Sharks are mysterious and scare people away from swimming in the ocean, but shark attacks are rare. In this episode of Ask The Experts, we delve into the underworld of sharks.
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00:00Welcome to AccuWeather's Ask the Experts, I'm your host Jeff Cornish.
00:16We go beyond the forecast to give you the how and why on all the cool and interesting
00:19things that you've wondered about and wanted to ask in weather, space and science.
00:25Today's show is about an animal that many people are frequently fascinated by and we're
00:30talking about sharks.
00:32We're going to look at everything from what triggers a shark attack to how climate trends
00:37can impact their migration.
00:39So joining us as today's expert is Gavin Naylor and he's the director of the Florida Program
00:45for Shark Research at the Florida Museum of Natural History.
00:48So Gavin, thank you so much for making time for us here today.
00:52It's a pleasure to be on the show.
00:53We're glad to speak with you and Gavin, big picture, what about sharks draws us in?
00:59Why are so many people interested in sharks more so than maybe dolphins or porpoises or
01:03something like that?
01:05That's an interesting question.
01:08I don't know, but I think it's because we have a deep-seated need to be terrified by
01:15mysterious monsters and it's like the monsters under the bed when you're a little child.
01:23The ocean is beautiful and calm and glassy.
01:27But right underneath that still surface are large animals, some of which can occasionally
01:33bite you.
01:34And I think that sort of titillates people and I think almost think people sort of want
01:38to be terrified.
01:40I think there's a human need to have that sort of adrenaline rush and that's the only
01:45thing I can come up with because it makes no rational sense.
01:49The number of people bitten by sharks is minuscule.
01:53So why we seem to enjoy talking about it and thinking about it is a little bit peculiar.
02:00I'm on board with some of that.
02:03And you've been studying sharks and their tendencies for many years.
02:06How did you get interested in sharks and how did you turn this into a career?
02:10Well, actually, I'm interested in evolution, so I'm a biologist.
02:15I'm really primarily fascinated by why there's so many different kinds of life forms on the
02:20planet and how they came to be.
02:23You can imagine another planet with life on it, and I'm sure there's many of them, but
02:27they might not have as much diversity.
02:29They might not have things like giant trees and bugs and bacteria and birds and whales.
02:36They might just have sort of a homogeneous bacterial kind of coating.
02:41But that's not the case here.
02:43So I'm really interested in how it is that these organisms become so different from one
02:48another and interact with one another and eat one another and have commensal relationships
02:53with one another.
02:54And sharks are particularly interesting because they are sort of the counterexample where
02:59they haven't really evolved as quickly as some of the other organisms.
03:04We've got 300,000 species of beetles, but we've only got about 1,200 species of sharks
03:11and rays, and they've been around for 400 million years.
03:14So their evolution is quite different from other animals, and when things are different,
03:19that can teach us quite a lot about all of the diversification process.
03:24So that's my real reason.
03:26Sharks are interesting for their own sake, but my particular interest is in their evolution.
03:31Well, they are amazing creatures, and they play a role in the ocean's ecosystem, obviously,
03:36as an inhabitant.
03:37So can you expand on that and also talk about how important sharks are to the health of
03:42marine ecosystems?
03:44That's a great question, and just for sort of complete transparency, we always assume
03:51that if sharks aren't around, that the oceans will completely collapse and go to hell.
03:59And that's very likely the case, but we don't actually know what would happen if we got
04:06rid of the sharks.
04:07Certainly, it would cause an adjustment.
04:11Some animals that sharks prey upon would be in higher numbers, and the organisms that
04:16they feed on would be in lower numbers.
04:18So there'd be a new steady state, and it would be very different from what we're used to
04:22seeing now.
04:23But we don't actually know what would happen or what their role is in the ocean.
04:29We know they have a role, but we don't know because of the sort of nonlinear nature of
04:34ecosystems that what would happen if we got rid of sharks.
04:39A lot of people say that they have an important role, which they very likely do, but we haven't
04:45really characterized what that role is.
04:49What are you most concerned about regarding keeping sharks safe and thriving?
04:53Well, I think that humans really like the world that we find ourselves in, and we're
04:59very frightened of change.
