Coast KZN

14 May 2023

Freshwater crabs can stay out of water for extended periods of time

(South Coast Sun) Picture: The freshwater crab was released near a water source.

Although many people are familiar with the local snake catcher on The Bluff, Warren Dick, not many know that he responds to distress calls for other animals too.

“The other day I received a call from a very stressed resident on The Bluff whose cats found and were playing with a crab near her back door. It turned out to be a freshwater crab, Potamonautes sidneyi. I brought it home to do a quick photo shoot for research purposes and for this article,” said Warren Dick.

Freshwater crabs are found in most fresh water streams, rivers and dams throughout KwaZulu-Natal and in most other provinces in South Africa, even in Mozambique. These crabs dig burrows into the muddy soil of riverbanks where they live, coming out at night or on rainy days to feed. Crabs play a very important role in the food chain; one could say that they are the rivers clean up crew, feeding on dead and decaying plant and animal matter.

“Detritivore is a word I’ve learned writing this article and it applies to crabs, earthworms, flies, cockroaches and any other animal that derives its nutrients by feeding on decaying animal and plant matter. The crabs poop then becomes a good food source for smaller filter feeders within the water system,” said Warren.

Crabs are a vital food source for many other creatures such as otters, nile monitors and herons.

According to Warren, freshwater crabs mate outside of the water and the mother crab keeps the eggs under her broad tail until they have hatched and formed into small crabs. The babies are then released into shallow waters where they fend for themselves. As the crabs get older they spend longer times away from the water and can even migrate from one water source to another during periods of rain. This is thanks to a crabs specialised lungs which enable them to keep water on them for breathing, kind of like humans holding our breath under water, only crabs can sometimes go days without having to take on more water to breathe.

“The particular crab that I rescued was about one kilometre from the nearest stream, but I released it close to a stream,” Warren added.