Shark species share resources by hunting at different times
Time-division-based resource sharing is quite rare in nature but sharks of different species has been found to hunt at different times so as to avoid each other.
A team of researchers from Murdoch University, the New England Aquarium and Mote Marine Laboratory who have been tagging and monitoring several species of sharks in the Gulf of Mexico discovered that some sharks share resources by foraging at different times.
Sufficient accelerometer data (more than 5 individuals each tracked for more than 24 h) for analyses of activity patterns were obtained from six sympatric*) species of large coastal sharks: blacktip sharks (Carcharhinus limbatus), bull sharks (Carcharhinus leucas), sandbar sharks (Carcharhinus plumbeus), tiger sharks (Galeocerdo cuvier), great hammerhead sharks (Sphyrna mokarran) and scalloped hammerhead sharks (Sphyrna lewini)
Time sharing
The researchers found that the largest sharks—tigers—foraged whenever they chose. Being the largest, they did not have to negotiate with other sharks for hunting time; plus, they have been known to kill and eat smaller sharks. They tended to hunt during the middle part of the day. That left the rest of the day for the other sharks.
The bulls tended to troll in the early morning hours, while sandbars hunted during the afternoon and blacktips hunted in the evening—both types of hammerheads (great and scalloped) hunted at night.
The minimal overlap in diel timing of peak activity in the six large coastal shark species examined (with the exception of the two hammerhead species) provides evidence for the occurrence of temporal partitioning.
Fact file
Sympatric: Species or populations occurring within the same or overlapping geographical areas.
Niche partitioning is one of the primary mechanisms allowing sympatric competitors to coexist through the division of resources.
Niche partitioning commonly takes several forms, including resource partitioning, where species specialise in different food or prey items, spatial partitioning, where species use different areas to forage or hunt, and temporal partitioning, where sympatric species rotate peak foraging times on a diel or seasonal scale.
