Have you ever wondered what is responsible for the crimson shade of a fox’s coat, or the distinctive stripes that distinguish a raccoon tail? The answer, in short, is pigments! Pigments are chemical compounds that determine the color an object appears to the human eye based on how much light they absorb or reflect. Melanin is a major group of pigments naturally produced by most animals. Two types of melanin, eumelanin and pheomelanin, control the color that hair appears. This is true from the hair on your head to the coats of the critters you see in the wild!
While most species maintain the same coat coloration year-round, some swap out their coats seasonally for white, “ecologically fashionable” winter coats. This process is known as molting. You may recall some species around the world that do this, including Arctic fox (Vulpes lagopus), White-tailed ptarmigan (Lagopus leacura) and various weasel species. Changing coats is not only a terrific way to help avoid predation, but may also serve as an extra tool to keep warm during the frigid winter months. Because the white fur lacks pigment, it is believed that there is extra space in the hair shafts for air that can be warmed by the animal’s body heat (think of a bird ruffling its feathers during a cool morning to trap in warm air).
Although the exact mechanisms behind this wardrobe change are not fully understood, there is evidence that suggests that the length of daylight, also known as photoperiod, plays a key role in when animals switch their coat color. Receptors in the retina transfer messages to the brain that it’s time to get a new outfit for the next season. Once this process begins, the hair begins to change color starting with the extremities.
A local expert at swapping out coats is Wisconsin’s own Snowshoe hare (Lepus americanus). You can most commonly find these long jump champions in the northern forests of Wisconsin. Contrary to the common Cottontail rabbit, Snowshoe hare swap brown summer coats for bright white during the snowy winter months to camouflage with their surroundings.
Snapshot Wisconsin cameras capture images of Snowshoe hares year-round across the state. This provides a unique opportunity to not only pinpoint the time of year that snowshoes go through their wardrobe change, but also identify the surrounding area’s brown down or green up state. Because Snowshoe hares rely heavily on their coat color to stay camouflaged and avoid predation, any mismatch between coat and season can make a hare an easy target for lunch. Snapshot Wisconsin cameras can capture images of these mismatches to help understand interactions between Snowshoe hares and predation, as well as Snowshoe hare molting biology across time.
My brother Ian was a picky eater. Breakfast was always a bowl of Crispex. For lunch, he ate a PB&J and refused to eat the crusts. I was the opposite. Even as a young child, I loved proverbially “gross” foods like mushrooms and started drinking coffee when I was twelve.
Turns out that some animals are like Ian and some are like me. For example, monarch caterpillars only eat milkweed. We call animals like the monarch specialists. Conversely, some animals will eat, well, just about anything. Raccoons, for example, are equally happy eating crayfish from the creek or scraps from your garbage can. We call such species generalists.
Diet isn’t the only thing to be picky about! Some species exhibit preferences for precise habitat types. For example, the Kirtland’s Warbler breeds only in young jack pine barrens, primarily in Michigan, but also occasionally in Wisconsin. On the other hand, some species are ubiquitous. The coyote is an exemplar habitat generalist—you might spot one in the wilds of the Chequamegon-Nicolet National Forest or in a suburb of Milwaukee.
Taken together, diet and habitat comprise what we call the ecological niche of a species. You can think of a niche as the “cubbyhole” that a species occupies within the broader tapestry of its environment. The breadth of a niche is a continuum from extreme specialists (like Kirtland’s Warblers) to extreme generalists (like raccoons). Some species fall between those extremes; deer are a great example. Deer are strict herbivores, but they can be found in many different habits, from forests to farmlands. So, not every species can be neatly classified as a generalist or a specialist.
Scientists are interested in generalists and specialists because they exhibit different responses to change. Like a trained craftsman whose job is replaced by a machine, the specialist has nowhere to go when the environment changes. Generalists, on the other hand, can capitalize on the vacant niche space and colonize altered landscapes. Given the widespread changes humans are exerting on the earth, we are seeing global proliferation of generalists while many specialists are disappearing, a process known as biotic homogenization.
