Why Did the Frog Cross the Road?

Every spring we go through this. It’s night and all is dark, so Sherry and I don our reflective safety vests and venture forth onto the street to begin our (usually) hour-long evening walk.

But it isn’t long before we notice small familiar shapes strewn about the
roadway. Upon closer examination, we confirm they are frogs, seemingly of all shapes and sizes, and maybe even a few toads. It takes all the care we can muster to avoid stepping on them. This occurs on a quarter mile stretch of road flanked on one side by a retention pond and on the other by a marshy area. There are many amphibians hopping away as you approach them, but, sadly, there are even more that cannot, due to the “splat” moment they experienced as a result of the heavy traffic on this busy street. Unfortunately, the carnage is often extensive and gruesome.

So what are so many animals doing here? The answer appears to be
simple: sex and food. The weather has warmed, and frogs, toads and salamanders are coming out of hibernation. Their immediate goal? Procreation.
Some of these amphibians live in a terrestrial environment, but since all
amphibians require water for reproduction, they go in search of it. Thus, in many areas there is an active amphibian migration--to water. Amphibians also
need to stay moist because they are prone to drying up, so they often travel
after or during a rainfall. Different species seem to get the same idea at the same time, so when the conditions are optimal, the number of animals on the
move can number in the hundreds of thousands.

Amphibians are drawn to the roads for a couple other reasons. They are attracted to the heat, since the sun-warmed surface retains some of the heat after the sun goes down. But probably more important is the fact that the
earthworms escape the water-logged soil and congregate on the street and are
easy prey for hungry post-hibernation amphibians. By the way, earthworms do
not leave the soil to avoid drowning (they cannot drown in water); rather they are seeking higher oxygen levels because they breathe through their skin. The increasing loss of natural amphibian habitat increases the danger
of such movement, because migration usually means crossing roads. Consequently, the morbidity rate is always on the upswing. We can attest to the rapidly shrinking habitat in Menomonee Falls as developers are rapidly snapping up even small out of the way bits of land to squeeze a house onto.

This is a problem not only for amphibians, but also for many other species as well.