Whale Sharks

Alex Re (00:01): Hello, welcome to On Wildlife. I'm your host Alex Re on this podcast, we ring the wild to you. We take you on a journey into the life of a different animal every week, and I guarantee you you're going to come out of here knowing more about your favorite animal than you did before. On this episode, we're heading out to the open ocean to talk about the largest fish in the sea. These animals are the definition of gentle giants, and I'll tell you how big they really are later on in the episode. So let's get out on the water to talk about one of the most breathtaking animals that you might ever have the pleasure of seeing whale sharks.

(00:55): Before we start the episode, I want to give a shout out to James from Georgia for suggesting that I talk about whale sharks. Whale sharks are not whales, but they're a species of shark. Their scientific name is Rinka on typists. Their closest living relatives are zebra sharks, but most of their actual close relatives are now extinct. These animals like to live in the open ocean, usually favoring warmer waters. They can be found in oceans all over the globe, but if you wanted to go looking for them, your best bet would probably be near Australia or India. It makes sense that whale sharks like to live in vast open waters because they are absolutely huge. They're actually the largest fish on the planet, and not only that, they're the largest non mammal on the planet. It makes sense why they're called whale sharks because they really are as big as whales. They can get to be around 40 feet long and weigh 11 tons. If you stacked two story houses on top of each other and measured their height, that would be about how long a whale shark is and they weigh as much as 22 grand pianos.

(02:15): So if you're wondering if you'd be able to identify a whale shark in the wild, trust me, you wouldn't mistake it for any other fish because of their massive size, you won't find them in many aquariums. In fact, the only aquarium in the entire United States that has a whale shark is the Georgia Aquarium in Atlanta. Another feature that you can use to identify whale sharks is the spotted and striped pattern on their back. Each pattern is completely unique to an individual whale shark. Just like our fingerprints, the spots on their back are light in color, and we still don't know the purpose of them for certain. Some researchers think that they help confuse predators, but adult whale sharks really don't have many other animals trying to eat them. Other researchers think that the spots are there to protect whale sharks from UV rays from the sun, kind of like a natural sunscreen. This makes sense because whale sharks spend most of their time toward the ocean surface where the sun's rays are the most powerful, but why do they spend so much time on the surface? We'll get to that right after the break. The science word that I want to tell you about today is carbon sequestration. This is a process where carbon dioxide gets taken out of the atmosphere, which helps to slow down climate change. This can be natural or artificial, but some of the best places for carbon sequestration are forests.

(04:07): Okay, we're back. So why do whale sharks spend so much time near the surface? Well, it's because that's where their prey lives. Whale sharks don't go after the usual prey of sharks. Their favorite food is plankton, and if you remember our plankton episode, you'll know that plankton can include many different types of organisms, including krill, other small animals and algae plankton live by the surface because that's where the sunlight is. Phytoplankton, which are plant-like use the sun as their food source and zooplankton, which are animal-like eat the phytoplankton. Whale sharks are known as filter feeders. Their strategy for eating food is basically to open their mouths as wide as they can and let the water filled. With plankton rush in their mouths can be over three feet wide. The water then rushes out of their mouths through their gills, which filter out the plankton. They'll usually do this while swimming, but occasionally they position themselves vertically in the water with their mouth facing toward the surface and take in plankton.

(05:15): As they float in the water, they can filter through over 400,000 gallons of water in an hour, even though their mouths are huge, their throats are actually only about two and a half centimeters wide, which is probably one of the reasons why they only eat very small organisms. The whale shark's genus name is rinka don, which means rasp tooth. In Latin, they have over 3000 teeth, but they don't need them for feeding purposes. What's really interesting is that they have tooth like structures all over their bodies called dermal identicals. These dermal des actually help them faster through the water by reducing drag. Whale sharks only swim at about three miles per hour, which isn't too fast, but they don't really have any need to go faster than that. For the most part, their food source doesn't swim away from them, and there aren't many predators trying to chase them.

(06:15): Whale sharks also have dermal identicals that surround their eyes. They're used as a source of protection. A whale shark's eyes are located on the side of their head, which leaves them vulnerable to be damaged. They're also able to retract their eyeballs into their sockets as another way to protect themselves. Whale sharks also have a tendency to migrate. I talked about those dermal dens helping at reducing drag. Well, not only do they help whale sharks move faster, they also help them save energy. Less water resistance means less energy spent trying to swim this, and the fact that they swim pretty slowly allows them to travel extremely long distances. Some research indicates that they can migrate over 20,000 kilometers, which is over 12,000 miles. The whale shark that the researchers tracked did this over a period of two years. What's really crazy is that they don't need a phone to tell them where to go because they already have an internal G P S.

(07:21): It's thought that whale sharks, along with many other types of sharks, are able to sense the earth's magnetic field, which helps them figure out where they're going. They're also able to detect ocean currents another amazing navigation tool. But why do they go through all of this effort to migrate? There are two main reasons food and reproduction. During different seasons, areas of the ocean become rich with nutrients, which brings in more food for whale sharks. Sometimes it's worth traveling these long distances to get a decent meal, and researchers believe that mothers to baby whale sharks, which are also known as calves, migrate to safer areas in order to give birth so that their calf is less exposed to dangerous predators. Even though these animals are hard to miss, a lot of their lives actually remain a mystery to us. This especially applies to their reproduction. For a long time, we didn't even know how they gave birth.

