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September 27, 2009

The Art of Observing: Signs of Life

Playing Detective

All Animals July/August 09 Observing Wildlife Chipmunk

Kathy Milani/The HSUS

by Ruthanne Johnson

The evidence of wildlife is everywhere.

It’s just a matter of recognizing the clues: A mouse drops a path of seed sheaths as he forages; a deer beds down in a tall patch of grass, leaving a circular impression; a snail’s glistening trail stretches across the top of a broad, green leaf, vanishing next to the imprint of a frog long gone.

A careful look at the ground may reveal evidence of dust baths and wallows, tunnels and trails, burrows and dens, recent meals, tooth cuttings, and territorial boundaries. These features tell a story about animals’ efforts to forage, escape predation, preen, mate, raise their young, and simply enjoy life. Use the following tips as a guide to recreate the narrative.

Home Sweet Home

Animal houses are diverse in materials used and the resourcefulness of the designs. Prairie dogs construct underground burrows, while beavers build lodges along streams and squirrels make nests known as dreys high in the trees.

Some birds make simple scrapes in the ground that they camouflage with stones or shells; others create platforms, crevices, nests, cavities, or burrows.

Many creations are subtle, says Pauli. “What might look like a clump of grass or merely a depression may be a nest with baby rabbits in it.”

When trying to identify the owner of a burrow or hole, consider the habitat where it was built and the range of likely inhabitants. The size and shape of the entrance provide hints, as do fur, scat, smells, and signs of feeding.

It is not always possible to know the original excavator because other animals may visit and use the hole, enlarging it in the process.

For example, abandoned prairie dog holes on the perimeter of active towns become homes for rabbits, burrowing owls, rattlesnakes, and even black widow spiders.

Pauli once cracked a den mystery when responding to a homeowner’s request for help.

A hole under the deck “looked like it had been dug by a yellow-bellied marmot, who have shorter legs and push the dirt to the side,” he says. But the noises coming from the den occurred at night, and marmots are active during the day.

After some sleuthing, Pauli discovered a skunk was occupying the old marmot hole. “Stuff like this happens all the time in the wild, especially with opportunists,” he says.

Foodstuffs and meal scraps

While some animals eat at the source and leave their scraps, chipmunks, gray squirrels, porcupines, voles, and birds create food caches or digs.

These stashes of seeds, nuts, grasses, bark, and fruit may be stored in a burrow or hidden under rocks or logs, in grass clumps or leaf litter, or behind loose bark.

Some species throw dirt when digging for food, while birds scratching for insects merely shuffle the ground.

Signs of foraging also include teeth marks on grasses, fruit, woody stalks, bark, stems, and flowers.

Your field guide can help you determine who’s been chowing down; ripped grasses indicate ungulates, while incisor marks in fruit may be evidence of a meadow vole or chipmunk. Foraging detective work can uncover new and surprising information, as happened with a discovery that Rezendes made about false truffles.

The root systems of these underground forest fungi, which are more than a mile long, connect to the root systems of trees. “They are very important to our ecosystem, and until I observed [evidence of] porcupines digging them up and eating them, we had no idea that they ate these things,” says Rezendes.

“Now we know that porcupines play a role in dispersing their spore.” When tracking predators such as coyotes, bobcats, and fishers, Rezendes often comes across a kill site, such as a deer carcass, that serves as a stepping stone for observing other animals. “The forest comes from all directions to converge on the life of that deer,” he says. “Even snowshoe hares will eat meat, and chickadees will peck at the bones.”

The scoop on scat

Droppings are also a species indicator, with undigested leftovers revealing an animal’s recent meals. The scat of wolf packs may carry indicators of status; scat belonging to the animals last in the pecking order often shows bits of hide and bone, the least nutritious and least favored parts.

Location of scat may say something about behavior. In their network of underground tunnels, prairie dogs build separate rooms to relieve themselves.

Small piles of their fertilizing scat can be seen aboveground after they sweep these rooms clean in the spring.

Reading the trees

To stake out their territory during the mating season, deer, elk, moose, caribou, and bison scrape trees with their antlers or horns.

Woodchucks leave bite marks on trees and low branches, perhaps to indicate their claim on an area. Even squirrels are thought to send territorial messages as they bite stripes in tree bark that are not deep enough for obtaining nutrition.

By looking at trees, you may also be able to surmise whether an animal was climbing to obtain food, reach the shelter of a cavity, or escape something that frightened him.

Bears who share habitat with humans frequently climb trees to avoid interaction, while wolves create resting places by chewing off lower branches of pines and settling on the ground underneath.

When Pauli united orphaned mallard ducklings with an adoptive mother duck on a Montana pond, he observed some interesting marks on several trees: They were chewed off at about 12 to 14 inches.

“This told me that a relatively young colony of beavers is living in the area, and I could estimate the size of the beavers and tell their age by the width of the tooth marks.”

Sounds and scents

Besides the familiar bird calls, animal sounds may include a beaver slapping his tail in warning, a turtle quietly crunching through leaves as she makes her way along the forest floor, or a hawk flapping her wings in flight. Even silence can indicate that something is wrong, says Pauli, such as a storm brewing or a predator lurking nearby.

But to hear these sounds, observers must be careful not to make their own noises, says Rezendes. “A human in the forest creates a perimeter, like the ripples that form when a rock is thrown into a pond,” he says.

“The noise perimeter is typically larger than the visual perimeter, and if you want to have a phenomenal wildlife experience, the trick is to see the animal before it sees you, to create a visual perimeter larger than the sound perimeter you are making.” Rezendes recommends a stealthy gait, with long stops between steps.

“For every five minutes of walking, you should stop, look, and listen for at least 10 minutes to give animals the chance to move into your perimeter of vision.” He also recommends hiking without the family dog, who may send wildlife into hiding. Smells, too, offer the keen observer information.

“With enough instinct and training you can pick up on smells,” Pauli says. “For example, beaver castor smells sweet, and you can smell where a fox has passed by and left his mark once you know how to identify the scent.”

Rezendes looks for stumps of a certain height and type that bobcats use to mark territory. “By smelling and observing the side of the scent post that has been sprayed, you can tell which direction the bobcat is going in and track the animal.”

Tread lightly

It’s almost always illegal to remove items such as feathers, eggs, and nests from the wild, but evidence such as fur, leftover foods, and objects with teeth or claw markings can be collected. Pauli suggests collecting fur samples by leaving a brush near an animal den, secured in place with duct tape.

Digital photographs are another means of gathering evidence without disturbing the environment. If you discover tracks leading to a den or resting site, “simply back down the trail to study the tracks so you won’t disturb the animal who left them,” Pauli says. “And always make sure you put things back the way you found them or even better, like picking up [other] people’s trash.”

Keep reading: A Good Impression»

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