Bear Food 101 - Acornology

As professionals in a particular field we often take for granted that people always know what we are talking about. Although I try to be cognizant of my audience I too sometimes fall into this trap. A wonderful follower of mine reminded me that not all people were aware of the importance of the "hard mast" crop to wildlife, in particular, bears. Hence, the lesson to explain the importance of bear food begins.

"Mast" is a technical term used by biologists to refer to the available fruit and nut crop for wild animals. Occasionally they refer to the summer berry crop (e.g. blueberry, blackberries, huckleberries, etc.) as soft mast but mostly we use the term in reference to hard mast, the fall "nut" crop. This is the food crop that drives many species simply because it is their main source of food that gets them through winter. Let me explain further why hard mast is so important.

Wild food crops occasionally fail. Whether it be from drought, excessive rain, or possibly even insect infestation, uncharacteristic events can wreak havoc on food production. When this occurs in the summer time and the berry, or soft mast, crop is impacted, there are usually secondary foods the animals can fall back on. Bears being omnivores can and will eat anything, including green leafy plants, insects and carrion (dead animals). These food items, though not necessarily nutritious or overly abundant can usually sustain them and are found throughout the summer. Now let's skip forward two seasons and look at our coldest and most difficult season to survive...winter.

Winter time is a period of famine. There are no succulent sprouts or new plants growing, most lie dormant and leafless in their winter slumber. When the temperature drops, insect life is almost non-existent, with most insect life-forms lying dormant deep under ground. Amphibians and reptiles also seek refuge deep beneath the snow layer. Their ability as cold-blooded animals to drop their body temperature allows them to lie dormant for long periods of time.

Birds fly south in the winter, not to escape the cold but to follow the food. After all we use bird feathers, also known as down, to keep warm so migration is simply a matter of finding enough food to eat. This leaves mammals getting stuck between a rock and a hard place. They must figure out a way to survive the long, cold, barren "food-less" season known as winter. Since this blog is about bears, we will focus on their strategy for surviving winter.

As you know, bears sleep through winter. There is a whole other blog I could write about how bears are not true hibernators like other animals, but rather super-hibernators, but that lesson will be told another time. Just think of bears going to bed and falling into a deep sleep (not hibernation) as the days begin to chill. Their restful slumber not stirring for about four months until the sun begins to warm the outside air once again. In order to do this and survive, the bears MUST fatten up. Since they're not going to be eating for months on end, the bodies will need to rely on their fat reserves. This makes those fat reserves absolutely essential for the bears survival, which brings us back around to the food discussion.

The fall is the critical time period in which bears rely to build those fat reserves, hence, they need a highly nutritious, high-caloric food item that will build up layers upon layers of fat. And voila...nature provides that for them in the form of nuts. Without natures bounty of hard mast (nuts), bears would have a difficult time surviving the winter.

Is a nut is a nut is a nut?

White oak leaf

Not necessarily. Although almost all nuts are edible it doesn't mean all nuts are palatable. Bears like all animals have preferred tastes and the acorn, a fruiting-body product of oak trees, is definitely their food of choice.

There are two main kinds of oak trees, those that are classified as white oaks and those that are classified as red oaks. The two groups are relatively easy to tell apart simply by looking at the leaves. Although there is great variation among the leaves of oak trees most have a uniform "oak-leaf" look to them. Generally speaking, if the lobes on the oak leaf are rounded it belongs to the white oak group. If the lobes are pointed then it goes into the red oak category. This is where it gets interesting, I swear.

Red oak leaf

Acorns are packed with protein, fats, and carbohydrates...the perfect energy food for pretty much all wildlife. Besides being a great source of nourishment they taste pretty good except for one thing, tannins.

Tannins, are nature's natural food preservative, they delay rotting and keep the nut viable and fresh while it lies motionless on the ground in anticipation of germination. Sometimes, this may take six months or more. Now imagine placing your lunchtime snack on the ground and coming back six months later and finding it as fresh as when you first placed it there...pretty freaking impressive don't ya' think? So tannins are pretty awesome...except for one thing. They taste awful. They turn a naturally sweet tasting acorn into a bitter tasting bite, the higher the level of tannins, the more bitter the nut.

Fortunately there's a distinction between the two oak groups. Trees in the white oak group produce acorns over the course of a single year. Since they're putting out acorns annually, they're tannin level is quite low. Each year there's a new crop of acorns so the nuts don't have to stay viable for long periods of time on the ground. Because of their low level of tannins, they taste really really good. All animals, especially bears, love them. So an acorn-producing white oak tree is a gold mine for attracting wildlife.

Red oak trees on the other hand have a two-year acorn maturation process. Since their bounty comes along less frequently than the white oaks it's more advantageous for them to produce an acorn that lasts a whole lot longer on the ground. Hence, they contain a much higher level of tannin. When an acorn from a red oak tree first falls to the ground it's not very tasty but the longer it sits, the more the tannic acid dissipates and the sweeter the acorn gets.

So think about how wonderfully clever Mother Nature is. She creates acorns, a bounty of high energy, power-packed tasty morsels that fall from the trees right before the leanest and harshest time of the year. And to boot, she devised a way for those same energy bites to be available all winter long should an animal need them or be fortunate enough to find them. And yes, come spring, if the red oak bounty was good, there will be sweet tasting acorns awaiting the bears upon their emergence from their long winter's slumber. On the flip side, if the oaks fail to produce a large bounty of acorns in any given year, the animals are stressed and nature begins its selection process keeping only the strongest. Hence goes the extreme importance of the mighty acorn.

Now when you hear biologists talk about the "mast crop driving bear populations," you'll hopefully have a better understanding of what exactly they're talking about.