How the Puff Adder Protects African Fields from Rodents

When people think of Africa’s deadliest animals, farming is unlikely to be the first thing that comes to mind. Yet new research from South Africa suggests that the puff adder, one of the continent’s most dangerous snakes, has a surprisingly important part to play in reducing crop losses and hunger. Its contribution does not take place in laboratories, but directly in the fields of smallholder farming families.

The deadly snake that protects fields

The puff adder (scientific name Bitis arietans) inhabits savannahs and grasslands south of the Sahara. Averaging around one metre in length, it has a stocky build and exceptionally effective camouflage. Across Africa, many people see it chiefly as a threat: according to the World Health Organization, its bites kill tens of thousands of people every year.

“The puff adder is among the snakes responsible for the highest number of deaths worldwide – yet it may also be a quiet ally of agriculture.”

A research team at the University of the Witwatersrand in Johannesburg is now challenging this usual perception. The scientists show that the snake is a key ally against damaging rodents, precisely in places where crop cultivation is vital to the survival of entire regions. In many African countries, 60 to 70 percent of the working population relies on agriculture either directly or indirectly.

Why rodents become a nightmare for farmers

On African farmland, droughts and storms are not the only threats. Rodents such as rats and mice can severely damage otherwise productive harvests within just a few weeks. They consume:

• seeds immediately after sowing;
• young shoots and roots;
• mature grains and tubers shortly before harvest.

There is also a second problem that is often overlooked: rodents contaminate stored crops, spread diseases and can infect livestock. For smallholder farmers with very limited reserves, these losses can mean that their families do not have enough food for months in the worst-case scenario.

The puff adder as a highly effective rodent hunter

This is where the latest study begins. The researchers sought to establish how much prey a puff adder can genuinely capture and what effect this has on rodent populations.

To do so, they used a new measurement approach called “factorial feeding capacity”. Put simply, the method calculates how much an animal can increase its food intake when prey is especially abundant – for instance, in years when rodent numbers rise sharply.

“The study shows that a single puff adder can capture up to ten rodents during one hunting period and increase its prey intake twelvefold.”

The researchers’ calculations indicate that a puff adder can take considerably more prey than it actually needs to meet its own energy requirements. When rat populations boom, it dramatically increases its hunting performance. In this way, the snakes regulate rodent populations on a scale that can make a noticeable difference for farmers.

Advantages over other predators

Puff adders are, of course, not the only rodent hunters in Africa. Various predatory mammals also help to keep these animals under control, including:

• jackals and foxes;
• several mongoose species;
• wild cats and feral domestic cats;