This volume is subtitled "Alternatives" because we wanted to devote at least a part of it to the alternative ways in which members of the same species behave in a given situation. Not so very long ago the supposition among many ethologists was that if one animal behaved in a particular way, then all other members of the same age and sex would do the same. Any differences in the ethogram between individuals were to be attributed to "normal biological variation. " Such thinking is less common nowadays after the discovery of dramatic differences between members of the same species which are of...