A ballot measure seeking to prohibit the hunting of mountain lions, bobcats, and lynx is losing, according to early results.

About 55% are opposing Proposition 127, according to unofficial preliminary results released posted after 10 p.m. The latest vote tally showed 44.5% voting in favor of the ban.

The initiative would banned the “trophy hunting” of these big cats, with an exception for acts of self-defense. Proponents of the measure, including the group Cats Aren’t Trophies, argue that trophy hunting is cruel, unnecessary, and violates the “fair chase” principle outlined in the North American Model of Wildlife Management, which is practiced by Colorado Parks and Wildlife. Notable celebrities including actor Robert Redford and primatologist Jane Goodall have also endorsed the measure.

Critics of the initiative, including Coloradans for Responsible Wildlife Management, argue it will do more harm to big cats than good and have expressed concerns that it may lead to future bans on other hunting activities. A coalition of sportsmen and biologists called Wildlife Deserves Better also rallied against the proposition, arguing it’s not based in science and is simply “ballot box biology”.

Bans on hunting big cats have been brought before the state legislature in the past, to no success.