Davis said he hopes to test a fifth generation this season, miniaturized to a degree that the whole package fits on the head of the animal. The system currently includes a backpack. Digital memory is no longer a limiting factor, at this point, Davis noted.
“What defines the minimum size of the instrument now is the size of the batteries. It dictates how long you can record,” he said. The high-density lithium batteries are good for a one time use only at a cost of about $300 to $400.
On the hunt
The fieldwork itself may not be as difficult as surviving an Antarctic winter, but the temperature is still well below zero and unsettled weather quite common.
But the real challenge is finding a suitable film star, Davis said. The subfreezing water is still warmer than the ambient temperature at that time of year, so it takes a little patience to locate a seal that has ventured out of a hole and onto the ice surface.
Then it’s time for a little muscle, capturing and hauling the seal to a covered tent called a Jamesway where Williams’ team takes metabolic measurements. One experiment involves placing a box over the seal and measuring oxygen uptake by the animal.
“If you understand how far you can push the mammalian heart or lung, you start to better understand the human condition,” said Williams, a professor of Ecology and Evolutionary Biology at University of California-Santa Cruz (UCSC).
Williams said previously in a press release from UCSC that she is also particularly interested in how the seals will respond to changes in their environment caused by global warming. “The seals are monitoring marked changes in the polar environment that will ultimately dictate their survival,” she said.
The team then outfits the animal with the video-data recorder instruments before releasing it into a nearby hole. “It’s about a two-day operation,” Davis said.
Each seal has a satellite transmitter and very high frequency (VHF) transmitter. When it eventually hauls out, it sends a signal to a satellite. Within about 90 minutes, the team receives the latitude and longitude location by e-mail, accurate to within 200 meters or so. Within a kilometer, the scientists can pick up the VHF signal and home in on their equipment.
They can track about a half-a-dozen seals in a season. Some may not reappear for several weeks, though the recovery rate is 100 percent, Davis said.
“It’s a waiting game.”
And, based on the results so far, well worth the wait.