Claw marks rip open tree bark, oozing sap like a botanical blood. Scratches like this scream a single message loud and clear: a bear was here. They aren’t subtle creatures.
As part of efforts to track bears without trapping them, US Geological Survey scientists find places frequented by bears to set up non-invasive hair traps. By analyzing hair, the researchers can track bears and learn about their diet and genetics without interfering with them.
Bear trail in Alaska. Image credit: Dawna Raven sky Zimbalist
The scientists look for bear-sign like these deep, parallel scars, bear scat, or paw prints to set out traps where they know bears already are, but also in places lacking in any bear-sign to look for more subtle activity.
Classic bear signs are direct traces can be as simple as pawprints, but also more indirect traces that mark signs of their activity. Bears create trails to their frequent destinations, sometimes even with pawprints directly overlapping as they retrace their own steps. They rub up against everything from power poles to boulders, leaving smooth, discoloured patches. They can also wallow in shallow, wet holes, the mud relieving itchy insect bites. Along with clawing trees, they’ll leave bite marks on just about everything.
Muddy bear paw print in Alberta. Image credit: Craig Morgan
Bears also leave signs of their feeding, with stripped trees where they fed on cambrium, the layer under bark where roots and stems sprout, or caches of dead animals too large to eat in one session. They even produce dig holes, rooting around for squirrels, tubers, or roots to munch on. And of course with all that eating, they also leave scat that can be analyzed to provide information about the bear’s health, diet, and genetics.
Bear rubbing against a tree in northwestern Montana. Image credit: USGS/Mika McKinnon
Researchers can even track where bears sleep, both from shallow depressions of short-term beds and with the more substantial hide-aways for hibernation. Either can be lined with branches or grass.
Top image: Bear scratches in Paradise Valley, Montana.Credit: Suzanna Soileau/USGS