Beaver Cuttings in Aspen Indirectly Detrimental to White Pine

Abstract

Recent beaver (Castor canadensis) activity in a large-tooth aspen (Populus grandidentata) woodland had an indirect and undesirable influence on underplanted white pine (Pinus strobus). The pine plantings, made in 1955, had grown well in the partial shade and had been free from the white-pine weevil (Pissodes strobi), which had severely attacked white pine in an adjacent open-grown plantation. In the fall of 1962, beavers moved into the area, felling the aspen, and opening up the woodland. The ecological conditions created were ideal for the weevil, which appeared during 1963 and attacked 75 percent of the pine. Beavers were active during the fall of 1962 in certain areas of Isabella County, located in the center of Michigan's Lower Peninsula. One woodland they selected was composed predominantly of 30-year-old large-tooth aspen which had been under861 been carried by these beavers for 17-22 months. Four plastic-marked beavers have been recaptured alive on the beaver study area in Manitoba. These beavers had gone through a winter with their plastic markers, and seven of the eight markers were still firmly fixed to the metal ear tags. Plastic-marked beavers have been readily identified while they were swimming freely on the surface of the water, and they have also been easily identified from as much as 30 feet away while swimming below the surface in clear water. There have been hundreds of positive observations made of individually known beavers in Newfoundland and Manitoba. Many of these observations were made at active colony sites, but some were made of transients traveling outside their normal territory. Identification of free swimming, individually known beavers has resulted in the accumulation of numerous data that was not possible with other tagging methods. This same plastic-marking technique was used to tag marten (Martes americana) in Manitoba during 1961, but a smaller marker is recommended for this animal. The same technique could probably be employed to mark other mammals such as fishers (Martes pennanti), otters (Lutra canadensis), squirrels, and groundhogs (Marmota monax).