I have reviewed the entire late August-late October card and some of the June-August card for what we’ve designated as deployment 5 – a three-years dead Sweetgum stub discussed last summer. Based on approximately six months of data from this deployment, I think squirrels can be excluded as the source of extensive bark removal from mature, thick-barked hardwood boles, just as the data suggest that Pileated Woodpecker can be excluded as the source of scaling on hickories.
The only potential sources of the extensive bark removal under discussion are gray or fox squirrel, Pileated Woodpecker, and Ivory-billed Woodpecker. Pileated Woodpeckers appear to be unable to remove large quantities of bark from hickories in large pieces, and squirrels appear to be unable to do so on the weaker, thinner-barked sweetgums. Based on trail cam captures obtained thus far, Ivory-billed Woodpecker is the likeliest source for the extensive bark-scaling on hickories that we’ve found infrequently in our search area and that I’ve hypothesized is diagnostic for that species.
There were no woodpecker hits on this target tree, but there are multiple sequences involving squirrels. There was minimal little bark removal, and only from previously scaled areas. In fact, I have only detected one visible change to the bark. A small quantity was removed on June 9, between 11:44:13 and 11:44:33. This is shown in the details below.
Squirrels were active on this scaled patch over the course of the deployment, but whatever removed the small strip of bark on the lower right did so during that 20-second interval and was not captured on the trail camera. I think a woodpecker of some sort is probable, since a squirrel would likely have been visible on the trunk in preceding or subsequent frames.
More importantly, squirrels were captured on or around the scaled areas on multiple occasions, and the captures shed light the way they interact with bark on standing boles and what may limit their capacity to remove it.
This deployment ran from August 19-October 21. Squirrels were detected on 17 days and on or near the scaled surfaces on at least 6 of those days. As previously documented, squirrels displayed interest in the edges of the scaling and frequently appeared to be gnawing; however, they removed little or no bark. We now have numerous captures of squirrels on target boles, both scaled and unscaled, and no captures showing them removing bark in quantity or in anything other than small strips.
Squirrels are clearly capable of rapidly and efficiently removing bark from limbs, downed trees, and thinner barked boles. However, I think there are physical limits – body structure and incisor length – on their capacity to remove thick bark from standing boles.
The following images and time lapse clips show what squirrels do when confronted with thicker bark and suggest that when hanging onto a standing trunk, they lack the leverage to remove bark quickly and leave large pieces behind. This should apparent in the selection of stills and video clips shown below as well as in the sequences posted previously. (A brief discussion of squirrels on hickories follows the images.)
Up to now, I have not been differentiating among squirrel hits on targeted trees, squirrel hits on or near scaled surfaces, and squirrel hits in other parts of the frame. Suffice it to say there many, far more than woodpecker hits on both sweet gums and hickories. Squirrels frequently show an interest in the scaled surfaces and also in other damaged areas (like the fracture in the hickory bark shown below). To date we have no examples of squirrels removing any bark from hickories, regardless of condition. It stands to reason that the limits of their capacity on hickories would far exceed what limits their capacity on sweet gums.