Shark Feeding, Finding food, shark week, Discovery

How do sharks find their prey?

1. Wherever there's sealife, a shark's there - ready to eat!

There are many factors that play into where and what a shark eats. Aside from geographic location, the varying levels of the sea and aquatic life found in certain areas affect the kind of food that’s available.

 

Oceanic whitetip sharks live in the wide-open areas of the ocean where food is often hard to find. These sharks have adapted to these conditions with incredible speed and tenacity—so when food is found, it’s as good as theirs. Large sharks like great whites often hang out around coastlines where they can easily pick off marine mammals like seals and sea lions.

 

Other sharks hunt far below the ocean’s surface. The frilled shark is an eel-like creature that dwells up to a mile below the surface where they eat deep-sea bony fish and squid.

 

And some sharks migrate long distances for their meals. Blacktip sharks and some spinner sharks make an annual journey from Cape Hatteras, North Carolina, to south Florida in search of large baitfish like mullet. Bronze whaler sharks intuitively follow millions of sardines during their migration up the southeast African coast and feed on shoals of fish.

 

Sharks are even found in the freezing waters of the sub-Arctic where they hunt fish and scavenge polar bears and reindeers.

 

2. Sharks are the Macgyvers of finding food. 

Few animals can hide from a hungry shark. Notorious for their intense and dogged manner of tracking prey, sharks are extremely tactical about finding and catching their food. They use a combination of keen hearing, exceptional sense of smell, sharp eyesight, a sixth sense called electro-sensory perception, and incredible speed to find their prey.

 

Many use camouflage to trick their prey, while others use stealth and ambush tactics to catch their prey unaware.

 

Some sharks prefer to hunt alone, like the oceanic whitetip and the tiger shark. Others use strength in numbers, like broadnose sevengills, which encircle their prey as a group and use diversion tactics to allow one a window to sneak in for the attack.

 

Scalloped hammerheads swarm in schools of over 100. They often swim above their prey, their white underbelly blending in with the sunlight above – a type of camouflage called countershading. They swim in a circular motion above their prey before closing in.

 

When a shark goes in for the kill, it will move very fast and violently to catch speedy fish and other animals, taking advantage of the element of surprise. Sometimes when sharks hunt together, or when some sharks catch others dining on a nice meal, they will join in, resulting in what is known as a feeding frenzy

 

3. Hammerhead hunting tactics: An interview with Greg Skomal

Dr. Gregory Skomal is an accomplished marine biologist, underwater explorer, photographer, aquarist, and author. He holds a master’s degree from the University of Rhode Island and a Ph.D. from Boston University. Through the Massachusetts Shark Research Program, Greg has been actively involved in the study of life history, ecology, and physiology of sharks. Shark Week fans will recognize him from shows like Jaws Comes Home, Jaws Strikes Back and Shark Trek.

Q: Can you tell us about the hammerhead’s unique cephalofoil and how it helps them detect prey?

A: There's a great debate in the scientific community as to the function of the hammerhead’s hammer, which is called a cephalofoil. This expanded head places the eyes, nostrils and electro-sensory organs across a broad plane of the shark’s skull, which is fascinating. In general, we think this augments or assists the shark in detecting prey much better. There's a lot of research that's currently being done in this area.

 

Q: What are some unique strategies hammerheads use when hunting prey, such as stingrays?

A: We know that great hammerheads love to eat stingrays. People who see stingrays probably don't see them at first because they tend to bury themselves in the sand, or at least cover their bodies with sand. So, the hammerhead’s skull has electro-sensory organs spread out across the underside of it. Think of it as detecting electricity, just like a metal detector would detect metal buried in the sand. Now, imagine a hammerhead coming over the sandy bottom, sensing the electrical field of that stingray, and being able to attack and kill it without the stingray know it was coming. It’s quite fascinating.

 

Q: Why do some hammerheads school? Does this give them a hunting advantage?

A: There’s a great debate in the scientific community as to why only a handful of species, including scalloped hammerheads, form shoals or schools. It's thought that they might facilitate feeding, allowing the hammerheads to more efficiently feed on massive schools of fish or squid. But not many people have ever seen scalloped hammerheads feed. And it's thought that schooling might facilitate reproductive behaviour; when it comes time to mate, all the males and females are hanging out in the same bar so to speak. Actually figuring out the true function of these aggregations is really, really tough.

 

Q: Are there any variances in hunting tactics amongst the various types of hammerhead species?

