The pocket gophers
are burrowing rodents
of the family Geomyidae
. These are the "true" [(animal)|gopher
]s, 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
. Pocket gophers are a symbol of the U.S. state of Minnesota
, sometimes called the "Gopher State".
Pocket gophers are widely distributed in North America
, extending into Central America
Gophers are heavily built, and most are moderately large, ranging from in length, and weighing a few hundred grams
. A few species
reach weights approaching . Males are always larger than the females and can be nearly double their weight. 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.
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 in diameter
. These mounds will often appear in vegetable gardens
, 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 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.
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.
- Family Geomyidae
- Genus Cratogeomys; some authors treat this genus as a subgenus of Pappogeomys.
- Genus Geomys - eastern pocket gophers; principally found in the south-western United States, east of the Sierra Nevada mountains.
- Genus Orthogeomys - giant pocket gophers or taltuzas; found in Mexico, Central America and Colombia.
- Genus Pappogeomys; found in Mexico.
- Genus Thomomys - western pocket gophers; widely distributed in North America, extending into the northwestern US, Canada and the southeastern US.
- Thomomys bottae; many subspecies, including the Botta's, Fish Spring, Bonneville, Clear Lake, San Antonio, Pistol River, Mount Ellen, Guadalupe, Limpia, Mearns', Stansbury Island, Antelope Island, Cebolleta, Salinas, Skull Valley, Swasey Springs, Harquahala and Limpia Greek Pocket Gophers.
- Camas Pocket Gopher (T. bulbivorus)
- Wyoming Pocket Gopher (T. clusius)
- Idaho Pocket Gopher (T. idahoensis)
- Mazama Pocket Gopher (T. mazama); several subspecies including the Western, Gold Beach, Olympic, and Tacoma Pocket Gophers.
- Mountain Pocket Gopher (T. monticola)
- Northern Pocket Gopher (T. talpoides); very widely distributed; several subspecies including the Cheyenne Northern Pocket Gopher
- Townsend´s Pocket Gopher (T. townsendii)
- Southern Pocket Gopher (T. umbrinus)
- Genus Zygogeomys
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.
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 and is not regulated by US federal law. In the State of Colorado, USA, the concussion method by the was approved for the control of prairie dogs in November of 2007.
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.