How do we measure an animal's size? | ECOVIEWS

Q. My brother (a basketball player) says giraffes are the biggest land animals because they are the tallest. How do scientists determine what the biggest animals are?

A. Scientists, as well as people in other professions, use various metrics when determining the size of an animal. Which just means they measure an animal's body size in several different ways depending on the context. For instance, a physiologist measuring oxygen intake of an organism might use volume to determine an animal's size. Postal workers and shipping agents would measure by weight. Body length is the critical measurement for “the longest Burmese python prize” in the annual Florida Python Challenge. The longest reptiles are pythons and anacondas, both of which have been reported to reach lengths of more than 30 feet.

The largest animals living in the world today, by any standard, are blue whales. When my grandson asked how big a whale was, I suggested he pace off 98 feet — the length of the largest known blue whale. We were both impressed.

Leaving whales out of the competition in the length category, other ocean inhabitants match or surpass snakes. The colossal squid, a mysterious, poorly understood sea creature, has been documented to reach lengths of more than 30 feet. They can weigh more than 1,000 pounds, have the largest eyes of any animal in the world — more than 12 inches in diameter — and are known to have sperm whales, like the iconic Moby Dick, in their diet. The length of snakes and squids pales in comparison to whale sharks (not true whales), the world’s largest fish. They commonly reach lengths exceeding 40 feet and have been reliably reported to be more than 50 or 60 feet long.

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For basketball players and giraffes, height is the coin of the realm. The top of the head of the tallest giraffes in zoos has been measured at 18 to 20 feet above the ground. A newborn giraffe is about 6 feet tall; a 1-year-old is twice that height.

An ornithologist is likely to use wingspan as a comparative measure of size for birds. Albatrosses hold the record with a 12-foot wingspan. This gives new insight into the idea of an albatross around your neck.

Basically, determining the world’s biggest animal depends on which aspect of the animal is being measured. In the weight category, African elephants qualify as the largest land animals. Records have been reported of elephants weighing more than 10 tons. By comparison the largest known hippopotamus weighed less than 5 tons. I’m not certain of the accuracy of such measurements since I know of no one, even a zookeeper, who carries around a set of scales to measure a chanced-upon elephant or hippopotamus.

One way to consider maximum size of animals is to compare within taxonomic groups. Some animals win a “biggest of their kind” participation trophy because of the category we place them in. For example, the colossal squid is the largest known invertebrate. Polar bears are considered to be not only the largest bears (bigger than grizzlies) but also the largest carnivorous land animals.

A Komodo dragon, one of the giant lizards from Indonesia, wins the biggest lizard contest with a length of 10 feet. The prize for the largest turtle in the world belongs to the leatherback sea turtle, which can reach a length of over 6 feet and weigh in at more than a ton. Most people would be awestruck if someone handed them a Chinese giant salamander that was 5 feet long. It's the largest salamander in the world.

No matter which measure of size we use, the blue whale wins the contest for biggest animal in every category: length, weight, height and volume. And just in case you were wondering, a blue whale suspended vertically in the ocean would be taller than five of the tallest giraffes or 13 of the tallest basketball players.

Whit Gibbons is professor of zoology and senior biologist at the University of Georgia’s Savannah River Ecology Laboratory. If you have an environmental question or comment, email ecoviews@gmail.com.

This article originally appeared on The Tuscaloosa News: How do we measure an animal's size? | ECOVIEWS