My review of the Natural History Museum’s very good exhibition on Sexual Nature, about the mating habits of animals, can be read at the New Statesman. It features slug sex, Guy the Gorilla and Isabella Rossellini.
For more on this sort of thing, you should read Melissa Harrison’s Tales Of The City blog, who writes about blossom, snowdrops, daffodils and foxes from the urban wilderness of sunny Streatham.
The Great Wen 
Those Isabella Rossolini videos are extraordinarily weird. Have you watched the whale one?!
The duck one is positively terrifying, while the snail film is considered too fruity for children.
More terrifying duck sex… http://www.guardian.co.uk/education/2005/mar/08/highereducation.research