Although leopard seals have a ferocious reputation, they do not attack humans, unless provoked. They have been known to swim placidly with scientists who have been studying them. They are naturally inquisitive and this behaviour is seen as aggressive to some humans, and as a result they may be shot. The leopard seal population is estimated at around 500,000 individuals, and they are in no great danger at present. As with all marine life, pollution of the oceans may become a threat to their future.