Great White Sharks May Eat a Lot More Baby Seals Than We Once Thought
It's a frightening sight.
A gargantuan great white shark leaps clear of the water, snatching a fur seal within its gaping jaws as it does. Glistening splashes of water bring sharp clarity to the show of pure, bestial power. Watching the kill makes an impression, one not easily forgotten. Yet though the deadly sight may frequent your memory, to the best of current knowledge, it doesn't happen all that often.
Not much is accurately known about the feeding frequency of great white sharks, but the little research which has been conducted makes the predatory fish seem more like a minimalist hunter than a ravenous monster. Research completed in 1982 estimated that a 2,160-pound specimen could survive on a mere 30 kilograms of animal blubber for approximately six weeks.
But in a new study, Australian biologists disagree. By monitoring the swimming speeds of 12 individual sharks feeding on seal colonies off Australia's Neptune Islands, they were able to develop a new estimate of great white sharks' daily energy expenditure, one they believe to be more accurate than the original 1982 value, which was based on observing only a single specimen that was likely at rest. (Above image: The path of a tracked great white shark.)
According to the new data, great white sharks' average metabolic rate may be almost three times higher! That means that the 2,160-pound shark described earlier would have to eat 30 kilograms of blubber every 11.6 days to remain in energy balance, not six weeks as originally thought.
Since great whites are apex predators, the novel information sheds new light on their respective ecosystems and the animals who share them, the researchers say.
But the current study also has more insidious undertones. Extrapolating from the authors' calculations, a 2,160-pound great white would have to eat a fur seal pup every 45.6 hours to remain sated. Based on the past data, that rate would have only been one pup every 173 hours. So this means that cute, cuddly, furry seal pups may be getting horrifically consumed much more often.
And keep in mind that some great white sharks can grow to be nearly 5,000 pounds! They probably sport a more voracious appetite...
Source: J. M. Semmens, N. L. Payne, C. Huveneers, D. W. Sims & B. D. Bruce (2013) Feeding requirements of white sharks may be higher than originally thought. Scientific Reports 3, Article number: 1471 doi:10.1038/srep01471