Is A Whale Shark A Mammal? Does It Lay Eggs?!

Whale sharks are some of the largest aquatic animals that can be found on Planet Earth. Native to tropical waters and warm climates, these gentle giants roam the world’s oceans as a reminder that not all sharks are like the blood-thirsty monster that stars in Jaws.

Whale sharks are filter feeders, meaning that they swim with their mouth wide open and feed on the tiny organisms that get caught in their filter pads.

Are whale sharks technically mammals? Even though they have “whale” in their name, whale sharks, unlike true whales, are not mammals. Whale sharks are technically classified as a type of fish and are one of only three known filter-feeding shark species (along with the basking shark and the megamouth shark).

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Table of Contents

What makes a mammal?

There are a number of ways that mammals are classified, namely:

  1. The production of milk via mammary glands
  2. The presence of hair
  3. A single-boned jaw
  4. Three bones in the inner ear
  5. One main artery coming from the heart that curves to the left
  6. The presence of a diaphragm
  7. The presence of a placenta in pregnant females
  8. No more than two sets of teeth, as well as teeth in various different shapes
  9. The presence of a false palate, meaning that mammals can eat and breathe at the same time
  10. The ability to self-regulate temperature

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According to these criteria, there are multiple reasons that whale sharks can’t be classified as mammals:

  1. Whale sharks don’t produce milk
  2. Whale sharks don’t have hair
  3. Whale sharks don’t technically have “bones”; they have skeletons made of hard cartilage
  4. Because whale sharks don’t have lungs, they also don’t have a diaphragm
  5. Although whale shark pups grow inside the mother, they don’t have a placenta that provides them with nutrition
  6. Sharks have multiple rows of jagged teeth that will be replaced many times throughout their entire life
  7. Whale sharks don’t have a false palate that would allow them to eat and breathe simultaneously
  8. Whale sharks are cold-blooded, and therefore can’t regulate their own body temperature

Although it may seem logical that sharks would be classified as mammals due to their large size, their physiology is vastly different from that of traditional mammals. Whales and dolphins, however, are technically classified as mammals. It’s strange to think that a dolphin has much more in common with a dog than it does with a shark!

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What makes a fish?

Unlike mammals, fish are significantly easier to identify. All fish have to meet the following four criteria:

  1. Fish have to be born with the ability to swim
  2. Fish have a lateral line system or a series of organs that allow them to sense vibrations in the water
  3. Fish breathe using gills, as opposed to lungs
  4. Fish reproduce sexually. While most fish reproduce externally via laying eggs that are later fertilized by a male, some fish have the male fertilize the eggs while they are still in the female’s body before they are released into the environment

Whale sharks easily meet the first three criteria. However, the fourth criteria is a little bit trickier. While not much is known about the exact way that whale sharks reproduce, it is widely believed that they are ovoviviparous.

So, do whale sharks lay eggs?

Whale sharks will keep the fertilized eggs inside of their body until the pups hatch from their eggs. However, even after hatching, they may remain inside the mother for an extended period of time until they are fully formed. Out of the few hundred pups that a mother whale shark may have at a time, only a tenth of them may survive past birth.

While it may seem strange that such a massive creature is in the same category as your pet goldfish, the two are actually a lot more alike than you’d originally think!

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Related Questions

How big are whale sharks?

Whale sharks are massive; they are the largest known species of shark, even larger than the monstrous great white. Whale sharks can typically grow to be up to 60 feet long and can weigh as much as 15 tons.

Are whale sharks dangerous?

Typically, there is no reason to fear whale sharks. Because they are filter feeders, they don’t have to hunt and kill their prey. Some divers even report that whale sharks are incredibly gentle, and may even enjoy playing with humans. As of 2020, there have been no reported instances of whale sharks actively attacking or threatening humans.

Are whale sharks and basking sharks the same thing?

While they are both filter feeders, whale sharks and basking sharks are not the same things. Basking sharks are significantly smaller than whale sharks and can live much farther north and south than whale sharks tend to wander.