05:02And if there is a lot of change and there's a new steady state, we're frightened that
05:08we may not like the future.
05:10We may not be able to deal with it.
05:12It may be hotter than we're used to.
05:14It may be more toxic than we're used to.
05:16We may not be able to go outside as much as we would like to.
05:19And so people don't like things that are different than they're used to.
05:24And so given that, we probably would like to keep these ocean systems and terrestrial
05:30systems the way they are because we're terrified of what they might be and that we might not
05:39like what they become.
05:41We don't have to look too far to find that to be the case.
05:45Even think about barrier islands.
05:46Naturally, they'd be moving, but we like to pave things, build houses and homes, and we
05:52want barrier islands to remain just as they were when we first settled them 80 years ago
05:56or whatever that may have been in some cases.
05:59With rising ocean temperatures, how does that affect the movement and behavioral patterns
06:03of sharks?
06:05That's a great question.
06:07So sharks have been around for a long time.
06:11They've been through the Permian extinction, the Cretaceous extinction.
06:15So sharks, when things get sort of bad, they go somewhere else.
06:19So they're quite capable of moving their large animals.
06:22But their movement patterns will be affected by the food that they rely on.
06:27So as waters warm, certain fishes that were not able to live in certain parts of the world,
06:36as waters warm, those tropical fishes will move into those areas and the sharks will
06:41follow them.
06:42And so, for example, we have sea trout, coral sea trout from the Great Barrier Reef showing
06:49up in Tasmania, which is called the water.
06:53And as they move down there, these sort of tropical reef fishes move to Tasmania, the
06:58sharks will follow them.
06:59So we'll find sharks in areas where we're not used to seeing them, but the sharks themselves
07:04will probably be okay.
07:06And going from climate to more immediate short-term weather impacts, when it comes to big storms,
07:12for example, hurricanes, typhoons, how do sharks cope with storms like hurricanes?
07:17Do they go elsewhere?
07:19Do they evacuate like a human would?
07:21Or do they go deeper down into the water?
07:24How do they, or are they really affected by it?
07:25That's a very good question.
07:27There's only one very rigorous study that I know of by a scientist in Australia.
07:32She's an American scientist, Michelle Huppel, and she studied a different species of sharks
07:37than the ones that we get here in the US.
07:39And she found that as barometric pressure fell, these animals will go to deeper water.
07:45So when there's a storm around, the sharks will go deep, this particular species.
07:52Now, just because one species responds that way doesn't mean they all will.
07:56And it's quite possible that storms will churn things up, there'll be different food available.
08:03And so some sharks may come into an area after a storm, whereas other species will go to
08:08deeper water.
08:09So it's really on a case-by-case basis.
08:12So the one that you're showing right now is a reef shark that's melanopterous.
08:17And that shark now that you're showing there is a tiger shark.
08:21So these are both tropical animals, and they're often associated with shallow water and reefs.
08:27So they would probably go to deeper water.
08:30And Gavin, we want to get to our first viewer question now.
08:33This comes from Adrienne in Maryland.
08:36So Adrienne writes, how do researchers like yourself determine the age of a shark?
08:42That's an excellent question.
08:44So in the past, what we've been able to do is we can tag animals when they're little.
08:51And then when we recapture them, we can measure how long they are.
08:56And we know how long from the tag, how long they've been at large, and we can see a relationship
09:01between the length and the age.
09:04And we can do a regression and see that a shark of a certain length is a certain age.
09:10But once they get fully grown, that becomes much harder.
09:13It's sort of asymptotic graph.
09:16So what people have done in the past is they've counted vertebral rings.
09:20It turns out that a lot of sharks lay down rings every year or two rings a year.
09:26So by counting the rings in the vertebra, you can actually age the animals.
09:31But that also is a bit fraught with problems when they get very big.
09:35So we're actually developing epigenetic or genomic methods to see if we can estimate
09:42the shark age solely from blood samples.
09:46And these are new techniques that are being developed by myself and some colleagues at
09:50the University of Georgia and the Georgia Aquarium based on blood samples.
09:56We don't know how well it's going to work, but we want to do non-lethal sampling that
10:00tells us about the age of a shark.
