Reptile Radar: Understanding Africa’s New Eco-Guardians In The Shadows

Revered by some, feared by many, snakes have a complicated history in Africa. their environmental impact is often overlooked, representing only a fragment of ecological studies. This seems to be changing and they are slowly creeping into the spotlight.

Across sub-Saharan Africa’s (SSA) plains, an unexpected hero slithers in the grass: the puff adder. These reptiles are responsible for some of the highest fatality rates on the continent. They’re also one of the most abundant, found throughout the continent–from Senegal to South Africa. 

Typically injecting prey with around 80-240mg of cytotoxic venom—the lethal dose for a human is 100mg—puff adders are now emerging as effective environmental stabilizers, able to control rodent populations at a remarkable rate. 

When rodents, such as mice and rats, are presented with the right conditions, these highly adaptable survivors breed at speed. A single female can produce hundreds of offspring a year. 

“Rodent blooms (increase in numbers) are often related to rainfall, and because they’ve got such short growth periods, their populations can explode in a very short period of time,” says Graham Alexander, Professor of Herpetology at the University of the Witwatersrand in Johannesburg, to FORBES AFRICA. 

Africa’s rapid urbanization, poor housing infrastructure, and inadequate waste management systems make it a highly suitable region for rodents to thrive, posing a plethora of potential concerns for human health and economic activity. 

Rats are a common headache for farmers, often found chewing through storage bags or feeding on seeds, roots, and crops, leaving entire regions vulnerable to food scarcity. 

In Western Kenya, a 2016 Gadisa et al. report revealed how ravaging rodents can be, reporting 34% loss in grain, and 20% damage in maize crops, while Ethiopia experienced between 9-48% loss in coffee, 21-60% in cotton, and 15-40% in pulses and oil seeds. 

During peak activity, nests of mice feed continuously, their high metabolism demanding several meals a day. It’s an endless cycle that makes farmlands a desirable destination. 

Their impact is similarly extreme in Africa’s urban areas, but for different reasons. A rodent’s constant need to gnaw its teeth—to avoid overgrowing, much like the reason humans cut their nails—means even wooden structures appear appetizing. 

They’ve been found nibbling on electrical cables, irrigation systems, machinery, and buildings—a multifaceted hazard for fires and costly repairs.  

Human health is also at risk–a Singla et al. report identified at least 80 zoonotic diseases in rodents, typically viruses, fungi, and bacteria. 

While rodents promote seed dispersal and soil health, they can become, when their populations soar, a menace to society, showcasing the critical role predators play. 

This is where puff adders come in–they are commonly considered, because of their ectothermic digestive physiology, to not have the capacity to consume multiple meals in quick succession, allowing pests to grow more than they can be consumed. 

However, a recent landmark study by Alexander, measuring the functional response of puff adders to high prey abundance, proves otherwise. 

Unlike rodents, puff adders—capable of growing upwards of six feet—are not in a constant pursuit for food as their cold-blooded, low metabolic physiology enables them to store energy for extended periods. 

Through feeding trials—which lasted 260 days on average—Alexander studied 18 adult puff adders born in captivity. 

“My measures looked at how puff adders’ fat reserves stunt weight loss following rodent blooms. So, it was looking into how long it would take puff adders to reach an average mass,” Alexander explains. “From this, we estimated that puff adders can fast for two years.” 

Alexander believes this to be a conservative measure, arguing that the timeframe could extend for certain puff adders. Whether more or not, the figure indicates immense dexterity. 

But, while puff adders can navigate years-long food shortages, they can also greedily consume. During Alexander’s experiment, they digested up to 10 rodents in a single session (the maximum offered) and were eating again in the next week’s session. 

“Puff adders can increase their food consumption by more than 12 times above their maintenance levels when rodent populations explode, thus far outperforming traditional mammalian predators and offering a natural solution to devastating rodent pest problems,” Dr Duncan MacFadyen, the Head of Oppenheimer Generations Research and Conservation, tells FORBES AFRICA. 

This ability to alternate between extensive fasting and buffet-style eating supports the notion that puff adders can be invaluable environmental allies.  

