Parts of the park will be closed off as scientists begin a grizzly bear research survey.

Visitors to Yellowstone National Park are being warned to avoid certain areas as biologists look to begin a grizzly bear research survey.

The survey, which is intended to monitor the bear’s population in the park as part of the Endangered Species Act, requires biologists with the Interagency Grizzly Bear Study Team to scientifically capture the bears, according to the National Park Service. When they do, they use bait, including natural food sources like road-killed deer and elk.

Visitors to the park are told to be aware of and obey posted warning signs, and to avoid areas where the signs have been posted. The scientific survey will start on Aug. 28 and last through Oct. 31.

“Monitoring of grizzly bear distribution and other activities are vital to ongoing recovery of grizzly bears in the Greater Yellowstone Ecosystem,” the NPS wrote in a statement. “Whenever bear capture activities are being conducted for scientific purposes, the area around the site will be posted with bright warning signs to inform the public of the activities occurring. These signs are posted along the major access points to the capture site. It is important that the public heed these signs and do not venture into an area that has been posted.”

The NPS added captured bears are “handled in accordance with strict safety and animal care protocols developed by the IGBST and approved by the U.S. Geological Survey and the National Park Service.”

There are thought to be about just over 1,000 grizzly bears in the greater Yellowstone area, according to the NPS, with males weighing up to 700 pounds. Grizzly bears are currently listed as a threatened species under the Endangered Species Act.

Park goers who do encounter a bear are warned to stay at least 100 yards away from it.

Yellowstone isn’t the only national park warning travelers to stay away from bears. Earlier this month, Great Smoky Mountains National Park closed a road due to bear activity during a time when the animals are foraging for food. And last year, the park closed several trails so the bears could feed in the area in preparation for hibernation.

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