Wednesday, January 28, 2015

Adirondack Snowshoe Hares in Winter

TOS_HareHomeFor the past 14 years, my Winter Ecology students and I have spent a lot of time outdoors, studying the preferred habitat features and winter foods of snowshoe hares. We’re likely to find hare tracks hopping in and around lowland conifers near wetland edges, and then again at higher elevations, where the forest transitions into fir, birch, and spruce. Where we won’t find them, at least not very often, is in broad bands of open, leafless hardwood. On the rare occasions that we find tracks in this habitat, they have almost always been single strands of widely spaced prints – suggesting an animal that’s really moving!

The highest densities of hares tend to be in regenerating conifer stands where the fir and spruce trees are tall enough to provide protection from owls and other avian predators, but still dense enough to offer lots of horizontal protection from terrestrial carnivores like coyotes. When hares aren’t feeding, they hunker down in depressions, called “forms.” These are typically protected by low hanging branches that are weighted down with snow, or under a mess of woody debris.

Protection is crucial to a hare, for despite their white winter coats and those famous hind feet that facilitate fast getaways across the snow, they are constantly at risk of being eaten. Adult survival rates are rarely more than 30%, even in ideal habitat, and an estimated 80% of hares die from predation. A three-year-old hare is both old and lucky.

So what do snowshoe hares eat in their protected hiding places? In winter, they subsist mostly on small twigs, about a tenth to a fifth of an inch in width. My students have repeatedly counted all the twigs in sampling areas that have been browsed by hares, as well as all the twigs that were left alone. What we’ve found is that, while hares mostly avoid the branches of conifers (no surprise – imagine licking a pitch pocket of balsam fir), they didn’t seem to have a preference among the shade tolerant hardwood species that grew in our study area. They tended to eat these species – striped maple, red maple, American beech, wild raisin and alder – in proportion to their availability.

We also tested hares’ taste for wood species that didn’t appear in our study area, including poplars and birch. Our experiments showed that the hares consistently preferred these hard-to-find twigs. As to why they had this preference, there’s no clear answer – there’s been extensive research on hare food preferences, but it points in different directions. A lack of chemical deterrents or the availability of particular nutrients, soluble carbohydrates, and perhaps sodium content may have been factors.

What we do know is that hares have an ingenious (if to many humans, repellent) way of making the most out of their meals: they digest them twice. Snowshoe hares, along with other hares and rabbits, have a small sac behind the intestines called a caecum. In this sac, there is a community of microorganisms that can break down the cellulose (the carbon compound that makes up most of wood). The only problem with this process, called hind-gut fermentation, is that it occurs after the food has passed the area where absorption takes place. To get around this, hares practice coprophagy – they defecate and then eat the soft pellets. Hares have a separate compartment in their stomachs where these re-ingested pellets ferment a little longer before passing through the intestines where the nutrients are absorbed.

So, if you’re out in a patch of conifers this winter, keep a look out for signs of snowshoe hares. Their tracks are distinctive – often, the impressions of their big hind feet appear just ahead of the impressions of their front feet – this is caused by their bounding motion. You may also find slightly flattened, fibrous brown pellets and signs of browsing – look for slender twigs neatly snipped at 45 degree angles.

Celia Evans is a Professor of Ecology at Paul Smith’s College in the Adirondack Park where, among other things, she teaches a course in Winter Ecology and studies snowshoe hares and other winter wonders with her students. The illustration for this column was drawn by Adelaide Tyrol. The Outside Story is assigned and edited by Northern Woodlands magazine and sponsored by the Wellborn Ecology Fund of New Hampshire Charitable Foundation: wellborn@nhcf.org

 


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4 Responses

  1. Ed Zahniser says:

    Thanks to you and your students for sharing this interesting research. Your predation stats confirm my long hunch — from thinking about hares/rabbits in Alaska, particularly, where they and their several predators are the few other bloods above ground in winter — that rabbits must get the feeling they exist to get the food web through winter.

    • AG says:

      “that rabbits must get the feeling they exist to get the food web through winter”

      Well yeah – that’s how God designed the ecosystems to work. Rodents are food for a multitude of predators – so their breeding rates are very high. The same is true in the waters as well. Some fish are food for almost all the big predators – so they breed a whole lot.
      Conversely look at alligators and crocs – most of their offspring don’t live… They are eaten by almost everything – including birds. No coincidence that alligators and crocs live a long time.
      Things tend to work fine – until we humans do things to throw the system off balance.

  2. Hillel B says:

    Does the hare’s range extend to the highest elevations of the Catskills, where there is the dense fir forest? ‘Never sure if that’s what I’m seeing there.

    Thanks!

  3. Paul says:

    I have spent a lot of time in the woods chasing hares (actually the dogs do most of the work!) and I see most of them in the habitat types that you describe. But I have also started to see a fair numbers of hares and tracks in open hardwoods, but only in hardwood stands that have been heavily logged and have lots of berry bushes and smaller shoots coming up. Celia, have you and your students conducted studies in these type of habitats? Perhaps on the easement lands north of the college?