Scientists on Wednesday tried to collect gas samples from the blowhole of a 45-foot gray whale stranded in the Klamath River in Northern California.
The researchers used a funnel on a long pole to capture the samples, which can tell them about the whale's nutritional state, stress level and disease.
The whale remained upstream after weeks spent trying to drive it from the river, said Sarah Wilkin, a coordinator with the National Oceanic and Atmospheric Association.
The mother gray whale and her 15-foot calf entered the river in late June during their northward journey from breeding ground in Baja California to Alaska. The rescue team spotted what they believed to be the calf swimming to sea on July 23, and scientists said the calf was mature enough to survive its journey to Alaska.
The mother whale was still in good condition Wednesday, Wilkin said, but researchers are concerned she won't get enough food in the fresh water.
So far the whale rescue team has tried playing killer whale sounds through speakers mounted on a boat in an effort to drive the 40-ton mammal back toward the Pacific Ocean.
As of now, those efforts have stopped and the rescue team is focusing on the whale's health.
In addition to concerns about food, scientists are studying the whale's skin closely each day, watching for signs of deterioration from the freshwater environment.
The whale has become something of a celebrity in the area, drawing crowds and traffic to a bridge spanning the Klamath in hopes of catching a glimpse of the behemoth.
The California Highway Patrol has begun urging people to avoid the bridge, assigning two officers to the span each day to help with crowds.