Sad yes......a problem yes. I dont see how injecting each and every wild mare with infertility drugs could be a possiblity.And read this excerpt from http://www.abc.net.au/rural/qld/content/2006/s1754581.htm #He also said the culls were conducted after three months of consultation with industry stakeholders, including the Environmental Protection Agency, RSPCA, the Department of Primary Industries, neighbouring land owners and the general public- all reaching a unanimous decision that the culls should take place.#

Introduced species are huge problem here,just living with cane-toads show me the reality of the problem..and they are not as cute as brumbys.

http://www.nrw.qld.gov.au/factsheets/pdf/pest/pa21.pdf