While the student naturalists were walking in the Arb recently, we found ourselves on the edge of the Cannon River. We had been looking for tracks, but had yet to find anything very interesting. Spying many trails weaving over the fro- zen surface of the river, we went down closer to investigate and discovered the unique track that you see in the picture. It turned out to be an opossum.

As you might be able to see from the picture, there are two distinct tracks. The forefoot, the left print in the picture, has four clearly splayed fingers and a thumb. Because opossums are tree-climbers, they have large pads on the palms of their “hands.” These pads made the deep semi- circular impression you can see in the picture below the fingers. The back foot can be seen here at a 90 degree angle to the front foot. It is less clear, but you can make out the four fingers and large thumb used for climbing.

North American Opossums (Didelphis virginiana) are the only marsupials found in North America. They are opportunistic omnivores who are known to have 50 teeth. Finding an opossum track in the winter is rare. Because they can’t store energy effectively for long periods of time, opossums do not hibernate. However, they do have greatly reduced activity during the winter months. If opossums are out less, there is less opportunity to catch them or their tracks. But, the warm winter we’ve been having has made it easier for opossums like ours to venture out for dinner. We can probably thank the warmer weather for this opportunity to spy an opossum track.