May 01, 2014
In Champagne in eastern France, hotter temperatures over the past few decades have resulted in earlier springs. But the timing of roe deer births—closely linked to the flush of spring vegetation—has remained unchanged, according to a team of scientists from France and UK who dug through a 27-year long dataset on roe-deer population and births in Trois Fontaines.
Over this period, temperatures in this region rose more than the global average. In response to these warmer and early springs, while vineyards in the region have been flowering earlier, roe deer seem unable to respond to environmental cues.
New fawn roe deer that has been ear tagged by scientists. Photo by: Maryline Pellerin.
"There is currently a huge interest in analyzing responses of organisms to ongoing climate change," said Jean-Michel Gaillard, a biologist at University Claude Bernard Lyon 1 in France. "In several cases, species have been shown to adjust to some extent. So taking advantage of an especially detailed long-term monitoring of a roe deer population (performed by the Office National de la Chasse et de la Faune Sauvage (ONCFS)), we looked for any response of roe deer [to climate change]."
Between 1985 and 2011, researchers from ONCFS marked, ear-tagged and weighed about a thousand newborn fawns. The survival of these marked deer was then monitored during winter each year. In addition to this data, Gaillard and his team also collected local daily temperatures from a nearby weather station for each year, and the annual mean flowering dates of the vineyards in the Champagne region. They used the latter as a proxy for the early arrival of spring.
Since both predation and hunting of roe deer in the region is limited, the scientists hypothesized that fawn deaths would most likely be due to a reduction in high-quality food.
"Very hot days in June (hyperthermia), heavy rain (hypothermia), and in very rare case predation by wild cats and red fox have been reported to lead to fawn death," said Gaillard. "However, by far, the most common mortality cause of newborn fawns is starvation." Tracking both the flowering dates of the vineyards and fawn birth timings over the study period, the scientists estimated the mismatch between the two. Their analysis confirmed that every year spring temperatures have been rising by 0.07 degrees Celsius, and flowering dates of vineyards have advanced by 0.6 days. The team thus expected that female roe deer would adapt to the early availability of high quality spring vegetation by giving birth sooner.
But the roe deer showed no such response.
In fact, by the end of the study, the mismatch between fawn birth dates and vineyard flowering dates increased. This meant that fawns were born increasingly late with respect to the timing of high-quality food availability. Additionally, roe deer fawns showed higher early mortality. So while the roe deer population was increasing over time, it was doing so at a continuously decreasing rate.
Unlike the roe deer, female red deer in Scotland advanced the dates of fawn births in response to local climate warming.
Daniel H. Nussey, an evolutionary ecologist at the University of Edinburgh, who headed the study on the red deer, said, "There's a lot of evidence now that birds and mammals are altering their phenology across Europe as springs warm. Cases like this [of the roe deer] where there's no apparent response, are obviously worrying."
Male roe deer on the left, female on the right. Photo by: Creative Commons 3.0.
"The authors of this paper have coupled that observation with evidence that there's a negative consequence for individual fitness, which is quite rare I think, and really does suggest some cause for concern, especially in such a cosmopolitan and generally successful species as roe deer," he added. Nussey was not a part of this study.
So why have female roe deer been unable to adjust fawn birth dates to adapt to warmer temperatures?
The authors suggest this could be due to the roe deer's peculiar reproductive cycle. They write that the various stages in their reproduction, like ovulation and conception dates, seem to be controlled by the length of day or photoperiod instead of temperature change or prime food availability. The roe deer, however, might be able to adapt to climate change in other ways.
"Roe deer do not resist (they showed increased fawn mortality) nor adjust (birth timing remains the same). However, they could move," said Gaillard. "Indeed, we studied a population in forest exclusively. Roe deer are colonizing open areas since the 1980s and such environments might allow roe deer to escape climate change."
Currently, there are several million roe deer across Europe, and the species is classified as Least Concern by the IUCN Red List. Their hardiness has enabled them to colonize and survive in a vast variety of habitats. Moreover, the absence of large predators has caused their numbers to soar. It is thus no wonder that roe deer are important game animals. In fact if you search for 'roe deer' on YouTube, you will be greeted by numerous videos of "how to hunt" and "how to skin" the animal.
But while the roe deer may have successfully come back from the brink of extinction, will climate change prove to be the test of its resilience? We'll have to wait and watch.
Roe deer in winter in Poland. Photo by: Jeremy Hance.
