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Beth Huning and Linda Yemoto
Squirrel activity in the Mariposa Grove of Giant Sequoias was evident all summer, but feeding activity accelerated tremendously in August. It is probable that the unusually cool August weather brought squirrels out in large numbers, possibly in anticipation of the early arrival of autumn. This acceleration drew attention to their feeding on the cone of the sugar pine(Pinus lambertiana).
The long, green sugar pine cones are prized by most squirrels. These cones have been recently falling like loaded projectiles, often narrowly missing unsuspecting hikers and tram passengers.
Most squirrels relish sugar pine cone seeds, possibly because of their size, number and flavor. However, only the tree dwellers are able to scurry out to branch tips and use their long incisors to cut off the green cones. Most cones in the Mariposa Grove have fallen due to the chickaree’s (Tamiasciurus douglasi, or Douglas Squirrel) efforts. The chickaree scrambles up the tree and cuts the cones which plunge to the ground. Being too small either to prevent the cone from falling or to haul it back up the tree, the chickaree must devour the cones on the ground.
As John Muir indicated in The Mountains of California, the chickaree often drags the fallen cone to the base of a tree before tearing it apart. As many as seven chickarees at one time have been observed working apart individual cones in large open areas.
In watching the lively chickaree at work, it appears that they are so determined to scratch the two seeds from the base of each scale that they literally rip the cone apart, flinging the scales rapidly in every direction, finally locating the choice morsels. Sitting on his haunches, he almost always holds the sugar pine seed in his front paws, cracking and discarding the outer shell and eating the seed. From the base of the cone the chickaree works in a spiral pattern, following that of the cone, turning it over with his paws or pulling it with his teeth. A messy midden results — a pile of scales and a lonely core in the vicinity. Fibers are often left dangling from the core and usually a small bundle of scales remains at the tip.
Although the California Gray Squirrel (Sciurus griseus) is more common at elevations lower than the Mariposa Grove, some make their homes there. Gray squirrels often eat seeds of ponderosa pine (Pinus ponderosa) cones but a sugar pine cone is a treat. Observing gray squirrels is not easy because they do most of their feeding in tree tops. Apparently these squirrels are large enough to cut cones from branches and yet hold them to prevent their falling, or, if the cones do fall, they are able to haul them back up a tree. Mature green sugar pine cones can be quite heavy, some weighing two pounds.
One gray squirrel was observed eating a sugar pine cone on the ground while another was seen eating cones in a tree. The one sat on his haunches, holding the cone between his front paws, similar to the way we eat corn on the cob. He pulled off the scales, then cracked the shells and devoured the seeds. As he worked, he twisted the cone between his paws,
[click to enlarge]
Chickaree, pamiasciurus douglasi.
Because tree squirrels must climb to the ground to claim their cones, ground squirrels, often waiting at the foot of a tree, intercept them. The California Ground Squirrel (Citellus beecheyi) often begins to eat the cone at its base, pulling off pieces of scales in a half-moon pattern, then, standing upon the cone, he leans over the sides in order to obtain as many seeds as possible. Thus he is able to roll the cone over while backing off of it. Apparently the ground squirrel not only eats the seed but much of the cone’s fleshy portions as well. He cuts the scales away from the core and strips the fleshy part of the scale, shredding it into many pieces. Thus, he usually leaves a very clean core, compared to that of the chickaree.
Because sugar pine cones contain much sap, most squirrels wipe their faces periodically with their paws, or in the dirt or on the bark of trees. Although the effort was undertaken to discover whether Golden Mantled Ground Squirrels (Citellus lateralis) eat sugar pine cone seeds, as has been reported, none was observed.
Interaction occurs among squirrels for possession of sugar pine cones. Chickarees will defend their cones actively against other chickarees. However, if a ground squirrel intrudes, a chickaree will give way, surrendering his cone.
Some semblance of a mock-defense was observed when a chickaree made several running leaps at a ground squirrel, twisting and turning in mid-air, but never touching the ground squirrel and never making a sound. When the ground squirrel momentarily left the cone to enter his burrow, the chickaree reclaimed the cone. As soon as the ground squirrel returned, the above incident reoccurred. No interaction was observed between a chickaree and a gray squirrel or between a gray squirrel and a ground squirrel.
Different circumstances, including shape of the cone and slope of the land, may necessitate eating a cone in a different fashion. There is also a ‘mystery cone,’ a pattern where strips of scales are removed from one end of the cone to the other. However, barring individual differences, it appears that there are definite patterns resulting from the methods various squirrels practice to work apart a green sugar pine cone. Therefore, to some extent the original ownership of a deserted cone, midden or core can be identified. However, since several squirrels may eat the same cone, it is often difficult to definitely distinguish ‘who did it’.
John Muir (1894, 1961), The Mountains of California, The Natural History Library, Anchor Books, Doubleday and Company, Inc. 300 pp. footnote page 180.
Lowell Sumner and Joseph S. Dixon (1953), Birds and Mammals of the Sierra Nevada, University of California Press, Berkeley and Los Angeles, 484 pp. footnote page 392.
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