|fwg is a long-term project of the ottawa field-naturalists' club|
Red squirrels (Tamiasciurus hudsonicus) at the FWG
by Christine Hanrahan
The American red squirrel, Tamiasciurus hudsonicus, is an engagingly feisty little animal. Although primarily a creature of coniferous forests, the diurnal red squirrel also inhabits deciduous woodlands and can even be found in suburban and near-urban areas throughout their range. Their adaptability in terms of both habitat and food sources has made them remarkably successful.
Red squirrels are often heard before they are seen. Their vocalizations include soft "clucking" sounds and high-pitched bird-like tones (that often cause beginning birders to ask what bird that is), as well as the more familiar angry-sounding chatter that occurs when an intruder is spotted. This latter vocalization is one of the most common sounds, not only in forests and woodlands, but also at the FWG.
These delicate looking little animals, weighing not much more than about 230 g, are in fact aggressively fearless, not at all reluctant to chase intruders many times their size. People get a kick out of seeing these squirrels stamping their feet, flicking their tails, and scolding vociferously in what seems like a paroxysm of rage. Anyone who has ventured near one of their food caches has been treated to this display. At times they get so agitated that they nearly fall out of the tree in their anxiety to see the interloper off.
They can often be seen chasing away larger gray squirrels (Sciurus carolinensis) who rarely put up a fight when confronted by these red terrors. A few years ago, I watched a red squirrel quite literally riding on the back of a gray squirrel and repeatedly biting its head. The gray was running, with difficulty, trying to shake the smaller animal from its back, with no success. I don't know what the outcome was because the gray managed to climb a tree and vanish, still with the red on its back! Was this simply a matter of chasing away an intruder taken to extreme, or was there a more insidious intent, with the gray being viewed as food?
Some years ago, I found a red squirrel feeding on the hindquarters of a gray squirrel (black phase). I never knew whether the gray squirrel had been killed by the red squirrel, or whether, as seems more likely, it had simply come across the animal already deceased and had taken advantage of a good source of protein (the flesh) and calcium and minerals (the bones). I watched this squirrel for a long time and it both ate the meaty part of the gray squirrel and gnawed on the bones. I have also seen red squirrels gnawing on bones of various animals, including those of a rabbit at the FWG.
As feisty as red squirrels are predatory on others, they themselves are preyed upon. At the FWG their biggest enemy is probably the domestic dog, but owls, hawks, weasels and foxes will also take these creatures. One year, a short-tailed weasel or ermine (Mustela erminea) took up residence in the doorframe of our Interpretive Centre. The mother moved in her 4 or 5 young, then went hunting for food. The first thing she brought back was a young red squirrel, considerably bigger than she was. Other volunteers at the garden have noticed red-tailed hawks eating red squirrels, and the great horned owls that sometimes stay around, although primarily nocturnal, will supplement their diet with both red and gray squirrels.
Unlike the gray squirrel whose diet consists largely (although not exclusively) of nuts and seeds, red squirrels are complete omnivores, consuming a tremendous variety of food. In addition to nuts, seeds, buds, bark, fruits, mushrooms (which are often hung to dry in tree branches), they are successful predators on bird's eggs, nestlings, voles, young rabbits, frogs, salamanders, and insects. In fact, I recall reading that they will eat anything that will not eat them.
At the FWG, I watched a red squirrel attempt to take the eggs from an American goldfinch nest lodged high in a Manitoba maple (Acer negundo). The adult birds were calling and flying around the squirrel who, initially undeterred, abandoned his quest when other birds joined in the fray. Their success as predators of eggs and nestlings gives them a bad name with some biologists concerned about their predation on songbirds with already low populations.
In spring, red squirrels often add sap to their diet. The red squirrel is an excellent tree-tapper, knowing the right time of year to gnaw away the tips of sugar maple (Acer saccharum) twigs allowing the sap to flow.
In late winter and early spring, there may be a carpet of spruce cuttings beneath the trees (see photo at left). Red squirrels will snip off the tips of branches and then scuttle down the tree to feed on the buds.
Black Walnuts (Juglans nigra) and Butternut (Juglans cinerea) are two more favourite food sources. I've also watched red squirrels at the FWG eating Manitoba maple seeds, staghorn sumac (Rhus typhina) seeds, and crabapples (Malus spp.).
One fascinating aspect of watching red squirrels is finding where they have set up "dining tables." Logs, stumps, rocks, brush piles, all serve the purpose, but the prettiest and most intriguing "table" I have found (although not at the FWG) was a set of very large polypores or bracket fungi, where it was clear that the squirrel had dined at leisure on a variety of foods (photo at left).
