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Project: Sharks on the urban edge

Living with sharks

Can we co-exist with our ocean's apex predators? Researcher Alison Kock examines our relationship with sharks.

“We are not afraid of predators, we’re transfixed by them, prone to weave stories and fables and chatter endlessly about them, because fascination creates preparedness, and preparedness, survival. In a deeply tribal way, we love our monsters…” E.O. Wilson, sociobiologist

Cape waters are home to one of the largest concentrations of great white sharks in the world. Fossil records, like the discoveries of preserved teeth found on the Cape flats, reveal their presence here for thousands of years. The earliest records of interactions between people and sharks in Cape Town are more than 100 years old. More recently research tells us that areas like False Bay are most likely critical habitats for the South African population, meaning the sharks depend on this area for their survival. But, surviving on the doorstep of a major city, with a population of 3.5 million people, may just be the biggest problem these animals have to face.

A white shark underwater. Photo © Save Our Seas Foundation/Peter Verhoog

Sharks have problems too
Great white sharks are without a doubt one of the most successful predators on the planet, but one of nature’s most triumphant designs did not factor in the negative impacts that humans, in the role of a dominant species, can have on them. As apex predators, sharks sit atop the food chain and with no natural enemies, shark numbers are designed to be low. Ironically, given their rule over the sea, this means they are particularly vulnerable to the way human’s fish and sometimes over-fish. Sharks are designed to mature slowly (taking up to 15 years), and produce few successful young (every two to three years). In areas where their populations have been depleted they are slow to recover to natural numbers.

Due to evidence of declining white shark populations around the world, these sharks are afforded some of the highest protections of any fish in the sea. Today, the great white is fully protected in seven countries, including South Africa. International conventions also protect the great white, with listings on Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), in the Convention of Migratory Species (CMS), and in the United Nations Convention on Law of the Sea (UNCLOS). The authority on which species face the most likely path to extinction, the World Conservation Union’s (IUCN) Red List of Threatened Species, identifies white sharks as globally “Vulnerable”. The message from the international community is great white sharks are at risk of extinction.

Why do we need great whites at all?
Great whites keep the ocean balanced. They feed on a variety of animals including numerous species of fish (in Cape Town those include yellowtail, steenbras and cob), other sharks (smooth hounds and guitar sharks), marine mammals (seals) and they even scavenge on dead whales. Furthermore, great whites are often the primary, and sometimes only, predators of some of the larger prey animals like seals. This means that there is a cascading effect in the ocean between the way sharks keep a balance of their prey and the hundreds of different species that are impacted (ecological dominoes if you will), and thus play vital roles in ecosystem function and biodiversity. Furthermore, studies around the world are increasingly highlighting the important role that sharks play. Without sharks, economically important fisheries have closed and there are losses to eco-tourism ventures, particularly important in countries dependent on tourism. Moreover, great white sharks are now celebrated as one of our “Big Seven”. They are an iconic species and a feature of our local and natural heritage, which we have a duty to preserve.

Shark nets, hunts and culling
Human-wildlife conflicts are difficult, but nothing new in Africa. Despite this, Africans have a proud history of dealing with this and respecting nature, and it is thus surprising to me that people still ask why we can’t just go out and kill the shark responsible.

Leading conservation managers from around the world advocate that we look for solutions to human-wildlife conflicts that provide a balance between human needs and that of our natural assets. Culling programmes like the implementation of shark nets (which are gill nets designed to catch and kill sharks), drumlines, shark hunts and other extractive methods go hand-in-hand with high environmental costs. These traditional approaches to human-wildlife conflicts are increasingly being criticized on the world stage as being out-dated, and short-sighted. New Zealand took down its shark nets this year and a local professor stated, “The notion that we need to kill any animal that might place us at risk when we enter the water is a totally unacceptable attitude in the modern world.” California and Florida also face the same kinds of issues we do and they have refused shark nets.