A: There are several hammerhead species. You've got the scalloped hammerhead, which form these large aggregations that may assist the sharks in finding and attacking large schools of fish or squid. You've got the great hammerhead, which is more of a lone solitary hunter. It doesn't really form any kind of aggregations; it feeds alone, using its cephalofoil to find and attack stingrays, which it seems to prefer. You've got a smaller hammerhead shark that really doesn't get much more than a meter long called the bonnethead. This is a shark that tends to occur in near-shore areas, like bays and estuaries where fresh and saltwater mix, and even in salty rivers. These are coastal sharks that probably use their cephalofoil to locate prey in a rather murky environment.

 

So you've got three or four different kinds of lifestyles just in that one family of sharks. You can only imagine the diversity that occurs in the over 500 species.

 

4. A sharks teeth perfectly match its hunting style 

Sharks are best known for their bite, but you can’t have a legendary bite without the teeth to back it up.

 

All sharks have slightly different teeth specifically designed for what they like to eat. Tiger sharks have teeth that are curved, pointy, and sharp enough to puncture turtle shells – even metal! Great white sharks have large teeth with knife-like serrated edges to help cut up meat, while makos have pointy teeth to pierce and trap prey.

 

 

Cookiecutters are small sharks that take their meals one bite at a time, using their sharp teeth to bite out chunks of flesh. Some animals that have escaped the cookiecutter have a cookie-shaped hole (about the size of a grapefruit) where the shark took a bite. Other sharks, like nurse sharks, ingest food by turning their mouths into a vacuum of sorts to suck in small fish and plankton. Some sharks, like basking sharks, even forego using their teeth altogether, instead using gill rakers to filter plankton from seawater.

 

But never tell a shark to chew its food – it can’t. A shark’s jaws are hinged in such a way that’s hard for the top and bottom parts to move separately. Instead, they clench meat with their strong jaws and sharp teeth to tear up meat, while shaking their heads wildly to rip off chunks of flesh.

 

Sometimes they lose teeth this way, but they have multiple rows of teeth that work like a conveyor belt to replace them as they fall out. Sharks can lose and replace thousands of teeth in a lifetime.

 

5. Great white hunting tactics: interview with Greg Skomal

 

Q: For you, what’s the most impressive thing about how great whites hunt?

A: White sharks are highly visual predators. When it comes to feeding on active prey like seals and sea lions, they rely quite heavily on their eyesight and their ability to ambush them at great speed using surprise. I think that's the most unique aspect of white sharks, being able to dispatch and kill large prey like seals and sea lions using surprise attack.

 

 

Q: Do great whites switch up their hunting tactics when targeting different types of prey?

A: Yes, based on surface observations of white sharks around the Farallon Islands, Seal Island and Guadalupe Island, there definitely does seem to be different strategies.

 

We used to think that all white sharks, when they attacked a seal or a sea lion, they would simply bite it, move away, let it bleed to death, and then go back and consume it after it's dead. It makes perfect sense and that seems to be the case for the juvenile northern elephant seals of the Farallon Islands, which are big and can probably render damage to the white shark.

 

It seems though that white sharks have adapted a different strategy when it comes to the islands’ California fur seals. They grab a hold of them, drag them down to the bottom, and swim along the bottom with the seal in their mouth. They’re probably continuing with the biting, causing mortal damage, and drowning the seal at the same time.

                                                                                                                        

Q: What about the great whites of South Africa and Guadalupe Island? How do their hunting strategies differ?

A: In South Africa, the white sharks in essence pin young seals returning from offshore against the surface. They strike them with great force, and will gobble them right down as they grab a hold of them at the surface.

 

And with some of our more recent research at Guadalupe Island, we've seen the predatory behaviour of white sharks at great depths. We're the first to actually film white sharks attacking at depth. The white sharks attacked a robot we sent down to about 300 feet, which is amazing. This means that because of the beautiful visibility at Guadalupe, white sharks can probably be detected easily by seals when they're near the surface, so they probably have to attack when they're deep. They go down into deep water waiting to ambush their prey at great depths. So that's another unique strategy that I think is emerging in this species, which appears to be very versatile when it comes to its feeding behaviour.

                                                                                                                        

Q: When most people think of white shark prey, they think seals and sea lions. What else do they eat?

A: Well, when you talk about the white shark, you're really talking about an animal that lives from along the coastline out to literally thousands of miles into the middle of the ocean. When you're spread out over a broad area, food can be few and far between, so you have to have a pretty broad diet. So even though we're all accustomed to seeing white sharks attack and kill seals and sea lions on Discovery Channel during Shark Week, they actually have a much broader diet than that. They will eat smaller sharks, they'll eat tunas, and they’ll eat a number of big fish that live on or close to the bottom like red drum. They'll attack and kill sea turtles, as well as dolphins and porpoises. So they have a much broader diet than we once thought.

