Thomas C Poulter
- waterbody:North Pacific OceanBaja California; Laguna Ojo de Liebre "Scammon's Lagoon"
The following will give you some background information and conditions under which the gray whale recordings were made in Laguna Ojo de Liebre (Scammon's Lagoon) Baja California, Mexico, in January and February, 1967. In all 60,000 feet of tape recordings were made from which 12,000 feet of almost continuous animal signals were made most of which are believed to be from the gray whale.
The gray whales seemed to be much more alerted to the plane or helicopter swooping down close to the water than they were to the motor boats in the water, and they paid almost no attention to the boats in the water if the engines were not running. In fact, on several occasions when the copter dived close to them to shoot a hypodermic dart or a small marker buoy harpoon into them, they would strike at it with their flukes and on one occasion threw enough water on the helicopter to kill its motor. Fortunately, he was able to get over to the beach before he came down. At first we thought their greater attention to the plane or copter was because all of the actual contacts with them in the way of darts or small marker buoy harpoons was from them rather than from the boats, but while making our recordings with the hydrophones in the water, we found that either the plane or the helicopter made vastly more noise in the water than did the motor boat even running at high speed. Further, since they completely disregarded the boats when they were drifting dead in the water suggests that it is primarily a matter of the loud noise.
We were able to drift with the boat dead in the water with 12 to 15 whales all around us for hours and a cow and calf would frequently pass within 20 to 50 feet of us and only on one occasion did they shy off when they saw us. On at least one occasion a cow and calf passed directly under our boat while we were recording, and the water was only about 30 feet deep. We obtained many hours of recordings with the boat dead in the water with whales all around us, but when they would pass on by and get a considerable distance from the boat, their sounds would reduce to a minimum.
With our sensitive recording equipment, we could pick up their sounds as long as we had a straight line of sight path in the water but in the lagoon this would seldom be more than a mile and a half or two miles before a sand bar would come between the whale and the hydrophone. Throughout the central portion of the tape the recording was made in the small nursery inlet of the lagoon with many cows with calves all around. From the unfiltered channel, you will notice that the snapping shrimp are very prominent. Then the last sequence starts under this same condition. It was late forenoon when they decided to attempt to tranquilize one of the cows. The first pass of the helicopter was not recorded but immediately thereafter the whale repeated a loud "Rasp" followed by the loud "BONG" three times. If you will notice the unfiltered channel, you will observe that immediately after the first rasp and bong all other whale noise ceases as does all of the snapping shrimp noise.
About that time the copter made its second pass during which the whale was silent. Just as soon as the noise of the plane had died out the whale starts its series of clicks which sound like tapping on a board with the knuckles. They occur in groups of 3 to 5 and these groups are separated by a few seconds. After several of these groups, the copter can be heard again and the clicking stops until after it has passed and its sound has died out and then it starts again and the tape ends. We suspect that the loud _rasp_ and _bong_ are alert signals but it is most surprising that not only the whales stop their vocalization but the snapping shrimp stop their snapping.
We made an additional 18,000 feet of tape in Scammon's Lagoon at a time when there were no gray whales there and any sounds that were heard when the gray whales were not there have been deleted from this tape. There were two types of signals thus deleted which we suspect were caused by sting rays feeding on shellfish. We hope that this tape will be both informative and interesting.
ML: This recording was not divided up with breaks where dropouts occur because it is unclear whether the recorder was turned off and on, or a filter was turned off and on, or the tape is looped.