10:03But to do that, we have to use aquarium animals of known age to see, you know, this animal
10:08really is 45 years old.
10:11Because if we don't know how old an animal is, how will we know that the measure that
10:14we're developing, how will we calibrate it?
10:17So we're currently in the stages of calibrating these samples.
10:21Very interesting, Gavin.
10:22Well, this is interesting information so far, and we're only just beginning.
10:26Sharks are not the only predators in the water.
10:29So coming up later in our WeatherWise segment, we'll have three things to know.
10:32We're going to reveal some of the most dangerous creatures in the sea.
10:35But next, find out what triggers a shark attack, and if rising ocean temperatures might
10:40be to blame.
10:41We're going to also answer more of your questions when Ask the Experts continues.
10:45Welcome back to AccuWeather's Ask the Experts.
11:07I'm your host, Jeff Cornish.
11:08We're talking sharks today, and we're back with Gavin Naylor.
11:11And Gavin is the director of the Florida Program for Shark Research at the Florida Museum of
11:15Natural History.
11:16So, Gavin, your team scientifically documents shark attacks in the International Shark Attack
11:23File.
11:24So, from your research, have there been more unprovoked shark attacks in recent years,
11:29or is this just media buzz and the need for headlines to be compelling?
11:36You've answered your own question.
11:38It's really no different.
11:41Every year, we get between about 50 and 70 unprovoked bites.
11:46And if anything, there's been a very slight trend down, but it's fairly consistent from
11:52one decade to the next.
11:56But who knows what the future will hold?
12:00There's a lot more sharks are protected, and some of the populations are coming back.
12:04And if they come back to the full numbers and people continue to frequent the same habitat
12:09where sharks live, then it's not unreasonable to think that there will be an increase in
12:14bites.
12:15But there hasn't been so far.
12:16But every year, every time we get the first one or two bites, everybody panics and says,
12:22why are there so many shark attacks this year?
12:24And I kind of feel a little bit of like a Debbie Downer, because I have to say, well,
12:28there haven't been.
12:31But the trend is fairly constant from one year to the next.
12:34Okay.
12:35Well, it still does happen at times, as you're mentioning.
12:38So it's a fact of life here as we're entering their environment.
12:41So what triggers a shark attack and are there better times of the day that perhaps might
12:47be safer or times that we should avoid if we're concerned about such a thing?
12:52That's a great question.
12:53So first of all, there are 530 different kinds of sharks.
12:58Only about 20 or 30 have ever been implicated in biting people.
13:03And obviously, these are coastal animals, and the ones that cause more of a problem
13:07are the larger animals.
13:10And so we should be focusing on the set that actually bite people and are a problem.
13:16Most animals take their cues for changing their behavior from changing environmental
13:23conditions.
13:24So nocturnal animals become active at sunset, diurnal animals become active at sunrise.
13:32Many animals change their behavior when the tide changes.
13:36And so animals start migrating based on photo period.
13:41So anything in the environment that induces a trigger changes the behavior of animals.
13:47So we tell people in general, don't go swimming at dawn or at dusk.
13:52These are big changes, light and dark, and it changes the behavior of a lot of animals.
13:58But more importantly, don't go swimming on your own, because if you do run into problems,
14:03there's nobody to help you.
14:05And if you swim in a group, it's less likely that the sharks will single you out out of
14:11curiosity and bite you.
14:14When they see a group of people swimming, they're going to avoid it more than they would
14:18do if they saw a single individual.
14:21So in terms of times of day, we say don't swim at dawn or dusk.
14:25But that said, the recent shark bites in North Florida in the Gulf and in Texas happened
14:32right in the middle of the day.
14:34And so it's no guarantee any time of the day that there is a very, very small risk of shark
14:42bite.
14:43It's slightly higher at dawn and dusk, but it doesn't mean that it's not the only time
14:50where shark attacks happen.
14:52Are increasing ocean temperatures to blame for any of these shark attacks maybe in spots
14:56where they would not have occurred otherwise?
14:59We don't have any data to support that claim.
15:02A lot of people have asserted it, but it's sort of proof by emphatic assertion.
15:07There's no data.
15:08It's not a summary of information.
