In what seems to be a similar problem to that of the Kaimanawa horses here, the US is grappling with its wild horse and burro problem. They currently have some 30,000 horses in care and are grappling with the issue of what to do with them as upkeep costs escalate and adoptions decline. A proposal to euthanise some of the horses has been shelved as other options are explored. Read the story on the National Geographic News site here;
http://news.nationalgeographic.com/news/2008/11/081118-wild-horses.htm