her nest, and will become somewhat aggressive to defend the area.[10]

As food

Squirrel meat is considered a favored meat in certain regions of the United States[11] where it can be listed as wild game.[12] This is evidenced by extensive recipes for its preparation found in cookbooks, including older copies of The Joy of Cooking. Squirrel meat can be exchanged for rabbit or chicken in recipes, though it can have a gamey taste. Unlike the most game meat, the American Heart Association has found squirrel to be high in cholesterol.[13]

In the U.S.

In many areas of the U.S., particularly areas of the American South, squirrels are hunted for food.[14] Republican Presidential candidate Mike Huckabee mentioned his experiences eating squirrel during the South Carolina primary, saying that "When I was in college, we used to take a popcorn popper, because that was the only thing they would let us use in the dorm, and we would fry squirrels in a popcorn popper in the dorm room." He later told Meet the Press anchor Tim Russert that squirrel constitutes "a Southern delicacy".[15] The Ramapough Mountain Indian Tribe of New Jesery considered eating squirrel to be a tradition.[16][17]

In the U.K.

For most of the history of the United Kingdom, squirrel has been a meat not commonly eaten, and even scorned by many.[18]

But in the early 21st century, wild squirrel has become a more popular meat to cook with,[19] showing up in restaurants and shops more often in Britain as a fashionable alternative meat.[18] Specifically, U.K. citizens are cooking with the invasive gray squirrel, which is being praised for its low fat content and the fact that it comes from free range sources.[19] Additionally, the novelty of a meat considered unusual or special has added to the spread of squirrel consumption.[18] Due to the difficulty of a clean kill and other factors, the majority of squirrel eaten in the U.K. is acquired from professional hunters, trappers, and gamekeepers.[18]

Some Britons are eating the gray squirrel as a direct attempt to help the native red squirrel, which has been dwindling since the introduction of the gray squirrel in the 19th century.[18] This factor was marketed by a national "Save Our Squirrels" campaign that used the slogan, “Save a red, eat a gray!”[18]

In culture

Despite periodic complaints about the animal as a pest, general public opinion towards the animal is favorable, thanks to its agreeable appearance, intelligence and its eating styles and habits.[citation needed] Squirrels are popular characters in many forms of media, such as the literary works of Beatrix Potter, Brian Jacques' Redwall series (including Jess Squirrel and numerous other squirrels), Pattertwig in C. S. Lewis' Prince Caspian, Michael Tod's Woodstock Saga of novels featuring squirrel communities in the style of Watership Down, and the Starwife and her subjects from Robin Jarvis's Deptford novels. Squirrels are also popular characters in cartoons, such as Scrat from Ice Age, Slappy Squirrel of the Animaniacs, Sandy Cheeks from SpongeBob SquarePants, Hammy from Over the Hedge, Benny in The Wild, Rodney and Leon and Darlene from Squirrel Boy, Secret Squirrel, Screwy Squirrel, Nutty from Happy Tree Friends, and Rocky, Bullwinkle's adventuring partner. Grace from the webcomic El Goonish Shive is often pictured as an anthropomorphic squirrel, since it is her most natural and favored form. Video games such as Rare's Conker series starring Conker the Squirrel, as well as Ocean Software's Mr. Nutz. There is even a squirrel-themed super-heroine, Squirrel Girl.

Albino and white squirrels

One of the ways that squirrels impact human society is inspired by the fascination that people seem to have over local populations of white squirrels (often mis-identified as being albino).[20] This manifests itself by the creation of social group communities that form from a commonly-shared interest in these rare animals. These groups demonstrate classic sociological group dynamics, including personal identity by belonging to a group, as well as hierarchical competition between white squirrel groups with each other over which has the best local white squirrel population. Other impacts on human society inspired by white squirrels include the creation of organizations that seek to protect them from human predation, and the use of the white squirrel image as a cultural icon.

Welcome sign for Kenton, Tennessee, an example of competition for "White Squirrel Capital".

Some examples of this cultural impact include:

In addition to the various towns that boast of their white squirrel populations, there also is a surprisingly large number of university campuses in North America that have white squirrels, including:

An true albino squirrel. Note the pink eyes.
A white squirrel. Note the non-pink eyes.

Although these squirrels are commonly referred to as albinos, most of them are likely non-albino squirrels that exhibit a rare white fur coloration known as leucism that is as a result of a recessive gene found within certain Eastern gray squirrel (Sciurus carolinensis) populations, and so technically they ought to be referred to as white squirrels, instead of albino.[20] Dr. Michael Stokes, a biology professor at Western Kentucky University, commented that the probable cause for the abundance of white squirrels on university campuses was due to them being originally introduced by someone:

We're not sure how they got here, but I'll tell you how it usually happens...When you see them, especially around a college campus or parks, somebody brought them in because they thought it would be neat to have white squirrels around.[20]

Dr. Albert Meier, another biology professor at Western Kentucky University, added that:

... white squirrels rarely survive in the wild because they can't easily hide. But on a college campus, they are less likely to be consumed by other animals.[20]

A list of white squirrel sightings around the world is maintained by the White Squirrel Research Institute, a group based in Brevard, North Carolina.

