In the mid-1980s gray wolves recolonized the Bow Valley in Banff National Park. They had been absent for 30 years due to systematic predator control hunting which began in 1850. Wolves filtered back to Banff and recolonized one zone of the Bow Valley in 1985 and another in 1991. A high level of human use surrounding a third zone at Banff townsite has deterred the wolves from that area. The wolves are important in controlling elk populations and improve the balance of the ecosystem. A routine park study to monitor the wolves in Banff has now grown into the Southern Rockies Canine Project – the largest wolf research project in North America. The estimated wolf population in Banff National Park and the surrounding areas is now 60–70 animals.