Automatic whale detectors keep track of migration

Something as large as a whale might seem an easy thing to keep tabs on, but for for the US National Oceanic and Atmospheric Administration (NOAA), tracking migrating pods of gray whales is a major undertaking. In hopes of making binoculars and clipboards a thing of the past, the agency has installed a new generation of whale detectors to keep an electronic eye on the passing leviathans.

Like birds, gray whales annually migrate thousands of miles as they go from their arctic feeding grounds to their wintering spot off Baja California. However, despite their great size, the whales can be as hard to track as submarines. According to NOAA, there are 20,000 grays in North American Pacific waters, which means they're no longer endangered, but monitoring them is still necessary to help protect the whales from accidents with ships or nets, as well as observing how their behavior adapts to changes in the climate

NOAA scientists regularly try to watch the animals to determine their population and condition as they swim past Monterey Bay, California, but their technique is one that Captain Ahab would appreciate, as one scientist scans with binoculars while another writes down the observations. It's tedious and expensive work, and because people can only focus for so long and it isn't possible to watch at night, many whales go uncounted. Worse, many get counted more than once as they dive and surface.

NOAA's answer is a system for automatically tracking the whales using infrared cameras that goes online this year under the supervision of more traditional observers. The agency says that what's new isn't the cameras, which are off-the-shelf designs of the sort used by helicopter police, but that they zero in on the thermal signatures of the whales as they spout.

"A whale is this great big motor that takes in a breath of air and holds it inside for a long time," says Wayne Perryman, a NOAA Fisheries scientist. "When it exhales, the air is much warmer than the background, and we can detect that difference very easily, both day and night."

These signatures are distinct because the imaging system uses new algorithms based on years of whale observation to detect and analyze the whales' behavior. This not only allows the system to tell one whale from another, but also to predict when and where it will resurface, which reduces the chances of missing or double-counting one of the animals. In addition, it helps to weed out false positives, such as birds or small boats.

Another advantage is that, being both a machine and working in the infrared, the new detectors can work at night, don't get fatigued, and don't mind hanging out on an inclement Northern California day. A bonus is that since the detectors don't draw salary, they can be used for the entire duration of the migration season, so vanguards and stragglers don't get missed.

"The biggest advantage of the new system is that it vastly increases our sample size," says survey team leader Dave Weller. "That means we can more accurately estimate the size of the population."

The video below shows the whale detector in action.

Source: NOAA