When the Endangered Species Act was passed in the US in 1973, almost the entire grey wolf population in the American West had disappeared.

By 2012, however, the number of wolves had reached such high numbers in the Rocky Mountain states of Wyoming and Montana that officials reintroduced some hunting and trapping.

The latest research shows grey wolf populations have declined 7% in the region in the past year. Environmental groups worry that the wolves' future is once again at risk, but the US Fish and Wildlife Service believes the animal is being appropriately controlled.

In fact, many lawmakers now want the wolf to be taken off the Endangered Species Act list across all the lower 48 states.

The BBC's Matt Danzico went to Wyoming and Montana to talk to ranchers, environmentalists and government officials about the ongoing debate over how humans and wolves can co-exist.