If we’d like to see what happens when top predators are removed, we only need to look to what has happened on land: one of the best examples comes from the western U. S. where gray wolf populations were hunted to local extinction, which resulted in negative cascading effects throughout the ecosystem and a subsequent re-introduction of wolves was needed to attempt to regain the balance between predators and their prey.

Above and beyond this, shark hunts or “selective culling” are scientifically proven to be ineffective at capturing the shark responsible or reducing shark-human encounters. A good example is Hawaii, where a shark control program ran in different parts of the state for years, costing thousands of dollars, and concluded that it was not reducing the rate of shark bites. Instead, we see taxpayer funds spent often to placate the public rather than find workable, long-term solutions.

The Save Our Seas Foundation opposes the implementation of shark nets, shark hunts or culling by other means. Shark nets have been declared a “key threatening process” by international bodies because they catch marine life indiscriminately. This includes endangered white sharks, turtles, dolphins and whales. In Cape Town, these methods would be particularly devastating because these waters are a natural gathering spot (in science-speak it’s called an “aggregation area”) for sharks. What this means is that shark nets and hunts have the potential to deplete Cape Town’s regional shark populations. These concerns are strongly supported by leading shark scientists from around the world.

A dead white shark. Photo © Alison Kock

Mindless killers?
Great white sharks, like all animals, are individuals with individual behaviours and characteristics. As the largest of predatory fish, reaching six meters, they don’t have much to fear and are confident and curious animals. They have large brains and display complex hunting and social behaviour. Great whites are not mindless feeding machines and are selective in what they eat, often preferring high calorific food, like blubber, over muscle. They are capable of migrating thousands of kilometers across ocean basins; only to return months later to the exact area they were last recorded. They are equally as capable of residing in one area for months at a time and timing their arrival at seal colonies to predate on naïve seals. But, great whites don’t just travel and swim around searching for food, they also hang out with one another, interact with other ocean creatures like whales, and spend time simply taking a rest from it all. For example, our research team once tracked a shark for 24 hours non-stop and all it did was swim at the surface, mingle with other white sharks in the area and swim slowly in a circle no more than 2 km ² (Check out the Google track). In Fish Hoek recently the sharks have displayed a combination of all of these behaviours.

That great whites have always been in the Cape is without question, however, we need to remember that our oceans are dynamic ecosystems and constantly changing. Animals respond to their external environment and some of these responses include distributional changes. Great whites will respond favourably to an abundance of natural prey, as it makes them easier to catch, like they do by timing their movements to co-incide with the abundance of naïve seals over the winter time. Spring and summer offer schools of steenbras, yellowtail and bottom dwelling sharks, genuine great white favourites. Even over the short period of our research we have distinguished that not all years are equal. We have noted inter-annual changes in the numbers of sharks using the bay, differences in arrival and departure times and differences in the amounts of time they use the bay. Reaching over 45 years old there are cycles in regional and local movement patterns which we don’t fully understand yet. But we are learning more than ever before and this will help us educate bathers and recreational water users.

One thing we do know is that reality and fiction of shark behavior is tested following shark attacks. If you are an avid monster movie watcher like me then you know all about rogue animals. But, the reality is that there isn’t a shred of evidence to support the rogue shark theory. In fact, the more we learn about sharks, the more the rogue shark theory only survives as part of a B-grade movie. The recent incident in Fish Hoek continues to punch holes in the theory. Shark Spotters recorded great whites in Fish Hoek bay everyday for four days in a row leading up to the tragic incident in Clovelly corner. Up to three different sharks were seen at one time in the area. Quite simply, they are being drawn to this particular area at this time because the area itself fulfils a specific requirement, not the people. The region provides an abundance of natural prey, but is also possibly an area to rest, travel through or socialize in. What we do know is that sharks are not coming to Fish Hoek for us.

