Aurélie C OHAS Christophe B ONENFANT Dominique A LLAINE Laboratoire Biométrie et Biologie évolutive Université Claude Bernard Lyon 1 43 Bd du 11 novembre 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: number age sex social status of individuals known

Environmental variables - Climate - 2 local variables: Summer temperature (STemp)

Climatic variables: Local variables - Temperature => Summer temperature (STemp) MayOctober

Environmental variables - Climate - 2 local variables: Summer temperature (STemp) Summer rainfall (SRain)

Climatic variables: Local variables - Rainfall => Summer rainfall (SRain) MayOctober

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 light reflects near-infrared light => HIGH NDVI Sparse vegetation reflects visible light absorbs near-infrared light => LOW NDVI near infraredvisible 50% 8% near infraredvisible 40% 30%

Vegetation index - Normalized Difference Vegetation Index (NDVI) => vegetation availability in spring (sNDVI) 15th of April

Predictions Prediction 1 Positive effect of proxys of primary productivity on survival higher temperature => less vegetation => lower survival more rain => more vegetation => higher survival early vegetation availability => higher survival BUT possible thermoregulation cost in marmots more rain => low survival Prediction 2 Higher environmental effects for young than for adults Prediction 3 Presence of helpers buffers environmental effects on juvenile survival

Estimating survival

Model and Explanatory variables CaptureSurvivalTransition from subordinate to dominant status age sex age sex Age sex period social status year social status presence of helpers at birth year Capture history: => capture probability not 1 => Multistate capture-recapture model to take into account capture probability and social status

Survival Age effect => survival increase with age Apparent survival

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 Helpers No helpers

Survival Marked temporal variation

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

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 SRainsNDVI STemp 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 => 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)

Juveniles => Negative effect of summer precipitation on juvenile survival (-0.23±0.11, p=0.06) 26.4% of deviance explained by environmental variables

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 => Negative effect of summer temperature on dominant marmots survival (-0.33±0.17, p=0.02) => Positive effect of summer rain on dominant marmots survival (0.40±0.21, p=0.06) Dominant adults

Back to predictions Prediction 1 PARTIALLY SUPPORTED Positive effect of proxys of primary productivity on survival higher temperature => less vegetation => lower survival in dominants more rain => more vegetation => higher survivalin dominants early vegetation availability => higher survivalin juveniles BUT possible thermoregulation cost in marmots more 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 cost heavy rain => thermoregulation costs => behavioral thermoregulation => no access to food => lower survival Prediction 1 Positive effects of proxys of primary productivity on survival

Back to predictions Prediction 1 PARTIALLY SUPPORTED Positive effect of proxys of primary productivity on survival higher temperature => less vegetation => lower survival in dominants more rain => more vegetation => higher survivalin dominants early vegetation availability => higher survivalin juveniles BUT possible thermoregulation cost in marmots more rain => low survival in juveniles Prediction 2 PARTIALLY SUPPORTED Higher environmental effects for young than for adults

PATIALLY SUPPORTED Juveniles SENSIBLE to environmental fluctuations Yearlings NOT SENSIBLE to environmental fluctuations Two year olds NOT SENSIBLE to environmental fluctuations Subordinate adultsNOT SENSIBLE to environmental fluctuations => Theory for long lived species: sensibility to environmental fluctuations decreases with age BUT dominant adultsSENSIBLE to environmental fluctuations => Possible cost of dominance and reproduction Prediction 2 Higher environmental effects for young than for adults

Back to predictions Prediction 1 PARTIALLY SUPPORTED Positive effect of proxys of primary productivity on survival higher temperature => less vegetation => lower survival in dominants more rain => more vegetation => higher survivalin dominants early vegetation availability => higher survivalin juveniles BUT possible thermoregulation cost in marmots more 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 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 Acknowledgements to the authorities of the Vanoise National Park

Many thanks for your attention