IS THERE A DIFFERENT PREFERENCE IN THE CHOICE OF BACKGROUND COLOR BETWEEN MELANISTIC AND CRYPTICALLY COLORED MORPHS OF THE ADDER, VIPERA-BERUS

Most natural populations of the adder (Vipera berus), including both c ryptically coloured (zig-zag) and melanistic (black) individuals, are polymorphic in dorsal colour pattern. In this study we report experime nts to test whether a difference in preference of background colour ex ists between these morphs. The occurrence of this difference between c olour morphs was studied in (1) indoor and outdoor enclosures, (2) bas king and not-basking animals, (3) during daylight and nocturnal hours. Our data show that cryptically coloured and melanistic adders manifes t a nearly identical preference in their choice of background colour, both in daylight and nocturnal hours: i.e., a clear-cut preference for dark substrates independent of sex. Some hypotheses are put forward t o explain this preference.