An animal so often feared and such a master of concealment, and so incredibly adapted to its environment in so many ways…
Leaving for game drive invariably takes you past one of the water holes close to camp, often even more than one. It is here where I frequently see something that I will often stop and show to guests; the tracks of where crocodiles have moved at night and left their own waterhole and walked towards the river or vice versa.
It’s almost impossible to miss the tracks in the road as you can see where these prehistoric creatures’ unmistakable feet have landed while dragging their big tail through the substrate.
These scrapes in the sand often spark a lot of questions. When do you think it moved through? and how do they move from one water source to another? are two common ones. The majority of the time we only see these prehistoric beings as they lay motionless basking of the banks of the river or waterholes, or we see just the top of their head as they are slowly gliding effortlessly through the water.
When we see them basking of the banks they are obtaining heat from the sun which is then converted into energy, unlike humans and other mammals who need food to convert energy, crocodiles are poikilotherms and derive their body temperature from the ambient temperature of their surroundings. But that’s a whole story in its own.
What fascinates me the most is how these reptiles are able to travel large distances in search of water.
I have personally seen crocodile tracks and the distinctive tail mark a few kilometres (!) away from any water point.
Which leads to me my next question: how do they walk and what allows them to walk such a great distance?
I’m sure a lot of you reading this have seen a crocodile or alligator dash into the water from the banks of a water source, whether it be here at Londolozi or on TV. There are two different locomotive methods they use; the first is called a “belly crawl”, which is what we see most often and is where most of their body is touching the substrate beneath them as they move into the water. This can be done at a rather slow pace and they pretty much push their body on the sand or grass and slide into the water, or if threatened at some serious speed as seen in the picture below.
The second; the “high walk”. It is so called because of how the crocodile is able to lift its entire body trunk on those short legs and at least the anterior half of its tail clear of the ground when it walks. It is usually a relatively slow gait when they are in the “high walk” posture; they often don’t exceed 2 to 3 kph. However, the crocodile can speed the gait up when threatened and reach speeds in excess of 5kph. When they do this they will exert a lot more energy.
The high walk is a product of a unique body adaption in the form of bony ligaments and scales. When a crocodile stands up there are interlocking bony plates on the dorsal scales and legs formed by complex ligaments which lock into place, allowing the crocodile to raise its entire body. This arrangement creates a semirigid “I-beam” structure which encloses the back muscles. This then becomes rigid but is flexible enough to allow an efficient transfer of energy from the tail of the crocodile to the erect body posture while walking.
Crocodiles have literally had millions of years to evolve to these types of locomotion.
I wonder how long ago this evolution specifically began or was it something they could do from the beginning?
Crocodiles to me are one of the most advanced creatures we are able to view when out on safari. They have stood the test of time, essentially being one of the most prehistoric creature which roams our planet today…