Watch: Shark eats shark in aquarium

In a dog eat dog world, sharks eat one another too.

Video from Seoul's COEX Aquarium in South Korea has emerged showing an 8-year-old female sand tiger shark swallowing a 5-year-old male shark. 

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The female sand tiger is the aquarium's biggest shark.

Keepers said the female likely reacted violently because it was "startled." 

In all, it took 21 hours for the female shark to swallow its prey, though keepers expect the female shark to regurgitate its kill because ingesting it would be extremely difficult.

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