Are whale sharks mammals?

In this article, you’ll find out whether or not whale sharks are mammals. You’ll also learn about the traits that justified the classification of whale sharks in their current group.  


Are whale sharks mammals?

Whale sharks are not mammals at all. They are sharks and therefore fishes that are nicknamed as ‘whales’ due to how excessively large their body sizes can get compared to other fishes in the ocean. Whale sharks have been observed to rival the sizes of most species of whales including the humpback and killer whales.


Taxonomical classification of whale sharks

Whale sharks are predatory fishes belonging to the shark family of cartilaginous fish.

Cartilaginous fish are basically fish that are characterized by having skeletons made up of cartilage rather than bone, and together with jawless and bony fish, they make up the three major classifications of fishes.

The member families of cartilaginous fish include Skates, Rays and Sharks; which of course includes the gigantic ‘whale’ shark nicknamed as “whale” to exaggerate its body size compared to other fishes in the ocean.

The fossil evidence of the earliest shark species dates back to around 400 million years ago while those of rays and skates dates back to approximately 150 million years ago, centuries later than former.

Modern day sharks are speculated to have evolved around 35 million years ago, which is relatively early in evolutionary history of fish.

The three groups of fish

  • Jawless fish
  • Cartilaginous fish
  • Bony fish
    • Ray finned group
    • Lobe finned group

Whale sharks vs mammals

Earlier on, we established that whale sharks aren’t mammal but instead fishes that belong to the shark family of cartilaginous fish.

In this section, we are going to be discussing the peculiarities that justify the placement of whale sharks as fishes and not as mammals. In other words, we are going to be looking at how fishes differ from mammals using comparative analogy.

To begin with, the are five different aspects that we would like to use to show how fishes differ from mammals, and these aspects aren’t by any means the only ways to distinguish between these two broad groups. Several other differences exist and can be used to tell apart fishes from mammals.

It is also important to note that the characteristics outlined below are not always present/true for all species within each group. They are only a representation of what majority of the group members of that class have in common.

Another important thing to bear in mind is that the outlined characteristics are not necessarily unique to the particular groups mentioned. As a matter of fact, they are not. Other animal classes outside these two can also have species with the traits, features or behaviors mentioned below.

If we are explicitly clear on this, then we can proceed further into the discussion.

The different aspects in which fishes differ from mammals.

  • Breathing
  • Reproduction
  • Habitat
  • Body hair
  • Thermoregulation
  • Maternal investment
  • Locomotion

Respiration (Breathing):

Fishes use gills to respire whereas both aquatic and terrestrial mammals use a pair of lungs. One of the fish exception to this rule of course are lung fishes that seem to retain primitive characteristics of being able to breath air. So they have a pair or single lung(s) for breathing depending on the species.

Marine mammals like whales, dolphins and seals despite frequently or permanently inhabiting the oceans, occasionally travel all the way to the surface of the ocean in order to breath air. They are designed to be able to hold in their breath for longer durations, up to 90 minutes in the case of sperm whales.

Whale sharks have 5 large gill slits on each side of their head region that they use to extract dissolved oxygen directly from the waters. The gills are specially built feathery slit structures and they eliminate the need for whales sharks to rise to the surface of the ocean to catch a breath, unlike the way aquatic mammals do.


Reproduction

Mammals give birth to their young ones alive as opposed to fishes that lay eggs in see weeds or within their bodies (as evident in ovipositors). The eggs can range from few to as many as 100, depending of the species.

Whale sharks are suspected to be ovoviviparous which means that the eggs they lay hatch within their bodies before the young ones are expelled. Their young are born 40 to 50 cm long and in large litters of well-formed pups (or babies)


Nurturing

One striking feature that all mammals have that set them apart from fishes and all other living things of the animal kingdom is the presence of a mammary gland which produces milk for nurturing their offspring. This means that parental care has to be common within mammals. And it is.

When mammals give birth to their young, they feed and nurture them with warm rich milk from their mammary gland for an extended period of time, as long as 1.5 years in some cases. During the course of this time, they teach their offspring basic feeding and survival skills and offer protection to them until they become independent and are able to fend for themselves. After which, they are chased away by their parents to begin a new life on their own.

When whale sharks give birth to their pups after they hatch from the mothers ovipositors, theres no maternal investment of time and energy to take care of the young. The offsprings are born precocial (able to feed on their own) and left to forage and survive with no help for their mothers.

The mothers simply give birth to them and abandon them for the rest of the time they have left before meeting with their demise.


Habitat

Virtually all fishes survive only in water and all terrestrial mammals survive only on land. The majority (if not all) of the populations comprising both groups can be found in the respective mediums mentioned above. Exchanging one with the other would be effectively killing it.

Of course there are fishes that can go days when pulled out of the waters, the amphibious fishes. But that’s the farthest they can go, days. As for mammals, there are a few exceptions that have evolved to live in the waters which include all cetaceans such as whales, dolphins and porpoise.

Whale shark as is pretty obvious, survive only in water and can go any longer than a day on land.


Thermoregulation

Fishes rely on temperature of their surrounding environment to regulate their internal temperatures. This is known and cold-bloodedness or ectothermy. Mammals on the other hand have evolved the ability to regulate their own body temperatures using their own internal means, and thus are regarded as endotherms.

As with many features on the list, there are indeed mammalian exceptions to this rule also. One example is the sloth who relies on external conditions to keep an optimal body temperature.

Whale sharks are cold-blooded animals and thus rely on ambient temperatures for thermoregulation. That’s why whenever their surrounding temperatures rise so high they swim to much colder bottoms to reduce heat and when conditions become too cold, they simply migrate to newer and hotter environments to keep warm.


Body hair

All mammals develop body hairs at least in one life cycle stage. Fishes on the other hand never develop body hair at any lifecycle stage, although may develop scales, in any of their lifecycle stages.

Whale sharks have bodies that are covered with pointed, toothlike scale that gives their bodies a texture rougher than sandpaper. This helps to protect their bodies against any foreign particles.


Locomotion

Fishes move with the aid of paired limbs known as fins. They move by action of horizontal strokes.Terrestrial mammals on the other hand move with the aid of paired limbs called legs. Both aquatic and terrestrial mammals move their limbs in a vertical plane as opposed to the horizontal plane observed in fishes.


In conclusion

Although whale sharks have the name “whale” in their nomenclature, this name represents nothing more than their enormous sizes relative to other fishes they share the same broader group with.

Whale sharks are the biggest fishes currently in the marine environment and are known to easily rival the sizes of most whales.

Despite their enormous nature however, whale sharks have been observed to be very friendly open water creatures!


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Cite this Article (APA Format)

Bunu. M. (2020, May 6). Are whale sharks mammals?. Retrieved from http://emborawild.com/are-whale-sharks-mammals/

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