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 2001 (the year of the last census). The herd reached a peak in 1989 and, between 1994 and 1998, it declined at a rate of 4% per year. In 2001, the herd was estimated at 123,000 caribou and this indicates the decline slowed since the 1998 census.

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 has not grown as quickly as other barren ground caribou herds, but its birth rate is comparable. This suggests that the Porcupine herd experiences greater natural adult mortality than other barren ground caribou herds.
• Biologists believe that the recent declining trend in the 1990s is probably related to weather conditions (high snow accumulations on the wintering grounds and short summers in the early 90s). The body condition of adult female caribou in March has also been declining over the same period. This supports the idea that environmental stresses on adult caribou are limiting current growth of the herd.
• Harvest levels have remained within 3-5% of the total herd size, so hunting is unlikely to be a cause of observed recent decreases in caribou numbers.

Why is it important?

• Caribou from this herd are the main large ungulate ranging across the Northern Yukon.
• People in communities 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.
• The most recent census (2004) was cancelled due to coastal fog and smoke from interior wildfires.
• The next census of the herd is scheduled for 2005.