Tooth marks in the bark on a fallen tree branch, probably made by a small mammal such as a squirrel. The whitish marks down the left-hand side look like where the animal placed its lower teeth while it used its upper teeth to scrape the bark. Here and at other places on this log there were signs of small black bobbles near the tooth marks, as if the animal was actually scraping these off to eat them.
The black bobbles may be a Rosellinia sp fungus. The bark, itself, also seem to be unusually dark and may have been covered in a black crust.
Photos taken in the Wilderness, Whiteknights Park, Reading University grounds, Reading, UK, on 2011-02-05.
The black bobbles look more like Eutypa spinosa than Rosellinia sp.
The whitish marks down the left-hand side could also be claw marks.