Yellowstone National Park Rangers are cautioning visitors that elk calving season has started in the park. During this time, cow elk are much more aggressive towards people and may charge or kick. Visitors are advised to stay alert, look around corners before exiting buildings or walking around blind spots, and be aware that cow elk may bed their calves near buildings and cars. Always stay at least 25 yards from elk at all times, and if an elk charges you, find shelter in your vehicle or behind a tall, sturdy barrier as quickly as possible. Yellowstone provides summer range for an estimated 10,000–20,000 elk from six to seven herds; most of which spend the winters at lower elevations outside the park.