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.

Nature Discovery Day Is July 13

On Saturday, July 13,  there is a great opportunity for visitors to the park to become more familiar with the wildflowers, butterflies, birds, mammals, trees — and more – of Eliza Howell Park: 9:00 – noon. Free and open to everyone.

There will be exhibits, activities, and options of guided walks designed to point out some of the natural wealth of this Detroit park. The park entrance is on Fenkell east of Telegraph. The event also includes an opportunity to learn more about the U-M wildlife motion-activated camera project (which includes Eliza Howell Park).

Among the highlights of mid-July are the meadow/prairie wildflowers. Among those catching my attention recently are these.

Clockwise from top left: Foxglove Beardtongue, Black-eyed Susan, Butterfly Weed, Common Milkweed

The event is organized by Eliza Howell Park Partnership (EHPP), a coalition of persons with different organizational affiliations and a common interest in highlighting Eliza Howell as a place for observing and enjoying nature in an urban environment.

Guides will be present to assist in identifying the varieties of flowers, as well as the specific species of butterflies they attract. These are among the common butterflies at this time of the year.

Clockwise from top left: Monarch, Common Ringlet, Red Admiral, Pearl Crescent.

While I am often unable to get a picture of a butterfly I see, it is never difficult to find flowers waiting to be photographed.

Clockwise from top left: Staghorn Sumac, Chicory, Wild Bergamot, St John’s Wort.

Eliza Howell is the kind of nature park it is, in significant part, because the Rouge River runs through it. For those who wish to take it on Saturday, a short walk to the footbridge provides a good view of the shaded river.

Back in the field, one flower not to be missed is Wild Bergamot, a mint family flower, sometimes called beebalm, that has only recently begun its summer blooming season. It is a magnet for a variety of insects. In this picture, the visitor is a Hummingbird Moth.

Many mammals are more active at night than during the day. The cameras used in the UM wildlife camera project have located and identified some of the mammals of the night, as will be reported on July 13.

Two that I have recently seen during the day are White-tailed Deer and Groundhog.

I thank EHPP for providing this opportunity to witness and enjoy the natural wealth of the park.

 

“Acornucopia”— and Wildlife Benefits

“Cornucopia” being abundance or profusion, vast numbers of acorns might be called “acornucopia.” Eliza Howell Park is home to many productive oak trees and the acorns seem especially plentiful this year.

There is a great variety of oak trees in the park. On an afternoon walk on September 19, I was noting the varieties of acorns and collected these examples in a very short period of time.

Acorn production varies from year to year and from species to species. Overall, 2018 is a bountiful year. Some trees have as many acorns as I ever remember seeing.

One of my favorite oaks, a type of red oak, is a large tree with several low hanging branches filled with acorns that fit my mental image of the archetypal acorn.

For many wildlife, an abundance of acorns means a valuable food source as winter approaches. Dozens of mammals and birds eat acorns. Acorns make up about 25% of the diet of White-tailed Deer in the fall. An abundant acorn crop often means healthier deer heading into the breeding season.

This stag, which crossed the EHP footbridge right before me one day last fall, may well have been foraging for acorns.

Rabbits, raccoons, opossums, even foxes, eat acorns. And squirrel consumption of acorns is so well known that I need not comment.

Many of the mammals feed at night, but it is easy to watch the different birds getting their acorns. The greatest in number are Blue Jays (see “Blue Jays Harvesting Acorns,” August 27, 2018). They, along with Red-bellied Woodpeckers and American Crows, pick the acorns in the tree. Grackles, on the other hand, feed on the ground under trees for the fallen ones. Jays crack the acorns open with repeated pecks with their beaks; grackles have a sharp ridge in their beak (keel) which they use to open the shell.

Some birds eat acorns whole and let their gizzards do the work of grinding the food. Wild Turkeys, birds that eat many acorns, have been found in EHP in recent years.

Wood Ducks also eat lots of acorns. They will be leaving the park soon, heading south for the winter, but they are still around now and are often on the banks of the river, where their nutrient sources include acorns.

Photo by Margaret Weber

Every year, in late summer and fall, the presence of acorns calls my attention to the number and variety of oak trees in the park and I spend some time trying to get to know them better. It is not easy to identify some of them by species name, since there are so many different species in the eastern U.S. and oaks do hybridize.

I recently collected a few acorns, each with a leaf from its tree, for more leisurely study at a later time.

We have all heard that “mighty oaks from little acorns grow.”

A few acorns do grow into large trees, but most of the many, many thousands of acorns present in Eliza Howell right now serve other valuable purposes: food for wildlife and an opportunity for me and others to admire, enjoy, and learn.

