30 June 1995
Vol 268, Issue 5219

About The Cover

A male gray seal issuing a threat. Colonially breeding gray seals are widely assumed to be typical polygynous mammals, with males competing for positions among groups of physically smaller, more numerous females. However, molecular genetic analysis reveals large numbers of full siblings. Such a pattern implies that many seals mate preferentially with previous partners. See page 1897. [Photo: P. P. Pomeroy/Sea Mammal Research Unit]