A SONIC RADIO TAG FOR MONITORING DIVE DEPTHS AND UNDERWATER MOVEMENTS OF WHALES

There has been much speculation about the ecology and behavior of whales, largely because effective techniques were not available for tracking them underwater, or for recording their dive depths. Thus, I developed a new tag and used it to mark free-swimming whales to monitor and record their geographical and vertical movements in real time. The tag contained 2 transmitters. The sonic transmitter (50 kHz) allowed submerged whales to be tracked from less-than-or-equal-to 2 km, and it produced a pulse rate or pulse interval-coded signal from which dive depths were recorded. A VHF radio transmitter (148.00 MHz band) allowed individuals to be tracked at the sea surface from 10's of km. Initial applications of these tags on right whales (Eubalaena glacialis) in the Bay of Fundy (n = 10; 1989-90) and off Massachusetts (n = 3; 1989), and on humpback whales (Megaptera novaeangliae) off Massachusetts (n = 2, 1991), Socorro Island, Mexico (n = 1; 1992), and Sitka, Alaska (n = 1; 1993) provided the first direct measurements of dive profiles for mysticete whales. I made 2 configurations of the tag's housing and attachment anchor (a stainless steel dart 6.5 cm long) to serve different short- and long-term objectives. One was designed to detach after approximately 2 days by means of a corrosible, galvanic release link, then float so it could be recovered and reused. The other was designed to stay attached and transmit for up to 2 months. No adverse effects to whales from the tags or the approaches were observed. My tagging and tracking system will allow collection of precise depths and dive profiles of whales, will make it possible to coordinate and direct prey sampling efforts next to tagged whales while they are submerged, and will reduce speculation about their behavior while diving.