Red Squirrel Damage to Coniferous Plantations and Its Relation to Changing Food Habits

Abstract

For several years a winter injury of unknown cause had been noticed in central Massachusetts coniferous planatations by members of the Harvard Forest staff. Twigs were cut off as cleanly as though by a knife, and in sufficient quantities to cause real damage to the trees. During the winter of I924-25. a study of the injury was made. To find the cause of the damage, several plantations were watched during early winter until, with the first heavy fall of snow, the clipping began. Then a plantation of Scotch pine (Pinus silvestris) where the activity appeared to be greatest, was watched from a blind until a red squirrel, Sciurus hudsonicus loquax Bangs I was seen doing the cutting. A study of the squirrel's habits here made it possible to identify him as the cause of all other fresh work found. He was also later seen eating European larch (Larix europaea) and white pine (Pinus strobus) buds. The next objective was to find out from the forester's standpoint how serious the injuries were. The damage takes place only when it is difficult or impossible for the squirrel to find food on the ground. A period of warm weather following such a time and resulting in the thinning of the snow to a few inches in depth greatly reduces the amount of damage per day. An exception to this general statement is that European larch and white pine buds, at least, are eaten when they are just beginning to swell in the spring. Scotch pine, Norway spruce (Picea Abies) and European larch are heavily injured. Only one red pine (Pinus resinosa) was found damaged out of hundreds examined. White pine is ordinarily immune, but in a winter of deep snow a heavy leader injury takes place. Often a group of young trees will be over ninety per cent injured, and in one case trees up to 25 feet tall lost their terminals. Red spruce (Picea rubens) is apparently ignored entirely. It was thought that white spruce (Picea canadensis), a species introduced from further north, but which grows vigorously in northern Massachusetts, would be strongly attacked. Examination of several hundred trees in a i9 year old plantation showed only one injury per hundred, while a nearby stand of Norway spruce was heavily damaged. Besides the region where the study was made, the author has found the injury in northeastern Massachusetts, northern Connecticut and central New York. So it is by no means local, and probably occurs throughout the range