Fun with Science Club®


			Guppies don’t like swimming with strangers. Beth Tyler 06.01.01 Many species of fish, including guppies, Poecilia reticulata, swim together in schools. Sticking together helps fish find food and defend themselves from predators. Two scientists in England hypothesized that female guppies preferred to swim with fish they already knew. They tested their hypothesis in streams in Trinidad, an island country off the coast of Spain. During the dry season when it rarely rains, the streams dry out in places, leaving many small, isolated pools of water. Some of the pools have schools of guppies in them. Because the guppies in one pool live isolated from other guppy populations for many months, these pools were the perfect place for the scientists to test their hypothesis. The scientists used seven pools with guppies in them and one observation pool without any fish in it. They moved four guppies from the same pool into the observation pool. They also moved four guppies from different pools into the observation pool. Then they made systematic observations on two of the fish from the same pool. They observed each fish separately, and recorded data on how often it schooled with familiar fish (fish from the same school) and unfamiliar fish (fish from a different school). They tested fish from each of the seven pools using this same method. As they hypothesized, the scientists found that the guppies preferred to school with familiar fish. Even though female guppies all look the same to us, the guppies can tell their schooling buddies from strangers.


			Griffiths, Sian W., and Anne E. Magurran. 1997. Schooling preferences for familiar fish vary with group size in a wild guppy population. Proceedings of the Royal Society of London, Series B 264: 547- 551.