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Pocket gopher

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Pocket gophers
Temporal range: Early Oligocene–Recent
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Mammalia
Order:
Rodentia
Superfamily:
Geomyoidea
Family:
Geomyidae

Bonaparte, 1845
Genera

Cratogeomys
Geomys
Orthogeomys
Pappogeomys
Thomomys
Zygogeomys

The pocket gophers are burrowing rodents of the family Geomyidae. These are the "true" gophers, though several ground squirrels of the family Sciuridae are often called gophers as well. The name "pocket gopher" on its own may be used to refer to any of a number of subspecies of the family.

Distribution

Pocket gophers are widely distributed in North America, extending into Central America.

Appearance

Gophers are heavily built, and most are moderately large, ranging from 12 to 30 cm (4.7 to 11.8 in) in length, and weighing a few hundred grams. A few species reach weights approaching 1 kg (2.2 lb). Males are always larger than the females and can be nearly double their weight.[1] Most gophers have brown fur which often closely matches the color of the soil in which they live. Their most characteristic feature is their large cheek pouches, from which the word "pocket" in their name derives. These pouches are fur-lined, and can be turned inside out. They extend from the side of the mouth well back onto the shoulders. They have small eyes and a short, hairy tail which they use to feel around tunnels when they walk backwards.

Behavior

All pocket gophers are burrowers. They are larder hoarders, and their cheek pouches are used for transporting food back to their burrows. Gophers can collect large hoards. Their presence is unambiguously announced by the appearance of mounds of fresh dirt about 20 cm (7.9 in) in diameter. These mounds will often appear in vegetable gardens, lawns, or farms, as gophers like moist soil. They also enjoy feeding on vegetables. For this reason, some species are considered agricultural pests. They may also damage trees in forests. Although they will attempt to flee when threatened, they may attack other animals, including cats and may even attack humans, and can inflict serious bites with their long, sharp teeth.

Pocket gophers are solitary outside of the breeding season, aggressively maintaining territories that vary in size depending on the resources available. Males and females may share some burrows and nesting chambers if their territories border each other, but in general, each pocket gopher inhabits its own individual tunnel system.

Depending on the species and local conditions, pocket gophers may have a specific annual breeding season, or may breed repeatedly through the year. Each litter typically consists of two to five young, although this may be much higher in some species. The young are born blind and helpless, and are weaned at around forty days[2].

Classification

There has been much debate among taxonomists about which races of pocket gopher should be recognised as full species, and the following list cannot be regarded as definitive.

Some sources also list a genus Hypogeomys, with one species, but this genus name is normally used for the Malagasy Giant Rat, which belongs to the family Nesomyidae.

Pest Management

Gopher gas poisoning, poison baiting, concussion

Carbon monoxide from vehicle exhaust is an effective and inexpensive method that some people use to exterminate gophers. However, poisoning animals with carbon monoxide is illegal in some states, including California. These people couple garden hoses to the exhaust pipes of their vehicles using such devices like the "Underground Exterminator". With one end of the hose connected to the exhaust and the other end in the gopher tunnel, they idle their vehicle until toxic carbon monoxide fills the tunnel network, killing the gophers. Tunnel networks are interconnected at deeper levels to other tunnel networks, and an area may become re-infested.

Gopher extermination can also be done by flooding the tunnels with aluminium phosphide, a restricted use pesticide. This is highly toxic gas that, in the United States, only registered exterminators may use. The aluminum phosphide pellets react with moisture in the air and soil to produce phosphine gas (not phosgene). While aluminum phosphide is a federally registered pesticide with highly acute inhalation toxicity to humans and other mammals, with proper safety precautions a professional may safely apply it without risk of secondary poisoning to pets or other wildlife. With most poison baits there is a risk to pets if it digs up and eats the gopher carcass. The gas slowly dissipates underground after several hours leaving only Aluminum hydroxide, which is naturally found in soil and is not a contaminant. Aluminum Phosphide + 3 Water = Aluminum hydroxide + Phosphine Gas

AlP + 3H2O = Al(OH)3 + PH3

Zinc phosphide bait is delivered in a compressed grain pellet. The phosphide creates phosphine gas in the gopher's stomach.

Gopher gassers and automotive type flares are sometimes used. They are ignited and placed in the burrows. The fumes kill the gopher.

Poison baits require the gopher to eat the bait. They include barley, wheat, and milo grains, sometimes with raisins, coated with strychnine. The disadvantages of poisoned baits include the following: The gopher must find and eat the bait. If the bait molds or rots, the gopher won't eat it. If a gopher eats a non-lethal dose and just gets sick, it will never eat it again (bait shy). Strychnine poisoned gophers may wander above ground in an intoxicated stupor, making themselves easy targets for predators. Resulting secondary poisoning of pets and predators, including owls, would prove to be counter-productive. A loss of predators means more gophers. Hence, these baits must be used with extreme caution.

A concussion method kills gophers instantly with a shock wave. Specialized equipment used by trained operators wearing personal protective equipment injects a mixture of propane and oxygen into the gopher burrow. An igniter on the end of the injection probe explodes the fuel mixture, destroying not only the gophers, but the burrows as well. It sends a fireball and intense shock wave throughout the tunnel network. This method is obviously not suited for urban residential areas, but rather to agricultural situations. The destruction of the burrows by this method prevents loss of irrigation water, prevents injury from collapse of the burrow underfoot (human, equine, etc.), and may make any re-infestation more quickly noticeable. Killing animals with explosives is illegal in some jurisdictions, although the concussion method is not considered explosive[citation needed] and is not regulated by US federal law. In the State of Colorado, USA, the concussion method was approved for the control of prairie dogs in November of 2007.

Gopher trapping

Gopher traps can be employed to kill them. These traps are very effective and need not be baited. The cocked trap is inserted jaws-first so that the entire trap is within the tunnel within the gopher mound, and then it is covered with dirt. The gopher will push against the trigger plate in order to reacquire access to the hole which has been blocked. In doing so, it will position its body directly above the jaws. When the jaws close, they will break the gopher's spine in the best case or merely maim the animal in the worst case. This method of gopher control is allowable in certified organic operations as there are no non-organic chemicals used. Mounds made by moles are different, with the dirt being more finely broken up, and gopher traps are ineffective against moles. In some places the DNR offers a bounty for these animals.

References

  1. ^ Macdonald (Ed), Professor David W. (2006). The Encyclopedia of Mammals. Oxford University Press. ISBN 0-19-920608-2. {{cite book}}: Cite has empty unknown parameter: |coauthors= (help)
  2. ^ Patton, James (1984). Macdonald, D. (ed.). The Encyclopedia of Mammals. New York: Facts on File. pp. 628–631. ISBN 0-87196-871-1.
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