Scientists from the Natural History Museum and Liverpool John Moores University (LJMU) have dated lion skulls discovered at the Tower of London back to the 13th century.
The big cat remains were discovered in the 1930s and have been stored at the Natural History Museum ever since.
Skulls from the lions and 19 dogs were radiocarbon-dated with funding from English Heritage. One of the lion skulls dates back to AD 1280-1385, making it the earliest medieval big cat in the British Isles.
'Museum collections play an important role in helping researchers to understand the life history, development and habits of animals,' says Richard Sabin, Curator of Mammals at the Natural History Museum.
'It's the physical remains, particularly the bones, that really tell the animals' stories'.
The lions would have been housed in the Tower's Royal Menagerie, or zoo, that was established by King John (1199-1216). Lions died out in Northern Europe more than 10,000 years ago so big cats were probably given to English monarchs as gifts from their allies.
The Menagerie would have contained other exotic species such as bears and leopards, and the animals would have also been used in baiting, where dogs are set to attack other animals for entertainment. This may explain the existence of so many dogs at the Tower and one of the dog skulls analysed had two puncture wounds to the top of the cranium, possibly the result of dog fighting.
Conditions at the zoo would have been very bad for the animals and the lions were probably kept in cages measuring just six square meters. Jeremy Ashbee, Inspector of Ancient Monuments and Historic Buildings at English Heritage and former Curator at the Tower of London, explained 'At its height, it was an immensely popular tourist attraction, in the same way that the Crown Jewels are today'. The menagerie was finally closed in 1835.
The research also gives an insight into the health of zoo animals as one of the skulls showed an abnormality associated with captive lions.
LJMU's Dr Hannah O'Regan, who led the research, explained the importance of this discovery 'Our research has highlighted a condition in captive lions that has been seen in specimens kept in different locations and different countries 500 years apart.'
'Such studies of past zoo or captive populations have the potential to inform not only archaeology but also conservation strategies'.
The research is published in the International Journal of Osteoarchaeology.