Field Trip EarthWhale Shark Expedition
Whale Shark FAQ
 
Whale Shark Expedition Home
Choose a Trip
Field Trip Earth Home

Field Trip Earth

Join Field Trip Earth
About Field Trip Earth
Interviews
Field Reports
What I Know About...
Educator Resources
Contact Field Trip Earth
Search

Home > Whale Shark Expedition > About The Species > Whale Shark FAQ

Whale Shark FAQ

by Shark Research Institute

Page 1 : Morphology

How much do we know about whale sharks?
The whale shark (Rhincodon typus) is still relatively mysterious. It wasn’t fully described in scientific literature until 1829 and, by 1986, there were only 320 recorded sightings of this animal.

Because it is simply hard to find in its natural habitat, and because it does not fare well in captive environments, we’re still learning about it. We do know that the whale shark is a member of the elasmobranch family, which includes carilagenous fish with multiple gill slits—in other words, like other sharks that we are more familiar with. They are not teleosts, which are bony fish with swim bladders.

How large is the whale shark?
The whale shark is by far the world’s largest fish-like vertebrate. However, it is hard for us to know exactly what its maximum size is. Old “eyewitness” records, as well as recent tagging studies and whale shark fishers’ reports, suggest a maximum length of 17 to 18 meters, or perhaps as many as 21.4 meters. Specimens longer than 12 meters are uncommon. Thirty whale sharks reported from South Africa ranged from 4 to 11 meters long. A length of 13.7 meters is often given as the maximum size measured, with 12.1 meters as the most recently accurately measured.

In 1925 a whale shark estimated to be 60 feet in length [18 meters] was caught in the Gulf of Thailand, but the largest accurately measured whale shark was a 40-foot, 7-inch [12.2 meter] male caught in Bombay, India, in 1983. Its mouth was 4.5 feet wide [1.14 meters], and its pectoral fins were more than 6.5 feet long [1.98 meters].

The size at birth of the whale shark is between 55 and 64 centimeters. Males are considered immature at 299 centimeters or less, and considered adolescent at 390 to 540 centimeters. Females ranging from 340 to 760 centimeters are immature. Records also show a pregnant female at around 10.6 meters long and weighing 16 tons. Another adult female was about 12 meters long.

Researchers are still working to determine an agreed-upon number. One researcher assumes a maximum length of 14 meters and a weight of approximately 20 tons, while recent field records suggest even higher maximum lengths. For example, researchers tracked 12 whale sharks by satellite. Size estimates generally ranged between 3.0 and 7.1 meters, but two big females tagged in 1996 and tracked for four months were 15.0 and 18.0 meters long.

What is the purpose of their distinctive coloring patterns?
Like many species of sharks that hunt near the sea’s surface, whale sharks are countershaded. They have white bellies (which makes them hard to see if a potential predator is underwater and looking up at them) and dark backs (which makes them difficult to see if the predator is looking down on them). It has been suggested that the pale spots and lines on their backs are camouflage. And, to some, the pattern resembles a school of fish, while to others it suggests reflections of sunlight on a shallow reef.

What are the Ampullae of Lorenzini and how do they work?
The Ampullae of Lorenzini is composed of a complex network of small pits concentrated near a whale shark's snout but running from its head to its tail. The pits are filled with a jelly rich in charged ions; these pits detect electrical fields and signals like those discharged by moving fish.

Try this experiment to see how these pits work. Blow steadily on the palm of your hand. Can you feel the air movement? Now, wave a finger between your lips and your hand, and feel the interruptions in the movement of the air. Just as you feel the breaks in air pressure, so the ampullae can detect changes in water pressure. The shark uses this sense of “distant touch” to determine the speed, size and form of an object moving through the water.

How can you tell male and female whale sharks apart?
A quick look at the pelvic fin area will differentiate males and females. Males have large extensions, called “claspers,” on both pelvic fins, while females do not. And, like other sharks, females tend to grow much larger than males of a similar age.

Next Page : Behaviors
Pages: 1, 2, 3, 4
---
(print) View printer-friendly version