Pocket Gophers

Thirty-four species of pocket gophers, represented by five genera, occupy the western hemisphere. In the United States there are 13 species and three genera. The major features differentiating these genera are the size of their forefeet, claws, and front surfaces of their chisel-like incisors. Thomomys have smooth-faced incisors and small forefeet with small claws. Northern pocket gophers (Thomomys talpoides) are typically from 6 1/2 to 10 inches (17 to 25 cm) long. Their fur is variable in color but is often yellowish brown with pale underparts. Botta’s (or valley) pocket gophers (Thomomys bottae) are extremely variable in size and color. Botta’s pocket gophers are 5 inches to about 13 1/2 inches (13 to 34 cm) long. Their color varies from almost white to black. Geomys have two grooves on each upper incisor and large forefeet and claws. Plains pocket gophers (Geomys bursarius) vary in length from almost 7 1/2 to 14 inches (18 to 36 cm). Their fur is typically brown but may vary to black. Desert pocket gophers (Geomys arenarius) are always brown and vary from nearly 8 3/4 to 11 inches (22 to 28 cm) long. Texas pocket gophers (Geomys personatus) are also brown and are from slightly larger than 8 3/4 to nearly 13 inches (22 to 34 cm) long. Southeastern pocket gophers (Geomys pinetis) are of various shades of brown, depending on soil color, and are from 9 to 13 1/4 inches (23 to 34 cm) long. Pappogeomys have a single groove on each upper incisor and, like Geomys, have large forefeet with large claws. Yellow-faced pocket gophers (Pappogeomys castanops) vary in length from slightly more than 5 1/2 to just less than 7 1/2 inches (14 to 19 cm). Their fur color varies from pale yellow to dark reddish brown. The underparts vary from whitish to bright yellowish buff. Some hairs on the back and top of the head are dark-tipped. Range: Pocket gophers are found only in the Western Hemisphere. They range from Panama in the south to Alberta in the north. With the exception of the southeastern pocket gopher, they occur throughout the western two-thirds of the United States. Exclusion: Generally not practical. Small mesh wire fence may provide protection for ornamental trees and shrubs or flower beds. Plastic netting protects seedlings. Cultural Methods: Damage resistant varieties of alfalfa. Crop rotation. Grain buffer strips. Control of tap-rooted forbs. Flood irrigation. Plant naturally resistant varieties of seedlings. Repellents: Synthetic predator odors are all of questionable benefit. Toxicants: Baits: Strychnine alkaloid. Zinc phosphide. Chlorophacinone. Diphacinone. Fumigants: Carbon monoxide from engine exhaust. Others are not considered very effective, but some are used: Aluminum phosphide. Gas cartridges. Trapping: Various specialized gopher kill traps. Common spring or pan trap (sizes No. 0 and No. 1). Shooting: Not practical. Other: Buried irrigation pipe or electrical cables can be protected with cylindrical pipe having an outside diameter of at least 2.9 inches (7.4 cm). Surrounding a buried cable with 6 to 8 inches (15 to 20 cm) of coarse gravel (1 inch [2.5 cm] in diameter) may provide some protection