 

 

 

 

 

 

 

 

A Winter Walk on the South River Path

Part of my regular winter walk in Eliza Howell Park is the path along the river, going to the right after crossing the footbridge (coming from the road loop side). This area of the park is wooded and a winter walk in a deciduous woods is hard to beat, especially when there is snow on the ground.

I think of this as the “south river path,” marked in the dotted red line on the map.

There is a Pignut Hickory tree near the path, a tree which was very productive in 2017. Before the snows came, I couldn’t avoid stepping on the nuts on the path and I was a little surprised that squirrels had not carried them off to store for winter eating.

Now I think I know the reason they didn’t. The leaves fell to cover the leaves and they were effectively stored right there. The squirrels are now digging them out, leaving the pieces of the outer shell behind as they carry off the nut. 

When the leaves are off the trees, one of the more intriguing and noticeable plants near the path is wild grape vine. These vines are long, often large in diameter, and appear to dangle from the high branches. They do not adhere to the trunk as many other vines do. There are many grape vines along the path and they suggest a number of questions: how big do they get, how old, how do they get so high in the tree without adhering to trunks? I plan to comment on them further at another time.

I always make sure I follow the path at least until I come to a patch of euonymus, a vine that adheres to the trunks of trees. Euonymus is an evergreen, providing the only green in this area of the park at this time of the year. A major part of their attraction is that they retain their attractive fruit in the heart of winter.

I always walk very slowly near the euonymus vines because this is an excellent place to look for birds. Even on cold winter days when many birds are sheltered and hard to spot, I usually can find a few here. This year, Northern Cardinals are the most common, but I also frequently see Dark-eyed Juncos Red-bellied Woodpeckers.

One of the winter birding surprises this year is a small flock of Mourning Doves often along the edge of the river here. They feed mainly on the ground and the side of the river bank is one of the few areas of uncovered ground available. Sometimes, an icy spot on the river serves as their foraging “ground.

The day or two following a snowfall is a good time to pay attention to animal tracks, which can always be found. On this most recent walk on the south river path, I saw many tracks, including those of deer.

The south river path does not reach a park entrance/exit. It simply ends a short distance past the euonymus. So I return the way I came, usually seeing something that I missed a little while ago. That is the nature of a nature walk — observational, not destinational.

After the Deer Died

On November 30, 2017, I first noticed the dead deer while I was walking through the bottomland in Eliza Howell Park, not far from where the two branches of the Rouge River meet. It was in the open, on the ground near the Main branch of the river. Based both on the animal’s appearance and on the fact that I take this route frequently, I think it had only recently died.

There were no wounds noticeable and I have no way of knowing what might have been the cause of death.

                           November 30, 2017

On subsequent walks, about every 2 – 3 days, I took a look at the carcass, wondering how long it might be before it was found by carrion eaters at this times of the year. Most of the Turkey Vultures had migrated a little earlier in the Fall, so it would more likely be a mammal.

The deer remained undisturbed as the weather turned colder.

                      December 7, 2017

When I checked on December 12, the carcass still appeared to be untouched, though it was a little difficult to be sure, since it was covered with snow.

Three days later, I came upon a very different picture. The carcass had been dragged several feet, torn open, and much of the meat taken.

                         December 15, 2017

There were many mammal tracks present, but the snow was all trampled down, the tracks were on top of one another, and it was very difficult to find a distinct and clear print. It looked like some animal or animals had had been working on the carcass for an extended period of time. The clearest tracks seemed to be about the size of those made by a medium-sized dog.

So what was it? Without any clear evidence, I can only speculate on what it might well have been, based on some key considerations. The fact that the carcass was moved several feet and that the carcass appeared to have had large chunks torn out suggests fairly large mammal(s). It is possible that small mammals might have been eating at the carcass as well, but this much consumption probably means something larger. It also might mean more than one.

My best guess is coyote. They have been seen in the park for some time, including recently, though I have no knowledge of the number. They are also known to be carrion eaters. They normally eat much smaller prey and do not attempt to bring down live deer. But a dead deer is different.  And, of course, coyotes can be in packs.

It is possible that it could be a pack of dogs. I have seen a few feral dogs in the park several times in past, but not recently, so I think it is more likely that this is the work of coyotes.

In my most recent visit, I saw that the skeleton had been further stripped.

                      December 20, 2017

Eliza Howell Park is a Detroit city park and observing some of what happened in the three weeks since the deer died provides another glimpse of the nature of urban wildlife activity.