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 Eastern Grey 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 grey squirrel and repeatedly biting its head. The grey 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 grey 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 grey being viewed as food?
Some years ago, I found a red squirrel feeding on the hindquarters of a grey squirrel (black phase). I never knew whether the grey 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 grey 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 door frame of our Resource 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 grey squirrels.