Cats and humans have shared the same households for at least 9,000 years, but we still know very little about how our feline friends became domesticated.

The scientists fitted GPS collars and motion sensors on 38 free-ranging lynx for the study. Credit: Image courtesy of Albert-Ludwigs-Universität Freiburg

An international research team recorded and analyzed the activity patterns of 38 wild cats over the course of months Whether a lynx hunts by day or by night and how active it is overall depend primarily on the behavior of the wild cat's most important prey and its individual traits -- lighting conditions, on the other hand, do not play a major role in its basic behavioral patterns. This is the key finding of a study published in the journal PLOS ONE by an international research team led by forest scientist Dr. Marco Heurich.

The scientists fitted GPS collars and motion sensors on 38 free-ranging lynx for the study. Since the study sites were located across a wide latitudinal range from Central Europe to northern Scandinavia, the length of days and nights varied greatly between them. The team recorded and analyzed the activity patterns of the wild cats on a total of more than 11,000 days. The results reveal that lynx in more southerly regions are most active at dawn and dusk and that they move more by night than by day. They take their longest break in the middle of the day, and this break is extended as daylight duration increases. However, the cats exhibit this basic behavioral pattern independently of lighting conditions: "Lynx keep to a 24-hour rhythm with an active and a resting phase even on the polar day and the polar night," reports Heurich.

What the study found to be more important for explaining the wild cats' activity patterns are their individual traits: Young lynx are more active than adult lynx, and male adults are more active than female adults. In addition, they move more in spring and summer than in fall and winter, and the farther north they live, the larger the territory they cover -- and this of course results in higher activity. Lynx adapt their hunting schedule to the behavior of their prey. In polar regions, the height of their activity at dusk is less pronounced. 

This corresponds to the behavioral pattern of reindeer, which exhibit a steady movement profile outside of their sleeping phases.. In Central Europe, by contrast, the team found a maximum amount of activity at dusk -- in lynx as well as in deer. "The findings of this study make an important contribution to our understanding of the habits of predatory animals in our landscape," says Heurich. "They also show that human activities in the areas included in the study do not have a general influence on the activity pattern of the animals."

Wild weather in the Arctic causes problems for people and wildlife

Svalbard's reindeer population can be severely affected by winter icing.
Credit: Brage Bremset Hansen

The residents of Longyearbyen, the largest town on the Norwegian Arctic island archipelago of Svalbard, remember it as the week that the weather gods caused trouble. Temperatures were ridiculously warm -- and reached a maximum of nearly +8 degrees C in one location at a time when mean temperatures are normally -15 degrees C. It rained in record amounts.

Snow packs became so saturated that slushy snow avalanches from the mountains surrounding Longyearbyen covered roads and took out a major pedestrian bridge. Snowy streets and the tundra were transformed into icy, rain-covered skating rinks that were difficult to navigate with snowmobiles. Flights were cancelled, the airport closed, and travel around town was tricky.

The situation was particularly problematic out on the Arctic tundra. Rain falling on snow can percolate to the base of a snowpack where it can pool at the soil surface and subsequently freeze. That makes it impossible for grazing reindeer to get at their food, for example, and extreme warm spells can even affect temperatures in the permanently frozen ground found throughout the archipelago.

But the extreme event also offered an interdisciplinary group of scientists, from climatologists to biologists to snow geophysicists and structural engineers, a chance to document the event and learn from it. Their cross-disciplinary report, "Warmer and wetter winters: characteristics and implications of an extreme weather event in the High Arctic," was published on 20 November in Environmental Research Letters.

"We had a unique opportunity to document what happened, and we did," said Brage Bremset Hansen, the first author on the paper, and co-author Øystein Varpe. "This was a case study from one event…but since it was an extreme event, and with all of our contacts in the different disciplines, we were able to compile this information into one story, which is quite rare."

Hansen is a biologist at the Norwegian University of Science and Technology's Centre for Biodiversity Dynamics, and Varpe is an associate professor at the University Centre in Svalbard.

Just a 0.2 percent chance of happening

Co-author Ketil Isaksen, a climatologist from the Norwegian Meteorological Institute, said that such an extreme event has a 500-year return period, which means that the probability of it happening in any one year is just 0.2 percent.

At the same time, climatologists say that Svalbard has seen the greatest increase in temperatures of any place in Europe over the last three decades.

