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Experienced shark researchers Scot Anderson and Paul Kanive on the known and unknown about the ocean’s apex predator.
By Steve Hawk
Light / Dark
Funny thing about white sharks: They are the most-studied shark species on the planet (based on the number of scientific papers published), yet researchers still have huge, fundamental gaps in their knowledge of them.
No human has ever seen a mating pair copulate. No one has seen a female give birth. No one knows how long they live, although 75 to 100 years is the best estimate these days. The white sharks that feed in Central California’s infamous “Red Triangle”—and chomp the occasional surfer—migrate each spring to a barren expanse of ocean between Baja and Hawaii, but no one’s been able to figure out exactly why. The leading hypothesis is that they go there to breed.
These factual voids have intractable roots. White sharks die quickly in captivity, so a lot of their basic behaviors have never been witnessed up close. They’re fish, not mammals, and thus do most of their business in a place where scientists can’t see them. And there simply aren’t that many of them. The Central California cohort—a discrete population that ranges from Bodega Bay to Santa Cruz and out to the Farallon Islands—consists of just 300 or so adults and sub-adults (meaning 8 feet or bigger). On top of all that, the California sharks are skittish as hell, which means most research involves spending many hours at sea to get only glimpses of them here and there.
On a recent outing to the Farallones, for instance, research- ers Scot Anderson and Paul Kanive set out from Half Moon Bay at dawn and got back at sunset. Using a seal-shaped decoy and the scent of whale blubber, they attracted and identified five different sharks. They spent 10 hours on the water to acquire five data points. And they considered that a good day. I got to join them on that trip and ask several questions that surfers might want answered. Top of everyone’s list: What’s the best way to avoid getting bit?
Between the two of them, Anderson, 65, and Kanive, 45, have authored or co-authored close to 40 research papers on white sharks. Anderson has been studying the species since the late 1980s. He began as a bird researcher on the Farallones but soon shifted to sharks. Some of the sharks he identified back in the ’90s still drop by occasionally to say hello, 25 years later.
Kanive took a more traditional scholastic route. After graduating from the University of Rhode Island, he worked as a fisheries observer in Alaska, then went on to get his PhD at Montana State University. His doctoral dissertation, published in 2020, provided the first empirical annual estimates of the Central California white shark population and growth rate. He’s the one who determined that there are about 300 of them and that their numbers are slowly rising.
SH The surf journalist Ben Marcus has interviewed almost every surfer who’s been hit by a white shark on the West Coast over the past 30 years. He says they all have one thing in common…
SA They didn’t see it coming.
SH Exactly. They had no idea it was there. The thing just came up from below and blasted them. I’ve always figured that, because they’re such good hunters, if a white shark allows you to see it, it’s probably not interested in eating you.
PK That’s absolutely right. Like the shark that hit Mick Fanning during that contest at Jeffreys Bay—I don’t think it was being predatory. I think it just came up to check him out and got caught in his leash, and then they both freaked out and started splashing. Because sharks usually figure out right away that you’re not something they want to eat, and they just leave without you even knowing they were there.
SA The species has been around since marine mammals came on the scene millions of years ago. So their hunting instincts are based on marine mammals, and those instincts are very well honed.
SH If you were in the water on a surfboard and a white shark came at you, what would you do?
SA I don’t think there’s any defensive action you can take, really. Maybe put your board between yourself and it, and try to make your way to shore.
PK Fanning punched that shark at J-Bay in the nose. That could possibly be effective. But chances are you’re not gonna see it.
SH Are there places you wouldn’t surf because of sharks?
SA I wouldn’t surf Salmon Creek, especially in October. In the prime months [August to January], I wouldn’t surf Ten Mile Beach in Point Reyes, or Shark Pit by Dillon Beach, or any place around here that’s way offshore with a rocky bottom and pinnipeds around.
SH Why do you think there are so few encounters at Ocean Beach in San Francisco?
PK My guess is that it’s because they tend to travel past big sandy beaches like that. There’s no concentration of prey, so there’s no reason for them to stick around.
SH I have a friend who’s been surfing Northern California a lot since the 1980s and has never seen a white shark. He thinks our fear of them is overblown.
PK He hasn’t seen them, but they’ve seen him.
SA Yeah, that’s the thing. Seeing one is almost as rare as being bitten by one.
PK Think about it. Right now we’re in an area with a high concentration of them, doing everything we can to see them, and they’re still hard to see. They don’t like to advertise themselves.
SA One of them has an acoustic tag, and we’ve detected it, so we know they’re nearby. They just haven’t allowed us to see them.
SH You always use water scented with marine-mammal blubber to lure them to the boat, which suggests that they’re not really interested in fish blood or human blood. Is the “sharks love blood” thing just a myth?
SA I think it is for white sharks. Blood does have an odor, but it’s the oil in the blubber that attracts them. Adult white sharks restrict their diet almost exclusively to marine mammals because of that fat content. It’s a high-energy food. It’s like eating butter. An elephant seal, if it’s healthy, is, like, 30 percent fat.
SH Does that explain why, when surfers around here get hit, the sharks almost always just swim away?
SA Yeah. When they encounter fiberglass or something hard like that, they don’t really like it. When they bite into a seal, they know it right away.
SH Because of the mouthfeel?
SA That’s probably part of it, yeah. They’ve also got these electroreceptors on their face that are little pores filled with jelly, and they can feel electrical pulses with that. That’s how they tell if something’s alive or dead.
