Food

[KittyGlitter]

How do wild animals know what food is poisonous and what isn't? I first thought about this regarding birds and how they know which berries are poisonous. Any ideas? Thanks :o)

[andy hughes]

It's down to evolution. The animals or birds that eat poisonous food don't survive to breed, the ones that avoided it, for what ever reason, do, so you finish up with a species that routinely avoids poisonous foods.

[New Forester]

There are several things which happen.  One is that most animals have some sort of taste and smell system.  They avoid things which taste nasty -- many poisons, for example, are bitter to us.

 

Another is that poisonous things may have warning coloration.  For example, wasps are yellow and black, and some snakes are similarly boldly marked.  The markings may not be "truthful" though -- hoverflies are harmless, but look like wasps.

cont...

[New Forester]

...cont

A third is that few poisons kill outright, and a small amount just makes you feel ill.  Many animals try a little of something and wait several days.  If they feel ill in that time they'll never eat it again, if not, they'll eat it ever after.

 

For example, we turned our cattle into a new field which had sycamore growing in it -- a new plant for them.  They were very curious, and licked, sniffed and nibbled it for three days.  On the fourth day all the sycamore vanished.

 

On another occasion I offered them box twigs.  They ate a little, but three days later they would not touch it.  Similarly, rat poisons do not work if they make the rats feel ill -- the rats realise it's bad, and never touch it again.  Even humans -- I've always been irrationally nervous of chick-peas since I got food poisoning from a curry about twenty years ago (it was not the chick-peas that made me ill).

Such learning may be passed down from generation to generation.  Humans are superb at this (it may even be why we have such huge brains), but even rats do it -- a colony will learn the danger of a poison or trap, and pass the information on to later generations.

Finally, some animals only eat certain food, such as a caterpillar eating only the leaves of one particular plant.  By being completely unadventurous they run no risk of eating something they are not adapted to.  Their particular plant may be poisonous to other species.  For example, the cabbage white butterfly eats only cabbage-family plants -- they contain mustard oil which would put other caterpillars off.

Most berries are in fact not poisonous to birds.  The bright colours are advertising their tastiness as bird-food, so birds are probably pretty safe.  Us mammals have to be more careful -- deadly nightshade berries, for example, are huge, juicy and very tasty-looking.

[ezapf]

I think my dogs are a good example of the beginning of NF's continuation: I have a yard full of oak trees which are poisonous to dogs. Our 6 year old lab will not touch the acorns, leaves, or branches. Our 1 year old lab still chews on fallen branches then vomits if she swollows any pieces. I guess she is still learning.