Identifying Nocturnal Mammal Activity
Animals like raccoons, skunks, and opossums may be difficult to observe live since they come out at night, but if you know what evidence to look for, you can figure out where they've been even during the day. Knowing the pathways and habits of animals in your yard and neighborhood can help you observe them more easily, and also inform your strategies to avoid human-wildlife conflict.
Trampled Pathways
You can learn a lot about wildlife activity in your yard or another space by looking at the routes animals are following at night. Animals often follow the same pathways multiple nights in a row, so these areas tend to be well worn and identifiable. Look for trampled-down grass and debris, or pathways on the ground where the grass doesn't seem to grow as well. Skunks, raccoons, and opossums tend to travel along fence perimeters, especially in yards where greenery is planted along the fence. In thick vegetation such as Mexican bamboo, you may be able to see "tunnels" along the fence that animals use. There also may be trampled depressions where animals go under the fence into the next yard.
Larger animals create trampled pathways as well. If you live where there are coyotes, or if you are visiting an open space like the Palermo Open Space, look for pathways through tall grass that seem too narrow for a person to have made. These may be from coyotes.
Detecting Active Pathways, Tunnels, and Burrows
How does one tell if a pathway or tunnel through vegetation or under a fence is active? You can detect recent activity with a simple experiment. Place a pile of straw or dry leaf litter in the path in the afternoon, large enough that you would be able to tell if it has been stepped on, but not so large as to deter animals from using the path. In the morning, check all of these "detectors" and see if any show new trampling. (The photo on the right shows where an animal went under the fence and created a path through the straw.) You can even put out a motion-detecting wildlife camera, or sit in your yard in the evening in person, to find out what specific animal is using the path. Often, paths will be used by more than one species.
The same technique works to see if a burrow is active. If there is more than one entrance to the burrow, place detectors at all entrances- just because one entrance does not appear to be active doesn't mean the burrow is unused. Always use caution near potential burrows, as there could be an animal inside! Place the detectors in broad daylight, long before the animal will likely come out. Avoid reaching into burrows with your hands, and if you can, place the detectors using a long stick or a trash picker to avoid getting too close to the burrow. And make sure to have an easy exit from the area if you accidentally disturb an animal. Most of the time, however, quietly placing leaves or straw in front of a burrow will not cause the animal to come out.
Burrows
If skunks, raccoons, and/or opossums are in your neighborhood, it's possible they might even be living in your yard! When inspecting the perimeter of your yard and vegetated areas for pathways and tunnels, it is possible that one may lead to a burrow. Skunks either dig their own burrows or reuse other cavities like hollow logs, other animals' burrows, or crawlspaces under buildings. Raccoons and opossums don't dig their own burrows, but reuse spaces they find. All three of these animals may be found nesting close to the ground, and raccoons and opossums sometimes nest aboveground (such as in tree branches hollowed out by woodpeckers) as well.
When looking for burrows, here are some signs to look out for:
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Tunnels that lead into thick vegetation and don't seem to come out on the other side. Many animals make their homes in these areas. However, it might just be another tunnel.
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Holes dug under structures or at the edges of paved areas. These may be burrows a skunk has made, which may be inhabited by the skunk itself or another animal like an opossum.
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Cavities in the trunks or branches or trees. These areas tend to appeal to raccoons and sometimes opossums. Look for signs of use, such as fur stuck to the edges of the hole or a trampled pathway leading to and from the tree.
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Trampled pathways leading into crawlspaces or other manmade cavities. Skunks, raccoons, and opossums sometimes make use of these areas to live in, and probably wouldn't be entering them if they're just passing by.
As with pathways, once you have identified possible burrows, you can monitor activity by making detectors with straw or leaves, by setting up a wildlife camera, or by simply sitting in your yard as it gets dark and watching for animals.
"Misplaced" Items
Skunks, raccoons, and opossums are opportunistic eaters, feeding on a wide range of items they can find in either natural settings or neighborhoods. Sometimes they will grab a piece of food and take it with them, leaving scraps along the way. If you have fruit trees, look for fruit or fruit scraps that seem out of place. For example, an opossum might have taken a fallen apple off the ground and brought it into the bushes to eat it, leaving part of it behind. Eggshells, bones, pieces of trash, and other items in unusual places could also be signs of nocturnal animal activity. They could also have been left behind by crows or jays.
Signs of Digging
Nocturnal animals, particularly skunks, sometimes dig small holes in the ground to forage for grubs. Look in areas of moist soil such as gardens and lawns, which are likely to support these insects. If you see a place where it looks like something was digging, but the hole doesn't go all the way into the ground like a gopher hole, it may signify skunk activity.
Scratched Wooden Fences
Raccoons can move between yards by climbing over fences, but they can be quite clumsy, leaving scratches on the wood as they try to get up. Look for these marks near trees or bushes along the perimeter of your yard, as these are the places where raccoons will likely be trying to climb over the fence. If you have a fence right outside your window, you may even be woken up by the sound of a raccoon climbing over it every once in awhile.
Tracks and Scat
Look closely on the ground and you may see the tracks or scat of animals. Tracks are most easily found when the ground is wet- look for imprints in muddy areas, or dirty footprints on a path or sidewalk. Scat can be found all year, and is most commonly located in areas that animals spend the most time- under bushes and around the perimeter of your yard, for example. You can use a field guide or the iNaturalist app to identify the specific type of animal from its tracks or scat, or simply monitor for these signs to determine what areas of your yard are most used by wildlife.