The contraceptive pill revolutionized human society in the 1960s, ushering in the sexual revolution. Now, scientists are aiming to bring similar transformative effects to wildlife control. Trials are underway in the United Kingdom and other European countries to administer contraceptives to animals such as pigeons, squirrels, and wild boar. Deer and invasive parakeets are also being considered for this innovative approach.
Faced with the extensive damage caused by pest species, researchers are utilizing bait boxes and feeders filled with contraceptive-laced food. This method is increasingly viewed as more effective and humane compared to traditional population control methods like poisoning, shooting, or trapping.
Dr. Giovanna Massei of York University emphasized the need for “creative solutions” due to the growing economic and environmental impacts of wildlife. Traditional methods like culling, she noted, are environmentally harmful, ineffective, inhumane, and face growing public opposition.
Grey Squirrels: A UK Problem
Grey squirrels are particularly troublesome in the United Kingdom. Introduced from the United States in the 1870s to enhance the aesthetic of stately homes, their population has since exploded to about three million. This has led to the decline of native red squirrels, which now number only around 160,000. Grey squirrels cause significant damage to woodlands by stripping bark to access the nutritious sap beneath, costing England and Wales an estimated £37 million annually, according to a National Forestry Society survey. They pose a greater threat to broadleaf trees, such as oak, than deer or disease.
To address this, trials are being conducted using oral contraceptives concealed in hazelnut spread, which grey squirrels favor over nuts. Feeders designed to open only for the heavier grey squirrels ensure that red squirrels are not affected. Remote cameras monitor the feeders, with studies showing that over 90% of the grey squirrel population visits these feeders. The UK Squirrel Accord, founded with the support of then-Prince Charles and comprising 39 organizations, endorses this method. Jason Gilchrist, an ecologist from Edinburgh Napier University, supports the use of contraception, calling it “better than the alternative: a shotgun.”
Pigeons: The “Flying Rats”
Former London Mayor Ken Livingstone famously called pigeons “flying rats” and banned the sale of pigeon feed in Trafalgar Square to reduce their numbers. Pigeons pose various problems, from spreading diseases like salmonella and tuberculosis to causing accidents with their droppings. They also damage buildings with their nests and faeces, create hazards for air travel, and attract other pests.
Contraceptive-laced corn grains have shown promising results in reducing pigeon populations. Dr. Marco Pellizzari, a veterinarian, noted the pigeons’ preference for these grains. In Ixelles, Belgium, the pigeon population was halved between November 2022 and August 2023. Countries like the Netherlands, Switzerland, and Spain have long used this method to control pigeon numbers, finding it more effective than culling, which often leads to increased breeding.
Rising Numbers of Wild Boar
Wild boar populations in Europe have surged due to milder winters, reforestation, and increased crop availability. In Italy, their numbers rose from 500,000 in 2010 to a million by 2020. The UK has also seen a resurgence of wild boar, with around 5,000 now roaming the country due to accidental and deliberate releases.
Wild boars are considered pests by many, attacking dogs, spreading diseases like African swine fever, disturbing crops, and causing traffic accidents. In 2022, the National Farmers Union Scotland called for government action to control or eliminate wild boar populations following a series of lethal attacks on livestock.
Contraceptives have been tested on wild boar using a boar-operated feeder system that only they can access. Dr. Massei highlighted the effectiveness of this method in ensuring only wild boars consume the contraceptives.
Challenges and Considerations
While fertility control offers a humane alternative to lethal methods, it presents challenges. Contraceptives in the environment can feminize male fish, and the effects on predators consuming treated animals are unknown. Ethical concerns about the psychological and physiological impacts on animals also need to be addressed. Prof. Steve Belmain from Greenwich University emphasized the importance of understanding these factors as part of the regulatory process.
As traditional methods of wildlife control face increasing scrutiny, contraceptive solutions offer a promising, humane alternative, however, careful consideration of environmental and ethical implications is crucial for their successful implementation.
