. Bulletin. Science; Natural history; Natural history. v* BULLETIN SOI nil Rh CALIFORNIA ACADEMY OF SCIENCES VOLUME 73. Figure 1. Seasonal distribution and migration route of the gray whale, Eschrichtius robustus: a, Baja California, Mexico: b. Scammon's Lagoon. Respiratory-diving behavior.—Within the stag- ing area, the whales were swimming slowly, exhibiting their typical respiratory-diving behav- ior, which is initiated by the crown of the head and paired blow-holes breaking the surface of the sea. Exhalation is signified by a visible, heart-shaped, vaporous spout and a very audible blow. T
. Bulletin. Science; Natural history; Natural history. v* BULLETIN SOI nil Rh CALIFORNIA ACADEMY OF SCIENCES VOLUME 73. Figure 1. Seasonal distribution and migration route of the gray whale, Eschrichtius robustus: a, Baja California, Mexico: b. Scammon's Lagoon. Respiratory-diving behavior.—Within the stag- ing area, the whales were swimming slowly, exhibiting their typical respiratory-diving behav- ior, which is initiated by the crown of the head and paired blow-holes breaking the surface of the sea. Exhalation is signified by a visible, heart-shaped, vaporous spout and a very audible blow. The whale then begins to round-out, exposing its dorsum to at least the primary dorsal ridge (sometimes called the dorsal bump) then submerges a few feet beneath the surface for one to two minutes and again resurfaces to exhale and inhale. This procedure is repeated, on the average, three to four times. After the last blow in the respiratory series or blast, as it was called by whalers (Slijper, 1962), the round-out is much more pronounced and delib- erate. The entire dorsum and caudal peduncle arches above the surface exposing its entire array of dorsal ridges. The sequence ends with its flukes breaking above the water in an arching motion and re-entering at about a 45 degree angle. This action initiates the deep-dive phase. Normally, the whale will remain submerged for an average of from five to eight minutes, but in the lagoon the mean is from three to five minutes. Upon resurfacing after the deep-dive, the animal repeats the entire respiratory-deep dive sequence. Gray whales will seldom deviate from this respiratory behavioral pattern unless frightened or agitated in some manner. SOCIAL INTERACTION AREA From the staging area the whales gradually swam south into the lagoon preferring the shallower waters along the west bank. Very few animals were observed moving down the deeper mid- channel or along the cast bank. Depths along the west bank vary from a few feet to less than
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