Dung beetles navigate better under a full moon

February 5, 2019, Lund University

Of all nocturnal animals, only dung beetles can hold their course using polarized moonlight. Researchers at Lund University in Sweden have now shown that beetles can use polarized light when its signal strength is weak, which may allow them to find their bearings when artificial light from cities swamps natural moonlight.

"Our investigation reveals that these beetles would be sufficiently sensitive to orient themselves underneath a light-polluted city sky during a full moon. But they would be lost during a quarter or crescent moon," explains James Foster, researcher at the Department of Biology at Lund University.

Moonlight becomes polarized when it strikes particles in the upper atmosphere on its journey to Earth. In the study, the researchers show that the strength of this polarized light signal changes depending on the moon's phase. Polarized light from a quarter moon is only one-third as strong as at full moon, and just one-fifth as strong for a crescent moon.

"This is the very first evidence that the polarization of skylight changes over the lunar cycle," says James Foster.

Together with colleagues in Lund, Germany, South Africa and the U.S., he tested how dung beetles cope with this weak signal at night when using polarization as their compass to roll a dung ball in a straight line across the African savannah. On clear nights, they perceive this polarized light in a blue sky like humans observe on a sunny day—but thousands of times darker.

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Ants use Sun and memories to navigate

By Helen Briggs BBC News

19 January 2017

Ants are even more impressive at navigating than we thought.

Scientists say they can follow a compass route, regardless of the direction in which they are facing.

It is the equivalent of trying to find your way home while walking backwards or even spinning round and round.

Experiments suggest ants keep to the right path by plotting the Sun's position in the sky which they combine with visual information about their surroundings.

"Our main finding is that ants can decouple their direction of travel from their body orientation," said Dr Antoine Wystrach of the University of Edinburgh and CNRS in Paris.

"They can maintain a direction of travel, let's say north, independently of their current body orientation."

Ants stand out in the insect world because of their navigational ability.

Living in large colonies, they need to forage for food and carry it back to their nest.

This often requires dragging food long distances backwards.

Scientists say that despite its small size, the brain of ants is remarkably sophisticated.

"They construct a more sophisticated representation of direction than we envisaged and they can incorporate or integrate information from different modalities into that representation," Dr Wystrach added.

 

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Pet whiskers are a navigation aid, early warning system, indicator of mood

Date: September 23, 2016

Source: University of Melbourne

It's hard to be cooler than the snake's hips, the kipper's knickers or the bee's knees. But with no disrespect to the monkey's eyebrows, when it comes to marrying style to function you can't go past the cat's whiskers.

Dr Leonie Richards, head of general practice at the University of Melbourne's U-Vet Veterinary Hospital, isn't sure of the origins of a saying that would be right at home in Gatsby's 1920s America. "Maybe people just think cats' whiskers are pretty cute and special," Dr Richards says.

She hastens to add that their value to our feline friends runs far more than skin deep -- they're also a crucial navigational tool, a pointer to impending danger and even an indicator of mood. Not to mention a great place to collect milk or food before going back for seconds.

Cats generally have a dozen whiskers arranged in four neat lines on each cheek, a few more where we have eyebrows, some under their chin and also on the wrists behind their front paws. "All of them basically serve the same purpose," Dr Richards says. "They're sensory, they help them work out where they are spatially."

Whiskers are a keratin product, the protein that makes up the outer casing of horns in animals ranging from cows to impalas. The follicles themselves don't contain nerves so in effect don't actually "feel" anything at all, but the point where they are embedded in the animal is packed with nerve endings fed by a strong blood supply. This, Dr Richards says, makes whiskers an ideal sensory organ.

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Walk this way: desert ants move backwards with heavy loads, study finds

Study shows that deserts ants can walk and navigate backwards when moving oversized food, a discovery that could inform robotics, researchers say

Naomi Stewart

Wednesday 20 July 201623.00 BST

There comes a time in a desert ant’s life when a piece of food is too large to ignore, but too heavy to lift, and the only way to get it home is to adopt a new style of walking.

The long-legged and speedy Cataglyphis fortis normally covers ground with a three-legged stride that moves two legs forwards on one side, and one on the other. For the next step, the insect mirrors the move with its other three legs.

