Dan Groebner

Has your metal roof been experiencing daily “meteor” showers recently when it's windy? Or have you had trouble with little brown “ball bearings” on the trail making traction tricky at times? The source of both of these is probably sloppy squirrels or the gluttonous acorn woodpeckers carelessly gathering their winter stores or maybe it's just ripe acorns in bunches plummeting from their oak branches to blanket the ground. For one reason or another, this year seems to be producing a bumper crop of all kinds of “mast”, including acorns.  

Mast is what provides the energy for many animals to survive the White Mountain (and elsewhere) winters, when other food sources disappear due to the cold and short days. Technically, mast is often separated into two types – hard and soft. Acorns and seeds are considered hard mast while fruits and berries like raspberries and blackberries are called soft mast.  

Plants package their seeds, which are vital for reproduction, encased in good tasting and nutritious carbohydrates as a “bribe” for animals to eat the mast, digest the hard outer seed coating, and then spread these prepared and immediately fertilized seeds in their excrement. The seeds are adapted to survive the digestive tracts of wildlife just fine. 

We certainly need to boil acorns with many water changes to wash out the bitter tasting tannins to humans, but most wildlife has no problems with consuming large quantities of raw acorns. In addition to the energy provided by the carbohydrates, which can make up more than half of an acorn, this mast can also provide a good source of fiber, protein and fats.  

Fruits and berries can provide even more calories with their sweeter simple sugars, but are much more seasonal and perishable than acorns. Bears are experts in finding berry bushes as they become ripe and won't leave a good patch until they've removed every ripe fruit. Coyotes and fox can vacuum up so many juniper berries after they ripen and fall to the ground that their scats are comprised completely of seeds with no fur or bones. This vegetarian eating style is only temporary because of the highly adaptable and diverse menu of these canids coupled with the short term availability of juniper berries.

So why do the oak trees around us, mostly Gambel's oak, seem to vary greatly in their annual production of acorns? Anybody spending time outdoors will certainly notice differences from year to year. Theories have ranged from just random fluctuations to more scientific examinations backed by research.  

It appears that oaks may go though cycles of different lengths depending on the species, producing a bumper crop of acorns every 4-10 years. Acorns are different than typical seeds in that they are more of an embryonic plant that does not survive passing through a digestive tract of an animal like most seeds found in berries.  

Scientists theorize that oak trees do not have enough food and water to produce more acorns than local wildlife can consume every year. So oak trees save up on these resources over a few years and then are able to produce so many acorns in one year that the local wildlife could not possibly eat all of them. It only takes a few new seedlings sprouting every few years from acorns undiscovered by wildlife to maintain the oak groves if other conditions are favorable.

Even with a cyclic explanation for oak tree acorn production, it sure seems like there is more mast in the woods than many folks can remember. With the early start to our monsoon season this year, and more than twice the normal amount of precipitation during the season, it would seem that more moisture means more acorns. But it's not that simple.

Acorns get their start on oak trees by being wind pollinated. Since each tree has both male and female flowers, it should be a slam dunk to have all of their flowers fertilized every year. Self-pollination eventually leads to in-breeding due to the lack of diversity in the oak gene pool, so oaks have evolved the trick of making sure the male and female flowers mature at different times on the same tree. This arrangement ensures that the pollen from one tree ends up fertilizing another oak tree's female flowers maintaining genetic diversity.  

This DNA diversity is healthy for oaks and other species, since the population has a better ability to adapt to changes in weather or pest species, for example. All oaks may not be well adapted to drier weather for instance, but some may have genes for deeper roots, so at least some will survive and pass on their genes. Oaks are also known for being able to hybridize between different oak species, so don't get too perplexed if you have trouble identifying a particular specimen as it could have characteristics of two different species. 

So was our early and abundant monsoon season good for the acorns? It sure was, as the embryonic acorns need that moisture to grow plump. But it also could have been a dry and windy spring that spread enough pollen among the trees (and not just coating our windshields every morning!). Or a mild winter that spared the tender new branches destined to support the tree's flowers. Or it could have been triggered by the oak's ingrained instincts written in the DNA to rest for 4-10 years in between the abundant acorn years.

Thanks to the overabundance of acorns, White Mountain bears and raccoons will have a chance to put on some more weight before settling in for the winter, while turkey, deer, elk, and javelina will scarf up as much as possible before having to scratch through the snow to sustain themselves through the winter. Squirrels and acorn woodpeckers plan well ahead by caching acorns in hollow snags and holes bored in trees and sometimes, unfortunately, the siding of our homes.

Although oaks in our area usually aren't that valuable for lumber, our local wildlife certainly benefits from the food and cover habitat they provide, especially overwinter. That's why oak firewood cutting is restricted to certain areas and managed by the US Forest Service with permits and seasons. There are limits on the amount of dead oak that can be cut and the seasons shut down when the leaves fall off the oaks, making it more difficult to distinguish dead from live oaks.  

Fortunately, many oak species are adapted to fires by storing most of their food reserves in their massive root systems, which are usually protected from all but the hottest fires. That's why oaks (and aspens for the same reason) are the first tree species to sprout in dense thickets after a wildfire if there were any present before the fire. 

Early predictions of a mild winter coupled with lots of healthy critters going into the season could translate into a good year for some White Mountain wildlife. It should be a great spring for taking pictures on one of our many trails or overlooks. See you Outdoors!!