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Studying Wildlife
involves a lot of engaging field work as well. Fortunately, there
are a variety of field techniques available for us.
Counting
Populations and measuring density
When populations
are too large to count by taking a direct census, scientists perform
what is called random sampling.
Random sampling-
is a technique where one selects certain representative samples
of the population randomly. For e.g. in a forest community, to examine
populations of ten different species, there would be an eminently
suitable technique. One would start by dividing the area into smaller
sectors and randomly selecting certain sectors and taking a census
count or a percentage cover of the sector.
| Quadrants
- quadrants come in all shapes-squares, rectangles, circles,etc.
The purpose of a quadrant is to enforce a certain boundary upon
the area that one has selected. Biodiversity is examined within
the quadrant only. The advantages of a quadrant are that is
portable, well-defined and simple. The disadvantage of a quadrant
is that it is not a suitable boundary for moving organisms like
animals. |
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Census
Count - a direct count of the number of organisms within a
population.
Percentage
Cover - an estimate of the percentage of the total area that
a certain population covers. This technique can prove useful
in circumstances where the individual organisms are too small
to be seen distinctly. For e.g. moss in a quadrant area. All
of the above techniques are useful when examining density,
but how would one determine distribution patterns within a
community.
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Distribution
pattern measurements
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Transect
line- this is an arbitrarily chosen straight line marked with
a measuring tape. This is useful in determining zonation patterns
along the ground. A popular technique is to record the dominant
species at each interval mark along the transect line. This
data is then used to construct a cross-profile of the community.
Profile
sticks- are long sticks marked with alternately coloured stripes.
They are useful for two reasons. They can be used to measure
height of plants since each stripe is painted at equal intervals.
They can also be used to measure elevation of the ground,
by line of sight. Profile sticks have several disadvantages-
they cannot be used to measure very high plants, they are
not easily portable and they are prone to errors in line of
sight.
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