                                                                                                                        

Q: Can you talk us through what a great white is sensing as it zeroes in on its prey from afar?

A: Sharks use sound to detect prey from great distances. They like very low frequency sound, which tend to sounds like a drum beat. A struggling fish, for example, will emit a low frequency sound. Perhaps seals and sea lions emit these low frequency sounds as well, drawing the sharks closer to them.

 

I imagine that prey items are also emitting a scent. If you think about seals and sea lions piled on a beach in very dense numbers, I imagine they're putting out a pretty hefty scent into the water column that's drawing the sharks in.

 

Q: And what happens as a great white gets closer to its prey?

A: As the sharks get closer they switch away from sound to smell, then switch off of smell to vision. But this of course depends on the visibility of the area. If you've got very good visibility, the sharks may be able to see their prey from far away. But if you're dealing with a place like Cape Cod where you've got very poor visibility, they may not see their prey until they're very close to it – within a couple of meters.

 

But generally, once they're really close, they rely heavily on their eyesight to be able to approach and attack. At some point during the approach, the shark will make a decision as to whether it's a prey item or not. If it's not a prey item it'll abort and move away.

 

If it's a prey item it'll continue with the attack and get very, very close. At this point, it probably starts to rely on its electro-sensory perception, which really only is about a meter. The shark will sense the electricity from the prey item as it closes to within a meter. Then, once it bites into the prey, it relies heavily on taste. I imagine that taste is critically important to the shark – if it doesn't taste good the shark's going to release it and move away.

 

 

 

6. Air jaws dissected: Interview with Chris Fallows

Chris Fallows has worked with great white sharks since commercial cage diving began in South Africa in 1992. His passion and knowledge about these animals is second to none. Two decades ago, Chris discovered that great whites breach, as seen on Shark Week's Air Jaws specials. There’s no one in the world who knows more about this phenomenon than Chris.

 

Q: You essentially discovered the breaching sharks of South Africa. What was it like making this incredible discovery?

A: It was amazing no doubt. I can remember the day well nearly two decades later. We were in my 10-foot inflatable boat five kilometres from land towing a tiny yellow lifejacket around Seal Island, not really expecting anything to happen, when boooooooom! A tiny great white, an eight-footer, rocketed into the sky with the lifejacket across its jaw like a crazy Jack Russell terrier chewing on a big bone. We retrieved our lifejacket once the shark spat it out, tied it on again and once again, this time a far bigger 12-foot shark, launched skywards. The rest as they say is history.

 

 

Q: What was going through your mind the first time you saw a great white breach?

A: Big sharks aren’t supposed to jump! It is bizarre to see a really big shark go flying, sometimes 10 feet clear of the water. It is also really amazing to see how athletic they can be.

 

Q: Why do great whites breach off Seal Island and practically nowhere else?

A: Great whites breach everywhere, but nowhere to the same extent as that which we see at Seal Island. The reason for this we believe is fourfold. One: right-sized sharks – sub-adults in the prime of their lives, full of power and energy. Two: right-sized prey, small enough that if you hit them going at full speed you will not hurt yourself. Three: large numbers of sharks competing for prey. And four: a good layout around the island that allows good chances for them to follow seals until the perfect ambush time, when they make a flat-out surface-ward attack which results in the breach.

 

Q: Can you describe the zones around Seal Island? Why do some, like the “Ring of Death,” show higher frequency of attacks than others?

A: Typically the west side is deeper than the east, and the south is deeper than the north. The island is only about 450 yards long and 80 wide. The Ring of Death is in the primary departure and return path of the seals and as such the sharks patrol this area looking for them. The Ring of Death is on the south-western side of the island.

 

Q: Can you describe what’s happening beneath the water before a breach?

A: Sharks typically locate a seal by sound and vibration. They will then follow the seal, both listening and watching, and using their array of senses to do this. When the time is right, or they are forced to by topography or other competing sharks, they will launch up at high speed and try to surprise the seal on the surface by a high-speed attack from the side or behind.

 

Q: And what's happening during the breach itself?

A: Every breach is different. Some are huge cartwheels with massive amounts of spray cascading off the shark like a broken chandelier. Others are innocuous tails slashes and low trajectory lunges. We see predatory breaches when they hunt seals, we see natural breaches when they simply jump for no visual reasons, and then we see breaches when decoys are towed.

 

Q: How about the seals – what tactics do they have to avoid breaches?