Pocket Gophers

Thirty-four species of pocket gophers, represented by five genera, occupy the western hemisphere. In the United States there are 13 species and three genera. The major features differentiating these genera are the size of their forefeet, claws, and front surfaces of their chisel-like incisors. Thomomys have smooth-faced incisors and small forefeet with small claws. Northern pocket gophers (Thomomys talpoides) are typically from 6 1/2 to 10 inches (17 to 25 cm) long. Their fur is variable in color but is often yellowish brown with pale underparts. Botta’s (or valley) pocket gophers (Thomomys bottae) are extremely variable in size and color. Botta’s pocket gophers are 5 inches to about 13 1/2 inches (13 to 34 cm) long. Their color varies from almost white to black. Geomys have two grooves on each upper incisor and large forefeet and claws. Plains pocket gophers (Geomys bursarius) vary in length from almost 7 1/2 to 14 inches (18 to 36 cm). Their fur is typically brown but may vary to black. Desert pocket gophers (Geomys arenarius) are always brown and vary from nearly 8 3/4 to 11 inches (22 to 28 cm) long. Texas pocket gophers (Geomys personatus) are also brown and are from slightly larger than 8 3/4 to nearly 13 inches (22 to 34 cm) long. Southeastern pocket gophers (Geomys pinetis) are of various shades of brown, depending on soil color, and are from 9 to 13 1/4 inches (23 to 34 cm) long. Pappogeomys have a single groove on each upper incisor and, like Geomys, have large forefeet with large claws. Yellow-faced pocket gophers (Pappogeomys castanops) vary in length from slightly more than 5 1/2 to just less than 7 1/2 inches (14 to 19 cm). Their fur color varies from pale yellow to dark reddish brown. The underparts vary from whitish to bright yellowish buff. Some hairs on the back and top of the head are dark-tipped. Range: Pocket gophers are found only in the Western Hemisphere. They range from Panama in the south to Alberta in the north. With the exception of the southeastern pocket gopher, they occur throughout the western two-thirds of the United States. Exclusion: Generally not practical. Small mesh wire fence may provide protection for ornamental trees and shrubs or flower beds. Plastic netting protects seedlings. Cultural Methods: Damage resistant varieties of alfalfa. Crop rotation. Grain buffer strips. Control of tap-rooted forbs. Flood irrigation. Plant naturally resistant varieties of seedlings. Repellents: Synthetic predator odors are all of questionable benefit. Toxicants: Baits: Strychnine alkaloid. Zinc phosphide. Chlorophacinone. Diphacinone. Fumigants: Carbon monoxide from engine exhaust. Others are not considered very effective, but some are used: Aluminum phosphide. Gas cartridges. Trapping: Various specialized gopher kill traps. Common spring or pan trap (sizes No. 0 and No. 1). Shooting: Not practical. Other: Buried irrigation pipe or electrical cables can be protected with cylindrical pipe having an outside diameter of at least 2.9 inches (7.4 cm). Surrounding a buried cable with 6 to 8 inches (15 to 20 cm) of coarse gravel (1 inch [2.5 cm] in diameter) may provide some protection

A CULTURAL METHOD OF REDUCING POCKET GOPHER IMPACT ON ALFALFA YIELD

Low Input Sustainable Agriculture (LISA) strives to minimize input of agrichemicals for farmers while maintaining profits. Alfalfa fits into this scheme in 2 ways. First, the plains pocket gophers (Geomys bursarius) can reduce yield of alfalfa, thus an effective, economical means of control with minimal environmental impact would be desirable. Second, the increased use of alfalfa in rotation with row crops to increase soil nitrogen may increase pocket gopher problems by increasing their habitat. Our objective was to evaluate a cultural method to control pocket gopher damage, namely, by comparing 2 different varieties of alfalfa. One variety is tap-rooted (Wrangler) while the other has a more fibrous-rooted system (Spredor 2). We hypothesized that damage would be less in the fibrous-rooted alfalfa as it is capable of vegetative reproduction and could recolonize areas. We released live-trapped pocket gophers on 4 treatment areas in each alfalfa variety. Pocket gophers were present on plots of each variety from the fall of 1988 through the fall of 1989. Damage caused by pocket gophers was measured by clipping 80 samples/harvest during the 1989 growing season. Yields were 15 to 19% less in treatment areas than in control areas for both varieties. Sampling continued through the 1990 growing season to determine the recovery rate of each variety after gophers had been removed. The tap-rooted variety showed no improvement in 1990 over 1989. On the other hand, the fibrous-rooted alfalfa exhibited a 4% increase in treatment over control areas after gopher removal

