Zebras follow their memory when migrating

Date: May 24, 2017

Source: Senckenberg Research Institute and Natural History Museum

 

Zebras may use memory to guide their migration each year. Memory based on past average conditions provides a clear signal that best directs zebras to their destination. In contrast, current vegetation conditions along the way are less important for the direction of the migration according to a computer simulation by researchers from Senckenberg. The study, published in Proceedings of the Royal Society B, highlights that migration routes of large terrestrial mammals such as zebras could be more inflexible than previously thought.

It's incredible to watch: each year thousands of animals, including zebras, wildebeests and gazelles, migrate in turn with the seasons between foraging grounds. The animals migrate long distances in their search for sufficient and highly nutritious forage. While science has explained certain aspects of this migration, it is not fully understood how the animals know where to go.

Chloe Bracis, a researcher at the German Senckenberg Biodiversity and Climate Research Centre and the Goethe University Frankfurt, has found that memory is the key to directing zebra migration: "Zebras appear to migrate to the location where foraging conditions were best in the past. They seem to navigate to their destination based on memory, and importantly, forecast conditions several months after arrival."

As part of the study, Bracis and her colleague Thomas Mueller modelled migration routes of zebras using computer simulations. Zebras migrate around 250 kilometers from the Okavango Delta, Botswana to the Makgadikgadi grasslands in November. "We tested two mechanisms which can influence the direction. Simulated zebras could use perception and sense, for example, the vegetation green up in their current surroundings. Alternatively, zebras could use memory, i.e. information from previous migrations, to forecast where to go ," explains Mueller.



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Zebras’ stripes not for camouflage, study finds

JANUARY 25, 2016

by Chuck Bednar

Why do zebras have stripes? It was a question we thought we had the answer to – because they serve as camouflage to protect the equine species from predators – but new research published in Friday’s edition of the journal PLOS One suggests that this may not be the case after all.

In the new study, lead author Amanda Melin, an assistant professor of biological anthropology at the University of Calgary, and colleagues from the University of California-Davis explained that the camouflage hypothesis is flawed because it looks at the issue “through human eyes.”

Melin’s team reframed the issue by performing a series of calculations through which they were able to estimate the distances at which lions, spotted hyenas or other zebras could spot the stripes during the daytimes, at twilight or during a moonless night. They found that the stripes could not help the creatures hide, because they would have already been detected in other ways.

“The results from this new study provide no support at all for the idea that the zebra’s stripes provide some type of anti-predator camouflaging effect,” study co-author Tim Caro, a professor of wildlife biology at UC-Davis, explained in a statement. “Instead, we reject this long-standing hypothesis that was debated by Charles Darwin and Alfred Russell Wallace.”

Read more at

Why Do Zebras Have Stripes? It's Not for Camouflage

by Laura Poppick, Live Science Contributor | January 14, 2015 06:57am ET

Zebras' thick, black stripes may have evolved to help these iconic creatures stay cool in the midday African heat, a new study suggests.

Many African animals sport somestripes on their bodies, but none of these patterns contrast as starkly as the zebra's. Researchers have long struggled to explain the purpose of the zebra's unique black-and-white coat. Some have suggested that the stripes may help zebras camouflage themselves and escape from lions and other predators; avoid nasty bites from disease-carrying flies; or control body heat by generating small-scale breezes over the zebra's body when light and dark stripes heat up at different rates.

Still, few scientists have tested these explanations, and many argue that the stripes serve a complex mix of purposes. 

Continued ...

Zebra stripes mystery 'explained'

Zebras' bold stripes protect the animals by masking their movements, according to a study.

The conspicuous colours do not blend in to the background and scientists have theorised they developed to dazzle predators.

Using computer models, researchers confirmed the markings create optical illusions when the animals move.

They suggest this confusion helps to protect the animals from both big cats and tiny insects.

The research, conducted by researchers from the University of Queensland, Australia, is published in the journal Zoology.

"Zebra stripes have long confused evolutionary biologists, right back to Darwin and Wallace," said lead author Dr Martin How.

Read on

What animal has black and white spots?

January 2013. When award winning photographer Paul Goldstein first saw this animal on Kenya's Masai Mara Reserve, he didn't have his camera with him, and no one quite believed him about the zebra with spots. Paul runs a camp on the Masai Mara, so has plenty of opportunity to keep an eye out for unusual sightings. 

Two years later, Paul saw the animal again, and this time he had his camera with him. Now all zebras have a different pattern (Who has checked that? How do they know?), but this one is more different than most. 

It appears his unusual coat does a great deal more than set him aside for photographers, he doesn't seem to mix with other zebras either. Zebras almost always travel as part of a herd, but this poor chap always seems to be alone.

Paul runs photographic safaris based at Kicheche Mara, and will be presenting at Destinations Travel Show in London on February 1st - 3rd.

PHOTOS COURTESY OF PAUL GOLDSTEIN 

http://www.wildlifeextra.com/go/news/zebra-spots.html

Zebra stripes evolved to keep biting flies at bay

By Victoria GillScience reporter, BBC Nature

Why zebras evolved their characteristic black-and-white stripes has been the subject of decades of debate among scientists.

Now researchers from Hungary and Sweden claim to have solved the mystery.

The stripes, they say, came about to keep away blood-sucking flies.

They report in the Journal of Experimental Biology that this pattern of narrow stripes makes zebras "unattractive" to the flies.

They key to this effect is in how the striped patterns reflect light.

"We started off studying horses with black, brown or white coats," explained Susanne Akesson from Lund University, a member of the international research team that carried out the study.

"We found that in the black and brown horses, we get horizontally polarised light." This effect made the dark-coloured horses very attractive to flies.

It means that the light that bounces off the horse's dark coat - and travels in waves to the eyes of a hungry fly - moves along a horizontal plane, like a snake slithering along with its body flat to the floor.

Dr Akesson and her colleagues found that horseflies, or tabanids, were very attracted by these "flat" waves of light.

"From a white coat, you get unpolarised light [reflected]," she explained. Unpolarised light waves travel along any and every plane, and are much less attractive to flies. As a result, white-coated horses are much less troubled by horseflies than their dark-coloured relatives.

http://news.bbcimg.co.uk/media/images/58391000/jpg/_58391196_dscf6956_gabor-horvath.jpg

Read on: http://www.bbc.co.uk/nature/16944753