Females give birth every two years between late August and October. For the adult females it can take its toll in terms of health as they fast prior to birth and it is so close to the hibernation period when they do eventually drop. They then take a few days to rest before the need to feed extensively before the cold weather comes to build up strength and stamina to survive the winter. It takes a full year for them to get back up to health, sometimes longer with younger females.
The young don't need to feed so much as they are at peak health upon being born. They do have voracious appetites though and eat whatever they can, including adult lizards which can be wider and longer than they are. I've seen a young adder eat a lizard so big that he couldn't bend afterwards at all. Generally they feed upon the prolific supply of juvenile common lizards that are available. The more they eat before going into hibernation, the greater the size and ability to handle the winter months. Pickings are lean when they come out of hibernation in mid to late February, so what they do now will increase their chances of survival into the next year.
