There was not a 12kg rat in London

12th Sep 2019

Claim

A photo shows a 12kg rat in London.

Conclusion

Incorrect. The photo makes the rat look deceptively big. It almost certainly weighed less than 3kg.

A Facebook post which has been shared over 10,000 times purports to show a picture of a 12kg rat in London.

The Facebook group posting the image (called Surrealistic Reality) specialises in posting optical illusions: which is a clue not to take this post seriously. The rat does not weigh 12 kg.

A number of websites have already debunked the image, which is real but which makes the rat look deceptively big.

The reason for this is an effect known as “forced perspective” where objects closer to the camera appear much bigger than those further away.

A classic example of the forced perspective effect is people pretending to prop up the leaning tower of Pisa with a single hand.The image first appeared in 2016, after the rat was found by engineers working at a block of flats in Hackney in London. Reports claimed the rat was four feet long (about 120cm) and weighed 25 pounds (about 11kg).

However Oliver O’Brien, a spatial data scientist at University College London, analysed the image and estimates that the rat was roughly two feet long (60cm).

Professor Jane Hurst, who specialises in mammalian behaviour and evolution at Liverpool University, said that it was most likely a Gambian pouched rat which was someone’s pet.

Gambian pouched rats (also known as African giant pouched rats) can reach around three foot (90cm) in length (body and tail combined) and weigh no more than 3kg.