March 11 - 20

 

Racine has 12 hours and nine minutes of daylight and Superior has 12 hours and nine minutes of daylight. Racine as an increase of 30 minutes from the previous period and Superior has an increase of 34 minutes. March 20 is the spring equinox. Accurate observers will notice the day length is greater than 12 hours and there are two reasons for this phenomenon. First, day length is recorded when the sun first appears above the horizon and sunset when the sun disappears below the horizon. The equinox occurs when the center of the sun and the center of the earth are in alignment. Therefore, the equinox calculations are not determined until the center of the sun is at the horizon. In addition, refraction of light by the atmosphere causes the sun’s upper edge to be visible from the earth several minutes before the actual sun reaches the horizon. In the evening, the same event occurs. These two facts combine to give us nine minutes more daylight, than the expected 12 hours.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Hibernating turtles: Painted turtles are most active from Early April to October. This turtle is the species almost every person in the state knows. It is by far our most common turtle and it can be found in nearly every waterbody statewide. Since we have over 15,000 lakes, thousands of miles of streams, and countless puddles, the painted turtle has a huge statewide population. They bask in the summer sun, but how do they survive the winter?

 

Painted turtles hibernate by burying themselves deep in the mud beneath streams and ponds. The mud helps insulate the turtle, which prevents freezing during the harsh winter months. The turtle may submerge itself in up to 3 feet deep in the muck. These remarkable critters can survive five to six months with minimal oxygen.

 

Several factors combine to permit this extreme oxygen deprivation.

 

Water absorbs and stores tremendous amounts of heat with only a slight increase in temperature, which means aquatic life sees relatively moderate fluctuations in temperature compared to land animals. Water also has its greatest density at 39 degrees Fahrenheit sinks to the bottom of ponds. At all other temperatures, both warmer and colder, it rises. For painted turtles, this means the bottom temperatures in winter will stabilize at about 39 degrees.

 

This microclimate is ideal for hibernating turtles and other creatures. If the water becomes cooler than 39 degrees, the cooler water rises. Thus, the bottom dwellers can never become frozen. Finally, the warmth of spring sets off a biological alarm clock in the turtle and it awakens.

Still that's a long time to hold a breath!  Living cells need oxygen. The turtle faces slow oxygen starvation and a lethal buildup of carbon dioxide. Hibernating frogs and salamanders solve this problem by breathing directly through their skin. Turtles, however, have skin cloaked with thick scales and a hard shell. Absorbing oxygen through the skin is no more an option than flying south.

 

Turtles have solved this conundrum by a couple of remarkable adaptations. Aquatic turtles, like the painted turtle, have two sources of supplemental oxygen to satisfy their winter needs. Their throat cavity lined with lots of minute blood vessels, which permits oxygen extraction. They also have a similar type of tissue present in two thin walled sacs near the anus.

 

These augmentation sources do not get a hibernating turtle through an entire winter. The hibernating painted turtle can get away with oxygen deprivation, because its metabolism is lower than mammals. They do not do much in the way of activity. In hibernation, their heart beats only about one beat every 10 minutes in the winter.

 

The buildup lactic acid needs to be dealt with for the months the turtle is sealed under the ice. Of course, turtle slows the process by doing next to nothing, but its body still functions and produces toxins. The solution is quite simple. Minute amounts of calcium from the turtle's shell are slowly dissolved into its bloodstream. This calcium acts like a buffering agent, neutralizing the lactic acid.

 

As the days grow longer, the ice melts and the water warms, the painted turtle once again poke its nose into the air, filling its lungs with oxygen. This first breath must be felt with some sense of emotion in that little turtle brain.

 

We have several species of turtles in Wisconsin and they hibernate in different locations:

• Snapping turtles hibernate in a congregated fashion. Massing in numbers, they can be found in muskrat tunnels, springs heads, holes in banks, and even beaver lodges.

• Wood turtles hibernate in banks along the same streams, which they inhabit in the summer.

