Mutated squirrel genes could cut population
Scientists believe genetic edit in interlopers could offer new way to control their spread and help reds
Genetically modified grey squirrels could be released to tackle the invasive population and potentially help the native red, under plans by Edinburgh University. The squirrels’ genes would be edited to promote infertility, meaning fewer would breed and populations would decrease. In their study, the researchers concluded that releasing 100 squirrels with mutated genes into a population of 3,000 greys would wipe out the population within 15 years.
MUTANT grey squirrels, genetically modified to spread infertility genes, could be released into the wild to tackle the burgeoning population, Edinburgh University has said.
North American grey squirrels were imported to Britain in the mid-19th century, and their population has now grown to more than two million. Not only do they out-compete the native red squirrel, they also strip trees of their bark and prey on eggs and chicks.
The Department of the Environment is currently looking at options for controlling grey squirrels, with culls and oral contraceptives being considered.
Edinburgh University has now suggested that genetically altering squirrels so they pass on infertility genes could dramatically cut populations.
In a new study, published in the journal Scientific Reports, researchers found that releasing 100 mutated squirrels into a population of 3,000 greys would wipe out the population within 15 years.
The technique is known as a gene drive, and has been successfully used to lower populations of mosquitoes to prevent malaria and Zika virus.
It works by preventing natural selection from weeding out harmful traits like infertility, essentially “driving” an unhelpful mutation through a population. Scientists insert the new genetic code using a process called Crispr, which snips away parts of the DNA and replace them with new code.
“Without intervention, red squirrels could be lost from the UK mainland within the next few decades,” the authors said. “Current control methods such as shooting, trapping, and poisoning are inhumane, labour-intensive, expensive, and ineffective. Although there are still technical challenges,
Crispr-based gene drives may offer a humane, efficient, species-specific and cost-effective method for controlling invasive species, including grey squirrels in the UK.”
In January, Lord Goldsmith, an environment minister, said that breeding infertility into grey squirrels could provide a “longer term” and “more humane way” of reducing numbers. The Royal Forestry Society is calling for a grey squirrel cull and is funding research into contraception, but experts said a gene drive could offer a new solution.
Prof Luke Alphey, group leader in arthropod genetics at the Pirbright Institute, said: “Invasive species are a major problem for biodiversity and conservation, in many cases there are no adequate methods for control.
“Most work on gene drives has focused on mosquitoes; this study is unusual in focusing on a vertebrate, the grey squirrel, though there has also been interest in targeting invasive populations of mice and rats on islands.
“‘Regulatory approval and public acceptance would be essential before any use of such technology, but this paper indicates gene drives could be valuable in the conservation toolbox.”
The authors say the gene-drive technique has not yet been tested in live animals, and further research is needed to ensure an abrupt suppression of the grey squirrel population does not have a damaging impact on the ecosystem as a whole. There are concerns a largescale release of animals in an environment which already has too many may lead to starvation or mass migration.
Nicky Faber, one of the researchers from Edinburgh University, said: “The modelling shows that our gene drive is very effective at reducing the population size.
“The next step is currently being done, in which a gene drive is tested for efficiency in a grey squirrel cell line in vitro in the lab. This does not involve any animals. There are many more steps of testing to be done after that, so we’ve still got a long way to go before the technology can be used.”