Aurélie COHAS

Christophe BONENFANT

Dominique ALLAINE

Laboratoire Biométrie et Biologie évolutiveUniversité Claude Bernard Lyon 1

43 Bd du 11 novembre 1918 69622 Villeurbanne France

EFFECTS OF SUMMER ENVIRONMENTAL FLUCTUATIONS

ON SURVIVAL OF ALPINE MARMOT

Climate effects on demography

Climate change => how climate acts on demography = necessity to assess the trajectory of species

Environmental conditions affect individuals’ performance through:

- direct effects

- indirect effects via primary productivity

=> Assess impact of summer climate on marmots survival, using long-term data on individually identified marmots

Field site

40 ha of alpine meadow located in the Grande Sassière national reserve(French Alps, 2340 m above see level)

Field protocol

From 1990 to 2007: 20 families studied 798 marked individuals 1621 encounters

For each family: numberagesex social status

of individuals known

Environmental variables

- Climate

- 2 local variables:

Summer temperature (STemp)

-10

-5

0

5

10

2 4 6 8 10 12

Tem

pera

ture

C°

Month

-10

-5

0

5

10

2 4 6 8 10 12

Tem

pera

ture

C°

Month

Climatic variables: Local variables

- Temperature

=> Summer temperature (STemp)

May October

5

6

7

8

9

10

1990 1995 2000 2005

Sum

mer

mea

n te

mpe

ratu

re C

°

Year

-10

-5

0

5

10

2 4 6 8 10 12

Tem

pera

ture

C°

Month

Environmental variables

- Climate

- 2 local variables:

Summer temperature (STemp)

Summer rainfall (SRain)

0

50

100

150

200

0

50

100

150

200

2 4 6 8 10 12

Cum

ulat

ive

rain

fall

mm

Month

0

50

100

150

200

0

50

100

150

200

2 4 6 8 10 12

Cum

ulat

ive

rain

fall

mm

Month

0

50

100

150

200

0

50

100

150

200

2 4 6 8 10 12

Cum

ulat

ive

rain

fall

mm

Month

0

50

100

150

200

0

50

100

150

200

2 4 6 8 10 12

Cum

ulat

ive

rain

fall

mm

Month

300

400

500

600

700

800

900

1990 1995 2000 2005

Sum

mer

cum

ulat

ive

prec

ipita

tion

mm

Year

Climatic variables: Local variables

- Rainfall

=> Summer rainfall (SRain)

May October

Environmental variables

- Climate

- 2 local variables:

Summer temperature (STemp)

Summer rainfall (SRain)

- Vegetation

Vegetation availability in spring (sNDVI)

Vegetation index

Normalized Difference Vegetation Index (NDVI)

difference from the visible and near-infrared light reflected by vegetation

Abundant vegetation

absorbs visible lightreflects near-infrared light

=> HIGH NDVI

Sparse vegetation

reflects visible lightabsorbs near-infrared light

=> LOW NDVI

near infraredvisible

50% 8%

near infraredvisible

40% 30%

72.008.050.0

08.050.0

14.030.040.0

30.040.0

0.00

0.05

0.10

0.15

0.20

0.25

0.30

1 2 3 4 5 6 7 8 9 10 12

ND

VI

Month

0.00

0.05

0.10

0.15

0.20

0.25

0.30

1 2 3 4 5 6 7 8 9 10 12

ND

VI

Month

0.00

0.05

0.10

0.15

0.20

0.25

0.30

1 2 3 4 5 6 7 8 9 10 12

ND

VI

Month

0.00

0.05

0.10

0.15

0.20

1990 1995 2000 2005

ND

VI

in s

prin

g

Year

Vegetation index

- Normalized Difference Vegetation Index (NDVI)

=> vegetation availability in spring (sNDVI)

15th of April

PredictionsPredictions

Prediction 1Positive effect of proxys of primary productivity on survival

higher temperature => less vegetation => lower survivalmore rain => more vegetation => higher survivalearly vegetation availability => higher survival

BUT possible thermoregulation cost in marmotsmore rain => low survival

Prediction 2Higher environmental effects for young than for adults

Prediction 3 Presence of helpers buffers environmental effects on juvenile survival

Estimating survival

Model and Explanatory variables

Capture Survival Transition from subordinate to

dominant status

agesex

agesex

Agesex

periodsocial status

yearsocial status

presence of helpers at birth

year

Capture history: 1001101220 => capture probability not 1

=> Multistate capture-recapture model to take into account capture probability and social status

Survival

0.0

0.2

0.4

0.6

0.8

1.0

Juv. Yearl. Two > 2

Ann

ual s

urvi

val

Age class

Average survival

Age effect

=> survival increase with age

Apparent survival

Survival

0.0

0.2

0.4

0.6

0.8

1.0

Juv. Yearl. Two > 2

Ann

ual s

urvi

val

Age class

Average survival

Social status effect

=> dominant show higher survival than subordinates due to dispersal effect

Dominant

Subordinate

Survival

Helpers effect

=> Juveniles show higher survival in presence of helpers

0.0

0.2

0.4

0.6

0.8

1.0

Juv. Yearl. Two > 2

Ann

ual s

urvi

val

Age class

Average survival

Helpers

No helpers

Survival

Marked temporal variation0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1990 1995 2000 2005

Juveniles

Ann

ual s

urvi

val

Year

with helperswithout helpers

Effects of summer environmental fluctuations on survival

De-trend of the environmental variables

Environmental variables show tendency

=> Necessity to de-trend variables = use of residuals of linear regression between variable and year

