Final Report Summary - ARC (Adaptive Responses to Climate Change)
Climate change represents one of the greatest environmental challenges in Europe and worldwide. Although there has been progress on the availability of scientific data, European Union’s 2001 target to significantly halt the loss of biodiversity by 2010 has not been achieved. The third edition of the Global Biodiversity Outlook demonstrates that today’s rate of loss of biodiversity is up to one thousand times higher than the background and historical rates of extinction. To take effective action, there is an urgent need to increase our knowledge of the consequences of climate change for biodiversity. The aim of this project was to provide a better mechanistic understanding of an alpine mammal’s responses to environmental changes. I studied the demographic and physiological responses of a hibernating mammal, the Alpine marmot (marmota marmota), an endemic species of the highly vulnerable ecosystems of the Alps. Using a 22-year (1991-2013) dataset (3586 captures from 1329 individuals) and data collected from a physiological experiment using advanced field technology, I provided an in-depth evaluation of species’ demographic performance and its potential adaptive responses to climate-driven constraints.
Over the 22 years of study, important environmental changes have been observed in the study site located in La Grande Sassière Nature Reserve (45°29’N, 6°59’E, 2280m) in the eastern part of Vanoise National Park, Savoie, French Alps. During spring, ambient temperature has increased by 0.08°C/year but the vegetation onset remained constant. In summer, strong inter-annual changes were recorded with severe drought becoming more frequent (1991, 1994, 2003, 2009, 2012 and 2013). Winters were harsher, with ambient temperature decreasing by 0.09°C/year favoring frost but not snow (mean depth recorded: 101± 23 cm). In response to these environmental changes, a decrease in litter size has previously been demonstrated, and preliminary analyses showed changes in population dynamic. I identified three intrinsic mechanisms that might underlie the relationship between environmental variables and population dynamics. Body size, body mass and body temperature are three phenotypic traits, strongly related to individual fitness, resulting from energy allocation to growth, energy storage and thermoregulation, respectively. Our results demonstrate the important differences in the dynamics of body size and mass in Alpine marmots. Both traits showed different temporal trends and responded to different environmental drivers but the inter-annual fluctuations observed in either trait were mostly phenotypic plasticity and did not have a genetic basis. Over the 22 years, juveniles were getting smaller at weaning and showed a slower growth from age one to age three. Contrary to our expectations, juveniles’ body mass and all age classes’ fattening from one year to the next were predominantly constant over the study period. Vegetation onset has been demonstrated as the most influential environmental variable, with shorter growing seasons being detrimental for both traits. These results demonstrate that the green-up season (April to June) is a strategic phase when the young grow and get fat, and adults store energy to reproduce and overcome the hibernation period. To a lesser extent, body fattening was also adjusted to summer and winter conditions, decreasing under adverse environmental conditions.
Preliminary analyses on body temperature recorded on 20 individuals over a year have suggested strong thermoregulatory flexibility. During hibernation, body temperature was mainly adjusted to burrow-specific ambient temperature. We also observed synchronized hibernation pattern in each family with major constraints on dominant individuals that support burrow warming. Surprisingly, outside the hibernation period, while hibernating species are supposed to maintain constant body temperature, marmots exhibit highly flexible pattern of body temperature and activity. During summer time, patterns of body temperature were associated to ambient air temperature, rainfall and wind speed. In particular, low body temperatures (< 32°C) and low activity were observed during cold and rainy days. From these data, I anticipate that marmots are capable of daily torpor when facing challenging environmental conditions in summer.
The plasticity demonstrated on these three energy-related traits might be adaptive if the range of resilience is large enough to compensate the environmental change. Analyses linking phenotypic traits to demographic rates are currently performed to determine if the flexible adjustments observed are adaptive, i.e if the most flexible individuals have the highest fitness.
