Changes in dates of emergence from
hibernation by chipmunks, ground squirrels, and
marmots at high altitude in the Colorado Rocky
Mountains: An effect of climate change?
David W. Inouye
University of Maryland and RMBL
billy barr
Rocky Mountain Biological Laboratory
Crested Butte, CO
Metadata: www.rmbl.org
Funding: NSF LTREB
The Rocky Mountain Biological Laboratory
1800
Winter Snowfall in Gothic
1600
Snowfall (cm)
1400
1200
1000
800
600
400
200
0
1975
1980
1985
1990
1995
2000
2005
Chipmunk (Tamius minimus)
Golden-mantled ground squirrels (Spermophilus lateralis)
Yellow-bellied marmots (Marmota flaviventris)
Day of year of first chipmunk sighting
130
120
110
100
90
1975
1980
1985
1990
1995
2000
2005
Day of year of first chipmunk sighting
130
120
110
100
90
1975
1980
1985
1990
1995
2000
2005
The North Pacific Oscillation (also known as PDO)
Typical wintertime Sea Surface Temperature (colors),
Sea Level Pressure (contours) and surface windstress (arrows) anomaly patterns
during warm and cool phases
warm phase
cool phase
http://tao.atmos.washington.edu/pdo/
Winter snowfall in Gothic (calculated from streamflow)
1800
2
r = .059
p = .0485
1600
19571995
1980
1952
1400
1978
1948
1200
1000
1973
1967
1964
1971
800
1965
1958
1949 1968
1938
1996
1951
1970
1943 1998
1985
1942
1982
1937
1989
1991
1947
1944
1969
1946
1945
1972
1974
1976
1990
1994
1960
1959
1939
1988
1966
2004
2000
1954
1953
1962
1975
1961
1979
2001
1963
2002
600
1977
400
-10
-5
0
5
Annual means for North Pacific Oscillation index
Total snowfall in Gothic (cm)
1800
2
1600
r = .159
p = .060
1400
1200
1000
800
600
400
1975
1980
1985
1990
1995
2000
2005
Total snowfall in Gothic (cm)
1800
2
1600
r = .159
p = .060
1400
?
1200
?
1000
?
800
?
600
400
1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 2025
Day of year of first chipmunk sighting
130
120
110
100
90
1975
1980
1985
1990
1995
2000
2005
Calendar day of first chipmunk sighting
170
19 June
160
150
140
130
r2 = .117
p = .05
120
110
10 April
10 May
100
100
110
120
130
Calendar day of first date of bare ground in Gothic
Calendar day of first chipmunk sighting
140
2
r = .237, p = .007
130
120
110
100
90
800
900
1000
Heating degree days in April
1100
Conclusions
• Chipmunks
– No trend over 33 years
– Some trend before/after 1998
– Date of snowmelt and April temperatures
important
Day of year of first ground squirrel sighting
140
130
120
110
100
90
1975
1980
1985
1990
1995
2000
2005
Day of year of first ground squirrel sighting
140
130
r2 = .371
p = .002
120
110
100
r2 = .622
p = .01
90
1975
1980
1985
1990
1995
2000
2005
Day of year of first ground squirrel sighting
140
r2 = .109, p = .066
130
120
110
100
90
110
120
130
140
150
160
Day of year of first bare ground
170
Calendar day of first ground squirrel sighting
140
r2 = .153
p = .036
130
1995
1986
1985
2000
120
2002
110
1992
100
1997
1994 1996
1993
1998
2001
1981
1990
2004
1989
1987
2003
1988
2006
1984
1999
1979
1991
1983
1982
1974
1976
90
2005
80
750
800
850
900
950
1000
April Heating Degree Days
1050
1100
1150
Conclusions
• Ground squirrels
– No trend over 33 years
– Significant trends before/after 1998
– Snowmelt dates and April HDD important
Date of first marmot sighting in Gothic
30 May
20 May
10 May
1 May
20 April
10 April
1 April
2
r = .399
p = .0002
25 March
1975
1980
1985
1990
1995
2000
2005
Calendar day of first marmot sighting
150
1984
140
1982
1999
1985
130
1983
1976
1991
1995
1993
120
1998
1987
2000
1996
1994
2003
110
1997
1986
2006
1988
20041990
2001
2005
1989
100
2002
r2 = .458, p < .0001
90
1992
26
28
30
32
34
36
April mean temperature (F)
38
40
Snowpack on date of first sighting (cm)
250
200
r2 = .322
p = .009
150
100
50
0
1980
1990
2000
Conclusions
• Marmots
– Are emerging significantly earlier
– April temperature increases may be
responsible
First chipmunk sighting (calendar day)
140
1995
130
1984 1999
1997
2000
120
1986
1996
1993
1998
1994
1985
2002
2001
110
1983
1981
1982
1987
2007
2003
1974
1980
1990
2004
100
1992
1989
1991
1988
1979
2006
1976
1977
r2 = .405
p = .0001
1978
90
100
110
120
130
First ground squirrel sighting (calendar day)
Calendar day of first ground squirrel sighting
140
130
120
110
100
90
80
90
100
110
120
130
Calendar day of first marmot sighting
140
Predicted winter snowfall for Gothic, CO (cm)
Historical snowfall predictions based on
peak spring runoff in the East River
at Almont, using snow data 1975-2000
2000
1500
1000
500
0
1940
1960
1980
2000
Days between first S. lateralis sighting and first Mertensia flower
70
r2 = .145
p = .05
60
50
40
30
20
10
1975
1980
1985
1990
1995
2000
2005
More conclusions
• Chipmunks and ground squirrels are
responding differently than marmots
• Phenology of animals and plants is
diverging
• Regional climate change (affecting
snowpack) may be important as well as
global climate change
Global climate
Regional climate
NPO
ENSO
Migration
Local climate
Snowpack
Snowmelt
Frost Effects
Flowering
Phenology
Abundance
Species
Interactions
Hibernation
Plant Demography
Adaptation?
• Phenotypic plasticity
• Evolutionary responses
National Phenology Network
• http://www.usanpn.org/
Special Feature on Phenology
Ecology, February 2008
Inouye, D. W. Consequences of climate change for phenology, frost damage,
and floral abundance of sub-alpine wildflowers.
Kudo, G., et al. Effects of phenology and carbon assimilation on plant
reproduction: Implications for climatic changes.
Rich, P., et al. Phenology of mixed woody-herbaceous ecosystems following
extreme events: Net changes from differential responses
Post, E., et al. Phenological sequences reveal aggregate life history response
to climatic warming
Miller-Rushing et al. Global warming and flowering times in Thoreau’s
Concord: A community perspective