By the so-called biological species concept, species are defined as populations that are able to breed freely among themselves but cannot breed freely with members of other populations. Those other populations, then, are defined as separate species. The biologist looks at places where different populations of similar animals come together to see if there are indications of breeding between the groups. Thus she is able to determine if two different species are involved or only one.
A problem arises, though, when the populations are in different
geographic areas and thus untestable under natural conditions. The seemingly obvious
solution is to bring individuals of the two populations together in the laboratory.
However, many animals rely heavily on behavior to determine suitable mates, and
behavior frequently breaks down under artificial conditions. Sometimes members of the
same species refuse to breed, while different species may overcome their reluctance. If
sea cows, one of nature's ugliest creatures, can inspire sailors at sea to endow
them with the beauty of mermaids, certainly two closely related, confined animals might
consider getting together.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.