This project produced a mechanistic understanding on the individual traits underlying population performances that, when integrated into bioenergetics models, would provide accurate population forecasting and conservation planning for policy makers. According to the IUCN red list, out of 15 extant marmot species two are critically endangered (M. marmota latirostius, M. vancouverensis). Local sub-populations of the Alpine marmot also appear to be threatened in Austria and Germany. As a result, this project represents the first step for developing proactive conservation strategies on endangered populations of Alpine marmots and for vulnerable sister species. Beyond the Alpine Marmot, an emblematic species and an important element of sustainable tourism in the Alps, our results have also high potential to raise public awareness of the impact of environmental changes in alpine habitats.
Over the 22 years of study, important environmental changes have been observed in the study site located in La Grande Sassière Nature Reserve (45°29’N, 6°59’E, 2280m) in the eastern part of Vanoise National Park, Savoie, French Alps. During spring, ambient temperature has increased by 0.08°C/year but the vegetation onset remained constant. In summer, strong inter-annual changes were recorded with severe drought becoming more frequent (1991, 1994, 2003, 2009, 2012 and 2013). Winters were harsher, with ambient temperature decreasing by 0.09°C/year favoring frost but not snow (mean depth recorded: 101± 23 cm). In response to these environmental changes, a decrease in litter size has previously been demonstrated, and preliminary analyses showed changes in population dynamic. I identified three intrinsic mechanisms that might underlie the relationship between environmental variables and population dynamics. Body size, body mass and body temperature are three phenotypic traits, strongly related to individual fitness, resulting from energy allocation to growth, energy storage and thermoregulation, respectively. Our results demonstrate the important differences in the dynamics of body size and mass in Alpine marmots. Both traits showed different temporal trends and responded to different environmental drivers but the inter-annual fluctuations observed in either trait were mostly phenotypic plasticity and did not have a genetic basis. Over the 22 years, juveniles were getting smaller at weaning and showed a slower growth from age one to age three. Contrary to our expectations, juveniles’ body mass and all age classes’ fattening from one year to the next were predominantly constant over the study period. Vegetation onset has been demonstrated as the most influential environmental variable, with shorter growing seasons being detrimental for both traits. These results demonstrate that the green-up season (April to June) is a strategic phase when the young grow and get fat, and adults store energy to reproduce and overcome the hibernation period. To a lesser extent, body fattening was also adjusted to summer and winter conditions, decreasing under adverse environmental conditions.
Preliminary analyses on body temperature recorded on 20 individuals over a year have suggested strong thermoregulatory flexibility. During hibernation, body temperature was mainly adjusted to burrow-specific ambient temperature. We also observed synchronized hibernation pattern in each family with major constraints on dominant individuals that support burrow warming. Surprisingly, outside the hibernation period, while hibernating species are supposed to maintain constant body temperature, marmots exhibit highly flexible pattern of body temperature and activity. During summer time, patterns of body temperature were associated to ambient air temperature, rainfall and wind speed. In particular, low body temperatures (< 32°C) and low activity were observed during cold and rainy days. From these data, I anticipate that marmots are capable of daily torpor when facing challenging environmental conditions in summer.
The plasticity demonstrated on these three energy-related traits might be adaptive if the range of resilience is large enough to compensate the environmental change. Analyses linking phenotypic traits to demographic rates are currently performed to determine if the flexible adjustments observed are adaptive, i.e if the most flexible individuals have the highest fitness.
This project produced a mechanistic understanding on the individual traits underlying population performances that, when integrated into bioenergetics models, would provide accurate population forecasting and conservation planning for policy makers. According to the IUCN red list, out of 15 extant marmot species two are critically endangered (M. marmota latirostius, M. vancouverensis). Local sub-populations of the Alpine marmot also appear to be threatened in Austria and Germany. As a result, this project represents the first step for developing proactive conservation strategies on endangered populations of Alpine marmots and for vulnerable sister species. Beyond the Alpine Marmot, an emblematic species and an important element of sustainable tourism in the Alps, our results have also high potential to raise public awareness of the impact of environmental changes in alpine habitats.