• Blanding’s turtles hibernate by burrowing itself into muddy bottoms to stay warm. Different than most turtles, the Blanding's is somewhat active in winter and occasionally can be seen slowly swimming underneath the ice in areas where they winter.

• Ornate box turtles bury themselves below the frost line in their sandy prairie habitat.

• Musk turtles bury themselves up to 3 feet deep in muck.

• Map turtle hibernate in muskrat and beaver burrows, springy areas or under logs and rocks.

• Ouachita map turtles hibernate in similar locations as the map turtle.

• False map turtles hibernate in similar locations as the map turtle and all three map turtle can be found together in hibernation concentrations.

• Smooth softshell turtle hibernates by burying itself in their riverine habitats substrate.

• Spiny softshell turtle hibernates by burying its body into the rivers substrate with only its head and snout protruding into the water column.

 

Pussy willows: Pussy willows trees are natives of wetlands in Canada and the eastern United States. The term pussy willow usually refers to both the name of the tree into the furry buds on the branches. These buds are also known as catkins. In early March, these catkins begin to swell. Unknown to most observers, there are both male and female pussy willow trees. The catkins on the male pussy willows usually appear earlier, oft times in early March. By mid-March in most years, the catkins of the females began to swell and become soft and furry. These flowers are one of the first harbingers of spring for many Wisconsin residents.

 

Wood frog: The wood frog is the first amphibian to appear in spring. They spend the winter in shallow burrows in the forest floor or underneath leaves. These wood frogs do not dig below the frost layer and are frozen solid in winter. This frog has the unique ability to have material between the cells freeze solid without actually freezing the cells. Laboratory studies have found that wood frogs can survive freezing up to three quarters of their body water. In most years, mid-March is the time when wood frogs recover from the frozen state and enter ephemeral ponds in woodlands for breeding.

 

Naturalist should listen for squawking doglike calls at this time. However, in far northern Wisconsin, wood frogs may not appear until early April. As soon as the ice melts, wood frogs may be on the ponds. They breed quite rapidly and are usually out of the ponds within 10 to 14 days. The rest of the season they spend foraging in the woods. Wood frogs tend to utilize the same breeding ponds every year and cooperatively placed their egg masses together, although, the location may change in the pond dependent upon water depth on a yearly basis.

 

Morning cloak butterfly: Morning cloaks are butterflies that overwinter in their adult stage. These are the first butterflies we see when things start warming up in spring. They overwinter in cracks and crevices and rocks and trees. Their blood contains glycogens (an anti-freeze like substance) that allow their tissues to withstand the winter’s cycles of freezing and thawing. Morning cloaks may be our longest lived butterflies, surviving as adults approximately 10 months. After emergence in spring, they lay their eggs and caterpillars feed on early spring foliage. The adults emerge usually in June, estivate until fall, then forage and find overwintering locations. They freeze and overwinter as adults until spring.

 

Whirligig beetles: Whirligig beetles occupy many types of aquatic habitat including ponds, lakes and streams. The adults often feed on land insects that fall into the water. The adults overwinter in mud and debris. In spring, they emerge from hibernation and form hunting groups. Naturalist should look for these interesting aquatic insects soon after the ice melts. By patiently watching, an observer may see a simple form of radar being used. When the water ripples, whirligig beetles will move towards the source of the ripple - a simple form of radar. These small predators and scavengers clean the water of dead and dying insects and help control populations of other invertebrates.

 

Other tidbits:

• The first opossum litters should be seen at this time.

• Check areas where the snow has recently melted for runways used by voles, mice and shrews during their subnivean cycle.

• Occasionally eastern moles will be seen on the surface.

• This is usually the time of the year when the first basking painted turtles are seen. Look for them on open ponds on warm sunny days.

• Spring canker worm moths emerge.

• This time period is average maple sap flow in far northern Wisconsin.

• Alder pollen is dispersed.

• Average date of crocus bloom in the south.

• Southern Wisconsin peak migration for Great Blue Heron, Greater White-fronted Goose, Snow Goose, Sandhill Crane, and Killdeer.

• Naturalists should listen for Saw-whet Owl calls during their annual migration.