Tag: red pine

Lean Times for Squirrels

With the coming of spring nature is breaking its winter dormancy, but we’re still a long way from the bounty of summer. In some years the food stores that carried squirrels through the winter are depleted by the time spring comes around, and when this happens the new season may bring food stress instead of abundance. This is especially true if there’s a new litter of young to raise. But over the last month or so I’ve been finding evidence that squirrels are still making use of winter’s leftovers. Digs like the one in the photo below show where an edible item was extracted. I’m confident that this was a recent dig, because the leaves around the dig were still pushed up and the soil was freshly disturbed. If this were an old dig the heavy rains we had earlier in the month would have flattened the leaves and washed the soil back into the hole.

Without further investigation it’s hard to see what the squirrel was after. When I carefully removed the leaves (as shown in the next photo), I saw not only evidence that this was a fresh disturbance but also evidence of what was removed: a firm-walled cavity that was the perfect shape of an acorn.

More proof that buried acorns are still being utilized by gray squirrels is shown in the next photo. The brightness of the acorn remnants indicates that they were not more than a few weeks old when the photo was taken in mid-April.

Instead of acorns, red squirrels rely on conifer seeds for survival over the winter, and in many locations they are still making use of the stores of cones that were gathered last summer. A few weeks ago I found a spot (shown in the next photo) where a red squirrel had extracted the seeds from a red pine cone. The bright colors of the cone core and cone scales show that the feeding activity occurred recently. Additional corroboration of recent feeding comes from weather observations. In early April we had several intense downpours, and if the cone remnants had resulted from winter feeding the heavy rain would have washed them off the log.

I’ve noticed lots of recent feeding on white pine cones this spring. In the next photo you see a midden at the base of a large white pine. The feeding perch was on the branch at the top center, and entrances to the underground storage areas can be see a little below on both sides of the feeding perch. Again, the brightness of the discarded cone scales suggests recent feeding.

A close-up of one of the tunnel entrances shows dry material that was brought out of the storage space as the resident red squirrel retrieved stored cones–more evidence of recent activity.

Even if winter leftovers are still available they may have suffered some deterioration, forcing squirrels to seek supplemental foods. A squirrel harvested the boxelder twigs shown in the next photo and fed on the buds. The end buds are missing from the twig on the left, and several lateral buds were taken off of both twigs. Why weren’t all of the buds eaten? Perhaps because there were so many buds and twigs available that the squirrel could be haphazard in its feeding.

Grubs are common in grassy areas, especially in suburban lawns, and they can be important in squirrels’ spring diet. I found the dig shown below in my back yard.

Squirrels are also known to eat conifer needles. In the next photo you see white pine needles that were fed on by a red squirrel. Compared to acorns and grubs, conifer needles don’t seem very nutritious, but they may fill a need for nutrients that are otherwise lacking.

The rising sap of deciduous trees is another source of calories, and it usually becomes available just when squirrels need an energy boost. A red squirrel tapped the black birch sapling shown in the photo below. There’s a fresh bite (with a slight greenish hue) about midway up the stem, and old bites from previous years can be seen above and below. There’s another fresh bite along the side of the stem near the top. Squirrels are expert sap harvesters and use an efficient method to extract the maximum benefit. Rather than lap up the dilute sap, the clever animals let the water evaporate and return the next day to eat the concentrated solids.

Some foods may become less available in spring, but other dietary options are simultaneously becoming more available. Squirrels are flexible in their eating habits, and this is the perfect time to observe their ability to make use of a wide range of foods.

Bounty From Above

The season is turning, and red squirrels are obsessed with gathering food stores for the winter. They will rely primarily on the cones of spruce, fir, and pine–and to a lesser extent on larch, eastern hemlock, and white cedar–for survival over the coming months. The squirrels’ preparations for the lean times ahead leave plenty of evidence. In the photo below the ground is littered with red pine cones. A few brown cones that fell the previous year contrast with the green of this year’s crop. When stored in a humid environment the tightly closed green cones will last through the winter without opening, preserving their precious seeds until a red squirrel pulls them apart to get at the nutritious nuggets inside.

The next photo was taken in a stand of Norway spruce, a tree that is native to northern Europe but was widely used in reforestation projects in the US during the twentieth century. Some of the trees in these plantations are large and produce copious crops of cones. The cones’ large size–some as long as eight inches–means they are a bonanza of food for red squirrels.

You can see another harvest in the photo below, this time the cones of white pine. Again, it’s the largest trees, the ones that tower over the rest of the forest, that produce the best crops of cones and attract red squirrels to harvest them.

These arrays of fallen cones don’t usually last long. After working in the tree tops to drop a supply of cones the squirrel descends and transports the bounty to an underground storage space, known as a larder. A red squirrel typically has a number of larders, often made by enlarging the natural spaces that form around large roots. Rock crevices and hollow trees may also be used, and cones are sometimes stored under fallen trees or even in abandoned buildings. Green cones stay tightly closed all winter and well into spring in these humid spaces.

The white pine cones shown in the next image were also nipped by a red squirrel, and these cones probably look more like the ones you’re used to seeing. There must have been an interruption before they could be transported to a storage cavity, because they’ve dried out and released their seeds. Our weather has been dry lately, so drying may have happened unusually quickly, making the cones useless for winter food. So if the seeds were released when the cones opened, where are they, you ask? Such a concentrated serving of edibles wouldn’t have gone unnoticed by birds and small mammals and would have been rapidly consumed.

I was curious about how the squirrels detach cones from branches. I imagined a a lot of yanking and chewing, which should have left tooth or claw indentations somewhere around the sides of the cones. But when I looked for marks, all I could find were small bits of exposed wood at the attachment sites. The photo below shows the lighter separation areas at the bases of some of the red pine cones I examined. On Norway spruce and white pine cones it was the same– all I saw were small separation wounds at the bases.

I realized I needed to see how cones are attached to twigs, and what I found suggests that nipping cones is pretty straightforward. In the next photo you see a red pine cone attached tightly to a twig. A squirrel need only bite through the attachment point by inserting its tiny incisors into the angle between the cone and the twig. This would produce a lighter colored spot at the separation point like the ones I observed on the dropped cones.

Image from TheSpruce.com

I’ve never seen this happening (how I would love to levitate to the top of a tree and watch!) but I did find a video of a red squirrel harvesting cones from a western pine, probably a ponderosa pine. You can see it here. (The clearest view starts at 2 minutes and lasts about a minute.) The squirrel perches on the branch and works from the back side of the cone, occasionally using its front feet but mostly just gnawing at the connection between the cone and the branch until the cone falls.

Finding the evidence left by these frenetic little creatures isn’t hard–just pay attention to what’s on the ground whenever you pass under conifers. You’re most likely to find signs of harvesting where there are middens (piles of discarded cone scales and cores) from previous years, since resident squirrels tend to keep the same territories year after year. And sound may guide you to a harvesting site. A falling cone lands with a thump; the bigger the cone the louder the thump. If a falling cone hits branches on the way down you’ll hear some plunks and bonks followed by a thump. Follow your ears toward the sounds and you’ll probably find nipped cones scattered on the ground and a red squirrel chattering angrily at you from high in the tree.