Built in Compass Helps Bats Find Their Way Home

Big brown bats use magnetic field to navigate long distance.
Bats have a novel device for guiding them home on starless nights. In addition to their well-known sensory talents, it seems that big brown bats can tune into the Earth's magnetic field, using it as a compass to guide them to roost.

This ability comes in handy on long-distance flights, where their usual mode of navigation — bouncing sounds waves off objects using ultrasound — doesn't do much good. Richard Holland from Princeton University, New Jersey, and colleagues looked at 15 North American big brown bats (Eptesicus fuscus), which travel up to 100 kilometres to find hibernation sites for the winter.

To first test the animals' natural navigational abilities, they attached small radio transmitters to the bats and transported them 20 kilometres from their roost. One by one they let them go, and tracked them from a small aircraft. All of them headed directly back to their roost.How did they do this? Researchers have previously suggested that bats might use the direction of the sunset to set their compass. Others have found traces of magnetic materials within bats, suggesting that they might use the planet's magnetic fields to find north.

To tease these effects apart in a single experiment, the researchers put the bats inside a helmet that generates a strong magnetic field offset from the planet's true north. They let the bats watch sunset while sitting in this artificial magnetic field for about an hour and a half. "We then took them to the same release site," says Holland. And they all took off in the wrong direction. "It was a neat trick."

Animal Magnetism

This seems to be convincing experimental proof that they do have a magnetic sense," says Gareth Jones, a biologist at the University of Bristol, UK.

The disorientated bats did eventually make it home, sometimes correcting their path within just a few hours. "That could be because of the short exposure of the rotated magnetic field," says Jones — perhaps they could correct their compass once back in the correct field. Or perhaps they switched to another method of navigation. "What this is we are just not sure. Perhaps they hit an area that is familiar to them," Holland suggests.

Many organisms, from the birds to the bees, are attuned to the world's magnetic pull. How they do it remains a bit of a mystery. Ants are thought to use tiny particles of magnetic iron minerals located throughout their bodies. When the magnetic iron reacts with the dense iron core of the earth it enables the ants body to act the same way a needle in a compass does (see 'Migratory magnetism'). Migratory birds use magnetic material along with several other environmental cues — including the sun, stars, visual references and maybe even the polarisation of light — to navigate.Restless hoppingBird navigational instincts are relatively easy to study in the lab thanks to a condition called migratory restlessness: when kept in captivity, birds will hop in the direction of their desired travel.

Bats aren't that easy to study say researchers. "Studying such small animals in the wild is labour intensive. They are too small to be tracked by current satellites," says Holland. The bats weigh just 15-25 grams, and can only carry equipment of less than 0.5 grams - too small for a standard GPS collar.The team is trying to get funding for a satellite to specifically track such small, migrating creatures. In the meantime they will continue their research, studying further exactly what mechanisms the bats use when they get lost.Visit our newsblog to read and post comments about this story.


References
Holland R. A., et al. Nature, 444 . 702 (2006).

(posted by Catherine S course participant [14])

Courting Works Better than Sneaking

Squid are so intriguing especially since they live way down in the deep blue sea. But as it turns out squid also have their own mating rituals and the females select their mates based on choosing the best males who can perform elaborate dances to lure them. The males display these dances for their potential mates from the wee hours of the morning until sun down. Females are drawn together to see these lekking displays. “Lekking is a behavior best known in a few species of birds; all the males gather together in a small area, put on elaborate displays, and the females stroll among the males flaunting their stuff to pick and choose the most desirable. It's a competitive scheme in which many males put on a show and fail…and it's an excellent example of sexual selection in which female mate choice is paramount.”(Sauer) It is amazing that these behaviors are displayed in cephalopods, when their species is so completely different from birds.

