Unlike in the film Jaws nor in the early literature, there's no evidence sharks "get a taste for human flesh". ( Supplied: HSI/AMCS/N McLachlan)įirstly, there's no such thing as a rogue shark. Taking out the apex predator has taken out the kelp beds right at the bottom of the food chain as well."įamously, in the case of Yellowstone National Park in the US, reintroducing wolves caused a trophic cascade with a positive outcome - it even changed the shape of the park's rivers Can't we just kill the really big ones?ĭrumlines often catch non-target species. They're keeping down the animals that prey on the fish and things that humans rely on too," Associate Professor Bucher said. "They're keeping the next level of predator down. This can result in what is called a "trophic cascade" where removing one keystone species sends ripples through an entire ecosystem causing it to permanently restructure, according to Daniel Bucher, a marine ecologist from Southern Cross University. Those mesopredators in turn deplete their prey, and on it goes down the food chain. If we wipe out the big sharks, so the theory goes, we get a boom in the population of the animals they eat - mesopredators like smaller sharks and seals. This in turn stops those animals from depleting resources.Īlthough it likely involves smaller species of reef sharks, a phenomenon known as "grazing halos" nicely demonstrates the predator-prey interaction. The effect here is two-fold: Firstly like the lion, sharks scatter their prey by chasing them, and secondly, even when they're not around the mere threat of sharks limits how far animals will stray from shelter and how long they will stay in one place to feed. Apex predators like sharks create what is called a "landscape of fear".
Underwater, sharks have the same effect on their prey - fish, turtles, seals, dolphins and even smaller sharks. We know as soon as the lion springs into action that the antelope will scatter to the winds.
If it helps, imagine David Attenborough narrating as a lion hides in long grass waiting to launch its attack. Imagine a grassy African plain covered in grazing antelope. ( Supplied: Queensland Museum - Gary Cranitch) The Great Barrier Reef will become much less diverse in the future according to climate forecasts.
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