Role of Size
We developed a new, innovative technique for measuring the sizes
of whales underwater. The technique uses a digital video camera
operated by a snorkeler to obtain lateral
or dorsal full-body views of a whale, and a hand-held sonar device
to measure the distance from camera to whale. The camera lens is
set at a fixed angle of view. The resulting images and distance
data are processed off-line through Photo Shop to obtain actual
sizes based on the ration of the whale’s image size to the known
field of view of the camera lens at the measured distance. Preliminary
results showed that females with calf (hence, sexually mature females)
were on
average larger than accompanying escorts. Further, the sizes obtained
for females with calf and escorts (males) compared well with measurements
made by biologists of sexually mature females and males killed by
whalers (Spitz, Herman & Pack, 2000).
Spitz,
S. S., Herman, L. M.
& Pack, A. A. (2000). Measuring sizes
of humpback whales (Megaptera
novaeangliae) through underwater videogrammetry.
Marine Mammal Science 16, 664-676.
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