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.

The Calendar Says Spring

March 21, 2018 (Walk # 1061)

This was my first walk after the vernal equinox and I was looking for signs of spring. I found a few, but winter is not over. A few observations from today:

The river water level is quite low for March. I use the extent of visible sycamore tree roots on the right for comparison purposes.

One advantage to the nature walker of the lower water level is that there is more mud along the river edge, the area between the sides of the bank and the water. More mud means more mammal tracks and, at least for me, tracks in mud are usually easier to read than tracks in snow.

Here is an example.

I circled two obviously different tracks here. The one in purple is typical of a raccoon and the one in red was made by a canine, probably a coyote.

Robins are abundant in the park now and, in this time between winter and spring, are exhibiting both winter and spring behaviors. Many are feeding on the ground, but others are still foraging for fruit and seeds, as they do in winter.

I posted about sumac seed clusters last December, about how long they persist. Some of last year’s seeds are still present now and today both chickadees and robins were feeding on them.

The number of bird species seen today – 18 – is the highest so far in 2018. A couple of these are winter visitors that have not yet returned north: Dark-eyed Juncos and American Tree Sparrow.

There are a few signs of spring. Some birds are pairing off, preparatory to breeding season. One Downy Woodpecker now usually means another is very close nearby. Canada Goose is one of the earliest birds to nest along the Rouge River and this pair appears to be getting in the mood.

 

While the park still has the brown winter look, it is possible to find a little bit of new green. As in home gardens, the first plants to emerge from the ground are those that grow from bulbs or rhizomes. I was pleased to see that a native species of marsh iris is back again this year.

Today’s observations indicate that this March is both colder and drier than normal. I anticipate rapid changes in the park as the weather warms.

Another Visit to the Footbridge: The Familiar and the Unexpected

It was 17 degrees F with a light snow falling in the morning of the Martin Luther King holiday when I arrived in the park.

As is my typical practice in winter, I headed to the footbridge; it is always an interesting view and often a key location of avian activity. A few years ago, a group of neighborhood kids painted the metal railings of the bridge, making it stand out as one of the brightest spots in the park on a gray day like this.

As I walked onto the bridge, I looked upriver and saw a coyote trotting away along the left bank. Though it is not unusual for me to see signs that coyotes are in the park (see my December 2017 post, “After the Deer Died”), I rarely actually see them. This glimpse is the first in months.

Attending to movement at the edge of the river close to the bridge, I see that the birds that I have come to expect in this locale are here – Dark-eyed Juncos, Black-capped Chickadees, and Northern Cardinals. At this time of the year, female and male Cardinals are often together, as they are today.

Photo by Margaret Weber

Photo by Margaret Weber

Changing weather can change the appearance of the Rouge River drastically. Following the cold spell in late December and early January, the river was completely frozen over. Then came warmer weather with rain. The water level rose rapidly, with water flowing both under and over the ice. When the weather turned cold recently, the river began to freeze again, before the water had fully receded. The result is uneven freezing and broken ice.

This stop on the bridge has included both the familiar/expected and the unexpected. These bird species are expected; the coyote is not; the appearance of the river surface is not typical, but it changes frequently with the winter weather, so it is difficult to know exactly what to expect.

The walk beyond the bridge included more of the familiar, including a visit to an old “friend,” a dead beech tree along the path, one of the landmarks I use in my notes for remembering the location of something observed (“near the old beech tree”). The top portion of the tree fell last summer.

The small bird that flitted up as I returned to the footbridge was no junco or chickadee. It was a Song Sparrow. Song Sparrows are summer residents in Eliza Howell and migrate south for the winter. Since the northern end of their winter range is not too far south of Detroit, they sometimes do show up in the park in the winter, though not often. This is the first one I have seen this winter is definitely unexpected.

Song Sparrows are well named; they do sing frequently from a branch perch. But they are not likely to sing before March here. Nevertheless, seeing one in winter can remind us that the singing Song Sparrow, as in this picture, will be the expected in a couple months.

Photo by Margaret Weber

This was my 1043^rd documented nature walk in Eliza Howell Park and, as on so many of the others, I saw some things that I expected to see and I saw some things that I did not expect to see. I am eager to take the same walk again.

 

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.