When it comes to determining the size of giant squid and other large sea animals, humans have a tendency to exaggerate, a new study suggests.
A team of researchers compared scientific and popular media reports of body sizes for 25 species of marine creatures, including whales, sharks, squids, and other giant ocean dwellers, and found that most of the animals were smaller than what was reported.
"It's human nature to tell a 'fishing story,'" said Craig McClain, a marine biologist at the National Evolutionary Synthesis Center in Durham, North Carolina. In reality, "we're horrible at saying what the size of something is, without actually taking a measurement." [Whale Album: Giants of the Deep]
It's been widely reported that giant squid (Architeuthis dux) can reach lengths of about 60 feet (18 meters). But real measurements show that these creatures are actually closer to 40 feet (12 m) long, and even that is extremely rare, McClain told Live Science.
When one of McClain's students noticed the same thing about reports of whale sharks (Rhincodon typus), the researchers decided to conduct a systematic study of reported sizes for large marine animals. They pored through the scientific literature and popular media accounts, examined museum collections and spoke with expert colleagues to track down real size measurements for the animals studied.
The researchers created a database for each colossal creature, with the average and maximum reported measurements, because, as McClain put it, "Asking how big a human is, on average, is a lot different than asking about the tallest human."
For many of these marine megafauna, reported sizes were overestimated, the researchers found. For example, the world's largest gastropod, an Australian trumpet snail (Syrinx aruanus), was reported to be about 35.8 inches (91 centimeters), but the correct measurement for that specimen is actually about 28.3 inches (72 cm).
The maximum size of a whale shark has also been exaggerated. Some reports put the animal's length at 65.6 feet (20 m), but its actual size is more likely 61.7 feet (18.8 m), the researchers said.
The largest reported great white shark (Carcharodon carcharias) is generally thought to be about 23 feet (7 m), although some controversial specimens have been larger, the researchers said.
Curiously, sharks that killed humans were reported as much longer than those involved in just a bite, McClain said. One explanation could be that people are more likely to exaggerate the size of a more deadly animal. Or, it could be that larger sharks are more aggressive. "We're not able to flesh that out," McClain said.
Weighing a whale
On the other hand, the reported sizes of a few of the species studied were fairly accurate. For instance, scientists know the largest blue whales (Balaenoptera musculus) reach lengths of about 108 feet (33 m) because of data from the whaling industry.
The sizes of other giant ocean creatures — such as the Japanese spider crab (Macrocheira kaempferi) or lion's mane jellyfish (Cyanea capillata) are harder to pin down because the reports are anecdotal, McClain said. Some estimates put the lion's mane at about 120 feet (36.6 m), which would make it larger than a blue whale.
How does one even measure the size of a giant squid or a blue whale? "It's difficult," McClain admits. Some animals, like squid, simply wash ashore. For whale sharks, researchers can put laser-reflective dots at a fixed interval on the creature's side and extrapolate the length. For blue whales, whalers would cook the animals down for fat, and determine the weight from how many pots they had to use, McClain said.