And while no one can attribute the event directly to global warming, virtually all climate studies show that the High Arctic, including Svalbard, will become increasingly warmer and wetter over time.

"We expect this to be more likely to happen," Isaksen said.

Reindeer mortality up

As a biologist, Hansen was very interested in how the extreme weather would affect the archipelago's natural communities. Only four vertebrate species overwinter on Svalbard -- the wild Svalbard reindeer (Rangifer tarandus platyrhynchus), the Svalbard rock ptarmigan (Lagopus muta hyperborea), and the sibling vole (Microtus levis), and one animal that eats them all, the Arctic fox (Vulpes lagopus).

When Hansen and his colleagues compared summer population counts of reindeer after the January 2012 event to counts conducted for the previous summer, they found that the number of reindeer carcasses in many populations was among the highest ever recorded.
But it could have been worse, he said, in part because recent increases in summer temperatures have made for better foraging conditions for Svalbard reindeer overall.

"It wasn't like there were dead reindeer all over the tundra," he said. "If this had happened in the colder 1980s, it could have been much worse. …They had a nice winter up to this event, which occurred rather late."

Rain and permafrost

Hansen and colleagues have previously published research on the overwintering animal community on Svalbard, suggesting that such extreme events can affect all species. But what makes the new findings unique is the collaboration between different disciplines that enabled researchers to assemble a picture of what happened to Svalbard's physical environment, and to people living in the outposts of Longyearbyen and Ny-Ålesund, a tiny community with a winter population of about 30 people.

In Ny-Ålesund, for example, it rained nearly 100 mm in one day -- which would be more typical of the Norwegian coastal town of Bergen, renowned for its heavy rains. That one-day amount represented a quarter of the precipitation that Ny-Ålesund typically gets in a year.

Isaksen documented a significant increase in ground temperatures in permafrost as deep as 5 metres below the surface as a result of the extreme warming. This temperature increase came on top of a decades-long larger trend of warming of the permafrost on Svalbard, the researchers said. Permafrost is permanently frozen ground that is found throughout the archipelago and the High Arctic. In regions in the Northern Hemisphere where permafrost is found, it occupies approximately 25% (23 million km²) of the land area.

Tourism and infrastructure

And for Svalbard residents, who are some of the most northerly inhabitants on the globe, there were significant socioeconomic effects. During and after the event, it was difficult for snowmobiles to travel out on the tundra on the thick layer of ice, Varpe said.

This thick layer, averaging 15.3 cm, persisted out on the tundra well after the event was over, said Jack Kohler, senior research scientist, glaciology, at the Norwegian Polar Institute.
"The winter rain event leads to the ground-ice formation, and the ice lasts the remainder of the melt season, until it melts, and that is what I would call the significant happening," Kohler said. "The rain is an event, for sure, but the ice is actually the (big) event."

The result was a strong decrease in tourism for the rest of the winter, specifically for activities such as guided snowmobile and dogsled tours. Tour numbers dropped by 28 percent compared to the previous winter, and were the lowest ever since 2001, which is when statistics were first continuously kept. The researchers also believe that had a ripple effect on hotel stays and other tourist activities.

Another potential problem exposed by the extreme event was the vulnerability of the town's infrastructure to avalanches. A major avalanche in June 1953 destroyed the town's hospital and other buildings, killing three people, but since then, many buildings have been constructed without regard to potential avalanche risks. If Svalbard's climate continues to warm as our downscaled climate scenarios predict, the likelihood of damaging avalanches will only increase, Hansen and colleagues say.

Hansen is continuing to investigate the consequences of a warmer Arctic on Svalbard's natural communities and human population with a research project called VINTERREGN (Winter rain). Of particular interest is whether or not plants, which usually do not grow taller than a couple of inches at this latitude, can withstand being completely covered in ice for several months.

Source:  The Norwegian University of Science and Technology (NTNU)

Lightning expected to increase by 50 percent with global warming

Today's climate models predict a 50 percent increase in lightning strikes across the United States during this century as a result of warming temperatures associated with climate change. Credit: © Sondem / Fotolia

Today's climate models predict a 50 percent increase in lightning strikes across the United States during this century as a result of warming temperatures associated with climate change.

