BOSTON (AP) — An underwater robot being perfected by Cape Cod researchers aims to help scientists search for rare whales for weeks at a time, in any weather.

The torpedo-shaped underwater robots, called gliders, can read calls from four types of endangered whales, including right whales, and relay their locations in real time. And they can do it in weather too harsh for the plane and boat surveys now used to find the whales.

On a three-week trip late last year, the gliders developed by the Woods Hole Oceanographic Institution located nine endangered North Atlantic right whales. The gliders also led researchers to an area where they could observe them firsthand.

The effort is all about protecting whales.

Locating the often hard-to-find whales can help regulators devise rules that prevent often-fatal ship strikes.