. Fig. 54. Humpback whale. Average monthly foetal length. (baleen lengths) shows that weaning takes place at a length of 7-5-8 m. Fig. 61 shows that the calf reaches this length at an age of about five months after birth, which period is, therefore, the duration of lactation. If, in Fig. 53, lines are drawn parallel to the average line but taking their origin at monthly intervals on each side of it, the points are divided up into a number of groups representing pregnancies starting in each month. When these pregnancies are counted and plotted by months the curve in Fig. 55 is obtained, which s
. Fig. 54. Humpback whale. Average monthly foetal length. (baleen lengths) shows that weaning takes place at a length of 7-5-8 m. Fig. 61 shows that the calf reaches this length at an age of about five months after birth, which period is, therefore, the duration of lactation. If, in Fig. 53, lines are drawn parallel to the average line but taking their origin at monthly intervals on each side of it, the points are divided up into a number of groups representing pregnancies starting in each month. When these pregnancies are counted and plotted by months the curve in Fig. 55 is obtained, which shows the frequencies of pairing by months. This indicates that the breeding season covers the months of August to November inclusive, with its highest intensity in September, and that a small amount of breeding occurs throughout the year. If the curve is replotted with the time scale shifted eleven months later, the curve showing the frequency of births in Fig. 56 is obtained, which shows that the majority of births occur in August. It should be noted that some, but not all, of the minority of pregnancies starting out of the regular breeding season may be those of whales, belonging to the schools of the northern hemisphere.
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Keywords: ., bookcentury1900, booksubjectocean, booksubjectscientificexpediti