This may seem dire, but the more we learn about generalists and specialists, the more we’ll be able to do to maintain biodiversity and lose fewer specialists. In the meantime, I encourage you to think about the animals you see on a regular basis. Is that squirrel outside your window an ecological jack-of-all-trades? Are there any habitat specialists that live on your property? And maybe even think about your own niche—are you a generalist, a specialist, or somewhere in between?
From the Snapshot Wisconsin program, you may be familiar with wildlife monitoring using trail cameras. Trail cameras are one wildlife monitoring tool classified into a group of monitoring techniques that are considered non-invasive, meaning that the technique causes little or no impact on the animal’s normal activity, ecology or physiology. By contrast, invasive monitoring techniques include any type of wildlife monitoring that has a direct, human caused impact on an animal (GPS collaring, tagging, close observation are a few examples).
Tracking involves locating animal footprints and identifying the species. This monitoring technique can be done during all times of year in snow, mud, dirt or sand. You can learn a lot about an animal by its tracks. For example, you can tell what gait the animal was in (walk, trot, lope, spring), where it was heading to and from and if the animal was travelling in a group or alone.
Researchers can use tracks to estimate abundance, home ranges and behavior patterns. This can be especially helpful for monitoring more elusive animals that are sensitive to human disturbance.
One research project that uses tracks to estimate abundance is the Wisconsin winter wolf count. Using tracks in the snow, the DNR can estimate a minimum wolf count. For more information about that project, check out this link.
As we proceed through Wisconsin’s four seasons each year, you may appreciate the sight of colorful songbirds in springtime and notice the distinctive V-shape formation of Canada Geese as they fly south in the fall. These species are referred to as “migratory birds”, or populations of birds that travel from one place to another at regular times during the year.
Why do birds migrate?
Birds migrate in search of resources needed for their survival. Migratory birds primarily pursue sources of food or nesting locations to raise their young. In Wisconsin, we see an influx of bird species in springtime as warm weather returns and insect populations increase. As temperatures begin to drop in the fall, food supply dwindles and the birds fly south.
How do birds migrate?
Scientists believe there are many factors that trigger the migration of bird populations. Birds respond to changes in their environment such as day length, temperature, and availability of food resources. Additionally many birds go through hormonal changes with the arrival of new seasons. These hormonal shifts may affect your caged birds at home, you may recognize restless behavior in spring and fall. This restlessness around migratory periods is referred to as zugunruhe.
It isn’t fully understood how birds have developed such impressive navigation skills, but there are several factors that guide them. Birds can use directional information using the sun, stars, and even earth’s magnetic field. Landmarks, position of the setting sun, and even smell plays a role for various species.
How do scientists study migratory birds?
Several methods have been developed to track and study migratory birds including banding, satellite tracking, and by attaching geolocators to individuals. At Snapshot Wisconsin, trail cameras are now being added to the list of tools! Using preliminary data gathered from Zooniverse, the below slideshow shows the detections of Sandhill Cranes on Snapshot Wisconsin cameras throughout the year. The study of migration can be immensely beneficial for conservation efforts by pinpointing wintering and nesting locations to monitor potentially threatened or endangered populations.
At last count, we are 38% of the way through Season Two of Snapshot Wisconsin! On behalf of the research team, thank you! Keep up the great work!
Today I am sharing some of our favorite photos of deer fawns, bear cubs, and other young from previous seasons. For the purposes of this project, we define “young” as offspring of the year, or animals less than one year old. Because it is difficult to tell juveniles from adults by late fall, spring and summer photos are a great time to spot photos of young. To differentiate young from adults look for differences in body size, as well as juvenile markings, like the spots on deer fawns. See our FAQ section for more details.
Have you spotted young of any other species? Share with us in the comments or on the Talk boards!