So imagine that you’ve just arrived for a visit to Planet Earth. One of your Earthling friends offers to take you on a marine discovery adventure. You are super stoked, because there are no seas on your home planet! You board a submarine and head into the Pacific Ocean’s deep waters, off the coast of Mexico. You brace yourself for the experience of a lifetime.
Before long, you hit the jackpot. First, you observe a large, spotted, creature slowly glide by the observation window. Your guide explains that the stunning animal you have just seen is a Whale Shark! A little while later, still in shock, you can’t believe your luck when an even bigger beast swims by. It is a majestic Gray Whale. Your guide proceeds to tell you all about the natural history of these gentle giants, who are both filter feeders that gorge on small plants and animals.
Wow! After the journey, you tell your friend how thrilled you are to have seen not one, but two members of this incredible family of aquatic creatures. “Whoa, not so fast”, says your friend. She tells you that these animals aren’t closely related at all! In fact, she explains, even though they both live in the ocean and have dorsal fins on their backs, sharks are remarkably different from Whales. “How are they so different?!”, you beg to know.
You would not be alone in thinking that sharks and whales are alike. In fact, it’s easy to make that mistake, especially when there are confusing names like “Whale Shark” used for a fish, not a whale!
Since you’re so curious, let’s take a look at how sharks are different from whales. There are many interesting distinctions between these animals. Here are some of the main ones:
Comparing Sharks & Whales
Fish Versus Mammals
Sharks are fish. They are vertebrates, meaning they have a rigid backbone. They are also very ancient beasts – this Class of aquatic animals has existed on the earth for more than 400 million years. They live in water and their bodies are covered in scales. To swim, they move their tails from side-to-side.
Whales on the other hand are mammals, a wholly different class of vertebrates. The history of these hairy creatures goes back about half as long as fish: they appeared on the earth about 180 to 200 million years ago. On an evolutionary time scale, whales are just babies, having appeared only about 50 to 60 million years ago! Compared to sharks, whales have smooth skin (no scales), and their tails move up-and-down for swimming.
Cartilage Versus Bone
The skeleton of sharks is made of a flexible material called cartilage. It’s the same stuff that gives structure to your ears and nose. In contrast, whales have a skeleton made of bone. This means that sharks have a much lighter skeleton, proportional to their size, than do whales.
Gills Versus Lungs
Sharks and other fish have the impressive talent of being able to absorb oxygen from water, which they take in through their gills. These feathery-looking organs are found in slits on the side of a shark’s head. They are made of highly folded, thin sections of tissue that are ideal for breathing.
Whales (like other mammals including us) use different organs called lungs to breathe. They can’t obtain oxygen from water. That means whales have to swim frequently to the water’s surface in order to breathe. Air is taken in through a blowhole, the opening at the top of a whale’s head.
Cold-Blooded Versus Warm-Blooded
Sharks are “ectothermic”, which is a fancy way of calling them cold-blooded. They are unable to regulate their own body temperature. Instead, it is determined by the surrounding environment. That is why most sharks like to stay in temperate or tropical waters, rather than polar environments (although there are some cold water sharks).
Whales are “endothermic” or warm-blooded. They are able to regulate their body temperature internally, which enables them to easily use cold as well as warm environments.
Good Luck! Versus Mama’s Milk
Some sharks lay eggs, while others give birth to live young, after eggs hatch within their bodies. In either case, newborn sharks receive little or no parental care. To give their offspring a better fighting chance, sharks produce a small number of eggs and embryos (usually less than 100) – compared to the hundreds or thousands of eggs produced by bony fish. Shark embryos are protected by tough egg cases that are deposited somewhere safe, or by hatching inside their mothers’ bodies and remaining there until birth.
In comparison, whales are lucky to get so much attention from their mothers. They are cared for after birth like all mammals. They are fed milk: in fact, the ability of females to produce milk from mammary glands is one of the defining features of mammals.
Now that you’ve started to learn more about sharks, we know, you’re completely hooked! Luckily, you’ve come to the right place. Here at sharksider, we’ll be happy to tell you all you want to know about these fascinating creatures, so please keep reading.
Written By: Kara Levevre
UK Natural History Museum
I am broadly interested in how human activities influence the ability of wildlife to persist in the modified environments that we create.
Specifically, my research investigates how the configuration and composition of landscapes influence the movement and population dynamics of forest birds. Both natural and human-derived fragmenting of habitat can influence where birds settle, how they access the resources they need to survive and reproduce, and these factors in turn affect population demographics. Most recently, I have been studying the ability of individuals to move through and utilize forested areas which have been modified through timber harvest as they seek out resources for the breeding and postfledging phases. As well I am working in collaboration with Parks Canada scientists to examine in the influence of high density moose populations on forest bird communities in Gros Morne National Park. Many of my projects are conducted in collaboration or consultation with representatives of industry and government agencies, seeking to improve the management and sustainability of natural resource extraction.