REPRODUCTIVE STRATEGIES OF VIPERIDAE IN COOL TO COLD TEMPERATE REGIONS

The Viperidae found between 40 and 68-degrees North share many common reproductive traits : summer pregnancies, prolongation of the sexual cycle in females between two and four years, no spring spermatogenesis, frequent storage of sperm in the male and/or female genital ducts, and delayed sexual maturity. But, the type of spermatogenesis (estival or mixed) and the date at which vitellogenesis and mating occur depend up on their systematic position. The intensity of the reproductive effort varies from one litter to the next but is roughly the same for all species ; its distribution, however, (few, but large, young, or the opposite) is linked to specific reproductive strategies which apparently depend on the mean size of the adults and the feeding habits of the young. In every respect, Vipera berus seems to be the Viperidae best adapted to life at high latitudes.