See also:

Caribou birth rates
 
Snow depths at Old Crow
 
Caribou and Climate Slide Show

Arctic Borderlands Ecological Knowledge Co-op

What is happening?

• This graph shows changes in the Porcupine Caribou Herd size from the early 1970s up to the most recent caribou count in 2010. The herd reached a peak in 1989 at 178,000 and then declined until 2001 when numbers were estimated at 123,000 caribou.
• The last population estimate in July 2010 was 169,000 caribou.

Why is it happening?

• The size of the Porcupine Caribou Herd depends on how many calves are born and survive and how many adult animals die during the year. The Porcupine herd did not grow as quickly other North American herds during the last decades of the 20th century. The birth rate during that period was high and managers suspected that the Porcupine herd experienced greater natural adult mortality than other barren ground caribou herds.
• Biologists believed that the population decline in the 1990s was probably related to weather conditions (high snow accumulations on the wintering grounds and short summers in the early 90s).

Why is it important?

• Caribou from this herd are the main large ungulate ranging across the Northern Yukon.
• People in the Yukon, Alaska and the Northwest Territories depend on the Porcupine Caribou Herd for food, and spiritual and cultural well-being.

Technical Notes

• The data points on the graph are based on total counts of the caribou on their calving grounds. The census is done by taking photos from an airplane and counting the caribou.
• Managers were unable to count the herd between 2001 and 2010 for several reasons. In some years the caribou did not group well enough for pictures to be effective and in other years bad weather or poor visibility due to smoke from forest fires prevented the caribou count.