Table 3. Environmental condition classes and climate variables for eight seasons for the Porcupine Caribou Herd, based on data from McNeil et al. (2005).

Model season Dates Measured environmental condition Weather-driven state Years true vs. false
1. Calving 6/1 – 6/10 % snow cover within extent of calving Early snowmelt < 20%
Late snowmelt > 20%
Early: 1985, 1990-91, 1993-1996, 1998, 2002-03
2. Postcalving 6/11-6/30 21 June NDVI – 1 June NDVI, within extent of calving Fast green-up > 0.1
Slow green-up < 0.1
Fast: 1988-89, 1993-95, 1997, 1999-2001
3. Early summer
4. Mid - late summer
7/1 – 7/15
7/6 – 8/7
Rank of total June precipitation & July mean max temperature, Old Crow Few insects < 20
Many insects > 20
Few: 1986-87, 1991-92, 1999-2001, 2003
5. Fall migration
6. Rut / Late fall
8/8 – 10/7
10/8 – 11/30
Total September snowfall, Old Crow Late snowfall < 4.5-cm Early snowfall > 4.5-cm Late: 1985-86, 1989, 1991, 1997-99, 2001-03
7. Winter 12/1 – 3/31 March snow depth, Eagle Plains Shallow snow < 75-cm
Deep snow > 75-cm
Shallow: 1985-87, 1994-97, 1999, 2002
8. Spring migration 4/1 – 5/31 (1 May snow depth) – (1 March snow depth), Old Crow Early snowmelt > 30-cm
Late snowmelt < 30-cm
Early: 1988-91, 1993-95, 1998, 2003
The eight seasons of a model year run from calving in calendar year through spring of the following calendar year, i.e., calving in model year 1985 represents June 1985, while spring migration represents April/May 1986.
NDVI = Normalized Difference Vegetation Index