Come hang out with the biggest fish in the ocean! Want to spend some time getting to know the whale shark? Here’s some fun facts about our big gentle spotty friends!
Shark, Not Whale
First up, let’s clear up the name confusion! The whale shark is a shark, not a whale. To begin with, the whale shark is a fish. Like all fish, it’s cold blooded – without a constant internal body temperature, and breathes with gills. Whales on the other hand, are mammals, meaning they are warm blooded, and breath air through their lungs and blow holes.
So what’s with the name? Well, whale sharks do have a lot in common with whales. They are massive like whales and they feed more like whales than a typical shark.
And now that we’re clear that they’re fish, let’s talk about what type of fish they are! Whale sharks are sharks – or more specifically, they are a type of carpet shark.
Yes, that’s right, the whale shark is the biggest fish in the ocean! The biggest confirmed individual had a length of 18.8 m – that’s longer than a bus! The whale shark holds many records for size in the animal kingdom, most notably being by far the largest living non-mammalian vertebrate.
The average size of an adult whale shark is thought to be about 10 m, and 9 tonnes. Females give birth to live pups who are 40 to 60 cm in length – they have a lot of growing up to do! It’s thought that they reach sexual maturity at 30 years, and can live up to 100 years.
Whale sharks backs and sides are grey to brown, with white spots and pale stripes. It’s thought that each shark has its own unique pattern of spots, just like fingerprints on humans. No hiding their IDs for whale sharks! Scientists use the unique arrangements of spots just behind their gills to identify, catalogue and track these gentle giants.
Interestingly, the algorithm used by whale shark identification programs to figure out if a photographed whale shark has already been previously ID-ed is derived from one used by NASA to identify star fields! I just like the idea of whale sharks being similar to serenely floating fields of stars in our oceans!
Being a shark, whale sharks have lots of teeth – more than 300 rows in fact! A whale shark has more than 3000 tiny individual teeth, each about the size of a match head. How’s that for a toothy grin!
They don’t however, use these teeth for very much. It is somewhat ironic, but the biggest fish in the ocean dines exclusively on some of the tinier life forms around – plankton, krill, fish eggs, and small fish. Whale sharks are filter feeders, and basically suck in a whole lot of water to feed. Attached to their gills are gill rakers, which work like a mesh to filter out food. The meal is then forced down the whale sharks narrow throat and digested. No chewing involved, but they can filter more than 6,000 litres of waters an hour through their gills!
Like all sharks, whale sharks have skin that is made out of a hard, tooth-like scale called dermal denticles. The skin on a whale shark’s back can be up to 4 inches thick! In addition, they can even clench the muscles that lie just beneath their backs to toughen up their skin even more! Talk about being defensive!
Nevertheless, although they have super protective skin, you should never be tempted to touch a whale shark. Touching may not only stress out the whale shark, but humans could even transmit diseases through contact which may cause an infection.
Centenarian Sharks & the Atomic Age
It was always thought that whale sharks lived to a great age, but until relatively recently, scientists struggled to pin down exactly how long. However, in a paper just published in March 2020, Dr Mark Meekan, from the Australian Institute of Marine Science, and his team, used Carbon-14 released into the atmosphere during atomic tests in the 1940s to accurately age sharks. The Carbon-14 was absorbed by all living organisms, including whale sharks, and can be used to date them. Based on the amount of Carbon-14 found in specimens of whale shark vertebrae, Dr Meekan has suggested that they can live to 100-150 years old!
Long Range Sharks
Being pelagics, whale sharks are great ocean travellers. They prefer to stay in tropical and sub tropical waters, but move around a lot. We don’t know exactly why – maybe it’s to follow aggregations of their prey animals, or moving to mating and pupping grounds. Scientists have found that in 3 years, a whale shark can travel 8000 miles or more. One tagged animal, dubbed “Rio Lady,” swam some 5,000 miles during a span of just 150 days. Another dove to a depth of 6,324 feet in the Gulf of Mexico. This is all the more amazing when you consider that they move relatively slowly for a shark, at speeds of little more than 3 miles an hour!
We do know of some seasonal aggregation sites, such as the Galapagos Islands, the Yucatan Peninsula as well as the Sea of Cortez. They’re definitely worth a visit to catch a glimpse of these amazing creatures!