Male dogs are up to five times more likely than females to develop a contagious type of cancer, scientists have said.

Canine Transmissible Venereal Tumour (CTVT) is an extremely unusual type of cancer. While almost every other cancer cannot survive the death of its host, CTVT’s living cells physically transfer from one dog to another in a process thought to have been taking place for as long as 11,000 years.

The parasite-like cancer, which responds well to chemotherapy and is rarely fatal, commonly grows in dogs’ genitals and is usually transmitted during mating. But in rarer cases, it can spread to the mouth and nose when dogs sniff or lick other dogs in these areas.