Face off: the great white shark vs the killer whale

Our oceans are full of predators, ranging from tiny carnivorous fish to poisonous snakes; from poisonous snakes to electrocuting eels; from electrocuting eels to murderous dolphins. In short, predators are everywhere and none are more feared than the great white shark and the killer whale. Both of these animals are titans – huge animals that can hunt and kill almost anything they want to (and yes, humans are included). But which of these is the top predator? Which of them would best the other in a fight?

The great white shark, Carcharodon carcharias, is one of the most feared animals in the oceans. The sharks often hunt by taking advantage of their huge strength, ambushing the seals they hunt from underneath while they rest on the surface. Unfortunately, surfers resting on their boards can look very similar to seals from underwater, which is believed to be the main cause of great white shark attacks on humans.

I’m sure many of you are thinking that this would be the great white. And why not? Great whites have been known to kill humans and there is a huge ‘fear culture’ around sharks after Peter Benchley’s Jaws was televised in a film. You would be wrong, however, and there is a case that to show that it is in fact orcas that rule the oceans.

In the first instance, you have to remember that orcas are social and hunt in packs (which has actually earned them the nickname of ‘the wolves of the sea’). Obviously, this provides killer whales with a huge advantage over the solitary great white and orcas can bring down prey much larger than themselves. In fact, orcas have even been known to go after small female sperm whales (which are actually the largest predator alive), so picking off a lone great white shouldn't be too much of a problem for them!

Like humans and other primates, killer whales are extremely social and live most of their lives in tight-knit social groups of close family members. To prevent the inbreeding that this would inevitably lead to, male orcas usually leave their maternal pod once they sexually mature and actively seek another pod to live with for the rest of their adult lives.

Secondly, you have to consider the intelligence of killer whales, which are part of the same family of oceanic dolphins (Delphinidae). All of the members in this family are extremely resourceful and have been seen to use complex, highly sophisticated tactics while hunting their prey. In fact, killer whales have actually been observed practicing to hunt (click here for more information) and it is one such tactic that leaves little doubt that orcas are hierarchically above great whites.

As you may or may not already be aware, orcas have different cultures (in much the same way as humans do) and different pods in various locations around the world specialise in hunting certain animals. Common examples of their sources of prey include fish and water mammals, such as seals. But it is the pods that specialise in hunting sharks that are really relevant for this post. Such orcas have realised and taken advantage of two very simple aspects of shark anatomy:

• Firstly, most species of shark go into a hypnotic state of sleep called tonic immobility when they are turned upside down
• Secondly, sharks have to keep swimming in order to breathe and, as soon as they stop moving, water ceases flowing through their gills and they begin to suffocate

Since great white sharks have to keep swimming in order to breathe, they have developed a remarkable method of sleep where they rest each half of their brain separately. This allows the neurotransmitters in their brain to recover to normal levels after waking activity, while simultaneously allowing the shark to keep moving and remain alert for prey and danger.

By taking advantage of these two simple facts, orcas can kill sharks extremely easily and with very little risk of injury to themselves (i.e. the sharks can’t fight back). To do this, orcas take advantage of their extreme agility and ambush sharks from above. As they near the unassuming shark, they bite it just above their dorsal fin and use their strength and body weight to roll the shark upside down, meaning that it falls asleep and stops struggling. Then, it’s just a simple case of the killer whale holding its breath while it waits for the shark to suffocate and die!

This tactic is merciless and brutal, but it is extremely effective and scientists have actually seen killer whales using it on great whites off the coast of California! What is also interesting, other than orcas being able to kill great whites so easily that is, is that great whites (like many species of shark) release chemicals called ‘death signals’ into the water when they are killed. These signals drive off all other great whites for miles and, for many years, scientists were baffled by why the massive predator suddenly vanished from Californian waters. It was only when they realised that the exodus of great whites coincided with the seasonal arrival of a certain pod of orcas from Antarctica that they put two and two together and began to observe how the two predators interacted. Just imagine their surprise!

Mountain gorillas seen disarming poachers traps!

Everyday, animal trackers set out from the Karisoke Research Center into an isolated area of Rwandan rainforest aiming to find and disarm as many of the dangerous and illegal traps set by poachers as they can find. The trackers efforts are crucial in helping to protect the extremely rare mountain gorillas (Gorilla beringei beringei) that inhabit the region, which are classified as being 'Critically Endangered' by the IUCN and are predicted to become extinct within 10 years if we fail to conserve them.