Citation: Plard F, Gaillard J-M, Coulson T, Hewison AJM, Delorme D, et al. (2014) Mismatch Between Birth Date and Vegetation Phenology Slows the Demography of Roe Deer. PLoS Biol 12(4): e1001828. doi:10.1371/journal.pbio.1001828
Rainforests on fire: climate change is pushing the Amazon over the edge
(04/18/2014) From 1999-2010, nearly three percent of the Amazon rainforest burned, and climate forecasts indicate dry conditions conducive to fire will only become more commonplace in the future. A new study indicates that rainforests are more vulnerable to fire than previously thought, and it warns the current combination of climate change and deforestation may be pushing Amazon forests past the breaking point.
Climate change solution? UN touts ambitious (but cheap) investment in renewable energy
(04/14/2014) The world is warming rapidly due to greenhouse gas emissions, threatening everything from our food supply to our ecosystems, but the solution may be surprisingly cheap, according to the third and final report from the Intergovernmental Panel on Climate Change (IPCC). The report recommends a rapid and aggressive switch from fossil fuel-based energy to renewables.
Extinction crisis: rising sea levels will submerge thousands of islands
(04/08/2014) Sea levels are rising at the highest rate in thousands of years, putting at risk low-lying islands around the world. In a new study published in Nature Conservation, researchers found that projected rises in sea level stand to swamp more than 10,000 islands, displacing human communities and wiping many unique species off the face of the earth.
From seals to starfish: polar bears radically shift diet as habitat melts
(04/07/2014) One of the most iconic species of the ongoing climate change drama, polar bears have dropped in numbers as their habitat melts, with previous estimates forecasting a further 30 percent reduction within three generations. However, their situation may not be as dire as it seems.
The incredible shrinking salamander: researchers find another casualty of climate change
(04/04/2014) Climate change is contributing to a slew of global problems, from rising seas to desertification. Now, researchers have added another repercussion: shrinking salamanders. Many amphibian populations around the world are currently experiencing precipitous declines, estimated to be at least 211 times normal extinction rates. Scientists believe these declines are due to a multitude of factors such as habitat loss, agricultural contamination, and the accidental introduction of a killer fungus, among others.
Apocalypse now? Climate change already damaging agriculture, acidifying seas, and worsening extreme weather
(03/31/2014) It's not just melting glaciers and bizarrely-early Springs anymore; climate change is impacting every facet of human civilization from our ability to grow enough crops to our ability to get along with each other, according to a new 2,300-page report from the Intergovernmental Panel on Climate Change (IPCC). The massive report states definitively that climate change is already affecting human societies on every continent.
Indigenous people witness climate change in the Congo Rainforest
(03/20/2014) Indigenous communities in the Republic of Congo are observing climate change even though they have no knowledge of the science, according to a unique collaboration between the Rainforest Foundation UK (RFUK) and local communities. The environmental changes witnessed by the locals in the Congo rainforest include increased temperature, less rainfall and alterations to the seasons, much as expected under global climate change.
Mountain thermostats: scientists discover surprising climate stabilizer that may be key to the longevity of life on Earth
(03/14/2014) What do mountains have to do with climate change? More than you'd expect: new research shows that the weathering rates of mountains caused by vegetation growth plays a major role in controlling global temperatures. Scientists from the University of Oxford and the University of Sheffield have shown how tree roots in certain mountains "acted like a thermostat" for the global climate.
Can penguins cope with climate change? Scientists find different types of ice elicit different responses
(03/13/2014) Human-caused climate change is altering the habitat of Adélie penguins (Pygoscelis adeliae). In an article recently published in PLOS ONE, a team of researchers led by Amélie Lescroël from the Centre d'Ecologie Fonctionnelle et Evolutive (CNRS) in France, found that changes in sea-ice content and newly formed icebergs significantly impacted Adélie penguin communities in the Ross Sea.
From theory to deadly reality: malaria moving upslope due to global warming
(03/06/2014) Malaria is a global scourge: despite centuries of efforts to combat the mosquito-borne disease, it still kills between 660,000 to 1.2 million people a year, according to World Health Organization data from 2010. Astoundingly, experts estimate that around 300 million people are infected with the disease every year or about 4 percent of the world's total population. And these stats may only get worse. For years scientists have vigorously debated whether or not malaria will expand as global warming worsens, but a new study in Science lays down the first hard evidence.