But recordings of ants in the Tunisian desert reveal that when faced with oversized lumps of food 10 times their own weight, the forward “tripod” walking style is abandoned. Unable to lift the morsels in their mandibles, the ants drag the food backwards instead, moving all six legs independently. “This is the first time we have seen this in any ants,” said lead author Sarah Pfeffer at the University of Ulm in Germany.

The ants’ long legs already help keep their bodies away from the scorching desert floor and enable them to speed around at up to 60cm per second.

“Think of Usain Bolt, who has very long legs compared to body size. The desert floor is also very hot, so the further away their bodies are from the surface, the better,” said co-author Matthias Wittlinger. The ants have also evolved to function at body temperatures of 50C in a desert where temperatures can soar to 70C. “They’re basically just trying to get out of the heat,” he added.

But more intriguing to the researchers was the ants’ skill at navigation. “At any point, they know the direction and distance back to their place of origin. Most ants are capable of this, but desert ants live in dried out salt lakes, which are flat and bare,” said Wittlinger. When they drag food backwards though, the ants cannot see where home is at all.

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'Kidnapped' Sharks Use Their Noses to Navigate Back to Shore

by Laura Geggel, Staff Writer | January 06, 2016 03:00pm ET

Sharks may use their keen sense of smell to navigate the vast ocean, a new study finds.

Researchers made the finding after catching leopard sharks (Triakis semifasciata), transporting them about 6 miles (9 kilometers) away from shore and stuffing some of the sharks' noses with Vaseline-soaked cotton. The scientists then released the sharks and tracked whether those with an impaired sense of smell had trouble finding their way back to shore.

The result? The sharks with nose plugs appeared lost, while those without stuffed noses were able to orient themselves to be homeward bound.

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Why are moths fatally attracted to light?

Saturday 28 February 2015

Moths are not attracted to light. They navigate by light, operating under the assumption that the main source of light is far, far away – ie, the moon. If, say, a moth keeps the moon always on its left-hand side, it will fly in a vaguely straight line for a fair while. (It's obviously more complicated than that, but the principle is the same.)

But if the light is a porch light, keeping that on its left-hand side will make the moth fly in circles (and we won't see it), in outward spirals (and we won't see it), or in inward spirals (and we will see it as flying 'towards the light').

This has worked out pretty well for them for 190,000,000 years, but in the past 50-75 years, man-made lights have made things occasionally confusing. Before that, the only thing that would confuse them would be rare small fires. (If a moth is in the middle of a forest fire, navigation is the least of its problems.) And again, even there, many of the confused moths would not be harmed, but would merely orbit in circles or outward spirals until the fire died out.

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Polarized Light Helps The Greater Mouse-Eared Bat Navigate

July 24, 2014

Rayshell Clapper for redOrbit.com – Your Universe Online

The manner in which bats use echolocation has long been of interest to scientists, but new research shows that bats use more than echolocation to get around. In fact, the Natural Environment Research Council (NERC) recently announced a new discovery about the greater mouse-eared bat and how it navigates.

The greater mouse-eared bat uses “polarization patterns in the sky to navigate…The bats use the way the Sun’s light is scattered in the atmosphere at sunset to calibrate their internal magnetic compass, which helps them to fly in the right direction,” according to a study published in Nature Communications.

The pattern of light polarization is the way light vibrates in one direction. In other words, sunlight scatters in the sky to create polarized light patterns. Studies show that these are mostly invisible to the human eye although with some training and know-how on what to look for humans can perceive polarization. However, science currently does not show a purpose for polarization patterns for human use.

According to National Geographic‘s Katie Langin, the study co-authors, Dr. Richard Holland and Stefan Greif of Queen’s University Belfast and colleagues from Tel Aviv University, took 70 female greater mouse-eared bats in Bulgaria. “The team placed each bat in a box that simulated polarized light at sunset. Some bats saw the natural pattern; others saw a band of polarization that was rotated 90 degrees…Next, they displaced the radio-tagged bats more than 14 miles (20 kilometers) from their roosting cave and tracked their movements in the night.”

What the researchers found was the bats with the altered polarization pattern of 90 degrees “went in directions that were rotated 90 degrees from the correct orientation.” However, the bats that were placed in the box with the correct simulated polarization found their way home.