When tracker John Ndayambaje set out one morning he was fully expecting to see poachers traps. Sure enough, he located a clan of gorillas and spotted a snare trap nearby. Although many poachers don't set snare traps to catch gorillas, as adults of the species are easily strong enough to break free, they are capable of killing juveniles so he knew that he must disarm it.

When John moved to approach the trap however, a silverback called Vubu grunted at him, presumably warning him to stay away. As John watched, two younger gorillas named Rwema and Dukore made their way over to it and carefully broke it, working confidently and quickly, which suggests that they've had extensive experience with the traps in the past. Rwema and Dukore then searched the surrounding foliage, joined by a third member of the Kuryama Clan called Tetero, and disarmed several more traps that John hadn't yet seen.

Rwema and Dukore work together to disarm a snare trap set by poachers.

This remarkable ingenuity has undoubtedly arisen in response to the very real dangers that the traps pose and is a superb example of mountain gorilla intelligence and their ability to learn. Researchers at the Karisoke Research Center believe that the gorillas watched human trackers tackling the traps and copied how they disarmed them. Although fascinating to watch, Veronica Vecellio (the Centre's gorilla program coordinator) was not surprised by the events and said that she is "always amazed and very proud when we [the Centre's researchers] can confirm that they are smart".

Silence of the hunter

The killer whale, Orcinus orca, is one of few species of toothed-whale and is closely related to oceanic dolphins, which first appeared around 11 million years ago. Often being called 'the wolves of the sea', killer whales are highly intelligent and are extremely successful predators that can be found throughout the world's oceans; being able to feed off a wide range of prey species that they hunt using echolocation.

The main prey that a pod of killer whales hunts appears to be culturally specific and typically, pods hunt either mammals, sharks, fish or birds. Cultures of killer whales are highly specialised and efficient at hunting their specific type of prey and use a variety of advanced and sinister tactics. These tactics can be very different depending on what animals the whales are hunting, but usually rely on the stealth or the strength and speed of the whales. Furthermore, these tactics are usually highly coordinated and individual whales have been seen to be 'talking' with each other and adjusting their behaviour accordingly!

Killer whales living at the poles can break up through ice in order to reach the surface and breathe. In order to this they swim upwards like a battering ram and strike the ice with enormous force. The power of such strikes is staggering and was highlighted by the famous British Antarctic explorer Sir Ernest Shackleton, who recorded fragments of ice being scattered for 20 - 30 feet around their holes! This behaviour is also used to knock seals off an ice floe into the water where another whale finishes it off - a fact that was of great concern for Shackleton and his expedition while they were stranded in Antarctica for nearly 2 years!

However, this behaviour has long baffled scientists who study the pods of killer whales that hunt mammals such as seals and sea lions, since all marine mammals have excellent hearing and the whiskers of these animals can detect even very subtle vibrations in water. Judging by this then, it would be expected that their prey should hear the very vocal whales coming and flee the area or climb out of the water to safety. However this isn't the case and often, their prey doesn't even know that the whales are there. New research conducted in partnership between St. Andrews University in the UK and North Carolina State University in the USA has helped to shed some light on this, finding that when they are hunting, killer whales "go into silent mode" and neither speak to each other nor use their echolocation to help them find their prey.

Instead, the whales seem to use a very sophisticated 'search and destroy' method in order to hunt where the members of a pod spread out over great distances and then close in again. This is repeated in silence until an animal is found, whereupon the whales close in on the unfortunate animal and kill it - remarkably, still in complete silence! It is only after they have killed their prey that they begin to talk again, a behaviour that Dr. Deecke from St. Andrews relates to humans: "it's a bit like us in a dinner party - they communicate while they eat then gradually wander off and go quite again".

Killer whales have a highly complex social organisation that is comparable to that of elephants and even humans. At its most basic level, their society is made up of units of closely-related females called matrilines that typically consist of 5 or 6 individuals. These matrilines then form 'pods' with around 4 other matrilines, with which they regularly interact and spend time with. Multiple pods regularly mingle with other pods to form 'clans' and finally, multiple clans interact forming larger aggregations called 'communities', which can be spread over huge areas of ocean.

Exactly how killer whales manage to conduct this very sophisticated behaviour in silence isn't definitively known, but it is believed that they rehearse their hunting tactics beforehand so that an individual whale knows exactly where they are supposed to be and what they supposed to be doing, as well as where the rest of their pod is supposed to be. Scientists at the two universities plan to continue their research by fitting sound recording devices and satellite tracking tags to killers in order to follow their behaviour much more closely and it is hoped that by implementing such technologies into their research, that they can determine for certain whether or not the whales are hunting in set patterns and conduct 'practice' runs.