Mammals of Michigan and Their Interactions With the Environment

Mammals of Michigan

There are many mammal species in Michigan, and this paper will discuss some of them, in terms of how they have evolved to live in the Michigan area, and how they have evolved to live off the land in the Michigan area. Something of the geological history of Michigan will also be discussed.

We will start with the extinct mammals of the Michigan area: about 12,500 to 11,800 years ago, the Michigan area was covered with boreal forest dominated by spruce trees, and the fauna that was dominant in this area over this period moved here from South of the area. The important mammals of Michigan during this period were: Scott's moose, giant beevers, flat-headed peccaries, woodland muskoxen, mammoths and mastodons. It has been suggested that the mammoths and mastodons, in particular, were drawn to Michigan because of the many salt seeps and the many sources of shallow water, from which they could drink. These mammoths and mastodons may therefore have been migratory in their behavior, and stayed in the Michigan area due to the well-suited surroundings. Around 10,000 years ago, these large mammals became extinct in the Michigan area (in common with their extinction in most of the rest of the world). The reasons for this extinction are unclear, but has been hypothesized to have been caused by: climate change; a drop in the water table, causing a reduction in the amount of available drinking water; human hunters hunting the species to extinction; new diseases, introduced from species immigrating across the Bering Strait.

We will now move on to discuss something of the appearance, behavior, and feeding habits of these extinct Michigan mammals. First, the giant beever. The giant beever, Castoroides ohioensis, was the largest North American rodent during the Ice Age (in the last two million years). They were distant cousins of the modern-day beever, with 15cm-long teeth which had prominently-ridged outer surfaces, with an S-shaped enamel pattern. From fossils of the giant beever, it has been estimated that they had scaly tails up to 65cm long, that was narrow at the end, and therefore well-adapted for swimming (as with the modern-day beever). From tracing the fossil record, it is thought that the giant beever was descended from Dipoides, a primitive beever that lived 5 million years ago (during the late Tertiary). It is thought that Dipoides gave rise to Procastoroides which eventually gave rise to the giant beever, Castoroides ohioensis. Studies of tooth enamel, and tooth shape patterns, supports this lineage: Dipoides, Procastoroides, Castoroides.

Giant beevers were found throughout North America during the period of their reign, but were not found outside of North America (information from the Yukon Beringia Interpretive Center notes).

During the period of the last glaciation, giant beevers seem to have flourished around the Michigan area; it is thought they lived in lodges (similar to modern-day beevers) and that these lodges were composed of saplings. A suspected giant beever lodge found near New Knoxsville, Ohio, was 1.2m high and 2.4m in diameter. From analysis of their fossils, giant beevers seem to have preferred swampy regions, as the majority of their fossil remains have been found near to ancient swamps (information from the Yukon Beringia Interpretive Center notes).

Next, we shall discuss the mammoth. Fossil mammoths are known only from the Pleistocene in the Michigan area. Michigan can boast two species of mammoth: the American mastodon and the Jefferson mammoth. Many of the fossil remains of the American mastodon and the Jefferson mammoth have been found in swampy deposits, which suggests that these were the preferred habits of these species throughout their lifetime. This is good for paleontologists, as swampy deposits are excellent sites for the preservation of fossils. Mammoths and mastodons were both huge, elephant-like mammals, with great protruding tusks and long, hairy, orange-colored fur, which covered the entirety of their body, and which is thought to have protected the species from the extremely low temperatures around in the Michigan area at the time in which they lived. It is thought that mammoths and mastodons, in particular, were hunted to extinction following the arrival of humans in the Michigan area, as stone hunting tools (spear points etc.) used by humans around this time have been found around the Michigan area. There is also other kinds of evidence that humans hunted mastodons and mammoths in the Michigan area, such as cut marks on mastodon bones, which could only have come from human-made tools (information from the Yukon Beringia Interpretive Center notes).

Next, the woodland muskoxen. This species, Bootherium bombifrons, was one of the five species of muskoxen (Tribe Ovibovini) that lived in the Michigan area during the Pleistocene (2 million to 10,000 years ago). The woodland muskoxen was found throughout North America, but was confined to this region. The Bootherium was tall, and much more slender than the modern-day muskoxen. The males had huge, flaring horns with fused bases, and both sexes had longer hair than their sibling species, or their modern-day counterparts, indicating an adaptation to the cold Michigan weather of this period; the orbits were also sunk further in to the skull, which is also an adaptation for low temperatures.

The earliest woodland muskoxen specimens are known from 130,000 years ago, and most of the latest specimens date from the late Wisconsin period, 43,000 to 17,000 years ago. The habitat of woodland muskoxen, as the name suggests, seem to have been woodland areas, but the species is also known from lake and forest margins where, presumably, they foraged. Fossil specimens have, however, also been found from alpine grasslands, and so the woodland muskoxen was perhaps a highly adaptable species (information from the Yukon Beringia Interpretive Center notes).

Next, the flat-headed peccary. The flat-headed peccary, Platygonus sp., is known from a huge number of fossil specimens, the latest of which is dated to 10,000 years ago. The flat-headed peccary was larger than its modern-day counterparts, and was pan-North American in its range (and as with most of the other extinct Michigan-area mammals) was exclusively North American in its range. Flat-headed peccary fossils have been found from all habitats, and as such, it is fair to say that this extinct mammal was adapted to most Pleistocene environments.