England’s otter population, once on the verge of extinction, has made a massive comeback, according to a survey by the Environment Agency.
They are now back in the rivers and waterways of every county in the country apart from Kent.
Once hunted for sport, the cause of their decline was in fact unintentional: pesticides widely used in the 1950s, thought to be safe, in fact became fatal for thousands of predatory animals and birds.
The reason: these chemicals built up in the livers of song birds and fish, concentrating their poisons in mammals and birds of prey that ate them.
Those pesticides were banned some 50 years ago and, along with a nationwide drive to clean up river pollution, the otter revival began. But it has taken half a century to reach its present healthy state.
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The news from the latest Otter Survey of England can only be taken as good news, as the Eurasian Otter has been one of the sad casualties of the 20th century, declining by 95% of its range in western Europe.
A lot of hard work has been carried out since the 1980s to improve the quality of our waterways and this is now beginning to pay off. The otter is an ambassador to a healthy environment – as they are at the top of the food chain and use both the land and water environments both habitats have to be in excellent condition.
Another positive aspect of the recovery of the otter is that there is a lot of scientific evidence to show that otters can have a major effect on keeping down populations of the non-native American mink.
However we cannot say that the comeback has been "massive" and we have to take this news with some caution as the way these surveys are carried out is by looking for spraint (droppings) at a certain number of sites for a distance of up to 600m. If spraint is found then the 10km grid square is marked as positive but this does not give any idea of otter numbers. Furthermore, it does not necessarily mean that otters are resident as the otter could merely have been passing through trying to establish a home range.
Numbers are increasing but only slowly and the reports that otters are “flooding” back into areas are greatly exaggerated. Otters cannot reproduce quickly: They do not become sexually mature until about 2 years old and the data indicates that they die at about 5-6 years old on average - there will be cases of older otters but this is an average. As the young stay with the female for 12-15 months they do not breed every year so a female may only have 2 litters in her lifetime. So it is not possible for the population to “explode”.
We also have to consider the actual numbers of otters - if we look at the whole of the UK there are less than 10,000 - that is less than the number of people who live on the Isle of Skye where we live. They do not live in groups and their numbers are very vulnerable.
In some areas anglers are becoming concerned about their fish but otters do not kill “for fun” and will only take to eat. If the habitat can support otters it means the water and the land are in excellent condition and this is also vital for the general biodiversity of the area.
Dr Paul Yoxon, International Otter Survival Fund Broadford, Isle of Skye