Squirrels Check Structural Integrity of Nuts to Determine Which to Bury and Which to Eat

Abstract

Squirrels (and chipmunks, and likely other rodents) examine nuts to determine which to bury and which to eat.

Question

Why do squirrels bury nuts? Why do they prefer in-shell nuts to shelled nuts?

Background

Living in a townhouse for quite a few years, Melody Soroudi has had the opportunity to be up close and personal with squirrels (primarily black and grey), as well as other related rodents such as chipmunks. She has been feeding them shelled nuts for years and later added in-shell nuts, or what David Suzuki calls “five-dollar bills”.

Feeding them in-shell nuts created an interesting behavior in the squirrels: they began to bury the nuts much more often than when they were getting only shelled nuts. Why?

Obviously they bury them in order to store them for later use (like the Aesop’s Fable about the Ant and the Grasshopper), specifically for use in the spring when plants are dead or dried up and not fruiting. But surely they cannot bury all of the nuts, they must eat during the summer as well.

The fact is that they do, but they are selective and discerning about which nuts they eat and which they bury.

Observations

If you watch squirrels closely, the behavior becomes apparent. When they get a hold of a nut, they turn it over and over in their hands while examining it with their mouths. If they detect significant cracks or broken or missing pieces of shell, they rip it open and eat the nut(s) inside. If they detect the shell to be structurally intact, they bury it. They do not eat nuts whose shells have a small crack along a seam which are still “closed”, only those they deem to be “compromised”.

This is a logical move because a nut that is compromised is like a coffin with a hole, it will be invaded by bugs and worms and the like and not only get covered in soil, but decompose, or even germinate and start to grow. In fact, nuts that squirrels have lost and forgotten is one method by which some plants reproduce; the shell eventually dissolves and the nuts inside (assuming that they are not roasted) begin to grow. Squirrels are essentially farmers who plant seeds.

Followup Question

Why do squirrels prefer in-shell nuts to shelled nuts? Obviously an in-shell nut provides less energy and nutrients than shelled nuts.

The ones that have the shell only contain two (or occasionally three, but sometimes even just one) nut. They also take up more space and thus can be packed less efficiently, wasting room on shells and air. Also, they require extra work to remove the shell.

Shelled nuts on the other hand require no extra work to get at the valuable part and can be packed better to put more food in less space.

Clearly shelled nuts are more optimal than in-shell nuts. So why do squirrels and other rodents prefer the shells? Why do they prefer to store food for the future than to use it now like some animals do?

This is simple to explain. Larger animals like bears and camels have the physical space to store the energy for future use by plumping up and storing fat in their bodies, however, small rodents do not have that physical capacity, so they must store the food externally in their homes or in the ground.

In addition, large animals tend not to move too much, and thus consume less energy while foraging than small animals like rodents do. Squirrels and chipmunks travel long distances from their nests to look for nuts and run up and down trees and such and thus burn a lot of energy just to get food. Therefore they need to accumulate and store a lot of food for future use.

Monsters are People Too… Literally!

Most of the classic monsters are not actually separate species but humans that have been damaged or changed somehow.

  • Vampires are just humans that have been infected with a virus
  • Werewolves are also humans that have been infected with a virus
  • Zombies are likewise virus-infected humans
  • Mummies are dead humans that have somehow come back (usually through magic)
  • Skeletons are the same as zombies/mummies, but without their flesh
  • Witches are humans who use magic (usually for evil)
  • Ghosts are dead humans

Even more contemporary monsters like Jason Voorhees, Freddy Kruger, Michael Myers, Pinhead, Chucky, creepy Japanese girls, etc. are just humans that have been changed in some manner.

Of course, there are some monsters that are not human whatsoever, for example the Creature from the Black Lagoon, Godzilla, demons, and such.

It is interesting however to realize that most monsters tend to be human. If one were to analyse that fact from a psychological viewpoint some interesting/obvious reasons would likely be found.

Technology Breeds “Patience”

Last night, CBS news did an article about the recent increase in airport security due to the attempted Christmas bombing. The anchor went to on to say how people have been okay with the extra wait times and delays that the increased security checks have created because passengers are more patient and understanding; that they are willing to put up with the extra wait times because they know that it is for their own good and safety, and that they are cheerful because it is the holidays, so they are in better, less rushed moods. Unfortunately the news team got it completely wrong.

The reason that people are more willing to put up with down time and delays these days, not just at airports, but everywhere: on the bus, at work, at the the DMV, in coffee-shop lines, etc. is because of technology. In the past, people disliked having to stand around and wait because it was such a waste of time. Having to stand or sit around and twiddle your thumbs, or at best read a book was really frustrating. Now however, with iPods, iPhones, PSPs, laptops, netbooks, Kindles, and so on, wait-time is no longer down-time, but break-time. Thanks to all of the varied gadgets and devices, we can now spend those two minutes here, 10 minutes there actually doing something useful, be it work or play, instead of waiting around, bored out of our minds.

To Move or Not to Move; That is the Question

This is a follow-up to When to Pull the Cord.

As social as people like to think of the human race, we also like our space. Aside from public bathrooms, the bus is one place where this is very evident.

What happens when you get on a bus and there are plenty of seats free? You sit where you want. What do you do when there are few seats free? You sit wherever you can. More often than not, unless they are getting on the bus with a friend, most people will put a seat or two between themselves and the next person, creating a buffer, personal space (even with a friend, a lot of people make a buffer). Only when there isn’t enough space will people usually sit immediately next to someone else.

The question then becomes, what happens when some people get off and seats free up? Do you get up and go get your own seat or do you stay next to the person you sat next to earlier? What would the person you’re sitting next to think if you do? If you don’t?

If you move, the person may be happy to get their own space again. Or the may feel insulted that you felt you needed to move, perhaps because you think they smell or something.

If you don’t move, they may be upset that they are still being crowded when there is space available. Or maybe they are relieved that you don’t find them offensive, and perhaps even that other people will think that there must be something appealing about them to keep you sitting next to them when there are now free seats.

No matter what you choose, there will be some people who will view it as good, and some people who will view it as bad (and some people who will view it in ways that normal minds cannot even conceive of). In the end it more or less balances out, so there is no mathematical solution, and you are better off just doing whatever you prefer if the person does not give you an indication of their preference.