RIVER VALLEY and OZARK AREA — To Arkansas’ human population, an abundant acorn crop means more debris to rake in the yard and sweep off the sidewalk. To the state’s wildlife, however, lots of acorns on the ground spell good fortune.
The acorn crop in an oak forest can reach hundreds of pounds per acre in a good year, when one mature tree can yield 15,000 nuts or more.
Acorns are easy to open and digest, making them significant food items for a variety of animals. More than 100 kinds of birds and mammals consume them. The geographic distribution of many animals coincides with or depends on the range of oaks.
Many Arkansas mammals eat acorns, including deer, white-footed mice, chipmunks, fox, gray squirrels, flying squirrels and black bears.
Acorns, particularly red oak acorns, are important food for wild turkeys, bobwhites, red-headed woodpeckers, red-bellied woodpeckers, blue jays, tufted titmice, common grackles, white-breasted nuthatches, sapsuckers, ruffed grouse and many species of waterfowl, including mallards, wood ducks, gadwalls and hooded mergansers.
For some animals - notably tree squirrels, woodland mice and blue jays - having an ample store of the burnished brown nuts is critical to winter survival.
If acorns are unavailable, these creatures may die or be forced to migrate to new areas where other food sources are available.
Biologists also have linked acorn crop failures - caused by late frost that kills the buds or spring rains that interrupt flower pollination - to poor black bear reproduction and meager antler growth on whitetail bucks.
To better understand the importance of acorns, let’s examine the ways some common species of wildlife utilize these packets of energy and how the relative abundance of acorns affects their lives and daily activities.
Deer connections
When available, acorns are the most preferred whitetailed deer food in autumn and winter, and may compose 50 percent or more of the animals’ diet.
When acorns are abundant, deer eat little else other than acorns until the acorn supply is exhausted.
Acorns are low in protein but high in carbohydrates. Deer fatten quickly in the fall and reproduce well the next year when acorns are plentiful.
Poor acorn crops result in lower winter survival, and surviving deer experience poor reproductive success and low fawn survival the following spring.
In the Ozarks, deer populations can fluctuate drastically according to acorn availability.
One study on deer habitat in this region found that when acorn yields were low (11 to 28 pounds per acre),deer numbers declined from one per 33 acres to one per 100 acres. When yields were 45 pounds per acre or more, deer density remained stable or grew.
Deer turn to other food sources when acorns are unavailable. Given the opportunity, however, deer will eat acorns, no matter what else is available.
Acorns and wild turkeys
When available, acorns are the principal food of the eastern wild turkey in winter and spring. Unlike deer, however, turkeys don’t eat acorns to the exclusion of other items.
Acorns compose a much smaller, though significant, percentage of their diet - up to 38 percent in some years.
As summer turns to fall,the succulent vegetation and insects that provide food for wild turkeys become less available in fields. At the same time, acorns become more available in the forest.
As a result, many turkeys move from field to forest habitat. The shift in habitat use can be abrupt in years of good acorn production.
Tu r k e y s b e g i n e a t i n g acorns as soon as they encounter them in the fall. Turkeys swallow acorns whole and grind them in their gizzards.
It has been said that when turkeys are feeding on acorns, the grinding and thumping sounds produced by their gizzards can be heard from a distance.
By mid-September, even poults can swallow the largest acorns.
The size of the acorn crop usually determines how far turkey f locks move from summer to fall range.
In years of poor acorn production, turkeys may relocate or expand their range to areas where row crops are abundant, and this seasonal range shift may be twice as far as that seen during years when acorns are abundant.
Blue jay’s cache
Among nongame birds native to Arkansas, the blue jay, more than most, eats acorns.
Each adult harvests and eats hundreds of acorns every autumn.
Additional acorns are hidden in caches, then relocated and eaten weeks, sometimes months, later.
Unlike deer and turkeys, which forage for acorns onthe ground, blue jays prefer acorns on trees.
They are often seen plucking green acorns from twigs. Some nuts are eaten immediately. Others are carried to caches.
In the latter case, the jays rank the acorns by size, with smaller ones being stowed down in the throat, and larger ones carried in the mouth and bill-tip.
Although blue jays sometimes tuck acorns in crevices of tree bark or clumps of foliage, they usually rely on thesoil to provide hiding places. Most caches are in relatively open patches near denser vegetation.
Upon arrival at a cache site, the jay places all its acorns in a pile, then buries them singly within a radius of 3 to 10 feet.
If acorns are scarce or widely scattered, jays may fly up to four miles to harvest them.
Each bird then returns to its breeding area to cache its treasures.
This tendenc y has led some scientists to speculate that blue jays were responsible for the unusually rapid dispersal of oaks following the Ice Age and the onset of a more temperate climate.
Blue jays are believed to have a poor sense of smell. They have little hope of appropriating another bird’s acorns unless lucky enough to see where a cache is placed, but they have no such difficulty in re-appropriating their own.
They have been known to bury acorns in the fall and recover them months later, inthe hungry days of late winter. When snow covers their caches, they still manage to uncover acorns, sometimes from depths of 1.5 feet or more.
The examples of all the animals we’ve discussed - deer, turkeys and jays - offer insights into the complex ecological relationships that exist between wildlife and oaks.
What affects oaks affects wildlife. What affects wildlife affects oaks. When one strand in this intricate web of life is plucked, the vibrations are felt throughout.
Acorn
Ups and Downs
Acorn production begins when trees are about
20 years old. Only a small percent of the nuts
ripen to maturity. The peak acorn fall is gener
ally in October and November, although the
period may extend from September to February.
Drought hastens the fall, and late spring freezes
kill buds, thus curtailing mast crops entirely.
Most acorns are eaten by animals soon after the
nuts fall, but some remain available until spring.
Weevil damage is heavy; up to 40 percent of the
acorn crop may be damaged within 30 days of
falling. Although animals eat weevil-damaged
acorns, the nutritional value is lessened.
The big disadvantage of acorns is their uncer
tainty of production. A good white-oak mast
year is generally followed by several poor years.
Black and red oaks are generally cyclic,
producing a good harvest one year and a poor
one the next.
Over one five-year period in the Ozarks, the number of acorns per tree on white oaks ranged from zero to 1,900, and on black oaks from 100 to 2,500.
River Valley Ozark, Pages 150 on 10/23/2011