While their presence is met with terror, more often than not, their dietary flexibility unlocks a domino effect of potentially positive outcomes. 

Yet, they’re mostly kept away from the ecological limelight. 

Without snakes, rodent populations could potentially reach unimaginable rates, infesting Africa in arguably the same manner locusts do crops. 

Humanity’s Impact 

Africa’s demographic boom, expected to reach over 2.4 billion people in 2050, suggests a concerning future for certain species of snakes. 

Boasting the world’s fastest continental growth rate—exceeding 3% annually—Africa’s rapid urbanization is tightening the proximity between humans and reptiles. 

A Farooq et al. report, Snakes in Africa might be at an alarming extinction risk, predicts that, by 2050, approximately 71% of snake ranges of conservation concern will overlap with areas occupied by 10 or more people per square kilometer, a 22% rise from 2020. 

“Snakes with the smallest ranges are, more often than not, restricted to unique ecosystems. Mountains, for example, may have unique species, and with human populations moving upwards or through the destruction of their natural habitat, the conflicts may result in the extirpation of those species,” Harith Farooq, Natural Sciences Lecturer at Mozambique’s Lúrio University, notes to FORBES AFRICA. 

SSA’s modernization shows no signs of slowing down and second cities, designed to ease the demands in already congested capitals, are emerging. 

Further, the Organisation for Economic Co-operation and Development (OECD) predicts that urban areas will account for 80% of Africa’s growth, with around 159 cities exceeding one million residents by 2050—up from 60 today. 

“Unlike other similar small creatures like frogs and lizards, that get ignored when seen, snakes are feared, and people will go out of their way to kill a snake,” Farooq points out. 

Such treatment is illustrated in Farooq et al.’s report, Species perceived to be dangerous are more likely to have distinctive local names, which discovered over 75% of the surveyed 1,037 households in Northern Mozambique’s Cabo Delgado province to actively kill snakes. 

There is reason to be cautious. In Africa, approximately 20,000 humans die annually from snake bites, per the Farooq et al. report. The most common suspects are reportedly puff adders, Mozambique spitting cobras, black-necked spitting cobras, and black mambas. 

Despite their lethal abilities, it should be noted that snakes don’t actively ‘hunt’ humans. Deaths are often accidental, such as stepping on, cornering, or attempting to handle a snake. 

From a policy perspective, there’s opportunity to reduce the threat of death dramatically. Once bitten, an anti-venom injection is the best solution and, depending on the snake, one has a limited time to receive this lifesaving procedure. 

With the majority of deaths occurring in rural areas, there is a need for greater access to anti-venom equipment through local clinics and hospitals. Snakes such as black mambas can kill humans in minutes. 

Contrary to popular belief, for an animal so dreaded, the majority of African snakes are harmless—roughly 25% of the some 600 species found in Africa are venomous.  

Education plays a vital role in shifting perceptions, and thus, protecting snake populations. It wouldn’t be overly presumptuous to assume that if everyone realized their ecological impact, which snakes are harmful, the role of anti-venoms, and the common cause for snake bites, humans would be more prone to conservation than eradication. 

Tim Brammer, Instructor at the African Snake Bite Institute, concurs, telling FORBES AFRICA: “Through education, we can replace fear with understanding, and understanding with respect and appreciation.” 

The Bioindicator PotentialIn tropical Durban, South Africa, an apex predator has been discovered as a potential sentinel against pollution. 

An accumulation of heavy metals has been discovered in black mamba scales, begging the question: Can Africa’s most venomous, largest, and fastest snake serve as an effective bioindicator? 

Led by University of the Witwatersrand professor Marc Humphries, alongside Nick Evans, Cormac Price, and Alexander, the breakthrough study, Black mambas as novel bioindicators of urban heavy metal pollution, marks Africa’s first published paper on heavy metal contamination in snakes. 

Endemic to SSA, these ectothermic (cold-blooded) reptiles, influenced by their preference for tropical climates, are common sights across the region’s urban and rural landscapes, including Uganda, Tanzania, and parts of South Africa. 

