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USDA National Wildlife Research Center - Staff U.S. Department of Agriculture: Animal and Publications Plant Health Inspection Service

July 2003

Is it a Pocket Gopher or Mole?

Wendy M. Arjo National Wildlife Research Center’s Olympia Field Station

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Arjo, Wendy M., "Is it a Pocket Gopher or Mole?" (2003). USDA National Wildlife Research Center - Staff Publications. 195. https://digitalcommons.unl.edu/icwdm_usdanwrc/195

This Article is brought to you for free and open access by the U.S. Department of Agriculture: Animal and Plant Health Inspection Service at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in USDA National Wildlife Research Center - Staff Publications by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. negative impacts on aboveground Is it a Pocket Gopher or Mole? non-target species; strychnine-baited pocket gophers, however, may still become a very tempting target to a BY WENDY M. ARJO pose a threat to subterranean preda- foraging pocket gopher. Commonly, tors such as weasels. In addition, gophers will prune seedling roots and epending on where you are, the pocket gophers and other small often pull the entire seedling into term “gopher” is applied to a mammals using pocket gopher bur- D their burrow. Stem clipping at ground variety of mammal species including rows may consume the bait and die level and girdling are also common ground squirrels, prairie dogs and aboveground. with seedlings less than half an inch moles. The true pocket gopher is The Olympia Field Station has con- in diameter the most vulnerable. In actually very distinguishable once ducted several tests to determine pri- deep snow conditions, aboveground you recognize their appearance and mary, secondary and tertiary risks girdling of larger trees can occur. sign, or indicators of the animal. that may occur while strychnine-bait- Although aboveground girdling is Pocket gophers are burrowing rodents ing pocket gophers. Population easy to detect, damage by pocket named for their external fur-lined responses of non-target species— gophers to root systems may go cheek pouches. Unlike mole mounds, golden mantled ground squirrels and unnoticed until seedlings become which have been characterized as yellow pine chipmunks—were moni- discolored or tip over. Several factors miniature volcanoes, gopher mounds tored on two reforested sites in have been noted that predispose a are fan-shaped in appearance. Pocket Oregon. Immediately after baiting, stand to pocket gopher damage: 1) gophers are distributed throughout ground squirrel numbers declined; current pocket gopher density; 2) soil the Pacific Northwest, but occur more however, the following spring the suitability for burrowing; 3) topogra- frequently in the drier climates of population recovered. Yellow pine phy; 4) herbaceous understory; 5) eastern Washington and Oregon. chipmunk populations were not amount of adjacent border with pre- Pocket gophers prefer roots and reduced by strychnine baiting, but in ferred forage; and 6) site preparation. stems of herbaceous annuals and fact increased in the treated plots the Management practices to reduce perennial plants that are often associ- following spring. This increase may pocket gopher damage include silvi- ated with early successional forests. reflect an invasion of chipmunks in cultural practices, such as minimizing Because of this preference, seedlings the absence of ground squirrels. disturbance of an area, habitat Regardless of ground cover, pocket manipulation, trapping, repellents, gophers usually die belowground in Burns & Williams fumigation and seedling barriers such the nest or close to it. This supports Lawyers as Vexar tubing. Strychnine baiting is the notion that fossorial (living below- Ann Forest Burns Bruce H. Williams the most widely used method to ground) rodents baited belowground Business (206) 527-5942 • Fax (206) 522-5392 reduce pocket gopher populations are unlikely to become secondary haz- 5508-35th Ave. N.E., Suite 102 • Seattle, WA 98105 prior to planting seedlings. Baits are ards. However, this does not entirely E-mail: [email protected] applied belowground to minimize eliminate the chance of an occasional aboveground death or the potential for underground predators like weasels to encounter carcasses. Predator-prey interactions are largely unknown since subterranean predator activity is difficult to observe. Artificial burrow systems were established to investigate interactions of weasels and pocket gophers at the Olympia Field Station. Weasels (80

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12 WESTERN FORESTER ◆ JULY/AUGUST 2003 PHOTO COURTESY OF NWRC OLYMPIA FIELD STATION Protecting seedlings from pocket gopher damage can be difficult since seedlings can be attacked from both belowground and aboveground. percent of those tested) readily killed The fate of small mammal carcass- Station. She can be reached at 360-705- and consumed healthy pocket es was determined on a study site in 4565 or [email protected]. gophers. All weasels ate strychnine- the Rogue River National Forest. baited gopher carcasses after 72 Carcasses disappeared equally from hours, but no weasels died from sec- both scavengers and insects. In addi- “Print Your Own Oregon ondary poisoning. Although weasels tion, several insect species were sam- Ownership Maps” killed and cached gophers, caches pled to determine strychnine concen- were composed of single animals tration levels and any potential risks only. Most of the weasels sampled, to insectivore species. Fly larvae and but not entirely consumed, both ants were found to contain high levels fresh-killed gophers and five-day-old of strychnine; however, little risk is carcasses. Although caching behavior posed to insectivores due to the of weasels may increase their expo- quantity of insects that would have to sure to secondary poisoning of be consumed to acquire a lethal dose. strychnine, this in turn may be mini- Studies by the Olympia Field Station mized by the fact that the majority of have shown that controlling pocket weasels only sampled carcasses. If gopher populations with strychnine Atterbury Consultants, Inc. is selling tim- strychnine-baited pocket gophers die baiting poses relatively little risk to berland ownership data in ArcReader Format aboveground, secondary hazards to non-target species. ◆ for the entire state of Oregon for $395.00. This price includes ownership data for the top scavengers and tertiary hazards to 30 timberland owners, sections, townships, insectivores (species that eat insects Wendy M. Arjo is a research wildlife county boundaries, and several highways for that cause decay of carcasses), may biologist for the National Wildlife the entire state. It also includes a free copy of occur. Research Center’s Olympia Field ESRI’s ArcReader program which allows users to print maps of the entire state or any portion of it. Users pick the scale and which layers to print. • Designed for non-GIS people • Very easy to use • No GIS experience needed Call Jon Aschenbach at 503-646-5393 for more information. Download a full sized brochure at www.atterbury.com. ATTERBURY CONSULTANTS, INC. 3800 SW Cedar Hills Blvd., #190 Beaverton, OR 97005

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