This "short-legged" creature weighs only 7 kilograms, but can hunt a 300-kilogram South American tapir?

There is a saying in Buddhism that goes "Even when a lion fights a rabbit, it uses all its strength", but it is actually wrong - because prey as small as rabbits cannot meet the lion's energy needs, lions almost never eat rabbits.

There is a basic principle in the ecology of terrestrial carnivores: large animals eat large prey, and small animals eat small prey . This is easy to understand, as small predators can survive on small prey, while large predators will not be able to make ends meet if they only eat small prey.

The dividing line between "big" and "small" is a weight of more than 20 kilograms. A study published in Nature in 1999 compared the diets of more than 150 terrestrial carnivores. The results showed that 52% of carnivores weighing more than 21.5 kilograms preyed on vertebrates, while only about 25% of carnivores weighing less than 21.5 kilograms preyed on vertebrates, 45% were omnivores, 10% ate invertebrates, and 19% ate both insects and small vertebrates.

So, are there any examples of breaking the rules?

It is easy to find examples of large carnivores "giving up" and giving up challenging large prey, such as our old friend the giant panda, which simply put down its butcher knife and became a vegetarian. But on the other hand, it is more surprising to see examples of small predators changing their jobs to fight big prey with small ones . There is such an alternative, it is the bush dog ( Speothos venaticus ) living in Central and South America.

议[sǒu]dog｜Karelj / Wikimedia Commons

The way for the “little soldier” to turn the tables

The bush dog has a short and stocky body, a round face and a short mouth, and looks like a combination of a jackal and a teddy bear. It belongs to the Cerdocyonina subtribe, a type of canid found in Central and South America. Most of them are fox-like and omnivorous - in addition to vertebrates, they also eat crabs, insects and wild fruits.

The bush dog is the only one that is mainly carnivorous , with more than 70% of its food being vertebrates. The only other canids that are carnivorous to this extent are wolves, jackals, and African wild dogs, all of which are famous hunters and weigh more than 20 kilograms. How big is a bush dog? The largest is 7 kilograms.

Of course, just eating meat doesn't show how ferocious it is, eating insects is also meat. The surprising thing about the bush dog is that most of its diet is animals that are the same size as itself, or even larger than itself , such as guinea pigs, capybaras, armadillos, and even occasionally attacking ring-necked peccaries ( Tayassu tajacu ) and South American tapirs.

An adult South American tapir ( Tapirus terrestris ) weighs 150 to 320 kg, much more than a bush dog. Charles J. Sharp / Wikimedia Commons

A report published in Mammalia in 2002 recorded an astonishing observation: Six bush dogs chased a South American tapir for three hours , biting the tapir's legs so badly that it eventually collapsed. The South American tapir is the largest terrestrial mammal in South America, weighing more than 20 times that of a bush dog. This is the largest "cross-weight" kill among carnivores. Although lions and tigers occasionally hunt rhinos and baby elephants, they have never fought such an extreme game.

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The most notable feature of a carnivore that hunts large prey is its strong bite force, which can not only deliver a fatal blow but also dismember large prey. Compared with its small body, the bite force of the bush dog is extraordinary - its bite force is about half that of a wolf, although it is only one-seventh the size of a wolf .

Bushdog teeth | exmoorzoo.co.uk

The bite force of a carnivore (relative to its body size) is measured by its bite force quotient (BFQ), which is directly proportional to the bite force and inversely proportional to body weight. Generally, animals that prey on large prey have a BFQ between 100 and 130, while the Bushdog has a BFQ of 160! It is unrivaled in the Carnivora order, and only carnivorous marsupials can surpass it.

To win a game against an opponent who is not in a favorable situation, in addition to absolute strength, behavioral adaptation is also important. Experiments have shown that when biting an object and pulling it back, the skulls of both bush dogs and wolves have shown considerable stress resistance .

Unlike cats, canines cannot hold prey with their front limbs. When hunting and dismembering prey, they often use the method of "biting it with one mouth and dragging it backwards" to drag the prey down or tear it apart. If you have ever seen a group of dogs playing, you will know that they like to "tug of war" by biting one end of the toy. Bush dogs are also familiar with this. Although we know little about the ecology of wild bush dogs, there are photos of a bush dog biting a rabbit and guinea pig, and the two of them pulled and tugged for 200 meters.

Video shows a group of bush dogs working together to hunt a guinea pig (Agouti paca) and pull it from the water to shore｜reddit: @a_synapside02

Teeth that are not involved in hunting can also reflect the special characteristics of carnivores. The bush dog has one molar in the upper jaw and two molars in the lower jaw, while the red fox and wolf both have two molars in the upper jaw and three molars in the lower jaw - the reduction in the number of molars is a characteristic of adaptation to carnivory. In addition, the carnassial teeth (molars and premolars specialized for carnivory) of the bush dog have a stronger bite force, almost twice that of canine teeth , which can help it tear tough large prey.

