Little nuts, big impact

When you stroll through a German forest in fall, they can be as numerous as the brown leaves that cover the forest floor: acorns. These leathery nuts that contain the seeds of oak trees are such a common sight that few people would even bother picking one up during an afternoon walk.

But it is this ubiquity, which makes them crucial to many ecosystems. If they abound, life is good. When they are scarce, life gets hard.

Many animals feed on the brown nuts, including certain bird species and small mammals like mice. But perhaps most famous among acorn-munching rodents are squirrels and chipmunks, although, deer, wild boar and even bears gorge themselves on the nutritious nuts as well. 

Nutritious — if you can handle them

Acorns are an attractive food source because they provide a lot of protein, carbohydrates and fats, as well as minerals and vitamins. On the downside, they also contain bitter tannins, which many species struggle to digest (including humans). When cattle eat large amounts of acorns, the tannic acid produced during digestion can cause kidney failure, for example.  

Obviously oak trees don't produce the nutritious nuts to feed the animals that live around them. They want to spread their seeds and since the wind won't carry the heavy nuts, they have to count on the hungry animals in the forest to do it for them. 

Counting on forgetfulness

When the nuts are eaten by deer or wild boar, that doesn't work so well as they will gobble up the whole acorn, seed and all. Squirrels, on the other hand, are a different story.

When they get the chance, the little rodents will eat the seeds as well but they also like to hoard the nuts in many different caches as a reserve for when food is scarce. Putting them in many different places has the advantage of reducing the risk of all their reserves being discovered by another hungry acorn-aficionado. 

The animals are generally very good at remembering where they've squirreled away their stashes. Still, occasionally, they will forget a cache, or worse, succumb to a predator or another cause of death before they can retrieve all of their nuts.

That's when the acorn gets its chance to grown into a mighty oak.