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Monarch butterfly uses magnetic, Sun compasses, study finds

The North American monarch butterfly uses the Sun as well as Earth's magnetic field as navigational tools for its famous long-distance migration, scientists said Tuesday.

The insects with their characteristic orange-and-black wings flutter thousands of kilometres each year from the United States and southern Canada to the Michoacan mountains in central Mexico, where they overwinter.

The butterflies, whose Latin name is Danaus plexippus, have long been known to use a type of solar compass in the brain.

Yet, curiously, they are also able to migrate when skies are heavily overcast, which suggested co-reliance on a magnetic compass.

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Christmas Carp Prefer to Float North-South

Live carp floating in tubs at traditional Czech Christmas markets like to align their bodies north-south, researchers say. The finding suggests the fish use the geomagnetic field to orient themselves and possibly even navigate through freshwater.

For their study, a team of scientists photographed common carp being sold out of containers at 25 holiday markets in Prague and elsewhere in Bohemia in December 2011. In total, they collected 817 pictures and documented more than 14,000 fish.

An analysis showed that fish lining up close to the north-south axis significantly outnumbered those floating over the east-west axis by a ratio of 1.44. In such cramped quarters, the fish lack orientation clues like wind, temperature, light, water flow, noise and vibrations. As such, the researchers say their findings suggest that carp rely primarily on geomagnetic cues to align themselves.

Read more:  http://www.livescience.com/25376-carp-fish-geomagnetism.html

Brainless slime mould has an external memory

Slime moulds use a form of spatial "memory" to navigate, despite not having a brain, a study
has found.

Scientists in Australia studied the organisms in an experiment normally used to test robots.

They found that the slime mould could navigate around a U-shaped maze to a food source, using their slimy deposits.

Researchers compare its path-finding method to Hansel and Gretel's breadcrumb trail.

Their full findings are published in the journal Proceedings of the National Academy of Sciences.

"A slime mould is not a fungus or mould, but is in fact a protist, which is really the odds and ends of the natural world that don't fit in with the rest of our taxonomic grouping system," said PhD student Christopher Reid who led the study.

Continued:  http://www.bbc.co.uk/nature/19846365

Likely Source of Animals' Magnetic Sense Identified

Researchers have isolated what are essentially tiny compass needles in the noses of rainbow trout that may explain these and many other animals' incredible ability to navigate across vast distances.

When cells scraped from the trout's nasal passages were placed in a rotating magnetic field, a clump of tiny iron-rich crystals inside the cells called magnetite — the same mineral used in compass needles — spun in synchrony with the field, turning the cells around with them.

The strength of the crystals' magnetic response, and their firm attachment to the surrounding cell membranes, lent strong support for what scientists have long suspected: That these crystals lean back and forth like a sail in response to Earth's weak magnetic field, and that the cells they are embedded in somehow convey their swaying movements to the brain. This is believed to confer trout and other migratory animals with a "magnetic sense" by which to judge direction.

Continued:  http://www.livescience.com/21473-source-animal-magnetic-sense.html

Seals use incredible navigation skills to return to site where they were born

Forget Satnav, now there is seal-nav. Scientists have discovered that some seals are capable of finding their way back to the exact spot where they were born even after spending five years out at sea.

The Antarctic fur seals' remarkable homing instinct, which is thought to be the most accurate of any sea mammal, allows the creatures to return to within a single body length of the spot where they were born to give birth to their own pups.

Nearly four million of the sea mammals breed in huge colonies on the virtually featureless beaches of South Georgia every year. After being born, the seals spend five years out at sea feeding before returning to the island to breed.

Using radio tags placed on 335 seals shortly after they were born, researchers at the British Antarctic Survey have discovered that each seal returns to exactly the same location on the beach once they start breeding year after year.

But while typical human Global Positioning Systems (GPS), which use satellites orbiting the earth, can pinpoint a location to an accuracy of around 15 feet, the seals were found to be accurate down to as little as six feet.

Exactly how the seals achieve this feat has left the scientists baffled, but they believe the creatures use a kind of internal compass that helps them find their way across the Southern Ocean to the correct location on the right beach.

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