A study showed that nine-banded armadillos make up 94.1% of the food consumed by bush dogs in the Pantanal wetlands. The armor on the front and back of an armadillo's body is strong enough to withstand a pressure of 1,500 megapascals, which is too much for a dog without good teeth.

This is a nine-banded armadillo (Dasypus novemcinctus) | gailhampshire / Wikimedia Commons

A good hand is no match for two fists. The team fighting ability of the Canidae family is not inferior to that of the bush dog. Bush dogs are social animals . A group can be up to 12, working together to hunt and dismember prey. Someone observed six bush dogs biting a duck in the zoo and working together to tear it apart. The family structure of bush dogs is very similar to that of wolves. The highest status is a "couple". The grown-up children will stay with their parents to help hunt and take care of their younger brothers and sisters.

A group of bush dogs in the zoo are working together to finish a large piece of meat｜mickeysutube

Make good use of the terrain, don’t worry about your short legs

Is the bush dog a smaller wolf? Actually, that's not the case. You've already seen the biggest difference between it and the wolf - its short legs. The bush dog can overcome the disadvantage of its small size in fighting, but it cannot overcome the disadvantage of its short legs in chasing prey . Wolves, jackals and African wild dogs all rely on speed and endurance to chase prey over long distances. If you can't outrun them, no matter how good you are, it's useless.

This is what makes the bush dog special. It does not rely on long-distance pursuit, nor does it rely on ambushes like cats. Instead, it chooses a unique path: water fights . Bush dogs often live near water and are good swimmers, with webbed toes. In the zoo, bush dogs not only dive, but also play with toys in the pool. Animals that are good at running will greatly reduce their speed when they go into the water; bush dogs can even achieve the effect of "catching turtles in a jar" by chasing prey near the water. By the way, jackals also use the method of driving prey into the water to restrict its movement.

Bush dogs live near water｜mikepeel.net

According to a document from 1940, an aboriginal told researchers that when the bush dogs hunted the agouti, they would split into two groups, one to drive it into the water from land, and the other to ambush in the water to "close the net" . If this record is true, "fighting in groups" and good water skills can achieve the effect of 1+1>2.

Another specialty of the short legs is digging holes . Bush dogs like to live in holes dug by armadillos. Interestingly, the Maste indigenous people of northeastern Peru believe that bush dogs will dig into the holes of the giant long-nosed armadillo ( Dasypus kappleri ) and drag it out. Neither wolves, jackals, nor African wild dogs have this ability, but we can find a similar one in domesticated dogs - dachshunds. Dachshunds were originally used to hunt badgers, and their super short legs are precisely for digging into badger holes. So... at least from a physical point of view, it is not impossible for the short legs to dig holes to hunt.

Having explored the mystery of the bush dog to this point, I am somewhat disappointed. Because our understanding of these small carnivores is often very limited, and we have to rely on anecdotes and skeleton measurements provided by locals, these "dead" knowledge, to imagine a "living" full picture . The bush dog reminds me of the yellow-throated marten, which also has the ability to hunt large prey, lives in groups, and is smaller than the bush dog. What secrets does it hide?

Yellow-throated marten (Martes flavigula) | Rushenb / Wikimedia Commons

Understanding the ecology of a species also directly affects its protection. For example, the range of a bush dog's habitat is much larger than that of canines of the same size. A study of a group of bush dogs in Brazil found that their habitat area reached 140 square kilometers. The habitat required by carnivores is often larger than that of herbivores and omnivores . A study by Professor Li Sheng's team at Peking University found that the giant panda reserve has limited shelter effect on carnivores (such as jackals) in the same area, because giant pandas eat bamboo and only need a very small habitat. Such a small area cannot support a population of carnivores. Therefore, if we don't know what this animal eats, we can't adopt effective strategies to protect it.

In short, we know too little about the vast majority of living beings, and there are so many unknowns. The mystery of the bush dog is just a small example.

Bush dogs and pups｜Chester Zoo

References

[1] Beisiegel BM, Ades C. The behavior of the bush dog (Speothos venaticus Lund, 1842) in the field: a review[J]. Revista de Etologia, 2002, 4(1): 17-23.

[2] Carbone C, Mace GM, Roberts SC, et al. Energetic constraints on the diet of terrestrial carnivores[J]. Nature, 1999, 402(6759): 286-288.

[3] de Souza Lima E, DeMatteo KE, Jorge RSP, et al. First telemetry study of bush dogs: home range, activity and habitat selection[J]. Wildlife Research, 2012, 39(6): 512-519.

[4] Ruiz JV, Ferreira GS, Lautenschlager S, et al. Different, but the same: Inferring the hunting behavior of the hypercarnivorous bush dog (Speothos venaticus) through finite element analysis[J]. Journal of Anatomy, 2023, 242(4): 553-567.

Author: Red Queen

Editor: Mai Mai

Title image source: mikepeel.net

This article comes from GuokrNature (ID: GuokrNature)

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