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  • How to Eat, but Not be Eaten — Foraging Strategies of Four Urban Squirrel Species

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    Tags: squirrel, squirrels, urban ecology, chipmunks, chipmunk, chicago, chicago wildlife

    Created: 9/19/2014      Updated: 8/9/2016

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    The most common tree squirrels in our region are the grey (Sciurus carolinensis) and the fox (S. niger). Both of these species are scatter hoarders. That is, they bury nuts in random places across the landscape. In contrast, the red squirrel (Tamiasciurus hudsonicus) is a larder hoarder. This means they put all of the food they have gathered in only a few places, like a hollow log or under a rock.

    Grey Squirrel digging in the ground

    Grey squirrel caching

    These two strategies have costs and benefits. A larder hoarder can defend its cache from other squirrels, nut and seed eating birds, and many other species that might rob it of food. Even you may have been scolded by a red squirrel when you inadvertently came too close to its larder. On the other hand, there’s not much a red squirrel can do to deter a determined black bear from raiding the squirrel’s cache. Scatter hoarders don’t have to worry about bears but they do lose a lot of their nuts to competing squirrels and birds, and simply because they can’t find the food once it is buried.

    Fox Squirrel eating in a hole in a tree

    Fox squirrel eating

    These two different foraging methods also result in red squirrels having relatively large territories. You don’t often see lots of red squirrels in the same place at the same time. On the other hand, there are many places where you might see more than a dozen grey squirrels foraging together. 

    Red squirrel on a rock

    Red squirrel

    One thing that does bring lots of squirrels together is bird seed. If seed is buried it either rots or germinates. Either way, it is not very useful to squirrels so, rather than run around caching, as they do with nuts, squirrels will simply sit and eat the seed. The threat of predators and more aggressive squirrels keeps them moving around a little but they are otherwise perfectly happy to sit at the dinner table and eat.

    Chipmunks, though, have a different strategy. They have check pouches. This allows chipmunks to literally stuff their faces full of food, then run back to their burrow, dump the food, and return for more once they think the coast is clear. In this way, they can collect plenty of food to eat, while only exposing themselves to the danger of predation for relatively short amounts of time. The seeds they gather are stored in cool, dry rooms (the same way we store grain) so it stays fresh and nutritious through the winter. This foraging strategy is so successful that chipmunks have become our most common ground squirrel in urban areas.

    Have you ever wondered why you don't see baby squirrels as often as you see adult squirrels? Learn why in this post.

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