A new study has revealed that Africa's most deadly snake, the black mamba, accumulates heavy metals such as lead, arsenic, cadmium and mercury in its scales. The discovery means scientists can now monitor environmental health by taking harmless scale clippings from the venomous reptiles.
The work, which focused on snakes captured in the port city of Durban in South Africa, is the first of its kind to study heavy metal build-up in an African snake. The findings were published in the journal Environmental Pollution.
Black mambas in the city
Averaging lengths of two to three metres, the black mamba is Africa’s largest venomous snake. It is an apex predator, feeding on rodents, birds and other animals. When these prey species are exposed to pollutants, they absorb heavy metals, which are then passed on to the feasting snakes. The metals gradually accumulate in the snakes' tissues.
“Black mambas are common in the Durban area, and individuals often live in the same refuge for years,” explains Professor Graham Alexander, a herpetologist (someone who studies amphibians and reptiles) at the University of the Witwatersrand in Johannesburg. “If the body tissue of individuals contains high levels of heavy metals, it is a strong sign that the local environment is under threat.”
The research team, led by Professor Marc Humphries, wanted to use this theory to compare pollution levels in Durban. With the help of snake expert Nick Evans, from KwaZulu-Natal Amphibian and Reptile Conservation, they captured 61 snakes from homes, businesses and factories across the city.
Scale clippings were taken from the snakes, before the individuals were relocated and released into suitable habitats, such as nearby nature reserves or open land away from human activity.
The team also examined tissue from 33 snakes that had died in road accidents or through conflict with humans.
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What was discovered?
Results showed that snakes from industrial and commercial zones contained far higher levels of pollutants than those found in protected green spaces such as Durban’s Metropolitan Open Space System (D’MOSS).
“We found a clear association between land use and heavy metal exposure in black mambas. Snakes living in connected green spaces around the city generally had significantly lower heavy metal concentrations in their scales compared to those in more industrial and commercial areas,” says Humphries.
“The exciting thing is that we can get this information from a quick, harmless scale clipping. It’s safe for the snake and could be used in cities across Africa where snakes are already being relocated from homes and businesses.”
Alexander hopes people will begin to see these snakes differently. “People are understandably scared of mambas, as they are one of Africa’s most dangerous snakes, but if we treat them correctly, they can be a valuable tool to assess pollution levels,” he says.
Find out more about the study: Black mambas (Dendroaspis polylepis) as novel bioindicators of urban heavy metal pollution
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