![Red squirrels are very isolated from other populations in the UK. Credit: Henk Bogaard/Shutterstock Feeding British red squirrels could change their jaws](https://oponame.com/wp-content/uploads/2022/10/Feeding-British-red-squirrels-could-change-their-jaws.jpg)
Red squirrels are very isolated from other populations in the UK. Credit: Henk Bogaard/Shutterstock
Feeding peanuts to red squirrels can impair the development of their jaws.
An endangered rodent population living in Formby, Merseyside, has uniquely shaped lower jaws, possibly because they were fed softer foods. Although the activity is now discouraged, the practice seems to have left a legacy for these squirrels, some of the last to live on mainland England.
Although it is currently unclear whether changes in jaw structure are the result of evolution or adaptations over its lifetime, researchers’ ability to track changes is an indication of isolation. squirrels.
Kim Chandler, Ph.D. a student at the University of York, is researching how red squirrels change due to their diet.
“I don’t think these kinds of changes would have been seen if red squirrel populations were larger,” Kim says. “Without genetic mixing between them, British populations have become very isolated from each other.”
“This means that the populations of northern Scotland, Formby and elsewhere are effectively acting as their own evolutionary islands.”
Why are red squirrels in decline?
Step back 150 years and red squirrels are said to have lived in forests across the country, as well as in outposts such as Jersey in the Channel Islands.
However, all this began to change at the end of the 19th century. Some of the first gray squirrels were introduced to Henbury, Cheshire in 1876, followed by further introductions to Bushey, Hertfordshire and Woburn, Bedfordshire over the following years.
![Woodland in Formby is one of the last sites where red squirrels are found in England. Credit: Brian Maudsley/Shutterstock Feeding British red squirrels is changing their skull](https://oponame.com/wp-content/uploads/2022/10/1666073369_757_Feeding-British-red-squirrels-could-change-their-jaws.jpg)
Woodland in Formby is one of the last sites where red squirrels are found in England. Credit: Brian Maudsley/Shutterstock
These introductions were primarily for ornamental reasons, with North American gray squirrels being released onto private estates by wealthy landowners. As rodents reproduce faster than their native counterparts, gray squirrels soon began to spread beyond the boundaries of these areas and across the country.
They were aided in their spread by squirrel pox, a viral disease transmitted mildly by gray squirrels but often fatal to red squirrels.
By the time the importation and ownership of invasive mammals was banned in the UK in 1937, it was already too late. Much of south east and central England was already dominated by the encroaching grays and over the past 85 years they have continued to push north and west.
Today, red squirrels survive in the coniferous and deciduous forests of Scotland, northern England and on islands such as the Isle of Wight and Anglesey. Although there have been occasional transfers between them, each population is, for the most part, isolated from the others.
How do red squirrel populations differ across the UK?
When populations are isolated from each other, the separated groups have the opportunity to diverge as they react to different resources and pressures in their respective environments.
As part of her PhD, Kim studied if and how these changes occur by examining a collection of red squirrel skeletons collected from across Britain and housed in the National Museum of Scotland.
“Museum collections are invaluable to my work, and it wouldn’t have been possible without them,” Kim says. “The collection of the National Museum of Scotland is continually being added to, which shows a clear trend over the past decades.”
Kim scanned the skeletons and used the scanned data to measure the shape of the skull and lower jaw, or mandible, of red squirrels in northern Scotland, northern England, Jersey and Formby over a period of time. of time.
The different populations all showed significantly different variation in the shape of their skull and mandible, with the bones of individuals from northern England and Scotland being significantly more robust than individuals from Formby.
The parts of the bone where the muscles are attached suggest that Formby individuals had smaller masseter muscles, which are used for chewing, than their counterparts further north. Kim linked this to the diets of different populations.
“Scotland has a lot of pines, while the north of England has a mix of trees such as pine, hazel and oak,” says Kim. “These produce harder nuts and cones that require larger muscles to eat.”
“In Formby, the situation is very different. Feeding red squirrels peanuts in the past has given them softer foods that wouldn’t normally be in their diet.”
One study suggests that in the 1990s, up to 56% of the diet of Formby’s squirrels came from peanuts alone. Feeding squirrels is now discouraged as it can affect animal health, as well as being a potential means of spreading disease in this large population.
While the study shows that the average shape of their mandibles has changed over the past decades, it is not enough to say whether or not this is evolution in action. Rather, the changes may be “plastic”, reflecting nonheritable adaptations to available food sources, with more specimens needed to solve this puzzle.
Kim also hopes to answer more questions about these adaptations in the rest of her PhD, delving deeper into the process of how squirrels eat. It aims to examine the strength of bites in different populations, as well as to investigate how difficult it is to eat each of their foods.
Studies like Kim’s will help scientists better understand these animals, fueling projects to conserve our native squirrels.
Feeding red squirrels peanuts can make natural food a tough nut to crack
Provided by Natural History Museum
Quote: Feeding British Red Squirrels Can Change Their Jaws (October 18, 2022) Retrieved October 18, 2022 from https://phys.org/news/2022-10-british-red-squirrels-jaws.html
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