Colo. Rev. Stat. § 35-44-102
No person shall take into his custody an estray animal unless the same is found trespassing upon lands owned, leased, or otherwise controlled by him. The state board of stock inspection commissioners or an authorized brand inspector representing said board has authority to move such estray animal to a safe and practical place within the immediate vicinity to be held during the legal advertising period. When any person takes into his custody an estray, within five days thereafter he shall make out a written description of such animal, setting forth all marks or brands appearing upon such animal and other marks of identity, such as color, age, size, sex, and possible owner, and forward the same by mail to the state board of stock inspection commissioners in Denver or notify the nearest authorized brand inspector. Any person having knowledge of any estray animal upon the public range may notify the state board of stock inspection commissioners, or any authorized brand inspector of said board, giving a description of said estray, and upon instructions from the board of stock inspection commissioners, or from an authorized inspector of the board, said estray shall be held by such person to be turned over to a duly authorized inspector of said board for disposition as the board may direct according to law.
C.R.S. § 35-44-102