"A herd of Critically Endangered wild Przewalski's horses in the Chernobyl exclusion zone is under threat from poachers, say scientists.
Researchers in Ukraine say that the population may be in decline because poachers have been removing the animals faster than they are breeding.
Thirty-one horses were taken from a Przewalski's horse reserve and from a local zoo.
They were released into the zone in 1998 and 1999.
Scientists from the state-run SSSIE Ecocentre in Chernobyl say the horses were introduced to "enrich the biodiversity" of the exclusion zone surrounding Chernobyl nuclear power station's damaged nuclear reactor.
The zone was evacuated in 1986 after reactor number four exploded.
Professor Tim Mousseau, a biologist from the University of South Carolina who visits the zone to work at least twice a year, says that the herd he has spotted has been "getting smaller" in recent years.
"Many people in this part of Ukraine are very poor," he told BBC Nature on a recent trip to the exclusion zone.
"So access to a readily available supply of horsemeat is tempting for people."
But Sergiy Paskevych, a researcher from the National Academy of Science in Ukraine and the author of a website dedicated to ecology and wildlife in the exclusion zone, told BBC Nature that poachers probably travelled long distances to the exclusion zone and took the carcasses away to be sold..."