the initial southerly movement of both non- 

 instrumented and instrumented animals appears 

 in order. 



Observation Studies 



Behavior of Instrumented Animal — 1974 



The depth record of the lagoon track of the male 

 calf showed patterns quite different from those we 

 have come to expect from cetaceans during radio 

 tracking. The most striking difference was long 

 periods (up to 3 h) when the calf apparently was at 

 or very near the surface. Although instrumenta- 

 tion circuitry functioned properly in pre- and 

 post-track tests, we prefer to wait for replicate 

 tests to check the validity of these curious ob- 

 servations before reporting the results in greater 

 detail. 



FISHERY BULLETIN: VOL. 75, NO. 1 

 Tidal and Water Depth Relations 



Whales observed from Colina Coyote responded 

 to the changing tide every day. Each time the high 

 tide turned and while it was still high, many 

 mother-calf pairs swam slowly northward into the 

 extensive deeper water of Bahia Grande. 

 Sometimes well before the tide was very low most 

 animals would be gone from in front of Colina 

 Coyote, with most stragglers travelling in the 

 deepest water available (see Figure 3). The return 

 movement began in similar fashion with the 

 beginning of flood tide. The variation in arrival 

 was so great that some animals did not appear 

 until approximately high tide. Casual observa- 

 tions in channels in upper Magdalena Bay suggest 

 that similar behavior may occur there, though in 

 the deeper and broader waters of that open bay 

 some whales were present throughout the tidal 



Caleta 

 Calloway*: 



Punta - ' 

 Nichols 



\ 







y I 234 



2 34 



HIGH 



TIDE 

 LEVEL 



LOW 



TIME RELATIVE TO 

 TIDAL CYCLE (HR) 



12 3 4 



12 34 





12 3 4 



2 34 



Playa 



. P^JJf^Kii 



12 34 



P 



B. 



^ 3 yg?» yj f?S3 



2 34 



■| 2 34 



g^frgra 



12 3 4 



Colina Coyote 



FIGURE 3.— Tidally related movements of adult gray whales in the calving lagoon at Colina Coyote, Baja California Sur, Mexico. 

 Sketch map of waterways in front of Colina Coyote observation post showing tidally related movements of adult California gray whales. 

 Data were acquired visually and recorded on a base map without the grid marks, as tracks against time. The grid was superimposed and 

 an enumeration of sightings per square made for the time period involved. Animals entered or left on the turning tide, thus low tide (1) 

 shows a concentration of animals in Canal Dohl, but also some deep in the Canal Central. The latter represent animals that entered the 

 area soon after the change to incoming tide. Bars for high to 2 h after high tide (3) and 2 h after high to mid-low tide (4) reveal first a high 

 concentration of animals coming up channel toward Bahia Grande and passing Colina Coyote, and finally a few stragglers making this 

 passage before low tide. Animals seen in the period from medium rising to high tide (2) represent the more or less static population of 

 animals that milled slowly in the channels in front of Colina Coyote before tidally related movement began. 



164 



