It was "The Mystery of the Pine Cone Stacks" for homeowners Marilyn (Cookie) and Roy (Buddy) Dorshimer.

For the last six years, Cookie and Buddy noticed someone or something was piling up pine cones underneath their Norway Spruce trees."The first time I saw it, I thought someone was piling them up to use but never came back for them," says Cookie.This year, there are huge piles of pine cones, all stacked up against the tree trunks in between the roots. Some of the larger of the 18 trees that border the edge of their Kunkletown home, have stacks of pine cones all around the trunks."We lived here for 45 years and it's only been the last five or six years that we noticed this," says Cookie.It has also been happening in Buddy's parents' yard (William and Lillian Dorshimer) across the street."My father-in-law saw squirrels doing it but this is the first year I actually saw a squirrel sitting there eating the seeds of one."According to Darryl Speicher, an environmental educator at Monroe County Conservation District's Environmental Education Center (MCCD/MCEEC) in Stroudsburg, this is common practice for the red squirrel."Red squirrels love spruce cones. They love eating the seeds and they will meticulously strip the cones. We have a healthy population of red squirrels in our area," Speicher says.In an online article from Michigan State University, it reports the findings of one of its assistant professors of wildlife and fisheries, Andrew McAdam."Red squirrels have figured out a way around the elaborate ruse trees have used to protect their crops of tasty seeds.The red squirrels dine almost exclusively on the seeds of spruce cones, which they gnaw off before the seeds ripen. The squirrels are a major enemy of the spruce trees. If the squirrels become too successful, their hoarding and gorging on the cones thwarts the trees' ability to cast seeds and reproduce.It is an intriguing battle of survival in the natural world.Over the years, the trees devised a strategy called masting in which they unpredictably, every few years, produce an overabundance of cones. It's called a "swamp and starve" strategy to take predators by surprise, flooding the market with more seeds than the squirrels could harvest. The starve part of the strategy comes from the few cones that are produced in the years between bumper crops.Swamp and starve is designed to play to the squirrels' weakness. Squirrels are territorial and need food to feed growing pups and provide a place for their offspring to call their own. Lots of cones means lots of food to feed pups. But adults also survive longer, which means young squirrels have to hunt for new homes."What the latest paper shows is that the squirrels are on to the trees' game," McAdam said. "Before masting seasons, the squirrels are producing second litters, an act that would be, well, squirrelly in seasons of low food supply. But a population boom that coincides with a seed boom is brilliant. More food means more places for juvenile squirrels to set up shop."The study shows squirrels also are playing an adaptive strategy."They're not just following along. They're making reproductive decisions that are best for them. This is about how red squirrels make a living in a variable world and how they make reproductive decisions in what seems like unpredictability."The study also shows that the buds the spruce trees put out the summer before cones develop may hold the clues to a masting event. In the summer, these buds either become tree branches or develop into cones. The squirrels eat the buds and may detect which destiny they'll follow, getting a tip-off to an upcoming masting event."I hope this gives people a better appreciation that these squirrels are not just taking what they get," McAdam said. "Both players, the squirrels and the trees, are following these strategies to try to maximize their fitness."While Cookie thinks all of this is fascinating, she's just thrilled that the squirrels continue stacking the pine cones into neat little piles."It's nice for us because in the spring when we clean up the yard for mowing, the pine cones are all piled up for us and we just have to scoop them up with a shovel."And so "The Mystery of the Pine Cone Stacks" has been solved.