Shark species takes turns hunting

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Shark species takes turns hunting

Mon, 19/07/2021 - 10:23
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Scientists monitoring the behaviour of different species of coastal sharks found that they actually do their hunting in shifts as a way of maintaining a harmonious co-existence.

Sharing resources in a civilised manner? Sharks at Tiger Beach don't get into a food fight but appear to wait patiently in line for their turn.

Niche partitioning of time, space or resources is considered the key to allowing the coexistence of competitor species, and particularly guilds of predators such as sharks.

However, the extent to which these processes occur in marine systems is poorly understood due to the difficulty in studying fine-scale movements and activity patterns in mobile underwater species.

To that end, scientists at Australia's Murdoch University used accelerometers to determine the activity patterns of six species of large free-ranging shark in the waters of the Gulf of Mexico; Blacktip sharks, bull sharks, sandbar sharks, great hammerhead sharks and scalloped hammerhead sharks.

The research, led by Dr Karissa Lear and Dr Adrian Gleiss at the Centre for Sustainable Aquatic Ecosystems, produced the first known example of marine predators partitioning resources by foraging at different times of the day.

“This is a relatively rare way of sharing resources in nature, but it could be more common than we think in understudied marine ecosystems,” said Dr Lear.

Such temporal partitioning of resources is likely to be driven by a combination of physiological and morphological constraints of each species and behavioural mechanisms, including a species's potential for behavioural plasticity.

The larger or more dominant predators, including tiger sharks, bull sharks and great hammerhead sharks, may be active and forage during the times of day that best suit them physiologically. For example, hammerhead sharks (most active here at night) are known to have superior binocular vision compared to carcharhinid species which may put them at an advantage in low light environments, while tiger sharks (most active here during midday) have been proposed to use visual silhouettes of prey on the surface as a main foraging mechanism, requiring higher light levels.

Proceedings of the Royal Society B
Murdoch University