In the midst of much-anticipated summer rains, Fourways residents may be lucky enough to glimpse the giant bullfrog (pyxicephalus adspersus) emerging to breed after long periods lying dormant underground. But these extraordinary amphibians, which can measure 20cm and live for up to 45 years, are under increasing stress from human population growth in Gauteng.
Due to the pressure of urbanisation on giant bullfrog populations in the province, the species was previously classified as ‘near threatened’ regionally on the IUCN Red List of Threatened Species. Site developers were required to take cognisance of frog populations, and a number of protected habitats were established, including reserves at Leeuwkop Prison and a Total Petroport on the N14.
However, with giant bullfrogs occurring widely throughout Africa, the frog’s perilous status in Gauteng is unlikely to threaten its survival as a species, and more recent assessments list the species as being of ‘least concern’.
According to Prof. Graham Alexander, herpetologist at the University of the Witwatersrand, while the species is secure, its Gauteng population has plummeted. Urbanisation continues apace in South Africa’s fastest-growing province, devouring the frog’s habitat and rendering its survival increasingly unlikely.
While local populations linger, there is a good chance of sighting the bullfrog’s impressive bulk around suitable breeding grounds in reserves such as Glen Austin, or open land north of Diepsloot – although in the face of unstoppable informal development, the Diepsloot population is doomed, said Alexander.
Bullfrogs are often glimpsed crossing roads, where lack of agility makes them vulnerable, particularly to the minority of drivers who, according to the Endangered Wildlife Trust, deliberately swerve to crush wildlife. Residents who wish to preserve the species are advised to drive cautiously.
In the bigger picture, meanwhile, Alexander said the cavalier treatment of the bullfrog on development sites is an indictment of the human attitude towards indigenous environments. He argues that the frog should be considered a flagship species for the wetlands it inhabits alongside more vulnerable fauna such as the grass owl, and not seen simply in the context of possible extinction.
“We should be looking at the intrinsic conservation value of the land…The underlying problem is human population growth,” he stressed.