Reporting in the Nov. 14 issue of the journal Science, University of California, Berkeley, climate scientist David Romps and his colleagues look at predictions of precipitation and cloud buoyancy in 11 different climate models and conclude that their combined effect will generate more frequent electrical discharges to the ground.

"With warming, thunderstorms become more explosive," said Romps, an assistant professor of earth and planetary science and a faculty scientist at Lawrence Berkeley National Laboratory. "This has to do with water vapor, which is the fuel for explosive deep convection in the atmosphere. Warming causes there to be more water vapor in the atmosphere, and if you have more fuel lying around, when you get ignition, it can go big time."

More lightning strikes mean more human injuries; estimates of people struck each year range from the hundreds to nearly a thousand, with scores of deaths. But another significant impact of increased lightning strikes would be more wildfires, since half of all fires -- and often the hardest to fight -- are ignited by lightning, Romps said. More lightning also would likely generate more nitrogen oxides in the atmosphere, which exert a strong control on atmospheric chemistry.

While some studies have shown changes in lightning associated with seasonal or year-to-year variations in temperature, there have been no reliable analyses to indicate what the future may hold. Romps and graduate student Jacob Seeley hypothesized that two atmospheric properties -- precipitation and cloud buoyancy -- together might be a predictor of lightning, and looked at observations during 2011 to see if there was a correlation.

"Lightning is caused by charge separation within clouds, and to maximize charge separation, you have to loft more water vapor and heavy ice particles into the atmosphere," he said. "We already know that the faster the updrafts, the more lightning, and the more precipitation, the more lightning."

Precipitation -- the total amount of water hitting the ground in the form of rain, snow, hail or other forms -- is basically a measure of how convective the atmosphere is, he said, and convection generates lightning. The ascent speeds of those convective clouds are determined by a factor called CAPE -- convective available potential energy -- which is measured by balloon-borne instruments, called radiosondes, released around the U.S. twice a day.

"CAPE is a measure of how potentially explosive the atmosphere is, that is, how buoyant a parcel of air would be if you got it convecting, if you got it to punch through overlying air into the free troposphere," Romps said. "We hypothesized that the product of precipitation and CAPE would predict lightning."

Using U.S. Weather Service data on precipitation, radiosonde measurements of CAPE and lightning- strike counts from the National Lightning Detection Network at the University of Albany, State University of New York (UAlbany), they concluded that 77 percent of the variations in lightning strikes could be predicted from knowing just these two parameters.

'Blown away'

"We were blown away by how incredibly well that worked to predict lightning strikes," he said.

They then looked at 11 different climate models that predict precipitation and CAPE through this century and are archived in the most recent Coupled Model Intercomparison Project (CMIP5). CMIP was established as a resource for climate modelers, providing a standard protocol for studying the output of coupled atmosphere-ocean general circulation models so that these models can be compared and validated.

"With CMIP5, we now have for the first time the CAPE and precipitation data to calculate these time series," Romps said.

On average, the models predicted an 11 percent increase in CAPE in the U.S. per degree Celsius rise in global average temperature by the end of the 21st century. Because the models predict little average precipitation increase nationwide over this period, the product of CAPE and precipitation gives about a 12 percent rise in cloud-to-ground lightning strikes per degree in the contiguous U.S., or a roughly 50 percent increase by 2100 if Earth sees the expected 4-degree Celsius increase (7 degrees Fahrenheit) in temperature. This assumes carbon dioxide emissions keep rising consistent with business as usual.

Exactly why CAPE increases as the climate warms is still an area of active research, Romps said, though it is clear that it has to do with the fundamental physics of water. Warm air typically contains more water vapor than cold air; in fact, the amount of water vapor that air can "hold" increases exponentially with temperature. Since water vapor is the fuel for thunderstorms, lightning rates can depend very sensitively on temperature.

In the future, Romps plans to look at the distribution of lightning-strike increases around the U.S. and also explore what lightning data can tell climatologists about atmospheric convection.

Romps' co-authors are Jacob Seeley, also of the Department of Earth and Planetary Science at UC Berkeley, and David Vollaro and John Molinari of the Department of Atmospheric and Environmental Sciences at UAlbany.

The work was supported by the U.S. Department of Energy's Office of Advanced Scientific Computing Research and Office of Biological and Environmental Research, and the National Science Foundation.

WATCH VIDEO


Source: University of California - Berkeley