One of world’s deadliest snakes help scientists find pollution

By Stephen Beech

One of the world's deadliest snakes can help sniff out pollution, according to new research.

Black Mambas could prove "key players" in tracking pollution - while at the same time keeping ecosystems healthy, say scientists.

Thy have shown that heavy metals - such as lead, arsenic, cadmium and mercury - accumulate in the scales of the world's second most venomous snake.

The study, conducted on Black Mambas snakes captured alive in Durban, South Africa, is the first of its kind to examine heavy metal accumulation in an African snake species.

The findings, published in the journal Environmental Pollution, mean that researchers can use scale clippings from the snakes to accurately measure environmental pollution levels, without harming the serpents.

Professor Graham Alexander, a herpetologist at the University of the Witwatersrand in South Africa, said: “Black Mambas are common in the Durban area, and individuals often live in the same refuge for years.

“If the body tissue of individuals contain high levels of heavy metals, it is a strong sign that the local environment is under threat.”

He explained that snakes such as Black Mambas are apex predators, which means they feed on various other animals such as birds and rodents.

The pollutants, absorbed from the food that birds and rodents eat, eventually accumulate in the body tissue of the snakes.

The research team analysed scale clippings from live snakes that were removed from domestic, industrial and commercial properties, and tissue samples from mambas that had died in road accidents or in conflicts with humans.

The snakes found in industrial and commercial areas had far higher metal levels than those from nature reserves and green spaces.

The researchers say their findings highlight the value of having connected green spaces around our cities, as they help protect wildlife from harmful pollution linked to urban development.

Study leader Professor Marc Humphries, an environmental chemist at the University of the Witwatersrand, said: “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.

“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.”

A second study, published in the Zoological Journal of the Linnean Society and also co-authored by Alexander, shows that Black Mambas also shape their environment in ways that benefit other species.

He said Mambas often use the same refuge sites - such as termite mounds, hollow logs, and abandoned buildings for years.

Alexander said the species serves a "valuable" role in the environment by controlling rodent populations, which may help protect crops and reduce the spread of rodent-borne diseases.

Snake expert Nick Evans, who collected a lot of the specimens for the study, says Black Mamba numbers appear to have been increasing in the Durban area in recent years.

Evans, of KwaZulu-Natal Amphibian and Reptile Conservation, said: “Humans often make their properties appealing to mambas by dumping rubbish over their fence, in their garden, having messy sheds or garages, creating rat breeding grounds.

“Durban also has high numbers of feral cats, and mambas feed on their kittens.

"So there is suitable habitat and an abundance of food.”

But he says unprovoked bites are extremely rare, with around three to five reported per year.

Evans added: “Almost all patients survive, unless they do not go to the hospital.

"Some of the bites are dry bites, warning bites where no venom is injected.”

The research team believes that recognising the value of Black Mambas could help shift public attitudes from fear to appreciation.

Alexander said: “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.

“Snakes in general can play a valuable role as biomarkers for environmental health, and should preferably be left to live in peace in their natural environments.”