11 Animals That Kill For No Perceivable Reason

It's often said that man is the only animal that kills for fun, but that's not true. Animals that thrill kill are fairly common, and scientists call the behavior "surplus killing." Animals that kill for no reason are usually mammals, but include a wide range of sizes, from tiny stoats to towering elephants. So, which animals kill for sport, and how do they do it? The subject is just as fascinating as it is horrifying.

Over centuries of study, scientists have seen animals use tools like humans and animals use disguises like humans, and now we know that they sometimes kill for fun like humans, too. By fun, we mean they don't do it over territorial disputes, in self-defense, to get food, or to move up in the pack hierarchy. Instead, these animals kill for seemingly no reason at all other than enjoyment. 

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  • Most people know that dolphins are very smart animals, and that they can be trained to do a wide range of tricks and tasks. What you might not be aware of is the fact that dolphins can also be vicious killers. They have been known to kill dolphin calves to get females to mate again, but they also kill porpoises just because they can.

    One example occurred in 1997, when a bunch of deceased porpoises washed up on the coasts of Scotland and Virginia. When biologists studied the bodies, they learned that the porpoises had died of broken ribs, ruptured livers, and punctured lungs. They were also bruised all over their bodies. With more research, scientists found bite marks that pointed to attacks from bottlenose dolphins.

    The most striking thing about this is that porpoises do not attack, harm, or generally mess with dolphins - and dolphins have no reason to attack or eat porpoises. Also, the methods of these killings were slow, precise, and focused. If the dolphins had wanted to cause fatal harm, they had the ability to do so much faster. The only explanation that remained for scientists was that the dolphins had prolonged the death just for fun. 

  • When you see your house cat playing with a toy, you probably think it's insanely adorable. Well, as cute as it may be, your cat is actually showing signs of killing for sport, even by playing with a simple toy. The kicking cats do with their back feet is a move used to attack prey, and that adorable little pounce is meant to pin an animal down. When they toss a toy around? It's a method for breaking a small animal's neck.

    Every year, cats are responsible for the deaths of billions of animals, most of which are never even eaten. After all, they have no need to hunt when they have a full food bowl at home. So, why do they kill animals?

    Well, they do it because they find enjoyment in the hunt and in the kill. They like chasing things, they like having live prey, and they like hunting more than they like eating. This can be so devastating for wild bird and rodent populations that some places (such as a village in New Zealand) have pushed to ban cats as pets.

  • Foxes are known for being very clever animals, and also for being agile hunters. For the most part, foxes have to scrape and search for food, especially during cold winters. However, in Australia, the winters aren't generally cold or harsh, and foxes end up being one of the most harmful invasive species the country has. 

    On multiple occasions, foxes have shown that they are not above surplus killing. They have preyed upon numerous wallabies in a single night without eating a single one. They have attacked chicken coops and then eaten only one or two of them. In one particular incident in 1994, about 1,800 penguins had come ashore to lay their eggs on Granite Island in South Australia. Things were going fine until a fox managed to get onto the island from a causeway. Over the course of the next three days, the fox killed 74 penguins, only eating a few.

    Surplus killing is a common behavior in foxes, where they sometimes hunt much more than they can eat. While foxes often bury their extra food, researchers suggest that saving food for later isn't a fox's initial intent. When they see prey that's easy to catch, it activates their prey drive, which is why they might kill animals even if they don't need more food.

  • Leopards Regularly Kill For Fun, Sometimes With Hundreds Of Victims

    Leopards are a serious problem for farmers in South Africa, but in Cape Province, it can get particularly bad. It seems that, unlike many other animals, leopards will participate in surplus killing regularly. To make matters worse, they sometimes leave the slaughtered, uneaten animals in the field. Out of 104 recorded incidents of leopards preying upon livestock, well over half involved surplus killing and uneaten remains.

    In one incident, a leopard killed 51 sheep and lambs in a single hunting spree. These animals were not killed for food or for territorial purposes, so it stands to reason that they were slaughtered just for the thrill.

  • In 1966, a researcher by the name of Hans Kruuk went to study the Serengeti plains of Tanzania. While he was there, he witnessed a horrifying slaughter. A small group of spotted hyenas went on a killing spree of gazelles, which is something that had rarely been seen before.

    They killed a total of 82 gazelle, far more than the group could eat, and badly injured 27 more, just leaving them there to perish slowly. As Kruuk looked into the incident, he found:

    Of a sample of 59 dead ones, 13 had been partially eaten (almost only soft parts)... Tracks indicated that spotted hyenas had walked very quietly from one victim to the next at a normal walking pace... When gazelle are hunted by hyenas in the usual manner, there is a long and fast chase before the gazelle is caught, over distances of up to 5 km.

    Given this unusual behavior, it seems that the hyenas went around killing these animals for no reason other than the fact that they could. The animals were not even dragged away to be meals for later.

    As it turns out, this wasn't a one-time incident though. Hyenas regularly participate in surplus killing among packs. While they often eat the food they leave behind, they will occasionally leave injured animals to perish. In fact, they commonly hunt baby lions for fun, even though the big cats aren't normally on their menu.

  • Lions behave similarly to house cats, so it's common to see them hunt more than they need to survive. They like to chase, play, and kill animals like birds and rodents, just like a smaller cat would. Take the example of a group of lionesses one biologist witnessed in Botswana. The lionesses were feasting on an elephant carcass when one of the lions spotted a group of doves. As if bitten by the hunting bug, the lion went over and began to chase the birds, even catching one and killing it. The other lionesses followed suit, jumping and playing with the birds as they tried to fly away. They quickly got bored, but the fact remains that they were full and did not need to hunt the doves.

    While a lion's surplus killing usually doesn't include bigger targets like humans, one peculiar incident proved othewise. In 1898, the people of Tsavo, Kenya, were terrorized by a pair of young lions that began hunting a surprising number of humans. They killed at least 28 people in a 10-month period, and possibly as many as 135. It started with railway workers, and people found that the humans who were killed were not always eaten, but instead left out as though to send a grisly message. 

    But the mystery remains: Why were the lions killing people? Lions don't tend to hunt humans. One possibility is that the lions killed simply for sport. Others suggest that thinning herds in the area or territory disputes led to the lions killing, but the manners in which many lions hunt still suggests that there is some level of play in the way they kill.