Brown and Black Bears

Some Interesting Observations about Brown (and Black) Bears

by Sue Pike

July 11 2017  The York Weekly/Portsmouth Herald/Foster's Daily Democrat/Exeter Herald

One of the most remarkable sights I’ve seen in Alaska (my new backyard for a short time this summer) has been the large coastal brown bears grazing on the meadows of sedges and grasses that ring the tidal inlets.  They move around like cows - grazing!  I didn’t think bears did this. 

These brown bears (Ursus arctos) are cousins to our local black bears (Ursus americanus).  Brown 

Brown bear eating sedges  Warm Srpings AK    Sue Pike photo

 bears are what we usually think of as grizzlies, but this isn’t always true.  A grizzly is a brown bear, but a brown bear isn’t always a grizzly.  According to the National Park Service “brown bears and grizzlies are the same species (Ursus arctos), but grizzly bears are currently considered to be a separate subspecies (Ursus arctos horribilis).  Brown bears are generally considered to be those of the species that have access to coastal food resources like salmon”.  This access to more abundant and higher energy food allows the coastal brown bears to get much larger than the inland grizzlies.  Also, because of this concentrated food source, the spawning salmon, the coastal brown bears congregate more.  You’re much more likely to see them hanging out in groups than grizzlies.

I had long known that bears were omnivores, I was first introduced to this notion as a youngster in that iconic book “Blueberries for Sal” in which a little girl and her mother cross paths with a mother black bear and her cub while collecting blueberries.  I knew bears ate berries, but hadn’t known bears graze on grass.  Both our local black bears and those Alaskan brown bears eat quite a bit of grass and sedge in the spring when there isn’t much else available to eat and the new, succulent growth of the grasses and sedges is an abundant and easy-to-access food.  Compared to carnivores, the omnivorous bears have an elongated digestive tract, an adaptation that allows bears to digest vegetation more efficiently than carnivores. But, they can’t digest the fiber in this vegetation very efficiently, so will typically eat grasses, sedges and leafy plants when the leaves have just emerged and have the least amount of cellulose and the highest nutrient availability.  The Alaskan brown bears eat a lot of sedges relative to grasses.  Sedges are grass-like plants that, among other differences, have triangular stems (grasses have hollow stems with periodic ‘knees’ or joints).  They tend to be abundant in wetlands—next time you are in one take a look at the stems of the grassy plants, you’ll find many are, in fact, sedges.

Another brown bear grazing on sedge   Sue Pike Photo

It’s interesting to think about the strategies employed by bears to get the most out of this not-very-digestible vegetation.  Feeding in the spring when these plants are most succulent makes sense.  They don’t want to spend much energy on chewing or digestion— “this is reflected in the bulk and structure retained by foliage in bear feces.” (David Mattson from his wonderful site allgrizzly.org). My interpretation of this is that they are putting as little energy as possible into acquiring this plant material and extracting what nutrients they can as it passes, relatively unharmed, through their digestive systems.

While we are well into summer by now and most bears have probably moved on to more nutrient-rich, lower fiber foods, I think it is worth thinking about how most wildlife is in a constant state of balancing energy output with energy input.  Those coastal brown bears are lucky, they get that huge influx of salmon every year, for a time they can relax.  However, we need to remember that every time we disturb wildlife, force them to move more than absolutely necessary, we are making them work that much harder to get the nutrients and calories necessary for survival.  Something to think about when we’re outside enjoying nature this summer.