...the answer is: very carefully. And loudly.

A prickly situation indeed:

BERLIN (Reuters) - German police called to investigate unusual noises in the garden of a Bremen house late on Monday were surprised to find that a pair of amorous hedgehogs were to blame.

After illuminating the garden with spotlights, officers discovered the animals making love beside the pond.

"The pair were loudly engaged in ensuring the continuity of their species," said Bremen police spokesman Ronald Walther.

"All those spectators did not worry them in the least, indeed they even intensified their activities, so the officers turned off the lights," he added.

The hedgehog breeding season runs from April to September and their lovemaking is typically accompanied by very loud puffing and snorting, usually by the female as she tries to ward off the male.

(Via Atlantic Review)