Photogrammetry: A Way to Study Whales
Wayne Perryman Shares His Research
Why is the number of gray whales born lower in some years than in others? What reasons might account for changes in numbers of babies (calves) born each year? What factors might trigger a low number of gray whale births? So many questions!
Meet Wayne Perryman, who is trying to find the answers. A biologist at NOAA's Southwest Science Center in San Diego, Wayne is the U.S. government's main specialist on gray whale birth rates. Wayne Perryman has counted gray whale mothers and calves migrating past Point Piedras Blancas, CA (35.40N, 121.17 W.) each spring since 1994. That's when the population was removed from the Endangered Species List. Wayne explains, "One of the agreements connected with that decision was to monitor reproduction in gray whales over a 5-year period. But because we have seen much wider fluctuations in the number of calves than we expected, we have extended the study." Now you're invited to think like a scientist. Wayne shares some of his research below.
What is Photogrammetry?
Wayne explains, "If the number of calves born fluctuates, that's a RESULT." Now he and his colleagues are gathering data, looking for causes and connections. One of their techniques is called photogrammetry. Wayne flies over the ocean in a twin-engine plane during migration. From the air, he uses a special camera to take photos of the moving whales. Wayne explains, "A computer tells the camera how high I am and how fast we're flying, and moves the film the same speed that your image at the ground is traveling. So every time I take a picture, it's as if I'm standing still." Such photos let scientists study the living whales. Wayne uses the photos to get information about the condition of the whales in terms of size and shape. He has focused his research on female gray whales. Wayne believes that the condition of the females may tip off scientists to future problems with the entire gray whale population.
Turn: Think Like a Scientist
in the top photo is indeed much bulkier; pregnancy (as well as more
blubber) is the reason. Wayne Perryman studies aerial whale photos like
these to detect reproductive status and changes in nutritive condition
during the southbound migration. Changes in girth are better indicators
of changes in a whale's condition than measurements of blubber thickness.
What inferences would you draw about the thin whale in the bottom
photo? The researchers found that gray whales lose between 11-25%
of their weight during approximately 60 days of fasting between their
southbound and northbound migrations past central California.
Try This! A Closer Look
National Science Education Standards