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How do we estimate herd populations?
Results from the July 2006 surveys of the Cape Bathurst and Bluenose-West caribou herds indicate these herds continue to decline. The July 2006 survey of the Bluenose East herd indicates this herd has remained the same size since last year.
These
results were determined using a technique called photo-census. A
photo-census
consists of four basic stages
outlined below. The procedure takes several months to complete, with Stage
1 beginning in early March, and Stages 3 and 4 taking place in July. The
methods used to carry out a photo-census are carefully designed to ensure
that estimates are reliable. A photo-census takes advantage of the natural
migration behaviours of barren-ground caribou.
Click on
the photographs provided in the Links to Results column to view the results
of each stage of the 2006 survey.
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Stage |
Description of procedure |
Timeframe |
Links to results
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1 |
Aerial surveys are conducted to locate caribou on winter ranges.
Aircraft fly in a grid pattern to spot caribou on the barren-grounds
and below the treeline (most of the winter ranges of the
Bluenose-West and Bluenose-East herds are below the treeline.
Typically some Cape Bathurst caribou winter above the treeline on
the Tuktoyaktuk Peninsula). The results are used to determine
late winter distribution of the herd.
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Early to mid-March |
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2 |
Biologists put radio collars on caribou throughout the winter range
of each herd as follows:
Cape Bathurst:
30 collars
Bluenose-West:
29 collars
Bluenose-East:
26 collars
Upper Tuk Peninsula:
21 collars
Approximately 43% of the caribou collared in each herd were males.
For more information on radio-collaring and radio-telemetry please
click here.
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March 2006 |
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3 |
Aerial surveys are flown to locate radio-collared caribou on
post-calving and summer ranges. During this time the caribou come
together to form large groups or summer aggregations. Groups vary
in size, ranging from several hundred to 15,000 to 20,000 caribou.
Fixed wing aircraft flying in a grid pattern are used to spot the
groups of caribou. Aerial surveys are also conducted on the winter
range to locate collared caribou that have died since collaring.
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Late June to early July |
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4 |
Finally, groups of caribou spotted in stage 3 are photographed from
the air using a high-resolution digital camera and photomaps of the
images are created using Global Positioning System (GPS) software.
GPS software is then used to count the caribou in each group.
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Early July |
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