Post-calving Groups - A Scientist's Activities

Late-June to July

Caribou scientists usually get to take a break back in their offices after their work during the calving period, but they return to the field in late June. They locate all the radio-collared cow caribou and see which ones still have calves. This gives the scientists a better idea of how calf survival related to calving location.

In order to find out how many caribou are in the Porcupine Herd, every two to three years caribou scientists take advantage of the large post-calving groups to do a photo-census of the herd. To quickly find the large aggregations of caribou, scientists locate the satellite-collared and radio-collared animals to see where the aggregations are. All of the cows and calves and many of the bulls in the herd are usually in just a few huge groups on the coastal plain or in the foothills of the mountains. Most collars are put onto cow caribou, but a few radiocollars on bulls help the scientists track down those males who are not within the large aggregations, but who instead may be a hundred miles away in the high mountains, or even on the south side of the Brooks Range.

Once the large groups have been located, scientists use an airplane with a special camera to fly over and photograph the caribou. They use a computer connected to a Global Positioning System (GPS) to calculate the correct overlap between photos so that each group gets completely photographed. Eventually they have photos of every caribou in the herd, except for a few that have not joined one of the large aggregations. Sometimes, the scientists fly very intensively over the areas away from the large groups in order to locate stray caribou and estimate how many were missed in the photos. When that has been done, the estimate for additional caribou not in the photographed groups has always been very small, so scientists usually rely on just the photographs to count the herd.

In conjunction with the photo-census, scientists sometimes get on the ground near the large aggregations so they can use binoculars or a spotting scope to identify individual caribou by their sex and age. Those data can be combined with data from the radio-collared caribou to estimate the overall makeup of the herd.

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