Mammals in an Urban Park: Herbivores, Omnivores, and Carnivores

During my many walks in Eliza Howell Park in Detroit in recent years, I have confirmed the presence of 15 different mammals (not including smaller mammals like voles, deer mice, and bats).

When animals are classified by what they eat, they are usually identified as herbivores, omnivores, or carnivores. Among the Eliza Howell herbivores is the Groundhog. In this picture, an adult is on the left, an immature on the right.

Herbivores eat plants and only plants, many having digestive systems that are able to digest many different kinds of plants, including grasses.

Of the 5 herbivores that I am aware of in the park, the White-tailed Deer is the most common. In the winter, when they are sometimes in herds, I have seen as many as 10 together. Here is a stag, watching me as I watched him.

I do not (yet) have any pictures of the two aquatic herbivores found in EHP: Muskrat and American Beaver. Beaver is the mammal most recently added to the list of those found in Eliza Howell and their practice of eating the stems, bark, and twigs of trees is evidenced by the many small trees they cut down and remove along the river.

The Eastern Cottontail is a fairly common herbivore in the park.

Omnivores are animals that eat both other animals and (parts of) plants. They may be primarily animal eaters or primarily plant eaters and omnivores make up the largest number of Eliza Howell mammal species.

The Virginia Opossum is largely nocturnal, but I do encounter one during the day from time to time. It is often slow moving and may allow one to get quite close.

Many omnivores are opportunistic feeders, eating whatever food is convenient. These include the various squirrels found in Eliza Howell. Tree squirrels are Fox Squirrel, Gray Squirrel (black variation in the picture below), and Red Squirrel. The ground squirrel is the Eastern Chipmunk.  Squirrels eat seeds and nuts and fruit, but they may also eat eggs, insects, baby birds.

(Clockwise from top left: Fox Squirrel, Red Squirrel, black Gray Squirrel, and Eastern Chipmunk)

Raccoons will eat almost anything, but they especially like small animals found in water, such as clams, crayfish, and frogs. I have seen them – and their tracks – most frequently by the river. They are also primarily nocturnal, sometimes seen resting in trees during the day. They also den in trees.

Photo by Kevin Murphy

Striped Skunk, another omnivore found in Eliza Howell, is mostly active at night and rarely seen.

Red Fox and Coyote are two mammals that are often considered carnivores, but perhaps should more accurately be considered omnivores. They eat mostly animals and carrion, but also eat fruit and berries.

In the last few years, I have seen Coyote more frequently than Red Fox in Eliza Howell. This picture of a Coyote was taken in nearby Rouge Park in Detroit.

Photo by Kevin Murphy

Carnivores are animals whose diet consists of other animals. The one mammal that I have seen in EHP that is strictly carnivore is Mink. It is semiaquatic (I have seen them only by the river) and eats fish, crayfish, mice, muskrats, birds, etc. I see it only occasionally.

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As noted above, these 15 species are not the only mammals in the park. There are some smaller species that I am aware of and, without a doubt, other species that I have not yet found. One example: I think the habitat is perfect for flying squirrels, but I have not yet seen any evidence of these nocturnal mammals.

There is much more to learn about my favorite urban park.

Some Recent FOYs

“FOY,” meaning first-of-the-year observation, appears frequently in my notes about my visits to Eliza Howell Park at this time of the year. There is something new to be seen every day.

Here are a few selected FOYs from recent walks, each of which seems noteworthy in its own way.

1.FOY Wild Lupine.

Lupine tends to be the first to bloom each year among the flowers in native wildflower field at Eliza Howell. It is starting to bloom now and I always note it both because of its attractiveness and as a herald of all that is to come.

2.FOY Baltimore Oriole Nest

Photo by Kevin Murphy

The nesting Baltimore Orioles are one of the highlights of the Detroit Audubon-sponsored field trip to Eliza Howell each June. (This year it is Saturday, June 8, at 8:00 a.m. – free and open to all.)

