Otters have now returned to every county in England, completing a dramatic comeback for a creature that nearly disappeared from the country three decades ago.
Wildlife experts recently spotted two otters in Kent, the only county in England that remained otter-free in 2010, according to a countrywide survey that found otters were recovering well in the rest of the country.
The recent sightings have delighted conservationists, who estimated the iconic aquatic mammals wouldn't return to Kent for another decade.
In the 1970s, English otters were in dire straits due to toxic effects from pesticides, and some feared the creatures would disappear from the country forever.
"The recovery of otters from near-extinction shows how far we've come in controlling pollution and improving water quality. Rivers in England are the healthiest for over 20 years, and otters, salmon and other wildlife are returning to many rivers for the first time since the industrial revolution," said Alastair Driver, the U.K. Environment Agency's national conservation manager, in a statement.
Otters are at the top of the food chain, and are therefore an important indicator of the health of rivers.
Although river otters (Lutra lutra) are classified as "near-threatened" according to the International Union for the Conservation of Nature, the species appears to be making a comeback in places outside England as well.
As of 2008, scientists found evidence that river otter populations were recovering in parts of western Europe, several former Soviet republics, and in south and southeast Asia.
Sea otters (Enhydra lutris) are not faring as well. The species is listed as endangered, and population numbers appear to have declined by 50 percent over the last three decades.
The otters discovered in Kent have built residences along two rivers, the Medway and the Eden.
In addition, a recent survey on the river Ribble in Lancashire showed a 44 percent increase in the number of otters since 2008.