Study Shows Sharks Species Can Work Together For Mutual Benefit
Scientists have discovered the first known case of different species of sharks working together to search for and capture prey.
Behavioural ecologist Johann Mourier has been studying the large groups of reef sharks found around the channels of Fakarava Atoll in French Polynesia.
More than 900 reefs, including grey reef, whitetip reef, silvertip and blacktip reef sharks can gather together at the narrow entrances to the atoll to hunt as vast numbers of fish spawn in the fast-moving waters of the channels.
In a paper published this month in Ecology, Mourier documents how the grey reef sharks and the whitetip reef sharks work together utilising their distinct skills to improve their chances of hunting down fish hiding in the reefs of the channels.
There are other documented cases of marine predators such as groupers and moray eels, or trevally and stingrays, hunting together. These are when one species initiates the foraging and the other picks up bits or even whole prey not consumed by the first species - known as ‘nuclear-follower associations’.
This is the first case where scientists have seen different species of sharks cooperate in a hunt. They studied 31 different events when the grey reef sharks and the whitetip sharks appeared to be hunting together.
They determined there were five different outcomes. The prey escapes unharmed (29 per cent of observations). The whitetip reef sharks successfully feed, but the grey reef sharks don’t (13 per cent). The whitetip sharks disturb the prey which is caught and consumed by a grey reef shark (36 per cent). The whitetip sharks disturb a fish that they don’t target and the grey reef sharks consume (six per cent). Both species compete for and each partially consumes the same fish (16 per cent).
Mourier, from the University of Montpellier in France, observed that the grey reef sharks tended to follow foraging whitetip sharks. As the whitetips searched for prey hiding in the crevices of the coral reef, the grey sharks would attempt to capture fishes the whitetips chased out of the reef.
Whitetips are smaller, slimmer, more flexible, and, unlike grey sharks, they are able to breathe without swimming. These characteristics allow whitetip sharks to extract fishes that hide within the reef. Since grey sharks cannot manoeuvre as well, they use the whitetip sharks to access additional prey. And the whitetip reef sharks benefit from the bits of fish the grey reef sharks leave in the water as they devour the prey forced out from the reef.
'Whitetip reef sharks have a greater ability than grey reef sharks to find and extract hidden prey from the reef,' the report states.
The study estimates that this increases the grey reef sharks predation success by almost 25 per cent. Mourier points that this shows even so-called 'primitive' species can cooperate with each other for mutual benefit.