While a black mamba’s average body length, for both males and females, is around 8.2 feet, they can reach over 14 feet, more than double that of an average adult’s height. 

Ventral scale clippings collected from 61 live black mambas—29 adult males and 32 adult females—found Arsenic and Cadmium in 49.2% of the subjects, while Mercury and Lead were present in 24.6%. Exposure to such toxic heavy metals pose serious risks, from cancer in humans to soil and water contamination. 

Each snake, caught by professional Durban-based herpetologist Evans, following calls from residents and businesses in urban and semi-urban environments, was released into natural habitats between June 2019 and May 2023. 

A sharp rise in black mamba removals, combined with Humphries’ expertise in contaminant research, prompted Evans to ask whether there was scope for a study. The professor, it seems, needed little persuading. 

“We saw this as a valuable opportunity to gather data from an apex predator that had not previously been studied from an ecotoxicological perspective. By taking small-scale clippings, we were able to obtain tissue samples for chemical analysis using an efficient, non-invasive method that caused no harm to the snake,” Humphries explains to FORBES AFRICA. 

Using animals to identify environmental conditions isn’t a scientific first; researchers have found Mercury in tuna and seals, as well as Lead in birds and frogs. However, unlike these free roamers, black mambas are notoriously territorial, insinuating the potential for area-specific data. 

“Black mambas tend to stay in a fairly small area,  

so you can detect spatial differences in the heavy metal concentrations, more specifically, in certain environments,” Alexander explains. 

Humphries adds: “We found that scale clippings taken from snakes inhabiting industrial and commercial parts of the city were exposed to significantly higher heavy metal loads than those from green spaces. This showed that black mambas could serve as valuable indicators of environmental contamination and aid in identifying urban pollution hotspots.” 

Because heavy metals are predominantly transferred through the food chain, their ability to offer a localized lens is amplified by their diet. 

“Black mambas are particular snakes in that they select only warm-blooded prey. So, if you’re thinking about rodents being their most common prey item, they also don’t move that much. That means they’re picking up pollutants, such heavy metals, in similar areas, but because black mambas are apex predators, they’re concentrating it,” says Alexander. 

Africa’s rapid urbanization increases the likelihood of rising pollution levels, already unbearable in several major cities, including Nigeria’s Kano and Uganda’s Kampala, for example. Bioindicators are imperative to informed solutions, and it seems black mambas absorb telling data. 

“Reptiles don’t feature in conservation management plans very much at all…We must consider them more and include them in conservation,” Alexander adds. 

Found in nearly every habitat, snakes rank among the most adaptable predators in the world, their frames ranging from a few grams to tens of kilograms. 

“The most remarkable element about snakes is this incredible radiation of more than 4,000 species globally, all of which are predators,” Bryan Maritz, Reptile Ecologist at the University of the Western Cape, notes to FORBES AFRICA. 

“They have fascinating adaptive physiology that means they eat everything from ant eggs to antelope, and sometimes, people. Then you have this multiple evolution, which has resulted in complicated chemical weapons that they utilize.” 

Humphries reminds us that perceptions of this reptile often overshadow their positive ecological roles. 

He adds: “To some extent, I think this perception has even influenced science, where research and conservation efforts have tended to focus on species that are perceived to be more charismatic. It is often difficult to attract funding for research involving snakes as they are typically not regarded as ‘flagship’ conservation species in the same way as pandas, rhinos, and whales are.” 

Maritz accepts this narrative but also believes their enigmatic nature to be an obstacle, saying, “The reason why snakes are underrepresented in studies is two-fold; one being that most humans don’t like them, and secondly, they’re exceptionally difficult to study. The time it takes to identify something as simple as population sizes is staggering.” 

While their diet makes them optimal environmental guardians, they are also a vital food source for various animals, including “birds of prey, mongooses, cats, and even other snakes”, Brammer adds.  

If snake populations wither, ecosystems will be impacted. 

As Africa evolves, snakes will become increasingly exposed to human threats and vice versa. It’s a growing convergence–between man and predator–that could signify a defining moment for the continent’s environment.