Hi Kids,
Today, we spent some time learning about how scientists
who study ecosystems gather data. It is really quite different from how we've
been collecting data so far this year in class, where we basically start with a
question and design an experiment with an independent variable, identify the
dependent variable that we can measure and then make sure we control all the
other variables. Clearly, if we want to study something in an ecosystem like
the Acadian forest, we can not do this. It really is not possible to control
anything in an ecosystem, like a forest.
But, scientists can measure how many animals there are (population size)
of the different animals over time and see if there are patterns that they can
then try to explain. The scientists have been gathering data here for 8 years
now.
Scientists basically either use direct or indirect
observations to determine the size of a population. Direct observation is when you simply count
all the members to find out how many there are. This is really so much harder
to do than you would imagine. For example we went for a walk and could see
signs that there was a porcupine around- it had eaten the bark from a tree and
we saw its poop on the ground. But to my great disappointment, we could not see
the porcupine.
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Can you see the evidence that a porcupine has been having
dinner here?
|
Indirect observation is when you look for signs of the
organisms rather than the actual organisms themselves. The porcupine poop for
incidence was evidence of a porcupine being around. We also found footprints of
a bobcat and many deer.
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Today we are setting things up for a method called mark
and recapture studies to estimate how many small rodents are in each hectare of
the forest. We spent time setting up 100 little traps that will trap mice or voles and keep them safe, comfortable, and fed, until we will go back to look
at the boxes tomorrow.
I'll tell you more about how we will figure out how many
mice or voles there are in based on how many we manage to trap by tomorrow. It
will be embarrassing if we don't manage to trap any mice. It would mean that
none of us were able to think like a mouse and set the traps in good mouse
spots.
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| Cages being prepared to capture rodents |
Challenge question for today: Make a list of all the
things you can think of that you can use for indirect observations that help
you know if there is an animal about or not. For example, finding poop or
footprints.
From Miss Green's C block class:
ReplyDelete1. What are all of the types/species of animals that you have seen?
2. How many types/species of animals do you hope to see?
3. What do you do during your free time?
4. Which population counting method is the most accurate? Why?
5. Will you try all of the methods of determining population size?
6. Do you think the winters are going to get longer over time? Why or why not?
Thank you for Skyping with our team today!
Hello Ms. Green's class,
DeleteThanks for all your questions.I'll try my best to answer them all for you.
1. So far because animals are so good at hiding, we have only seen voles in the forest.
2. Again, because animals are so good at hiding, we don't expect to see many animals though we see many signs of them. However I am really hoping to see porcupine.
3. We don't have a lot of free time, but I like going for walks because the cottage is right on the cost.
4. It depends on the kind of animal. For example elephants in the savanna are best counted by direct counting methods to get an absolute number. But the mice and voles as best counted by the capture mark recapture method.
5. No, because the direct method won't work out here in the forest where the animals are so good at hiding.
6. No one really knows exactly what to expect. Some models even predict that we may at some point slip into another ice age. Also, we really have to see certain patterns happening for many more years before we can say for certain that we are in fact seeing that winter is arriving later and lasting later into the year (as it has for the last few years).