A CULTURAL METHOD OF REDUCING POCKET GOPHER IMPACT ON ALFALFA YIELD

Low Input Sustainable Agriculture (LISA) strives to minimize input of agrichemicals for farmers while maintaining profits. Alfalfa fits into this scheme in 2 ways. First, the plains pocket gophers (Geomys bursarius) can reduce yield of alfalfa, thus an effective, economical means of control with minimal environmental impact would be desirable. Second, the increased use of alfalfa in rotation with row crops to increase soil nitrogen may increase pocket gopher problems by increasing their habitat. Our objective was to evaluate a cultural method to control pocket gopher damage, namely, by comparing 2 different varieties of alfalfa. One variety is tap-rooted (Wrangler) while the other has a more fibrous-rooted system (Spredor 2). We hypothesized that damage would be less in the fibrous-rooted alfalfa as it is capable of vegetative reproduction and could recolonize areas. We released live-trapped pocket gophers on 4 treatment areas in each alfalfa variety. Pocket gophers were present on plots of each variety from the fall of 1988 through the fall of 1989. Damage caused by pocket gophers was measured by clipping 80 samples/harvest during the 1989 growing season. Yields were 15 to 19% less in treatment areas than in control areas for both varieties. Sampling continued through the 1990 growing season to determine the recovery rate of each variety after gophers had been removed. The tap-rooted variety showed no improvement in 1990 over 1989. On the other hand, the fibrous-rooted alfalfa exhibited a 4% increase in treatment over control areas after gopher removal

Dynamical Scaling Behavior of Percolation Clusters in Scale-free Networks

In this work we investigate the spectra of Laplacian matrices that determine many dynamic properties of scale-free networks below and at the percolation threshold. We use a replica formalism to develop analytically, based on an integral equation, a systematic way to determine the ensemble averaged eigenvalue spectrum for a general type of tree-like networks. Close to the percolation threshold we find characteristic scaling functions for the density of states rho(lambda) of scale-free networks. rho(lambda) shows characteristic power laws rho(lambda) ~ lambda^alpha_1 or rho(lambda) ~ lambda^alpha_2 for small lambda, where alpha_1 holds below and alpha_2 at the percolation threshold. In the range where the spectra are accessible from a numerical diagonalization procedure the two methods lead to very similar results.Comment: 9 pages, 6 figure

Monte Carlo critical isotherms for Ising lattices

Monte Carlo investigations of magnetization versus field, $M_c(H)$, at the critical temperature provide direct accurate results on the critical exponent $\delta^{-1}$ for one, two, three and four-dimensional lattices: $\delta_{1D}^{-1}$=0, $\delta_{2D}^{-1}$=0.0666(2)$\simeq$1/15, $\delta_{3D}^{-1}$=0.1997(4)$\simeq$1/5, $\delta_{4D}^{-1}$=0.332(5)$\simeq$1/3. This type of Monte Carlo data on $\delta$, which is not easily found in studies of Ising lattices in the current literature, as far as we know, defines extremely well the numerical value of this exponent within very stringent limits.Comment: 5 pages, 4 figures. Sent to Europhysics Letter

Scaling Properties of Random Walks on Small-World Networks

Using both numerical simulations and scaling arguments, we study the behavior of a random walker on a one-dimensional small-world network. For the properties we study, we find that the random walk obeys a characteristic scaling form. These properties include the average number of distinct sites visited by the random walker, the mean-square displacement of the walker, and the distribution of first-return times. The scaling form has three characteristic time regimes. At short times, the walker does not see the small-world shortcuts and effectively probes an ordinary Euclidean network in $d$-dimensions. At intermediate times, the properties of the walker shows scaling behavior characteristic of an infinite small-world network. Finally, at long times, the finite size of the network becomes important, and many of the properties of the walker saturate. We propose general analytical forms for the scaling properties in all three regimes, and show that these analytical forms are consistent with our numerical simulations.Comment: 7 pages, 8 figures, two-column format. Submitted to PR

Invaded cluster simulations of the XY model in two and three dimensions

The invaded cluster algorithm is used to study the XY model in two and three dimensions up to sizes 2000^2 and 120^3 respectively. A soft spin O(2) model, in the same universality class as the 3D XY model, is also studied. The static critical properties of the model and the dynamical properties of the algorithm are reported. The results are K_c=0.45412(2) for the 3D XY model and eta=0.037(2) for the 3D XY universality class. For the 2D XY model the results are K_c=1.120(1) and eta=0.251(5). The invaded cluster algorithm does not show any critical slowing for the magnetization or critical temperature estimator for the 2D or 3D XY models.Comment: 30 pages, 11 figures, problem viewing figures corrected in v