Research Claims Oral Contraceptives Are an Effective Method to Reduce Gray Squirrel Population

The UK has been having difficulties controlling the damages gray squirrels have brought — especially in the countryside. Gray squirrels are most harmful to red squirrels, and it has been determined that gray squirrels out-compete red squirrels. Based on reports, gray squirrels are stronger in numbers, with a population of 2.5 million — whereas there are only 140,000 reds in Britain. The gray ones overpower red squirrels in terms of food and space. Also, the troubling rodents steal the seeds that red squirrels have been saving for the winter.

Photo: Pexels/Altaf Shah

Aside from harming the reds’ basic needs, gray squirrels are carriers of squirrel pox. The disease does not affect them, but it heavily impacts red squirrels — which mostly leads to fatality after fifteen days. Squirrel pox can cause skin ulcers, lesions, scabs, and swelling in body parts such as the mouth, feet, and genitalia. Moreover, it causes discharge near the eyes. Up to this day, there is still not enough information about why squirrel pox exists.

Another reason Britain seeks a solution for controlling the rodent population is woodland damage. Gray squirrels damage trees when they strip the bark from the trunks and branches to feed on sap. Unfortunately, being completely bark-stripped can lead to a tree’s death — especially for younger trees. For this reason, hardwood materials and habitat for woodland creatures are severely affected by a gray squirrel’s lifestyle. With the ongoing threats, scientists had to find a solution that would control the population — without harming gray squirrels.

Photo: Pexels/Sebastian Angarita

Recently, a study has achieved remarkable progress, as revealed by the UK Squirrel Accord. Scientists have been trying oral contraceptives to stop grey squirrels from breeding. After some attempts, they finally tested out a product that is ensured to be safe and effective. It was a contraceptive produced by the Animal and Plant Health Agency. The lead scientist of the project was Dr. Giovanna Massei. Along with her team, they created a vaccine that triggers the immune system to regulate the production of sex hormones in grey squirrels.

The team has yet to develop a drug that has a longer-lasting effect than what they have. Part of the research is to test the drug out in an actual environment. The team designed a special feeding hopper with a weighted door to secure the contraceptives for the gray squirrels. Experimental trials have started in Yorkshire and Wales — pots of hazelnut paste blended with the contraceptive will serve as baits to attract the target. A new special feeder will be in the works — one where only a gray squirrel can get access to it.

Photo: Pixabay/gianninalin

The special feeders should keep out red squirrels from feeding on the contraceptive. Body weight can be a distinguishing factor — gray squirrels are heavier than red ones. During the research, other methods were also considered to help reduce the number of gray squirrels. Releasing pine martens was one of those ideas, since those woodland mammals prey on gray squirrels. Although effective, gray squirrels still outnumber the predators in urban and city areas.

“Fertility control can be an effective method, complementing other approaches to wildlife management. This … study aims to produce an immunocontraceptive that can be orally administered to gray squirrels through a species-specific delivery mechanism,” explains Gideon Henderson, the chief scientific adviser at the Department for Environment, Food, and Rural Affairs. “This innovative research has great potential to provide an effective, easily applied, and nonlethal method for managing gray squirrel populations. It will help red squirrels – native to the UK – expand back into their natural habitats,, as well as protecting UK woodland and increasing biodiversity.”

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