DO SCALE ANOMALIES CAUSE DIFFERENTIAL SURVIVAL IN VIPER0-BERUS

Many snake populations contain moderate to high frequencies of individ uals with ventral scale anomalies, which are often associated with dup licated or fused vertebrae and ribs and are known to impair locomotion and growth. In an attempt to test whether such anomalies may influenc e survival, we examined their frequency among cage-reared juvenile add ers, Vipera berus, and wild-caught individuals that presumably had bee n exposed to natural selection. Midbody ventral scale anomalies were s ignificantly less frequent among snakes exposed to selection than amon g cage-reared juveniles in one of three populations studied, indicatin g that they might indeed reduce survival. Furthermore, midbody anomali es were less common among large than among small wild-caught individua ls, although not significantly so. The association between anomalies a mong captive mothers and their offspring was very weak, indicating low heritability of this trait. This low heritability might explain why s cale anomalies are common in adder populations in spite of the apparen t selection against anomalous individuals. We also found the proportio n of anomalous offspring to increase with litter size, suggesting a tr ade-off between number and quality of young.