Research and Management of Black Bears in Crater Lake National Park, Oregon, 1974

 METHODS

Data concerning black bear activity were obtained from observations reported by park personnel and tourists, park files, field notes, and studies of marked and radio equipped bears. Bears were captured with culvert-type live traps, Aldrich foot snares, and by the immobilization of froe-roaming and treed bears.

Live traps were set using the methods of Erickson (1957). Cubby sets similar to those described by Jonkel and Cowan (1971) were used for foot snares. Live traps were set at the Munson dumpsite and at problem bear areas. Foot snares were generally used in more remote areas or when bears became trap-shy. Baits used included salmon and deer carcasses, meat scraps, canned cat food, sardines, apples, honey, and table scraps.

Attempts were made to immobilize free-roaming bears when they came into campgrounds or other developed areas. These bears could usually be approached to within 20 to 40 feet and darted with an immobilizing agent. If not spooked or chased, bears seldom traveled more than 50 to 75 yards before complete ataxis. Bears were captured in this manner during both night and daytime.

Immobilizing drugs were administered with a projectile syringe fired by a carbon dioxide-powered long range projector (Cap-Chur gun, Palmer Chemical Co., Inc., Douglasville, Georgia). Phencyclidine hydrochloride ( Sernylan, Bio-Ceutic Laboratories, Inc., St. Joseph Missouri) was administered intramuscularly at dosages ranging from 0.5 to 2.0 mg per pound of body weight. Limited use was made of” Etorphine and its antagonist Diprenorphine (X99 and M50-50, American Cyanamid Co., Princeton, New Jersey. An intramuscular injection of penicillin (Durbiotic, Burn Pharmaceuticals, Oakland, California) was administered to bears handled during 1973.

Immobilized bears were weighed, measured, and examined to determine their general physical condition and reproductive status. Bears were then ear tagged with a metal tag (Perfect Ear Tags, Salt Lake Stamp Co., Salt Lake City, Utah) supplied by the Oregon Game Commission- All tags, except number 1, had the phrase “RET ORE GAME COMM” stamped on the back. In addition to tagging, most bears were tattooed inside the lower lip.

Transplants were limited to the park and surrounding portions of the Cascade Mountain Range. All bears involved in the trap-and-transfer studies were nuisance animals. In this report, “nuisance” bears are distinguished from “wild” bears in that the former were captured in, or known to frequent, developed areas. Bears classified as wild were captured at wilderness sites and were not known to frequent developed areas.

Radio transmitters were attached by collar to several bears to obtain data on movements and home range size. Receiver and transmitters (Electronics Unlimited, Sacramento, California) operated between 31.38 and 31.56 MHz. Initial contact with instrumented bears was made by driving available roads and using the’ receiver connected to a 102 inch whip antenna. When a good signal was heard a directional antenna constructed of television cable and attached to a collapsible 15 foot beam was set up. The bear’s location was triangulated by taking directional bearings from several locations. In several cases, locations triangulated in this manner were verified by walking in with hand-held tracking equipment., Locations determined from triangulation were generally within one-eighth mile of the bears actual position. The range of both the whip and the directional antenna was two to four miles, provided the antenna was in line of sight with the transmitter.

Food habit data were determined from the collection and analysis of bear scats. The majority of scats were collected near developed areas and all collections were within the Hudsonian Life Zone. When possible, scats were aged to the nearest 15 day period. Scat analysis was accomplished by modifying the point frame technique described by Chamrad and Box (1964) for sampling rumen contents. A thorough explanation of equipment used and procedures followed is given by Knuckles (1972).