Cows
and Calves and Ice, Oh My!
Looking
for Correlations
Biologist
Wayne Perryman is the government's leading authority on gray whale
calf production. When Mr. Perryman saw interesting fluctuations
in numbers of calves born each year since he started counting in
1994,
he
knew
it was a result of some factor. What might cause it? He noted other
significant events during this period, including these:
- High
numbers of whales died in strandings in 1999 and 2000, and many
whales were thin and undernourished.
- Calf
births hit an alarming low during his study years.
- Scientists
did not see a large number of dead calves in the lagoons or along
the beaches, as they would if the babies were being born and then
died for some other reason.
- Especially
in
1999 and 2000, some whales appeared skinnier than normal.
- The
Bering and Chukchi seas saw abnormally heavy seasonal ice
in the early years of the study, while in more recent years ice
melt has been later.
Number
of Northbound Newborns
(as of end-of-season counts):
Rating
|
Newborns |
Year
|
Highest
|
106
|
1997-98
|
2nd
|
44
|
1996-97
|
3rd
|
43
|
1993-94
|
4th
|
35
|
2001-2002
|
5th
|
34
|
1995-96
|
Scientists look for correlations between variables. Mr.
Perryman wondered: Do gray whales have access to their food over the
same amount of time every year? (Or, How long was their feeding ground
ice-free?)
He wrote a scientific paper that looked at how skinny whales
may be linked to low calf production and ice conditions from 1997 to
2002. Mr. Perryman concedes that many pieces
need to be studied before the puzzle is solved. This is your chance
to think
like a scientist as you look at a bit of Mr. Perryman's research.
|
Try
This! Journaling or Discussion Questions
- What two
variables are the scientists investigating, as shown on this graph?
- Do you
ever see a year with a long feeding season and a low of number of calves?
Do you see a short feeding season followed by a high number of calves?
What hypothesis might you pose?
- Does this
graph seem to show any correlations? Explain your thinking.
- Where
might a dot on the graph show up if these variables were NOT correlated?
Can you suggest (1) a number of calves and (2) a length of feeding season
that would NOT fit the pattern that Wayne Perryman has found so far?
For
More:
See Photogrammetry:
A Way to Study Whales. Examine photos that help Wayne Perryman learn
more about the condition of gray whales.
National
Science Education Standards
- Use data
to conduct a reasonable explanation.
- Think
critically and logically to make relationship between evidence and explanations.
- Science
investigations involve asking and answering a question and comparing
that to what scientists already know about the world.
- Scientists
develop explanations using observations (evidence) and what they already
know about the world.
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