Red squirrel at feeding tray in the lake district.

Red and gray squirrels in the UK

A decline of the red squirrel and the rise of the eastern gray squirrel has been widely remarked upon in British popular culture. It is mostly regarded as the invading grays driving out the native red species.[28] Evidence also shows that gray squirrels are vectors of the Squirrel parapoxvirus for which no vaccine is presently available and which is deadly to red squirrels but does not seem to affect the host.[29] Currently the red squirrel only resides in a few isolated areas of the UK, notably in Scotland, and in England Formby, the Lake District, Brownsea Island, and the Isle of Wight. Special measures are in place to contain and remove any infiltration of gray squirrels into these areas.

Under British law, the eastern gray squirrel is regarded as vermin, and at one point it was illegal to release any into the wild; any caught had to be either destroyed or kept captive. In 2008 the law was altered, allowing those with the proper license to release captured gray squirrels.[30]

References

  1. ^ a b c Musser, Guy G. (2007-). "Squirrel". Encyclopaedia Britannica online Academic edition. Chicago, Illinois: Encyclopædia Britannica. OCLC 263690320. http://www.search.eb.com/eb/article-226105. Retrieved 20 February 2010. 
  2. ^ Thorington, R.W., Jr.; Hoffmann, R.S. (2005). "Family Sciuridae". in Wilson, D.E.; Reeder, D.M. Mammal Species of the World: a taxonomic and geographic reference (3rd ed.). The Johns Hopkins University Press. pp. 754–818. ISBN 0-8018-8221-4. OCLC 26158608. http://www.bucknell.edu/msw3/browse.asp?s=y&id=12400001. 
  3. ^ http://rabies.emedtv.com/rabies/rabies-and-squirrels.html
  4. ^ K. Muston. "Getting Squirrely". Daily Kos:. http://www.dailykos.com/story/2007/9/22/10818/1400. Retrieved 2008-02-07. 
  5. ^ Tree Squirrels – University of Georgia
  6. ^ "Levee Safety Program: Burrowing Animals". Santa Clara Valley Water District. 2006. http://www.valleywater.org/water/watersheds_-_streams_and_floods/Taking_care_of_streams/Levee_safety/Burrowing_animals.shtm. Retrieved 2008-02-07. 
  7. ^ Jon Gottshall. "Jon's World o' Squirrels". Jon's World o' Squirrels. http://www.gottshall.com/squirrels/fhtml04e.htm#0. Retrieved 2007-02-07. 
  8. ^ Susan Saliga. "Backyard Squirrel Feeding Tips". Wisconsin Squirrel Connection. http://wisquirrelrehab.com/BACKYARD%20SQUIRREL%20FEEDING%20TIPS.htm. Retrieved 2007-02-07. 
  9. ^ Sara Rowe. "Squirrel Tales: Care Instructions For Infant Squirrels". Squirreltales. http://www.squirreltales.org/#Section-H. Retrieved 2007-02-07. 
  10. ^ http://www.vivavegie.org/BernieandSquirrel.htm
  11. ^ http://www.boingboing.net/2008/09/11/how-to-make-a-squirr.html
  12. ^ It tasted like chicken. Retrieved December 19, 2008.
  13. ^ Davidson, Alan (1999). "Squirrel". Oxford Companion to Food. Oxford University Press. p. 750. ISBN 0192115790. 
  14. ^ Kurlanksy, Mark. The Food of a Younger Land: A Portrait of American Food—Before the National Highway System, Before Chain Restaurants, and Before Frozen Food, when the Nation's Food was Seasonal. Penguin, 2009, p. 112
  15. ^ 'Meet the Press' transcript for Feb. 10, 2008. Msnbc.com. Retrieved December 19, 2008.
  16. ^ http://wcbstv.com/local/ringwood.squirrel.myrtle.2.241671.html
  17. ^ http://www.9news.com/news/watercooler/article.aspx?storyid=63739
  18. ^ a b c d e f Speiler, Marlena (January 6, 2009). "Saving a Squirrel by Eating One". The New York Times. http://www.nytimes.com/2009/01/07/dining/07squirrel.html?_r=3&emc=eta1&pagewanted=all. Retrieved 2009-01-16. 
  19. ^ a b First, catch your squirrel...
  20. ^ Creative Commons Attribution Share Alike 3.0 (CC BY-SA 3.0)

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