By Jenny Reece
Ever wondered why grey squirrels are painted as the bad guy? Or why Asian Hornets are bad news for honeybees? We’ve put together a blog on the invasive species you find in the UK and what damage they can cause.
What are invasive species?
Invasive species are species that are not indigenous or native to that particular area. They are usually introduced accidentally by humans and can cause economic and environmental harm to the new area they inhabit. Some species are purposely introduced to new areas and are often used as pest control, whereas others are introduced as pets that escaped or were released. However, not all non-native species are invasive. To be invasive the species must quickly adapt to the new environment and cause harm to the native ecosystem. Invasive species thrive because they out compete native species for food and/or have no predators to hunt them.
What are the consequences of invasive species?
• Predation. The introduction of new species could disrupt the food chain by adding predators for species that have evolved in the absence of predators. The biodiversity on islands is especially susceptible to this (see Asian hornet).
• Competition. Introduced species outcompete native species for food, space etc, which can change the structure of certain habitats, making it unliveable for other species (see grey squirrel).
• Diseases. The introduction of new diseases that native species have no immunity against could have serious consequences (see grey squirrel).
• Hybridisation. Some species can breed with other related species forming hybrids. Over time genetic diversity of one of the species is lost and it becomes extinct (see ruddy ducks).
Asian Hornet
This hornet is from Asia and was first detected in the UK in late 2016. They were first introduced in France in 2004 and were thought to have been brought over inside Chinese pot plants and then they crossed the channel to England. They are a predator of honeybees and other pollinating insects so they could cause a lot of damage to our already dwindling honeybee population.
Grey Squirrel
Native to North America they were deliberately released into the wild in 1876, they out compete native red squirrels leading to near eradication of their populations. Red squirrels have been in the UK for around 10,000 years and their population has dropped to about 140,000 whereas grey squirrels have a population of about 2.5 million. Grey squirrels also have a prolific breeding cycle have two litters (~3 per litter) of young per year.
Signal Crayfish
Signal crayfish were introduced to the UK from North America in the 1970s to be farmed as food, but they are a carrier of crayfish plague and are thought to be responsible for passing this disease onto the native white-clawed crayfish in the UK.
Ruddy Ducks
They were first introduced in the UK from North America in the 30s and 40s for captive wildfowl collections. Some escaped and bred in the wild in 1952. Ruddy ducks interbreed with white-headed ducks to produce fertile hybrids. They are more promiscuous in their mating behaviour so the population would contain an increasing number of hybrids showing fewer characteristics of the white-headed duck until the species is eradicated. This has been shown in New Zealand where the introduction of mallards has caused a dramatic decline in the native grey duck due to hybridisation.
What can be done
An important component is educating people about the dangers of transporting wildlife to new areas. There are numerous policies and legislation in place to tackle the future spread of invasive species as preventative measures are much cheaper and easier than methods to combat species that have already arrived in the UK.
For species already in the UK there are many different ways to minimise damages for example with Asian hornets when nests are discovered they are destroyed immediately to try to prevent them becoming an established species. Another example is that signal crayfish can be controlled by introduction of their natural predators such as otters and predatory fish.
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