Security has been stepped up at wildlife parks after police were tipped off about a plot to hunt rhinos in south-east England.
Two animal parks in Kent - Port Lympne and Howletts - have called for volunteers to help them carry out 24-hour patrols, while police have also stepped up surveillance.
Pc Michael Laidlow, wildlife crime officer for Kent Police, said: "There was anonymous information through Crimestoppers saying there was a possible attack on rhinos.
"We've spoken to all the owners of rhinos in the South East and they are taking measures to combat it."
Bob O'Connor, managing director of Howletts and Port Lympne, said: "We've upped our night-time patrols, we doubled that straight away with our keepers who live on site.
"We have to take this as a credible threat."
Rhino horn is worth £65,000 a kilo, which makes it more valuable than cocaine, heroin and gold.