According to the Alaska Department of Fish and Game, the populations of two types of arctic caribou herds are on the rise. The Teshekpuk Herd increased from 45,000 caribou in 2002 to 64,000 in 2009, and the Central Arctic Herd increased from 32,000 animals in 2002 to 67,000 in 2009.

The Teshekpuk and Central Arctic herds are the only herds known to be increasing in numbers at this time. Researchers attribute this growth to good production rates, good weather, low predation, and good habitat.

The populations of other herds are on the decline, although the specific causes for these declines are currently undetermined. Some theorize that these changes in herd numbers are due to a mixing of caribou from several different herds. However, this theory has not been substantiated through photocensus or radio-tracking data.