Fish and elephants
Have you ever wondered where expressions like ‘an elephant never forgets’ or he has got ‘the memory of a fish’ come from? Well we don’t know the answer to this question, but we have found out some interesting, if not a little random stuff, about fish and elephants.
The memory of a fish
There are over 125 types of goldfish. This is the result of careful selective breeding, begun when goldfish were first domesticated during the Chinese Sung Dynasty, about a thousand years ago - not that the goldfish would know anything about it! The popular belief is that no goldfish can remember anything that happened more than a few seconds ago. So every circuit of their tank or pond should be fresh and new - because supposedly, they can't remember the last loop.
So do fish have a memory? And how would you show that a fish has a memory?
Jonathan Lovell from Plymouth University's Institute of Marine Studies is convinced that some fish have a memory. He has successfully trained fish to swim towards a sound. He wants to release domesticated fish into the open sea, and call them back with special sounds to a feeding station, to supplement their natural diet.
Culum Brown (of the Institute of Cell, Animal and Population Biology at the University of Edinburgh) studied the crimson spotted rainbow fish that lives in Queensland. He compared fish that knew their tanks well, with fish that had just been placed in tanks. He introduced a net with a central hole into a tank, and then swept it from one end to the other. The fish that had a strong memory of their tank were better able to escape through the central hole - presumably because they could ignore what they remembered to be familiar and non-threatening to them (their tank), and instead, could concentrate on the new threat (the net). The fish that knew their tank remembered the trawling net so well, that they could escape it in a follow-up study some 11 months later.
By the way, 11 months is nearly one third of his fish's 3-year lifespan. That's a very long time to remember something that has happened to you only once. This would be the equivalent of remembering what you had for breakfast 25 years ago!
Yoichi Oda of Osaka University in Japan has spent years studying the fine details of memory in goldfish - and is also convinced that goldfish have a good memory.
Some goldfish will come to the glass of their tank whenever people walk into the room. These particular goldfish have worked out that when people turn up, so will food - at least, sometimes. In other words, People = Food. This is called "associative learning". The fish now associate people with food.
Fish also do "social learning", where they learn by watching their fellow fish. Fish are very good at 26 "social learning", because some species of fish are very social. They all hang out together in schools. To survive in the school, they spend a lot of time paying attention to what their school mates do.
Some fish can learn music - probably because it's important for them, in the wild, to be able to distinguish between different sounds in their environment. Ava Chase of the Rowland Institute for Science in Cambridge, Massachusetts taught carp to tell the difference between John Lee Hooker (blues) and a Bach Oboe concerto (classical), by feeding them smaller fish as a food reward. The music was played to the fish through loudspeakers in their tank. She then discovered that the carp could generalize from what they had learnt, and classify music that they had not heard before, into the categories of blues or classical.
Some owners even say that their goldfish remember their faces and freely frolic in the tank when they're the only ones present, but hide for an hour or so, when strangers enter the room. How odd is that?
Elephants never forget
According to BBC News Online's Helen Briggs, the saying that elephants never forget has been verified by science, particularly in the case of matriarchs, who lead the herd.
A study of wild African elephants by Karen McComb, an animal communication expert, has revealed that dominant females build up a social memory as they get older, enabling them to recognise "friendly" faces. Elephants often travel large distances in search of food. A typical group of elephants consists of a matriarch grandmother and a number of her daughters and granddaughters. When the female elephants encounter other individuals they do not recognise, family members bunch together defensively to protect their young. They signal whether an outsider is a friend or foe to the rest of the herd, allowing family members to focus on feeding and breeding when there is no danger.
The older and more experienced the matriarch, the better she is at recognising old friends, and the more calves the family is likely to produce.
The implications for this go way beyond an interesting bit of trivia for memory buffs. These findings also have important implications for conservation. Poachers tend to kill the bigger, older elephants. If they were to kill the matriarch this could affect the survival chances of the whole herd.