The ecology of the slow-worm (Anguis Fragilis L.) in Southern England

Abstract

The slow-worm, Anguis fraqilis, is a legless lizard in the family Anguidae. The ecology of the species was studied by weekly visits to two sites on the Isle of Purbeck, Dorset, England from 1981 to 1988. Other sites were visited less often. Animals were found under pieces of corrugated iron sheet that had been placed on the ground. Adults were photographed and identified on recapture by the pattern on the underside of the head. Pregnant females were retained in captivity until the birth of the young.

A total of 3456 slow-worms were found. Capture rates of known individuals were low, often less than once a year. There were differences in rate of captures of four sex and size class over the season. Males predominated in spring, females were found most often in summer and sub-adults and juveniles were commonest in autumn. Rates of movement were low. There was no evidence of territory formation.

Mating was only observed once. Females with sperm in the cloaca were found in May. The litters of 1 to 18 (average 8) were born in late summer. Larger females had larger litters but not larger young. In 1986, litter sizes were small with many of the young deformed. The sex ratios were not equal. The bias was to females at one site and to males at the other.

Cloacal temperatures, low for a temperate reptile, ranged from 9.8 to 33.2 "C, with a median of 24.9 °C. There was little evidence of precise thermoregulation. Cloacal temperatures were highest in summer on sunny days, but varied little with time of day. The distribution in the Iberian peninsula was shown by discriminant function analysis to be correlated with cooler, wetter climates.

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