Scientists captured disturbing sexual behavior between species in the Antarctic - seals are trying to have sex with penguins.

While the video below shows only one seal in the act, scientists have seen more of these actions that involve multiple seals and penguins. Scientists documented the first incident in 2006 between a fur seal and a king penguin on Marion Island in the sub-Antarctic island. During the time, researchers presumed that it was a rare incident and a mere case of "mistaken identity," but the new incident disproved that initial thought.

"Honestly I did not expect that follow up sightings of a similar nature to that 2006 one would ever be made again, and certainly not on multiple occasions," Nico de Bruyn, of the Mammal Research Institute at the University of Pretoria, South Africa, said to BBC.

Researchers have documented at least three sightings of this unusual behavior from different areas. De Bruyn and his colleague, William Haddad, are still uncertain of the gender of the penguins that the male seals are sexually coercing themselves onto. 

The scientists observed a pattern following this bizarre sexual behavior. The seal chases the penguin, captures it, and then mounts it. It happens several times with five minutes of rest in between.

"The seal ran up to the penguin and bumped it down. It lay on top of the penguin and started thrusting its hips in a copulatory fashion. The seal's erect penis was clearly visible," de Bruyn wrote.

The seals usually released the penguins after, but there was one incident that the seal killed the penguin and ate it.

Scientists are bothered by the seal-penguin sexual encounters because they affect the reproductive fitness of the penguins and endanger the seal population. Penguins lose their fitness as they bleed when the seals force sexual acts with them, while seals are wasting their time and energy mating with other species instead of their own.

"Reproductive interference occurs when individuals of one species engage in reproductive activities with individuals of another species, and when these interactions reduce the fitness of one or both species," Emily Burdfield-Steel, who is a researcher at the University of Jyväskylä in Finland, explained to Discovery News.

Details of the discovery were published in the journal Polar Biology.