Colchester Zoo has spent thousands of pounds on security to protect the horns of its rhinos from poachers.

A big-money alarm system has been installed to deter poachers who might be planning to sneak in at night and saw off the animals’ horns.

Rhino horn has long been a sought-after commodity, but prices are currently almost $40,000 a kilo because it is reputed to be a cure for cancer.

The National Wildlife Crime Unit has warned all British zoos with rhinos poachers will stop at nothing to get hold of horns, even targeting animals in captivity.

Colchester Zoo, in Maldon Road, Stanway, has three adult males, three adult females and one male calf and has taken the warning seriously.

Zoo director Anthony Tropeano said: “Poachers in Africa either shoot the animal or anaesthetise it with a dart and saw off the horns. It is very traumatic for the rhino and they rarely survive for very long afterwards.

“These are organised operations with helicopters and veterinary drugs and the threat to UK zoos is very real. Many poachers have stolen old horn from museums or from antiques, but these have either been taken or are locked down securely. The next easiest option is for them to enter a zoo.”

Night wardens regularly patrol around the park, but the rhinos now have extra protection in the form of an alarmed fence, which directly alerts police and zoo staff living on site. If the alarm goes off, they can be at the enclosure in minutes.

Alan Roberts, investigative support officer for the National Wildlife Crime Unit, said: “No one has killed any animals in zoos in Europe, but there are parts of the world where they wouldn’t think twice.

“The threat is very real and Colchester Zoo has been very sensible in protecting their rhinos in this way.

Smuggler Donald Allison was jailed for a year after being caught with horn from Simba, a 41-year-old male rhino, who died at Colchester Zoo, in June 2009.

His £180,000 haul was stolen from the rhino’s body at an Essex abattoir while it awaited cremation.