Let The Great Wheel Turn: Springtime Perks Up Animals

Editor's note: This piece by Bob Engel was first published in April 2015. Bob was a much loved Marlboro College professor and a frequent contributor to our blog and active workshop leader here at the Museum. Sadly, Bob passed away last month. Bob was tireless in his support for the Museum and he will be greatly missed.

Years ago, on a college field trip to the U.S. deserts, we ran across a guy working on Gila monsters. Monsters are the biggest lizard in the U.S., are venomous, and are related to the huge Komodo dragons on several small islands of Indonesia. Our guy was following individual monsters as they went about their lives. He had caught some and had sewn small radio transmitters into their abdominal cavities. Then, if they were above ground, he could track them with a hand-held antenna.  

He took us out and we soon got a signal from a lizard I'll call George. We headed off after George, but the several hills in the area caused reflection of the signal, and I looked down to see George calmly resting at my feet. For an almost two-foot-long pink and black lizard, he was amazingly hard to see.

We measured and weighed George, only to find out that he had lost twenty percent of his body weight in a little over a month. Was he ill?  Nope.  Cherchez la femme. He was tromping around looking for females. Judging from his loss of weight, he had covered a lot of ground. Okay, now we can get back to Vermont. 

Near the end of January, a relatively quiet tracking scene went absolutely crazy at our place. There were coyote tracks everywhere. Both foxes, too. Friends in the rest of town reported the same. What was the deal? 

I think they were courting and sparking. Because of the many programs at the Museum, by now we are all good phenologists - we know when things happen. But why do things happen when they do? The answer often boils down to successful reproduction. Like all animals, mammals need to locate mates, and sometime down the line, the females also have to give birth. If you lived out there, when would you want to have your pups stick their little noses out of the den? Right, not November.

Gestation times are evolved, but there are limits, given the evolutionary history of the species. In the case of canids like coyotes, wolves, and foxes, the developing babies are born after about two months in utero, and they start peering out of the den a couple of weeks after that: just about income tax day, if all those tracks really told the story I think they did. Personally, I'd hold out for the middle of May, but spring is going strong by the middle of April. 

On the first of March, there were ten sets of snowshoe hare tracks crossing our too-long driveway. I'm used to seeing a few hare crossings each winter, but not ten over the course of a day or two. What's going on? Well, we have to be careful here (and with the above). The statistics of small numbers are tricky and potentially very misleading. For all of the thirteen years we've been here, our sample is small, just a few bunnies. Maybe what I have seen is just one hare training for the Easter marathon. But maybe the population is up. Hares are famous for sharp, regular population cycles. There have been many good studies of this phenomenon in Canada (people counting skins collected by Hudson Bay trappers, and an ambitious recent study by John Krebs in British Columbia). In any event, I also think that for the first time all winter, these fuzzballs are also getting their wind up. 

All of us Vermonters live through a tough winter. But life goes on, and just about now, the pace is picking up. Romance is in the air. Pileated and hairy woodpeckers are drumming, and the tracks in the snow hint at the turning of the great wheel of life.