Thanks Alexa. It is good that National Geographic are keen to have the facts right.
It is important that people know that there are indeed 13 species of otter worldwide and they are all at risk, largely as a result of man. In the UK, the population does indeed seem to have improved as waters are cleaner but we also have to be wary as the data is based on spraint (droppings) which gives no indication of actual numbers. The same otter may of course be recorded several times.
Over the last year there has been drought and floods - both of which are not good for otters. In fact it was recently announced that 2012 was a bad year for otters. So if they are being seen in new areas it could well be that they have been displaced from somewhere else or that their home ranges are now larger.
Only further studies will reveal the truth.
Grace M Yoxon
International Otter Survival Fund