A: They often travel in groups, especially the older seals. They by and large leave at night to make it harder for sharks to pick out a single prey item. They have incredibly sensitive whiskers that can detect water movement and therefore, at the last minute, appear to be able to detect the approach of a great white. They have great endurance, and if they can avoid the shark’s jaws in their deadly dance with the sharks, they will always outlast their faster and more powerful adversary. Seals themselves are apex predators and are certainly not an easy meal. It is a very finely balanced affair.

 

Q: What time of year is the best time to see great whites breaching and why?

A: The best time is June, July, August and sometimes the first half of September if the season carries on a bit. This is when the young seals are at their fattest, having been weaned off their moms fat-rich milk. They are inexperienced and they are now fending and feeding for themselves. This is the sharks’ time of plenty.

 

Q: How can people see great whites breaching for themselves?

A: Join us on one of our Apex Shark Expeditions during the peak season at Seal Island. As with all of nature, there are no guarantees and each season has its quirks and variations, but by spending a few days in magical False Bay at Seal Island aboard our vessel White Pointer 2, you will have as good a chance as any of seeing this amazing behaviour for yourself with a crew that are passionate about the animals that they are privileged to work with.

 

 

7. Makro shark hunting tactics: interview with Greg Skomal

Dr. Gregory Skomal is an accomplished marine biologist, underwater explorer, photographer, aquarist, and author. He holds a master’s degree from the University of Rhode Island and a Ph.D. from Boston University. Through the Massachusetts Shark Research Program, Greg has been actively involved in the study of life history, ecology, and physiology of sharks. Shark Week fans will recognize him from shows like Jaws Comes Home, Jaws Strikes Back and Shark Trek.

 

Q: What’s the fastest recorded speed for a mako shark?

A: As a scientist it's really hard to measure the speed of a free swimming shark. The technology's not perfect. The speed estimates for the shortfin mako, which is considered to be the fastest shark, range anywhere from 25 to 55 mph. I personally think that 55 is probably way beyond what these sharks are capable of, but certainly between 30 and 40 mph is certainly plausible.

 

 

Q: What makes them so fast?

A: The reason that the mako can swim so fast is because its body is shaped perfectly for speed. It is a very streamlined body. It's got various fin shapes, like a tail that's shaped like a tuna’s tail (tunas are very fast fish). It’s got a fleshy ridge called a caudal keel that translates energy from the shark’s muscle mass to its tail. And it's got a very high metabolic rate that allows it to contract its muscles at a remarkably fast rate.

 

Its nose is streamlined. Its dorsal and pectoral fins are short and streamlined. Its body is perfectly torpedo-shaped. All those add up to features that reduce drag and allow for remarkable speed through a very dense medium: water. So they're really, really fine-tuned and able to accelerate and bring their speed up quite fast.

 

Q: Why do mako sharks need such incredible speed – what are they hunting?

A: The mako shark is what we consider to be a pelagic predator. That means it lives almost exclusively in the blue open ocean many, many miles from the coastline. The farther away you move from the shoreline, the probability of finding food drops remarkably fast – the densities of prey items 30, 40, 50 miles offshore are patchy.

 

The mako shark has evolved to exploit these patches of food with speed. They particularly love feeding on a coastal species of fish called blue fish, which are fast fish that form schools. But a mako shark is faster. They can catch and kill large numbers of blue fish very effectively. I think that's why they have speed.

 

As mako sharks get larger, they shift their diet. They'll still eat blue fish, but they start to include bigger prey items like dolphins and porpoises. In order to be able to kill a dolphin or a porpoise you need size, you need big teeth and you need speed. And that's exactly what mako sharks have.

 

Q: Can you describe how a mako shark attacks its prey?

A: Well, we can only really guesstimate how a mako shark attacks its prey. There's some underwater video footage that shows mako sharks coming up really fast on trolled lures. I imagine that, like white sharks, makos are very visual predators. They have really big eyes that are very well adapted for bright light. So they rely heavily on seeing their prey, probably silhouetted against the surface, and then attacking it with great speed. The mako's teeth are well-shaped for grasping. So they get a hold of the prey, grasp onto it, and either bite it in half or swallow it whole.

 

Q: What’s your favourite little-known fact about makos?

A: Fishermen know about this but the average person may not. One significant feature of mako sharks is that they hit with such speed that sometimes they don't realize that the water's surface is right there and they come flying out of the water. They make spectacular jumps – 10, 15 or 20 feet out of the water, somersaulting through the air. So the white shark isn't the only shark that comes flying out of the water when it feeds.