Head shapes of viper and viperine snakes.

Natrix maura has a narrow colubrid-like head shape (a). When disturbed, they flatten their heads making the head more triangular in shape (b). Vipera latastei gaditana exhibit the typical triangular head shape of European vipers (c). Triangular, viper-like and narrow, colubrid-like head shapes of plasticine models (d). Attacks of raptors (e) and mammals (f) can be separated from imprints left during predation events. A dorsal zigzag pattern was painted on half of the snake replicas (g).