In this most recent tragic case, the Shark Spotting system functioned well. Shark sighted, siren sounded, beach cleared, shark-presence flag flown. Many people got out the water and went to sit next to the spotters observing the sharks from above doing what sharks do naturally. Their behaviour described as swimming leisurely at the surface, or circling and even feeding in front of the Silvermine River mouth. At the time of the incident on the 28 September 2011 there were at least two sharks in the immediate area. Mr. Cohen entered the water under these conditions, swam about hundred meters parallel to shore on a collision course with an approaching great white. The behaviour described by the Shark Spotter Ashley Sullivan and eyewitness, Kyle James, suggests that the shark swam slowly around Mr. Cohen, swam up behind him and took a bite, before slowly swimming away.

This incident provides good evidence that in this case the shark made an exploratory bite, possibly investigating whether the swimmer was something to eat or not. While the bite inflicted severe damage, this is not the behavior that we see from sharks when they attack a seal or other prey. If we compare this to a recent video taken by Stuart Dawes, a resident of Noordhoek, two days after the incident one can clearly see the fast swimming, and repeated quick changes in direction of a great white chasing a Cape fur seal at the surface which we expect to see.

The reality of shark-human interactions
Great whites didn’t evolve into the successful predators they are today by randomly swimming around and ignoring unfamiliar objects. Having spent thousands of hours studying them in Cape Town, tagging and tracking them, cataloguing which animals are present and how long they stay for, and even attaching small animal-borne cameras to them I am constantly amazed at how curious, opportunistic and investigatory they are. Their curiosity makes it all the more important to note how few shark-human interactions there are. We go into the water in large numbers and over long periods of time, yet shark bites on people are rare.

My parents fostered my respect of our oceans and its creatures and I recognize the enormous value sharks bring to our local region. But, at the same time, it would be irresponsible for those of us educating the public on the role of sharks, with specific reference to large predatory sharks, to portray them as harmless or to lose our respect for them as predators. A number of people have demonstrated that diving alongside great whites under specific conditions is possible which help break down the “maneater” stereotypes, however, it would be foolish to forget that great whites are formidable predators and potentially dangerous to people.

Into the future
Sharks live in the sea; therefore, as long as people enter the sea the two will encounter one another. Our relationship with sharks is a comparatively new one, unlike our relationship with land predators, and as a good friend said to me recently “the ocean seems to be getting smaller for all of us”. We need to learn from our mistakes on land, and look for innovative ways to reduce wild-life human conflict. Research and awareness are key components of a safety strategy, but it’s also essential that we keep our fingers on the pulse of potential new solutions which become available and continuously investigate and test workable and environmentally conscious ways of addressing the issue. The Save Our Seas Foundation is committed to staying informed of the technologies available and supporting projects that aim to find suitable solutions.

Finally, to answer the question on whether people and large sharks can co-exist; I believe we answer ‘yes’ to that question every day.

ALISON KOCK is the lead investigator of the white shark research programme in False Bay, a member of the Save Our Seas Foundation scientific committee, a doctoral student at the University of Cape Town completing a thesis on the behaviour and ecology of great white sharks and the scientific manager for the Cape Town based Shark Spotters programme.

The SAVE OUR SEAS FOUNDATION is committed to protecting our oceans by funding research, education, awareness and conservation projects focusing on the major threats to the marine environment. Furthermore, the Foundation is committed to playing a positive role in the global conservation of great white shark populations and currently supports six white shark projects around the world. http://saveourseas.com

The SHARK SPOTTERS programme is a pioneering shark safety programme that has attracted international and local attention because of the novel way it seeks to find a pro-active solution to shark-human conflict on the Cape Peninsula. http://www.sharkspotters.org.za

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False Bay, South Africa

Sharks on the urban edge

False Bay is home to one of the world’s largest white shark populations and a growing human community. This creates a number of challenges for both people and sharks. Alison is finding out how these apex predators shape the bay and what would happen if they disappeared.