These little ghost crabs that live on the beach in the Eastern Cape are super camouflaged. They are almost impossible to see on the sand unless they are moving. This species is highly adapted to survive in its environment and the process of evolution and adaption is really very simple.
If a group of crabs are living on the beach and being hunted by birds, the first crabs to be eaten are probably those that are the most easily seen by birds against the sandy background. Scientifically speaking, the common trait shared by the surviving crabs was better camouflage than the crabs being caught by the birds.
This means that the remaining group of better camouflaged crabs will breed and produce better camouflaged offspring. This is because physical traits are controlled by genes and will be passed from the parents to the offspring.
The new group of crabs will still be hunted by birds, and again, those who are the most easily spotted on the sand will get caught first. The result is a group of crabs with even better camouflage and offspring who will inherit the ‘better camouflage’ gene.
This process is called survival of the fittest or natural selection. The cycle repeats itself over many generations and the result is an entire species of very well camouflaged crabs.
The example of crab camouflage and birds is very simple; but in nature the process is much more sophisticated because lots of different characteristics are being selected for at the same time.
Other physical traits that might help crabs avoid being eaten by birds include running fast, or efficient burrowing into the sand to avoid being caught. These characteristics will also be influenced by genetics so natural selection will also apply to these. The result: a super crab highly specialised to survive in its environment by not getting eaten by birds.
