What’s wrong with them?
Photos and videos are often out of focus and low resolution, producing fuzzy images when enlarged. We automatically fill in the ‘gaps’ that are created in poor-quality images with what we have previously seen and what is suggested by the photograph.
How else can they mislead us?
Something of a known size may be used as a comparison with the ‘big cat’, but these photos could be taken from a different place or using a different lens, leading to distorted size and shape. It can be difficult to judge distances and how big something really is, leading to an exaggeration of size.
Give an example.
In June 2009, an alleged black panther was filmed walking along railway lines near Helensburgh, Argyll. The grainy, shaky footage makes it difficult to identify the cat, though it’s clearly not very big compared to the railway tracks. Later footage, using a different camera, showed a perfectly normal domestic cat.
A trailcam photo of an alleged big cat taken in July 2016 in Gloucestershire was compared in news reports with a photo of a fox in the same location, but in fact the photos confirm the animal as the size of a domestic cat. Grainy, out-of-focus footage of an animal identified as a lynx reported in November 2016 was nothing more than a long-tailed cat. Lynx are bigger and have short tails.
What would be proof?
The best evidence would be high-quality trailcam images or a road casualty – a post mortem could establish conclusively whether or not it had been living in the wild.
Are any big cats living wild in the UK?
It depends what you mean. Non-native wild cats may escape or be released into the wild and survive, but most are recaptured or eventually die. Breeding animals are very unlikely.