Example of de-trending with STemp

Increasing trend

5

6

7

8

9

10

1990 1995 2000 2005

Sum

mer

mea

n te

mpe

ratu

re C

°

Year

-2

-1

0

1

2

1990 1995 2000 2005DE

-TR

EN

DE

D s

umm

er m

ean

tem

pera

ture

C°

Year

Correlation coefficient between de-trended variables

No significant correlation

De-trend of the environmental variables

Environmental variables show tendency

=> Necessity to de-trend variables = use of residuals of linear regression between variable and year

SRain sNDVI

STemp -0.24 -0.20

SRain 0.25

Effects of the environmental variables

For each age class separately,

Test whether fluctuations of each environmental variable correlates with survival variations

Juveniles

-0.4

-0.2

0.0

0.2

0.4

0.6

-2 -1 0 1

Res

idua

l ann

ual s

urvi

val

sNDVI

Juvenile marmots with helpers

=> Positive effect of availability of vegetation in spring on juvenile survival

=> Positive effect more important in absence of helpers (with: 0.06±0.16, without: 0.74±0.23, p=0.02)

-0.4

-0.2

0.0

0.2

0.4

0.6

-2 -1 0 1R

esid

ual a

nnua

l sur

viva

l

sNDVI

Juvenile marmots without helpers

Juveniles

=> Negative effect of summer precipitation on juvenile survival(-0.23±0.11, p=0.06)

26.4% of deviance explained by environmental variables

0.0

0.2

0.4

0.6

0.8

1.0

-2 -1 0 1 2

Ann

ual s

urvi

val

SRain

Juvenile marmots

Yearlings

No effect of any of the summer environmental variables

Two year olds and subordinate adults

No effect of any of the summer environmental variables

33.8% of deviance explained by environmental variables

-0.4

-0.2

0.0

0.2

0.4

-2 -1 0 1 2

Res

idua

l ann

ual s

urvi

val

SRain

Dominant marmots

0.0

0.2

0.4

0.6

0.8

1.0

-2 -1 0 1 2

Ann

ual s

urvi

val

STemp

Dominant marmots

=> Negative effect of summer temperature on dominant marmots survival (-0.33±0.17, p=0.02)

=> Positive effect of summer rainon dominant marmots survival(0.40±0.21, p=0.06)

Dominant adults

Back to predictionsBack to predictions

Prediction 1 PARTIALLY SUPPORTED

Positive effect of proxys of primary productivity on survivalhigher temperature => less vegetation => lower survival in

dominantsmore rain => more vegetation => higher survival in

dominantsearly vegetation availability => higher survival in juveniles

BUT possible thermoregulation cost in marmotsmore rain => low survival in juveniles

PARTIALLY SUPPORTED

Climate = > Food availability

Food availability seems a limiting factor

for dominant adults through food availability during summer

for juveniles through food availability early in spring=> mother condition + match plant phenology / emergence

BUT for juveniles evidence of direct costheavy rain => thermoregulation costs => behavioral

thermoregulation => no access to food => lower survival

Prediction 1Prediction 1Positive effects of proxys of primary productivity on survival

Back to predictionsBack to predictions

Prediction 1 PARTIALLY SUPPORTED

Positive effect of proxys of primary productivity on survivalhigher temperature => less vegetation => lower survival in

dominantsmore rain => more vegetation => higher survival in

dominantsearly vegetation availability => higher survival in juveniles

BUT possible thermoregulation cost in marmotsmore rain => low survival in juveniles

Prediction 2 PARTIALLY SUPPORTED

Higher environmental effects for young than for adults

PATIALLY SUPPORTED

Juveniles SENSIBLE to environmental fluctuationsYearlings NOT SENSIBLE to environmental fluctuationsTwo year olds NOT SENSIBLE to environmental fluctuationsSubordinate adults NOT SENSIBLE to environmental fluctuations

=> Theory for long lived species: sensibility to environmental fluctuations decreases with age

BUT dominant adults SENSIBLE to environmental fluctuations

=> Possible cost of dominance and reproduction

Prediction 2Prediction 2Higher environmental effects for young than for adults

Back to predictionsBack to predictions

Prediction 1 PARTIALLY SUPPORTED

Positive effect of proxys of primary productivity on survivalhigher temperature => less vegetation => lower survival in

dominantsmore rain => more vegetation => higher survival in

dominantsearly vegetation availability => higher survival in juveniles

BUT possible thermoregulation cost in marmotsmore rain => low survival in juveniles

Prediction 2 PARTIALLY SUPPORTED

Higher environmental effects for young than for adults

Prediction 3 SUPPORTED

Presence of helpers buffers environmental effects on juvenile survival

Prediction 3 Prediction 3 Presence of helpers buffers environmental effects on juvenile survival

SUPPORTED

Juveniles

with helpers LOW SENSIBILITY to environmental fluctuations

without helpers HIGH SENSIBILITY to environmental fluctuations

=> Weight at entry in hibernation is driven by food availability but being fat is more critical for juveniles without helpers than for juveniles with helpers

Age specific and complex effects of environment on survival

- climate impacts survival via primary productivity

- but effects modulated by social factors

=>Next step:

- taking into account winter conditions

- quantifying impact of these effects on marmot population growth rate

Conclusions

to all students involved in marmots trapping and observations

AcknowledgementsAcknowledgements

to the authorities of the Vanoise National Park

Many thanks for your attention