Age structure, growth and reproduction of Anguis colchica (Reptilia, Anguidae) in Sochi National Park (Western Transcaucasia, Russia)

Within the boundaries of its range in the Caucasus, Anguis colchica is distributed from the lowlands to the subalpine belt. In Sochi National Park (Russia), the species is one of the most numerous among reptiles. The studied animals were collected in April and July 2019; the body length was measured and the tip of the tail was docked. Adult females were kept in the laboratory until the offspring were born. Three newborn individuals were kept continuously under artificial conditions for two years, twice arranging for them to winter at a temperature of 6–11°C for 90 days. The age determination was carried out using the standard method of skeletochronology. Tail vertebrae were used as recording structures, and dental bones of the lower jaw and ribs were also used in individuals, died on the road. After carrying out all the procedures, adult lizards and their offspring were released into nature. The studied dead individuals formed an equal number of lines of arrested growth on sections of the caudal vertebrae, ribs, and the dental bone of the lower jaw. Laboratory experiments show that the number of these lines corresponds to the number of winterings. In general, lizards in the studied population live up to 9 (females) – 11 (males) years. Intensive growth continues until the age of 2–3 years, and then it almost stops. Females are reproduced from the age of three and retain the ability to reproduce until the end of their lives. The majority of adult females (77.3% of all individuals aged 3 years and older) annually participate in reproduction. In the foothill belt of the Sochi National Park, Anguis colchica is characterised by relatively low fertility (up to 13 individuals, six ones in average), but large size of newborns (body length up to 59.8 mm). At the same time, the number of juveniles in the offspring increases with the age of females, and the mass of juveniles increases with increasing fertility of females. The authors conclude that the peculiarities of reproductive biology, along with comparative high life expectancy, contribute to the high abundance of the species in Western Transcaucasia.