Okavango Delta: Frogs in the inland delta
Botswana's Okavango Delta is a true paradise for diverse amphibian and reptile species. One of the typical and particularly more eye-catching amphibian species is the African bullfrog. In our blog you can learn more.
The Okavango Delta in the north-west of Botswana is one of the largest natural wetlands in Africa. As an inland delta, it is not located near the coast of an ocean like other river deltas, but fans out in the landscape before its waters seep away in the so-called Kalahari Basin. The Okavango Delta is home to countless animal and plant species, some of which are extremely rare.
Since 2014 it has therefore been listed on UNESCO's World Heritage List. Particularly amphibians and reptiles can be observed and studied in their natural habitat. The African bullfrog (Pyxicephalus adspersus) is one of the typical and most conspicuous amphibian species. With a maximum head-torso-length of 24,5 cm and a weight of up to 1,4 kg it is one of the largest representatives within the order of the frog-lurge. It is characterized by a compact body shape, strong hind legs as well as distinct skin folds on the upper side of the body.
Like many frog species, the bullfrog also has a broad spectrum of vocal communication. So a spring walk through the Okavango Delta can quickly turn into a concert where all sorts of species are part of a large frog orchestra.
For the production of the various sounds air is usually moved back and forth between the lung and the so-called throat sac at the bottom side of the lower jaw. The sound is produced by the vibration of the vocal chords in the larynx and then amplified in the throat sac, which functions as a resonating body.
This kind of “singing” plays an important role between males – on the one hand when it comes to defending opposite rivals, on the other hand when it comes to marking their territory. It is also used to impress females during the mating season in spring; the louder and stronger the song, the more attractive it is to the female.
When listening to this concert you might get the impression that the frogs sing simply together uncoordinatedly. But – in order to ensure that the different songs do not interfere, there is a sophisticated timeshare calling system: males sitting close to each other take turns singing or vary their pitch, making it easier for the courted female to keep the individual songs apart.
By the way: The females also produce sounds to signal to the males that the spawning was successful.