Marine Myths Measured

SCIENCE

The ocean is home to some of the world’s biggest creatures. The ocean is also home to big exaggerations. So, how big do the biggest animals in the ocean get? (National Geographic)

Put size into perspective with our activity—size yourself up to a blue whale!

Teachers, scroll down for a short list of key resources in our Teachers’ Toolkit.

Thanks to my favorite and soon-to-be missed coworker, Sean, for the heads-up on this great Current Event Connection!

Marine biologist Craig McClain, a team of undergraduates, and some massive and mysterious marine critters have put to rest some fishy tales about our ocean's giants. Size up some more animals here. Illustration by Emily M. Eng, National Geographic

Marine biologist Craig McClain, a team of undergraduates, and some massive and mysterious marine critters have put to rest some fishy tales about our ocean’s giants. Size up some more animals here.
Illustration by Emily M. Eng, National Geographic

Discussion Ideas

  • Marine biologist Craig McClain was inspired to validate the sizes of marine creatures after hearing one too many stories about not-quite-so-giant squid. Why have marine biologists had trouble sizing up legendary leviathans of the deep?
    • It’s hard to track them down: According to the Nat Geo blog, “Many are rare, elusive, or live in inaccessible parts of the sea. . . Some are only measured when they wash ashore, after dry land distends or deflates their bodies.”
    • Old data: Some data predate the use of the International System of Units. (Learn a little more about the SI here.) Other data were reported, but unverified.
    • Shoddy data had been unleashed upon the kraken“—or, not everyone knows how to measure: Some people stretch or manipulate an animal to make it seem bigger, while “[o]ne size estimate even came from someone counting his paces next to a beached squid!”

 

  • How did the “Story of Size” team gather data for their measurements?
    • Hard work!!! “These measurements are all as accurate as possible; finding them often involved a labyrinth of references and phone calls.”
      • They trawled the scientific literature for measurements.
      • They combed through books, newsletters, and newspapers.
      • They asked colleagues at museums to measure specimens in their collections.
      • They contacted conservation networks.
      • They reeled in eBay records to find the measurements of giant clams and snail shells.

 

  • In their exhaustive research process, the “Story of Size” team discovered that a lot of data were simply outdated. What are some reasons why older data (from the 1960s and before) reported larger measurements?
    • Some measurements were unverified.
    • Some measurements were estimated with technologically imprecise instruments or measuring systems.
    • “Some animals may just not be getting as big as they used to get,” says McClain. Overfishing, pollution, and climate change are some of the reasons why scientists can’t find as many examples of mega-megafauna as they used to.

 

  • Here are a few different types of giant sea creatures:
NGS Picture ID:1936625

The largest specimen of this cnidarian (jelly), the lion’s mane jelly, may have reached 120 feet! As the scientists noted, this data may not be, uh, accurate. Accurate, verifiable data for the lion’s mane jelly just don’t exist. The lion’s mane jelly is indigenous to cold, Arctic ocean water. This one is hanging out in Bonne Bay, part of Gros Morne National Park, Newfoundland, Canada. Photograph by David Doubilet, National Geographic

The largest specimen of this cetacean (mammal), the blue whale, reached just over 108 feet! Photograph courtesy NOAA Fisheries

The largest specimen of this cetacean (mammal), the blue whale, reached just over 108 feet!
Photograph courtesy NOAA Fisheries

The largest specimen of manta ray (fish), like this one cruising Australia's Great Barrier Reef, reached nearly 23 feet! Photograph by David Doubilet, National Geographic

The largest specimen of manta ray (fish), like this one cruising Australia’s Great Barrier Reef, reached nearly 23 feet!
Photograph by David Doubilet, National Geographic

The largest specimen of Japanese spider crab (crustacean), like this one avoiding an ROV in Suruga Bay, Honshu, Japan, was about 12 feet wide. Photograph by Emory Kristof, National Geographic

The largest specimen of Japanese spider crab (crustacean), like this one avoiding an ROV in Suruga Bay, Honshu, Japan, was about 12 feet wide.
Photograph by Emory Kristof, National Geographic

The largest specimen of Caribbean giant barrel sponge (sponge) (this one is off the coast of Belize) reached over 8 feet! Photograph by Brian Skerry, National Geographic

The largest specimen of Caribbean giant barrel sponge (sponge) (this one is off the coast of Belize) reached over 8 feet!
Photograph by Brian Skerry, National Geographic

The largest specimen of the leatherback sea turtle (reptile) (this one is swimming off the Azores in the Atlantic Ocean) reached almost 7 feet! Photograph by Brian Skerry, National Geographic

The largest specimen of the leatherback sea turtle (reptile) (this one is swimming off the Azores in the Atlantic Ocean) reached almost 7 feet!
Photograph by Brian Skerry, National Geographic

The Pacific Remote Islands Marine National Monument is home to a colorful variety of giant clams. Photograph by Amanda Pollock, courtesy U.S. Fish and Wildlife Service.  This file is licensed under the Creative Commons Attribution 2.0 Generic license.

The larges specimen of the giant clam (mollusk) (like these beauties at the Pacific Remote Islands Marine National Monument) reached 4.5 feet.
Photograph by Amanda Pollock, courtesy U.S. Fish and Wildlife Service. This file is licensed under the Creative Commons Attribution 2.0 Generic license.

 

  • Read our great activity, “Size Me Up—to a Blue Whale!” Adapt the activity for use with the new data on ocean animals’ sizes. This requires precisely one step!
    • Substitute the activity’s photo gallery for the animals depicted in the graphic at the top of this post, the gallery above, or (ideally) the graphic “What are the largest sizes of ocean giants?”
      • “Size up” the marine creatures:
        • About how many basking sharks make up the length of a lion’s mane jellyfish? (3)
        • What is the biggest vertebrate? (blue whale)
        • what’s the biggest animal with teeth? (sperm whale)
        • Which is bigger—the giant squid or the colossal squid? (giant squid)
        • Is your class longer or shorter than the blue whale?

 

 

TEACHERS’ TOOLKIT

Nat Geo: How Big Are The Biggest Squid, Whales, Sharks, Jellyfish?

Nat Geo: Size Me Up—to a Blue Whale!

(extra credit!) PeerJ: Sizing ocean giants: patterns of intraspecific size variation in marine megafauna

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