These orioles typically arrive in the first week of May and begin building nests in the third week of the month. The picture here was taken on May 18; the female was weaving.

3.FOY Burrowing Crayfish Hole

Crayfish (also called crawfish and sometimes crawdads) are gilled and clawed crustaceans, related to lobsters. Some are terrestrial, spending most of their lives away from bodies of water. They burrow down to groundwater and come up at night to eat on land. They are nocturnal and I have no pictures from Eliza Howell, but this hole is evidence that they remain present in the park. This one will probably continue to remove mud as it digs deeper, piling it up near the entrance in the shape of a chimney (or volcano).

4.FOY Common Milkweed

The common milkweed is a wildflower made famous as a host plant for Monarch butterfly eggs and larvae. Right after I saw the FOY Monarch on May 15, I checked a spot where I have found early milkweeds in other years. They are up and growing and will be ready any time the Monarchs are ready to lay eggs.

5.FOY Fledgling Robins

The day after I took this picture of 4 young robins filling the nest, they left it. While I have been observing a number of different bird nests this spring, this is the first that I have watched successful fledging.

6.FOY Opossum Encounter

On a recent walk in the EHP woods, I met this opossum along the path. “Possums” are nocturnal mammals and this daytime encounter reminds me that they are sometimes visible during the day. Maybe someday I see a mother opossum with several young on her back. That would be a great lifetime first (designated in my notes by “L” for “lifer.”)

7.FOY Honeysuckle Blossoms

The redbuds and the crabapples have already been blooming for some time, but one of my favorite blossoms, honeysuckle, is just beginning. Most of the honeysuckle in the park have white blossoms, but a few, like this one, tend toward pink. The picture was taken on May 21.

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This list of recent FOYs could be considerably longer, but it is time to get away from the desk and back to the park to see what is new today!

OPOSSUM AND ITS TRACKS

During my walks in Eliza Howell Park over the years, I have seen 14 mammal species, not including anything smaller than chipmunk (like vole and deer mouse) and not including feral domestic animals like dogs and cats.

One of the most fascinating is Virginia Opossum. Opossum is a mostly nocturnal mammal that is occasionally active in daytime, probably when it has a harder time finding adequate food. I do not see them often, but when I do, it is usually in winter. I saw one on my most recent nature walk. Though I was not in a position to get a picture at that time (it was walking away from me behind thick shrubs), I had been able to a close-up picture at Lake Erie Metropark only a day before.

Opossum is different from most other local mammals in several ways. 1) It is the only native North American marsupial, mammals that carry their young in a pouch. 2) One of its defenses is to feign death to prevent attack by rolling over, shutting its eyes, and letting its tongue to loll (“playing possum”). 3) Its hairless tail is prehensile, able to grasp things.

The opossum is an omnivore. Its diet includes earthworms, insects, frogs, birds, snakes, berries, and carrion. It has adapted to areas populated by humans and includes garbage in its diet.

It walks rather slowly (I have never seen one run) and I can often walk up to it when it is in the open. It is usually seen, like this, not paying any particular attention to humans.

There is another opossum feature that I find very interesting, especially in tracking season: the feet. The front feet have 5 quite evenly spaced pink toes that look like fingers with nails.

The rear feet also have 5 toes, but with a difference. The innermost toe is opposable, sticks out to the side like a thumb, different from other local mammals. Because of the angle, this toe does not show clearly in the picture.

Winter is the most common time to see opossum during the day. It is also the best time of the year to see the tracks, in the snow or in the mud at thaw time. I have not seen any opossum tracks recently, but this drawing (from the Peterson Field Guide to Animal Tracks) shows what the tracks look like (rear foot on the left and front on the right) and shows, as well, the bottom of the feet.

Perhaps because it looks something like a mouse or rat, some people do not find the opossum attractive. Whether seen as attractive or not, it is a fascinating part of the biological diversity of Eliza Howell Park.

ADDENDUM:

A couple days after posting the above, I did find opossum tracks. This is what they look like “in real life.”