Red squirrels build large grassy nests (also called dreys), familiar sights to anyone who walks around the FWG. In the first years of the garden's life, they built their nests primarily in the tall spruce and pines that existed onsite before the area became the FWG. As other trees have matured, and as the squirrel population has expanded, they have taken to making nests in deciduous trees, sometimes in less than ideal situations. For example, the red squirrels living near the pond made a large grassy nest on the branches of a walnut tree overhanging the pond. This nest disintegrated fairly quickly. Others have been made in sumacs, manitoba maples, red elderberry (Sambucus racemosa) crabapples and a variety of other shrubs and trees. The best support and the greatest protection is offered by conifers, particularly spruce, and nests made in these trees last longer.
Many of the grassy nests fall down at some point, of course, and I've looked at a number of them. There is very little other vegetative matter used apart from grass although some have been lined with bits of bark or vines. These large bulky nests, particularly those in deciduous trees, are used primarily in summer. However, at the FWG, some of the squirrels use nest boxes for rearing young instead of grassy nests. And sometimes they will use both, moving their young from a grassy nest to a nest box when the young are a few weeks old. I've occasionally seen red squirrels denning under logs and under stone piles, but this appears to be an unusual occurrence.
Young red squirrels are usually born in April through to early May. Tiny and naked at first, they grow quickly and within a month are almost fully furred. One spring, Dale Crook an FWG volunteer, and myself, were cleaning out nest boxes. In the Old Field habitat we opened a box and out fell four tiny just-born squirrels. We quickly put them back in the box along with nest material and then Dale watched over the next few weeks to make sure they had survived. They had. And one day the mother moved them, one by one, to another nest box from where they soon emerged into the world.
Nobody knows for sure how long a red squirrel lives, but it is estimated that in the wild it is probably one to three years. At the FWG, our population seems to be doing quite well and we have at least 10 individuals at present, living on our 5-hectare site. Their numbers have increased over the years as the garden has matured with trees, particularly evergreens, planted 15 years ago now a good size.
At the FWG, the red squirrels have set up very distinct and separate territories. In the wild, their population density would probably be much less than it is at the FWG. We have at least 10 (and perhaps more) red squirrels on 5 hectares. In wilderness areas, estimates show that there would likely be about one red squirrel for every 2 hectares. If that was true at FWG, we'd only have 2,5 squirrels! Red squirrels tend to have fairly small home ranges and at FWG this can be clearly seen. Once you have figured out where they are, you can almost guarantee that you'll find them in the same location. Colour marking these animals in some way would be a good way of determining their range at FWG which is probably smaller than average given the density of animals.
Some years ago, one enterprising pair moved into a bird box situated between two walnut trees and they, or their descendants, have been there ever since. In 2006, another squirrel took up residence under the red barn; it uses a nearby log as its dining table and the remains of walnuts and cones can be found there in abundance.
If you look under conifers at the FWG, you'll find great piles of cones placed there by red squirrels. In their hurry to amass food, they will chew off branches holding the cones and let them fall to the ground. Every so often, they will descend to stack them into piles before going back to gather more. We have found these caches under Norway spruce (Picea abies), white spruce (Picea glauca) and Scotch pine (Pinus sylvestris). Most are small, but in some cases I have found caches nearly 3.5 feet deep.
In addition to their industrious caching of food, red squirrels also develop a very thick fur coat. Look at the red squirrels in winter and see how much bushier their coats look compared to those in the warmer seasons. Most non-hibernating animals develop similarly thick coats, including our domestic dogs and cats when housed outdoors.
The third ingredient for surviving winter successfully involves having a snug, warm, dry place to spend the night and those rare days, when the weather is so fierce that even red squirrels don't venture out. Cavities in trees afford much warmth, and around the FWG, nest boxes are good alternatives. Sometimes squirrels will create a winter den under a tree stump or fallen log. Whether they actually use underground dens seems open to debate. There is no doubt that they are quite comfortable going underground, and will make limited use of tunnels to store some food. During the winter months I have come across many holes leading underground (as opposed to snow tunnels which remain above ground), most with heaps of cone bracts around the entrance. Whether they are subterranean food chambers or places to spend the night, I am not sure. One way to discover this would be to dig up some of the tunnels and see what is there, but I wouldn't have the heart to do this in winter in case they are being used as shelter from the cold.
Red squirrels are endlessly entertaining and their behaviour coupled with their undeniable cuteness, makes them a favourite even of people who profess not to like squirrels. If you have stories about red squirrels that you've observed around the FWG, we'd be happy to hear about them. You can contact me at firstname.lastname@example.org.