SH So those electrified shark repellents: Are they effective?
PK The studies I’ve seen aren’t really definitive, and I’m not sure they’re relevant for surfers. In those experiments, they use bait, so the sharks come in curious and slow. No surfer’s gonna bait himself. And, like you pointed out, all of the attacks on surfers around here are ambush attacks, fast and from below.
SA A white shark that comes in slow to sniff dead bait is a totally different animal than one that spots prey and decides to attack. Given the speed at which they attack, a small electrical field is unlikely to stop them.
SH When they attack a seal or sea lion, are they more likely to bite the body or the head?
PK They typically attack from below and behind, but with elephant seals you’ll often see them come up with no head. My thinking is that [the seals] realize they can’t outrun it, so they turn around to fight, but the shark’s mouth is so much bigger that it can just bite off the head.
SH The elephant seals actually fight back?
PK For sure. A full-grown elephant seal is a high-risk meal for a shark. Those big bulls can mess you up. We’ll see bite wounds from elephant seals on sharks, and they’re intense.
SH Is there a preferred depth at which they hunt?
PK Sometimes they hunt at depth, but most of their attacks are at the surface. In one research project, we used a tag that could measure depth. We found that when the shark was searching for prey in water that’s 60 to 90 feet deep, it stayed close to the bottom. When it was hunting in water deeper than that, it remained at that 60- to 90-foot depth, presumably so it could see the surface. It’s optimal to hunt near the surface because the prey has no place to run. Surfers, obviously, get hit in much shallower water, sometimes when it’s only 6 or 8 feet deep, but it appears that a white shark’s preferred hunting depth is considerably deeper than that.
SH How much does water clarity matter when they hunt?
SA It’s really important, and that’s something for surfers to think about. If it’s super murky, you probably won’t get hit, because they can’t see you. And if it’s super clear, they also are less likely to attack, because they can tell you’re not something they want to eat. It’s those in-between days that I’d worry about.
SH If you see porpoises or dolphins swimming by, does that mean there aren’t any sharks around?
SA The thing about porpoises and dolphins is that they’re always on the move. They don’t stay in one place all day, like sharks tend to do. So I don’t think that means anything.
SH Does splashing attract them?
SA Not really. Sometimes I’ll splash to see if that works, and they’ve never really responded to it. The thing is, white sharks are really smart.
PK They’re also extremely risk-averse. Remember, the big ones live a very long time—like, as long or longer than humans. So they obviously don’t take a lot of stupid risks.
SH What are the biggest threats to a full-grown adult?
PK Orcas. Maybe other white sharks. High-seas fisheries can be a threat also, although that’s mostly a concern for sub-adults, because the big ones are not likely to get tangled in fishing gear. Other than killer whales, white sharks are the ocean’s apex predator.
SH But orca attacks on white sharks are pretty rare, yes? Or at least rarely observed.
PK That could be because the sharks clear out at the first sign of an orca. Our team published a paper about an orca event that someone witnessed at the Farallones in 2009. A pod of orcas came through and one of them attacked and killed something. The witnesses weren’t able to identify the prey, but there’s a good chance it was a white shark. The day that happened, there were 17 tagged sharks in the area. We know that because we had underwater receivers collecting data on them. They’d been happily swimming around the islands for several weeks, and the same day the orcas were seen, all those sharks went away—within minutes of each other. They just split. And for the rest of the season, nobody saw a shark out there.
SH That’s amazing.
PK Not long after, three more tagged sharks came back to the islands, very briefly, and they left too. It was like they realized that all the other sharks were gone and something wasn’t right. That pod of orcas was at the Farallones for only two and a half hours, and they chased all the sharks away for the whole season.
SH What about painting the bottom of your board black and white so it looks like an orca?
PK I don’t think that would work, because you’re backlit, so they can’t see the colors on the bottom of your board. You’re really just a silhouette to them.
SH Why do the orcas only eat the sharks’ livers?
SA Because that’s where the fat is. When the sharks are out here feeding, all that fat gets condensed into the liver. And it’s huge—like, 1,000 pounds. The liver can be a third of the body weight of a shark.
SH You both surf, yes?
SA I used to, but not really anymore.
PK I do. I’d say I’m, like, an intermediate-level surfer.
SA He’s pretty good.
SH When you do surf, how scared are you of a shark attack?
SA Look, when people talk about making decisions to maximize your safety, it’s really just a matter of managing risk. If you don’t want to ever get bit by a shark, then don’t go in the water. You have a choice there—that one’s simple. That’s how you reduce the shark risk to zero. What’s the next choice? You can go to a place that has a history of shark attacks or a place that’s never had a shark attack. Again, you’re managing risk. Is there a pinniped haul-out nearby? If so, maybe avoid it. You can do that each step of the way. What month of the year is it? Is it the time of year when the sharks are on the coast feeding or when they’re far offshore breeding? Any time between March and July around here, you’re probably safe. Then, when it comes to really mitigating risk, the other questions to ask are: How far away is the surf spot from the parking lot? Or from emergency services? Are you with somebody? Is there cell phone coverage? It’s like a checklist. You just go down the list and add up the risks, and maybe you don’t surf that day.
[Feature image: Rising to the bait in the Farallon Islands. According to Anderson and Kanive, white sharks prefer to hunt from a depth of 60 to 90 feet—but will opportunistically enter much shallower water and often use the surface to trap their prey. Photo by Scot Anderson]
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