The Greenland Shark

The Greenland shark isn’t the type of predator that often gets mentioned on TV shows or dramatized in movies. However, this giant, slow-moving resident of the North Atlantic may deserve the spotlight every once in a while for its potentially record-setting size and lifespan.

Photo: Discovery

Also known as sleeper sharks, the largest Greenland shark ever recorded was 21 feet long. However, it is believed that these sharks can exceed 24 feet in length. If this is the case, the Greenland shark would be the largest predatory shark in the world, even surpassing the great white; only filter-feeding basking sharks and whale sharks are larger.

Part of the reason this shark is so difficult to study is because of the extreme depths at which it lives. Greenland sharks have been recorded at depths of more than 7000 feet, and usually only come to the surface near ice floes in the winter.

Greenland sharks are thought to be ambush predators, pinning and consuming a large variety of bottom-dwelling fish and crustaceans. They are also known to be scavengers, and like many sharks will eat just about anything, living or not, that they can find. Despite their size, Greenland sharks are notoriously sluggish by nature and are not considered dangerous to humans.

The exact lifespan of the Greenland shark is uncertain. However, scientists have determined that they grow at an extremely slow rate of less than one centimeter per year. If this is the case, fully grown adults specimens may be well over 200 years old, making this shark the longest-lived vertebrate on the planet.

The Killer Whale - King of the Sea

Though some may think large sharks are the most fearsome animals in the ocean, even predators such as the great white exist below one animal on the food chain; the killer whale. Also known as orcas, killer whales are the largest of all dolphins and are true apex predators, even hunting great white sharks on occasion.

At up to 32 feet long and weighing 15,000lbs, the largest killer whales can equal a city bus in size. If their size isn’t enough of an indicator, orcas can be easily recognized by their black coloring with characteristic white patches above their eyes and on their bellies as well as a massive six foot dorsal fin.

There are a variety of different types of orcas living in every ocean in the world, though there are slight differences in appearance, feeding and social habits depending upon habitat. Some are residents of the same area year-round and form strong family bonds, whereas other types are transient and move from place to place. Most live and travel in groups of anywhere from 2 to 75 depending on type.

As apex predators, killer whales hunt an enormous variety of sea life. Resident killer whales usually prey upon fish and squid, whereas transient orcas eat other marine mammals such as seals, porpoises and other whales almost exclusively. Killer whales may also prey upon large sharks, using their superior intelligence to hold sharks upside down and suffocate them. Much like a pack of wolves, killer whales hunt large prey such as other whales in packs. Interestingly enough, resident killer whales may swim or play with dolphins and porpoises, both prey animals to transient orcas.

Despite their name, wild killer whales have never been responsible for a fatal attack on a human. Their intelligence along with their playful nature seems to suggest that it is easy for orcas to differentiate between humans and their natural prey. However, there have been several attacks by captive killer whales, leading many to condemn the practice of keeping these animals in aquariums. Most killer whales can live well into their thirties in the wild, with some females reaching 90 years of age.

Basking Sharks - The Lazy Predators

As we close out this week, we’d like to focus on a shark that just doesn’t get any respect; the basking shark. Although it’s one of the largest species of fish in the world, the whale shark is larger, so it won’t set any records there. It isn’t a vicious predator either, and despite being as long as a city bus poses absolutely no danger to humans or any large creature of the sea.

The basking shark gets its name from its appearance of relaxing (i.e. basking) in warmer waters near the surface while it feeds; and due to their massive size they are quite hard to miss. Basking sharks are usually 20-35 feet in length and weigh about 4 tons. The largest specimen ever confirmed was over 40 feet long and weighed an estimated 34,000lbs!

Basking shark filter feeding

Although basking sharks are sometimes mistaken for great white sharks, the two could not be more different. Whereas great whites are active hunters, the basking shark is a passive filter feeder. It feeds on zooplankton and small fish simply by swimming around very slowly with its enormous mouth wide open. Prey is snagged by the basking shark’s many sets of gill rakers. During this process, the shark naturally takes in a massive amount of water. However, unlike other filter feeding sharks that can close their mouths and pump this water out manually, the basking shark can only expel water by continuing to swim at its lumbering 3mph pace.

Basking shark head

Basking sharks do migrate throughout the year and can travel thousands of miles in a season. It is assumed that this travel is related to reproduction or following plankton blooms. Due to this migration, at certain times of the year basking sharks may be found in nearly every ocean of the world.