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Photogrammetry: A Way to Study Whales
Wayne Perryman Shares His Research
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Biologist Wayne Perryman

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?

Describe how the whales in these phtos are different. What inferences can you make to account for the differences? Photo W. Perryman

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.

Your Turn: Think Like a Scientist
See the photos above and think like a scientist to answer the questions in the caption. After discussing or journaling your thoughts, read on.

The whale 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.


Photos Wayne Perryman

Try This! A Closer Look

  • Wayne Perryman took these 3 aerial photos to study and measure the size, shape, and condition of the whales during migration.
    Which photo do you think shows a pregnant whale?
    How do the two mother whales differ in girth, and what might explain the differences?
  • In 1996-1998, nearly 500 calves were counted for the season. In 2001, total calves counted by May 15 stood at just 66, the lowest count by that date in the (then) 8 years of surveys from Piedras Blancas. Wayne says, "The good news was that strandings were down from the alarming 274 dead gray whales counted in 1999, the majority of which were thin and starved-looking." What might account for whales being thin? Wayne's other research gives you more to think about as you ponder that question. See

National Science Education Standards

  • Science investigations involve asking and answering a question and comparing that to what scientists already know about the world.
  • Scientists use different kinds of investigations depending on the questions they are trying to answer.
  • Scientists develop explanations using observations (evidence) and what they already know about the world.
  • Many people choose science as a career and devote their entire lives to studying it. Many people derive great pleasure from doing science.


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