(08:23): Up until recently, it was thought that whale sharks laid their eggs on the ocean floor where they would hatch, but now we know that isn't the case. Whale sharks are actually avo vi viris, which means that they give birth to live young. The female still has eggs inside of her as part of the development of the embryo, but the eggs also hatch inside of the mother. Before their birthed, a female whale shark in Taiwan was found to have over 300 embryos inside of her, and some of them were at different stages of development. We don't even know much about where whale shark babies are born and sightings of calves in the wild are very rare. The calves are already massive. When they're born, they can be about two feet long, and whale sharks are extremely long-lived animals. Some reports say that they can get to be over 150 years old, but we're not totally sure. We do know that they reach maturity around 30 years old. We're going to take our last break, but when we get back we'll talk more about some whale shark adaptations and why they're important to the ecosystems that they live in.

(09:47): Time for our trivia question, what is the most venomous animal in the world? The answer is the box jellyfish. You can die only minutes after you get stung.

(10:18): All right, welcome back. Now, it's important to remember that whale sharks are not whales, they're sharks, and because of that, they have similar characteristics to other sharks. For instance, they have really great senses of smell. They can smell food from miles away. Another shark that you may have heard this about is a great white shark being able to smell blood from great distances. Whale sharks also have a sense that we don't. They have a special organ called the pui of lorenzini, which are a bunch of nerve cells that are able to pick up very faint electrical signals given off by other animals. These are really great adaptations to have because whale sharks don't have the most amazing eyesight. Their eyes are pretty small and are located far away from each other. The water can also get pretty murky and have low visibility. Another characteristic that you can see in all sharks is that they don't have bones like we do.

(11:19): Sharks have been around for about 400 million years way before T-Rex has ever walked the earth, and they evolved to have a different kind of skeleton. Before animals evolved to have bones, their skeleton is made out of cartilage, which is the same stuff that makes up our ears and nose. Now, the cartilage that sharks have is extremely strong, but having a cartilaginous skeleton can give some advantages. One advantage is that it allows them to be more flexible so they can maneuver better to catch prey. It also makes their jaws more flexible so they can open their mouths much wider than those of us that are made of bone. Another huge advantage is that cartilage is lighter than bone, which means that it's easier for sharks to stay afloat in the water. Unlike other fish, sharks don't have a swim bladder that helps them float. Instead, their liver is filled with this oil, which is supposed to help keep them afloat, but it doesn't work as well as a swim bladder, so their lighter skeleton removes some of the weight that the bones would've had.

(12:28): So whales have bony skeletons and whale sharks have cartilaginous skeletons. One more key difference that can tell you a hundred percent that whale sharks are sharks is by looking at how they swim. You'll notice that marine mammals, like whales, dolphins, narwals, and manatees all swim by moving their hind fin up and down. Meanwhile, sharks and other types of fish move their fins left and right to swim. This is because marine mammals ancestors once lived on land and had to evolve to live in the water. That means their bodies are structured similarly to how land animals are. The way their hips are built makes it much easier to move up and down. Think about how you would swim. If your legs were duct taped together, it would look more like a whale and less like a shark. Whale sharks are very important to the ecosystems that they live in because they eat so much food, they also have to release a lot of waste back into the ocean.

(13:32): This is really important because it puts vital nutrients back into the water, which helps marine plants grow. They also have symbiotic relationships with different organisms like remora fish. Remoras are those fish that you see latching onto the bottom of whale sharks. They use the whale shark as protection from predators and also eat some of the scraps that are left over from their meals. This doesn't harm whale sharks and they kind of just go about their day. Whale sharks are also important to humans in more ways than one. Tourists from all over the world come to specific locations to swim alongside whale sharks. The tourism brings in revenue and jobs to countries that need it. In Madagascar, in 2019, tourism for whale sharks generated about $1.5 million in a three month span. Whale sharks can also help us understand the oceans better. They're indicator species, which means that if they're around, it's a sign of a healthy ecosystem.

(14:38): Unfortunately, these sharks are listed as endangered on the I U C N red list. There are about 200,000 of them left in the wild, which seems like a lot, but this number is half of what it was just 75 years ago. It also doesn't help their populations that they reproduce so slowly. Whale sharks are still hunted for food and oil, and because they hang out near the ocean surface, they're susceptible to being hit by boats. This happens more frequently than you think and is really hurting their populations. Climate change and overfishing are also major problems that whale sharks have to face. So if you want to help whale sharks, you should definitely check out the Whale Shark Conservation Project. Whale Shark and Oceanic Research Center and Shark and Marine Research Institute, thank you so much for coming on this adventure with me as we explored the world of Whale Sharks. You can find the sources that we use for this podcast and links to organizations that we reference at onwildlife.org. You can also email us with any questions at On Wildlife dot podcast@gmail.com, and you could follow us on Instagram at On Wildlife or on TikTok at wildlife. Don't forget to tune in next month for another awesome episode, and that's On Wildlife

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