I know we say it a lot but our summer season is truly wonderful. The scenery and beauty is stunning. Driving along during the game drive there is new life everywhere, with wildebeest calves, impala lambs and the occasional warthog piglet. Our summers mean that there is a lot of water around with it being our rainy season. Often we will see small tufts of white foam dangling over the water. This will often attract guests attention, and also happens to be something that I find particularly fascinating. So I thought I would dive a bit deeper into how they come about.
They are in fact frog nests, made by a very aptly named frog known as the Foam Nest Frog. There are a handful of species of this frog that are found in the tropics of Africa, and the one we see here at Londolozi is called Southern Foam Nest Frog. It is a grey-looking frog, sometimes even whitish in colour. They can often be seen in cooler places in and around buildings and can be seen at some of the Londolozi camps if you look carefully enough.
How does the foam nest come about?
Between October and February, which is the breeding season for this frog, males will select calling sites in trees that overhang the water, often after recent rains. They will then call to advertise themselves. If the female is interested and attracted to the calling male, the female will approach the call site, and one of the males will clasp on to her, and the mating process begins.
A secretion is then released by the female when the male is in position. The other males then begin to compete in order to get into the best position in order to try to fertilise the eggs when the females release them. The commotion centred around this competition then begins to churn the secretion into the foam through the kicking of the frogs’ legs. This is then followed by her depositing up 1200 eggs as they churn the foam, the male, that is still clasping onto the female, will then fertilize the eggs as she begins to lay them.
This process usually happens at night, the female will need to take a break to rehydrate herself, she will do this by descending the tree and making her way to the water below. On her return, she will most likely end up mating with a different male. The following night she will return to the nest site to add more foam.
The outer layer of the nest will harden to form a crust which will act as an insulator and protect the eggs as they grow and develop into tadpoles. After four to six days the tadpoles begin to wriggle down to the bottom of the foam where they will eventually drop into the water and continue to develop into a frog.
By being protected in the foam nest, it is not worth a predators time and energy to search through the foam for each individual egg. The foam is semi-foul tasting and not attractive to eat. By the time the tadpoles wriggle down and drop into the water, they are at a much later stage in their development and their chances of survival are much greater when compared to other frogs that lay their eggs directly into the water and risk the eggs being eaten by any predators.
So next time you are here at Londolozi during summer and you see these nests, you will know a little more about this fascinating process of the start of new life.