Why Do Kangaroos Hop?

To find out why kangaroos hop, you would need to ask a kangaroo. Their answer (if you could understand roo) might be “because my mum always did.” Our friends at Echidna Walkabout Tours are full of knowledge about these incredible marsupials, and with their help, we’ve discovered some of the advantages of hopping.

1. Hopping is energy efficient. 

Hopping uses less energy than four-legged running at the same speed, which is probably the most important single factor. 

In dry, unpredictable environments, it is critical to be efficient with resources. Kangaroos sometimes must travel long distances in oppressive heat, with very little water to drink and poor food in their bellies. Most mammals would not survive these journeys. 

Kangaroos eat grass. Australian grasses can be low in digestibility and sparsely cover the ground. The grass dries off quickly during the summer, with only the first few millimetres of grass being green—the rest is dry and golden. So, for the whole summer (and sometimes longer in drought), adult kangaroos need to move around, socialize, breed, and feed their babies on a diet that wouldn’t feed a lamb. Food is energy. Hopping doesn’t use much energy compared to other forms of locomotion, allowing kangaroos to survive on their poor diet. 

Like most grazers, kangaroos need to drink water daily. But in Australia, surface water can be hard to find and unreliable. When the surface water dries up, they must hop to better watering sites. Exertion depletes the body of water, so an efficient means of movement, like hopping, saves precious water better than other forms of movement. 

2. Hopping is quiet. 

While not completely silent, kangaroos move exceptionally quietly compared to other animals. It might be because they are in contact with the ground so little or because their feet are soft (like a dog's or cat’s). It could be because they have only two feet to worry about that they can place carefully. Whatever the reason, a large mob of kangaroos can move very quickly without much sound at all, even through a Bush full of sticks and dry leaves. 

The stride length of a kangaroo hopping at speed is long: 20 ft (6 m) at 31 m/hr (50 km/hr. That means they are only touching the ground two times a second. In contrast, a galloping horse touches the ground four times in each stride and always has a foot in contact with the ground, creating a constant drumming sound. At the same speed, a horse touches the ground eight times a second. Why is this useful? Kangaroos’ natural predator is humans. Being able to escape quietly could mean the difference between life and death. 

3. Hopping is flexible and allows for sudden changes of direction. 

Kangaroos have an amazing ability to turn quickly! They can achieve a 180-degree turn in a single hop. Hopping as a means of locomotion probably gives kangaroos the ability to turn “on a pinhead” which would be very useful for escaping predators. There is no knowledge of any terrestrial mammal that can turn as sharply as a macropod. 

Most land-based mammals have a long body, with their weight centred between the front and back legs. The length of the body limits the turning circle. In a way, they must wait for their back legs to catch up. Also, the speed limits the turn – the faster they go, the harder it is for them to turn, and the more stress it puts on their legs, ankles, and feet. Even at speed, a kangaroo could execute sharp turns without causing damage to their legs, as most of the turn occurs while airborne. Kangaroos live all over Australia, in grasslands, and mountains—hopping allows them to move quickly over any surface, no matter how rough, steep, or uneven. 

4. Kangaroos have evolved from possum-like ancestors who bounded along tree branches and the ground. Hopping could be just an adjustment on four-footed bounding. 

Small macropods, such as the musky rat-kangaroo, bound along the ground, utilizing their front feet. Brushtail Possums can bound or run and sometimes sit up on their back legs like a small kangaroo. So, it’s not hard to imagine the possum-like ancestors of kangaroos—bounding on the ground, running along branches. Over time, they got bigger and moved into the grasslands where there were no branches to clamber along and their ability to bound got them out of danger quickly. Over time, their ability to run ceased altogether. It is interesting to note that kangaroos can use their legs independently in an alternating fashion. But only when they swim!