ARBORETUM NEWS (NATURALISTSNOTES)

Life in Winter

SUNDAY, FEBRUARY 9, 2014

Holding true to this winter’s weather trends, the day was cold, but we did have the sun shining during this tour. The much-appreciated brightness made the wind feel a little less brisk and allowed for easier viewing of tracks. There was also a fresh layer of snow from the day before, so events that played out in the landscape from the last 24 hours were more visible.

Along the fire lane on East Curtis we found a lot of deer browse, as indicated by the torn, frayed stems and large chunks of bark missing from young tree saplings. These markings can be differentiated from and attributed to rabbit browse when the stem is cleanly cut at a 45-degree angle. The deer’s messier eating habit is due to the fact that they lack teeth on their upper palate and cannot clip plant tissue as precisely as rabbits.

As we passed under the pocket of needle-less tamaracks south of Teal Pond, someone noticed a barred owl perched on an aspen tree in the Marsh Connection. This area has been recently forestry mowed and is now much more open, allowing birds of prey to roost and hunt with ease. I was surprised to see an owl out in the middle of the day, but what a wonderful sight to behold on a cold winter day. It is getting close to breeding season for these stately birds; perhaps this owl was scouting for a mate and an early dinner.

We stopped at Icke Boardwalk and noticed many narrow, winding tracks in the snow around the boardwalk made by the tiny feet of mice or voles. One of these tracks ended with a depression in the snow, surrounded on two flanks by faint wing patterns. It’s always more interesting when the tracks tell a story, and this was a dramatic one of the struggle for survival, with an owl or hawk getting the upper ‘talon’. Possibly this was evidence of our barred owl at work. A fresh snowfall offers a great opportunity to find evidence of this scenario, since the wing tips momentarily grace the surface of the snow as the bird touches down to the earth to grab its prey.

Further down the trail, we also saw a singular, linear track with steps about six inches apart, leading up to from a large, decaying cottonwood stump.

Fox_tracks

Although we couldn’t see the actual details of the individual tracks, we suspected they might have been the tracks of a fox heading to its winter lair. Most other mammals of this size are still fairly dormant at this time of year and not likely to be wandering far from their dens, especially with the frigid temperatures as of late. This finding led us to consider what makes a true hibernator. Skunks and raccoons undergo a form of winter lethargy, but do not hibernate. Bear can sleep for long periods of time, but do not technically hibernate. Groundhogs, chipmunks and some bats hibernate. Animals that hibernate undergo a sustained, controlled regulation of metabolism, where the heart rate, body temperature and breathing are significantly reduced so as to expend very little energy, thus not needing to eat for several months. For example, the groundhog or woodchuck reduces its heart rate from the normal 80 or 100 beats per minute to five beats per minute, and takes only one breath every six minutes. Hibernators are also difficult to rouse from their winter slumber. There are no bears residing in the Arboretum, but do not make the mistake elsewhere of thinking a bear is fast asleep during this time of year. They can be easily aroused and the females give birth to cubs in their winter dens! Much like other non-hibernator mammals, bear may wake on warmer winter days and leave their dens to expel waste, forage for food or eat from their stored caches.

We also intended to scout out insect galls and snow fleas on the tour, but were fairly distracted by the intriguing tracks, potential overwintering dens and animal sightings on the tour. It may seem that the landscape is lifeless in the winter months, but it is all a matter of being a little more observant and having more than one pair of eyes to find the myriad of mysteries available for discovery. For those who like puzzles, interpreting those discoveries is the best part.

Amy Jo Dusick, Arboretum Naturalist

Located between Lake Wingra and the West Beltline Highway at 1207 Seminole Highway, the University of Wisconsin-Madison Arboretum features the restored prairies, forests and wetlands of pre-settlement Wisconsin. This 1,260-acre arboretum also houses flowering trees, shrubs and a world-famous lilac collection. Educational tours for groups and the general public, science and nature-based classes for all ages and abilities, and a wide variety of volunteer opportunities for groups, families and individuals are available.