15:10It's just a speculation.
15:12So it's really not scientific.
15:14But by the time we have data to really address that issue, you know, it could be long after,
15:21you know, people want to know what's driving everything.
15:24So right now, we don't think that climate change is increasing shark bites.
15:29It's certainly changing the distribution of fishes that sharks feed on.
15:34And if sharks come into areas where they didn't used to swim and there's people there, then
15:40the chance of encountering a shark certainly goes up.
15:43And Gavin, we want to get to our next viewer question.
15:45This one comes from Spencer in Pennsylvania.
15:48So Spencer, what would you like to ask the experts?
15:51So I've heard sharks kind of have a sixth sense.
15:54Is that true?
15:55And what does that exactly mean?
15:58Sure, you're exactly right, Spencer.
16:00Sharks do have a sixth sense.
16:02They have these ampullae of Lorenzini, which allows them these kind of receptors like pores
16:10all over the snout and around the face.
16:12And they can detect electrical activity, but not just a strong electrical activity.
16:18They can detect 10 to the minus 12 amps.
16:22So they can detect the potential difference in a D cell battery with one pole, one side
16:27of the Atlantic and the other, the other side.
16:30So it is, in fact, the most sensitive electrical detector known in living systems.
16:37And because it's so sensitive, they can use it for a number of things.
16:41An object moving through the water, when it cuts lines of magnetic flux, induces an electrical
16:51current.
16:52And so if you move from one side of the room to the other, you induce a small electrical
16:57potential.
16:58But we don't have the equipment to detect it, but sharks do.
17:03So as they move, they can detect a little tingling in their nose as they cut lines of
17:09magnetic flux.
17:11And if they move from east to west or west to east, they're going to cut more lines of
17:15magnetic flux than if they move north to south.
17:19They do indeed have a sixth sense, and it's this electrical sense.
17:24Many animals have it, but nothing quite as refined as sharks.
17:28Very fascinating, Gavin.
17:29I learned a lot here through that last answer.
17:31And this does, unfortunately, wrap up our question and answer segment.
17:35So we do want to thank you, Gavin Naylor, once again for joining us today.
17:38A pleasure speaking with you and learning all about sharks.
17:41Thanks again, Gavin.
17:43Thank you very much.
17:44Appreciate it.
17:45It's our pleasure.
17:46Up next, three things to know.
17:47Today, we're going to reveal the three most dangerous creatures in the sea when Ask the
17:51Experts returns.
17:52Welcome back to AccuWeather's Ask the Experts.
18:06It is now time for WeatherWise.
18:09Sharks kill about 10 people a year around the world.
18:12But did you know that there are other ocean creatures that can also be very deadly?
18:16So today, we have three interesting things to know about dangerous sea creatures.
18:19First, the Australian box jellyfish is the most venomous marine animal.
18:24A box jellyfish can sting, and that sting can bring extraordinary pain and even heart
18:30failure.
18:31This thing has 24 eyes, and they're the only jellyfish that can see, making them skilled
18:36predators in the ocean.
18:38Next is the stingray.
18:40You may have pet them in an aquarium tank, but those stingrays have had their stingers
18:45removed.
18:46In the ocean, venomous barbs on stingrays can kill.
18:49They're located on their tails.
18:50There are about 1,500 to 2,000 stingray injuries reported in the United States each year.
18:57And the third dangerous sea creature is the titan triggerfish.
19:00This thing sounds scary.
19:02Divers are more likely to be bitten by a triggerfish than attacked by a shark.
19:06So they're found in coral reefs from Australia to Thailand.
19:09Triggerfish aggressively defend their territory, often charging toward an invading diver or
19:14snorkeler.
19:15While they're not poisonous, their large, powerful teeth can bite right through divers'
19:19fins and flesh.
19:21That does not sound too good.
19:23Well, thanks so much for joining us here on AccuWeather's Ask the Experts.
19:27I'm your host, Jeff Cornish.
19:28And don't forget, whenever you have a question about weather, space, or science, you can
19:32write us or send us a video question at asktheexperts at accuweather.com.
19:37You can also always call us at 888-566-6606.
19:43Thanks so much for being with us.
19:44Have a great one.