Sun Sentinel Palm Beach Edition
Crunch under your tires? Sounds like acorn season
MELBOURNE — Seems the nuts are out in droves lately.
Acorns are piling up in Florida parking lots, sidewalks, lawns and streets as oak trees drop way more nuts than voracious squirrels, raccoons and wild hogs can wolf down anytime soon.
While most crunch harmlessly under foot, some nuts can weaponize. They ricochet off lawnmower blades like bullets, ding new cars like hail, or pelt passersby in the noggin.
All that crackling under our feet and tires hints that we’re in the midst of a mass “masting,” when oaks near and afar shed their acorns, seemingly in sync.
“There is not really valid understanding of what causes masting events,” said Holly Ober, associate professor of wildlife biology at the University of Florida.
Oak acorn production varies markedly year to year and by species. But every several years, like clockwork, masting oaks somehow synchronize the timing and quantity of seed production. Biologists suspect it may be some evolutionary adaptation to produce more nuts than foraging animals can eat. They aren’t exactly sure how and why oaks suddenly shift into acorn overdrive, then go nearly dormant for years. It seems to happen about once every four to seven years, when oaks — even those located thousands of miles apart — produce and drop acorns en masse, in unison.
Weather alone can’t explain it, scientists say.
Other trees, such as hickory, maple, fir and birch, also show patterns of producing bumper crops of seeds.
Florida hunters and wildlife viewers keep watch for acorn mass droppings, which can herald healthy deer, duck and turkey influxes. But there’s a potential downside to all these nuts. Biologists say such acorn onslaughts also bring in rodents. Heavy masting years have been known to help raccoons, rats, mice and other rodents flourish.
One theory suggests oak tree masting is triggered by ideal winds. Others point to rain, drought and hurricanes. Scientists also suggest the mass acorn dumps may be something simply ingrained in the tree’s genetic makeup, a hedge to guarantee germination of the next generation by flooding the ground with acorns.
Like many trees, for oaks propagation is a numbers game. Only one acorn in 10,000 lives to be an oak tree. A single large oak can dump that many in a mast year, biologists say.
But oaks don’t play those odds every year. Making acorns annually would sap too much energy from the tree, scientists say.
Following any mass masting event, oaks produce hardly any acorns for several years. Call it a sort of second-tier survival strategy — a way to keep seed predators at bay.
Deer, bears and other acorn eaters will roam farther for food in years when the nuts are less plentiful. So that makes them harder for hunters and wildlife viewers to find, but it also can increase “nuisance” bear complaints, as bears expand their ranges in search for food.
Threatened Florida scrub jays survive on their ability to trace their way back to acorns they buried months earlier.
Synchronized masting of nuts maximizes the chances of satiating all those seedeaters, ecologists say, allowing enough acorns to escape being gobbled up, germinate and grow the next generation.
Then the multiyear acorn “off” cycle limits the local food supply, forcing squirrels and other seed seekers to skedaddle.
A 2003 study at the Archbold Biological Station in Venus found oak acorn productivity of five oak species is mostly driven by the timing of rain and other weather factors during various reproductive stages in the years leading up to the large masting events.
They found the factors that drive bumper acorn crops vary by species.
“It can be rain that occurred even three years before,” Abrahamson said.
Trees in canopy settings produced fewer acorns than those in more open settings, suggesting light also is a factor, the researchers found. White oaks generally produce acorns in roughly 2- to 2 cycles, while red oaks do so every 3 1/2 to 5 1/2 years, they found.