I first became aware of the incredible mating habits of the leopard slug whilst working on Life in the Undergrowth and managed to see it for myself for the first time last August. So this year I have again kept some ‘pet’ slugs and paired them off to watch this amazing behaviour.
The slugs have been kept in captivity since June and have done very well on a diet of mushrooms. The mating season is in August so a week or so back I put two of them out on a branch in the patio at dusk – 9.15pm. One immediately started following the other as they moved about. Last year I had to wait an hour before they mated but after an hour these two were still following each other and had climbed up another branch. I was sure they would mate so kept watching and at 10.50pm they started to follow each others tail – a sure sign that mating is imminent. They then entwined their bodies and one (or both?) produced a thick orange ‘mucus rope’ and they hung about 20 centimetres below the branch.
Each then unfurled its strange blue sexual organ from the side of the head! These were slowly entwined to form the beautiful glacier blue ‘mating flower’. Mating lasted about 20 minutes after which one fell to the ground whilst the other climbed up the ‘rope’ and they went there separate ways.