Sexual coercion is the use of force to achieve mating, while reproductive interference encompasses many forms of interspecific interactions during mating. We describe three new occurrences of the sexual coercion of king penguins (Aptenodytes patagonicus) by Antarctic fur seals (Arctocephalus gazella) on sub-Antarctic Marion Island. These recurrent observations follow a common pattern where the seal chases, captures and mounts the penguin, followed by copulation attempts. These observations are similar to a previously published observation from the same island, and we suggest that this may be an emergent behaviour. Two hypotheses directed at possible drivers for these coercive actions are examined: it may be learned behaviour associated with some sort of reward or it may be an extreme case of reproductive interference that can be explained by the ‘mate deprivation hypothesis’, resulting from the continued growth of the A. gazella population on the island. Reporting of similar occurrences from a range of species may allow more robust inference towards the ultimate drivers of the behaviour.