ITHACA, N.Y., July 29 (UPI) -- Electronic "ears" are being placed in the Gulf of Mexico to listen in on whales and investigate their health since the massive oil spill, researchers say.

Scientists from Cornell University, in cooperation with the National Oceanic and Atmospheric Administration, have placed 22 "marine autonomous recording units" in the gulf, a university release said Thursday.

The goal is to document the state of the whales in the ecosystem over an extended period of time, the release said.

"Night after night, on TV and on Web cams, we saw oil spewing from the bottom of the ocean," said Christopher Clark, head of the Cornell team. "You wonder, 'What can we do? What's the impact of this?' In the case of marine mammals, we don't know because we don't even know what's there."

The recording units have been anchored to the sea floor in an arc stretching from Texas to western Florida along the edge of the continental shelf.

After recording underwater sounds for three months, they will release their tethers and float to the surface for retrieval.

"This will be the first large-scale, long-term, acoustic monitoring survey in the Gulf of Mexico," Clark said. "The whales are like oversized canaries in the coal mine -- they reflect the health of the environment they live in."