DOES POLYMORPHISM PROTECT - AN EXPERIMENT WITH HUMAN PREDATORS

Authors
Citation
R. Knill et Ja. Allen, DOES POLYMORPHISM PROTECT - AN EXPERIMENT WITH HUMAN PREDATORS, Ethology, 99(2), 1995, pp. 127-138
Citations number
32
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Zoology,"Behavioral Sciences",Zoology,"Behavioral Sciences
Journal title
ISSN journal
0179-1613
Volume
99
Issue
2
Year of publication
1995
Pages
127 - 138
Database
ISI
SICI code
0179-1613(1995)99:2<127:DPP-AE>2.0.ZU;2-6
Abstract
Polymorphism in cryptic prey species may be 'protective', in the sense of reducing the rare of predation by visual predators. We tested this supposed function by presenting 80 schoolgirls (aged 12-13) with popu lations of square 'prey' on backgrounds displayed on computer screens. The backgrounds were composed of random distributions of small colour ed squares and the prey were composed of the same small squares, the g rid of the prey being parallel to (but usually imperfectly aligned wit h) that of the background. Different 'morphs' of prey were defined by the spatial distribution of the small squares, and prey of a given mor ph were always presented in the same orientation. Each subject was pre sented with a sequence of 40 screens, of which 36 were background cont aining a single randomly positioned prey, while four were background a lone. Subjects 'zapped' prey with the mouse, or pressed the space bar if the screen was judged to be empty, and then moved automatically to the next screen in the sequence. Each subject received a single 'treat ment': high or low crypsis combined with one of four levels of polymor phism (1, 2, 6 or 12 morphs). The results showed that hit ('predation' ) rare tended to be lower on populations with high crypsis and was inv ersely related to the number of morphs in the population. We thus conc lude that polymorphism may indeed 'protect'.