These lekking displays only occurs during egg laying period for squids, but once a female squid chooses her mate she will go away with him and reproduce. The mating process of a squid is also impressive. The male squid will position its body in a manner that his mate feels is most comfortable, then it will reach unto its mantle (which is the equivalent of its mouth) and pull out a sperm packet. It attaches the sperm packet to a special arm called a hetocotyl arm, which is a sort of penis. The reason it is not completely determined to be a penis is because of its length. The length of the hetocotyl arm (penis) is the same length as the rest of the squid’s legs and not distinguishable as a reproductive organ nor does the arm produce its own sperm. Once the squid has attached the sperm packet to its hetocotyl arm it will then reach into the females mantel and deposit this packet deep with in her, sometimes a part of the arm will break off leaving deep with in the female ensuring 95% success in fecundation.

Not all males are successful in obtaining a mate therefore they resort to “sneaking”. Sneaker males will disguise themselves as females to get near another female and then resort to throwing its sperm packets at the female they are stocking. As would be expected, the success rate in this situation is pretty low - usually less that 44%. The reason the rate is so low is because the female will see this happening and try to escape. Usually the sperm packets will land someplace on the female’s arms or on her head and not allow for necessary fecundation.

So I have a wise word to all those potential sneaking male squids out there. “For a better chance of passing on genetic information you need to learn how to do the jiggy jiggy la-la dance better”.

-http://scienceblogs.com/pharyngula/2006/02/tentacle_sex_part_deux.php

-Sauer WHH, Roberts MJ, Lipinski MR, Smale MJ, Hanlon RT, Webber DM, O'Dor RK (1997) Choreography of the Squid’s "Nuptial Dance". Bio. Bull. 192: 203-207.

KJCV (14)

Team Super Fish
Through this semester in class we have learned that different species of animals have varying ways in which they forage for food. Some species may forage alone, some have groups that forage together. One thing though, which we have not seen is a “super team” of sorts. This is exactly what ecologist Redouan Bshary discovered when he was observing a grouper fish in the Red Sea. Two different species were communicating and working together in order to optimize foraging. The grouper went to a moray eel and shook their head, the moray eel’s response; it came out of the nook in which it was tucked away and went with the grouper.

This created a great deal of interest for Bshary and his colleagues, so they began to study a group of groupers and moray eels in a saltwater coral reef in Egypt. Bshary’s research team noticed that this relationship between the groupers and the eels seemed to go even deeper than Bshary’s original observation might have indicated. The two different species of fish work as a team in varying ways while foraging for food. It was found that the original observation seen (mentioned above), was a signal to the eel to come forage with the grouper. It was also observed that a grouper which had difficulties in foraging on their own is more likely to acquire the help of an eel than an abundantly successful one. Not only did the eel assist the troubled grouper in foraging, but other observations found the relationship to be a truly symbiotic one. For the eel, the grouper would do a headstand of sorts above any small fish it would find. The eel would then come and eat the fish. This is truly only a small look at this revolutionary discovery and the different behavior patterns that exist.

Another ecologist, Chris Stallings, cautioned that this is not the first time to the cooperation between groupers and eels has been noticed, but the aspect of communication denoted by the grouper’s head shaking is in fact exciting and never before noted. Another ecologist, Craig Packer, added to this subject saying that this is proof that communication between animals with small brains is in fact a possibility. Other models that denote communication created in the past have been very complicated requiring the organisms to have long-term memory. This shows a different mode, allowing the groupers to go up to any eel and communicate the desire to forage together.

http://sciencenow.sciencemag.org/cgi/content/full/2006/1207/2

published by Rachel Baritz (14)

That Lesbian Seagull Song Just Got a Whole New Meaning

In a 2006 article in Behavioral Ecology four Australian ornithologists decided to take a look at something that isn’t very widely studied in science, homosexual interactions between birds. Now many people might not know this, or may have heard in passing about homosexual penguin behavior for warmth, but over 130 bird species in the world exhibit some form of homosexual behavior. Not every species in this group necessarily exhibits homosexual behavior in both sexes, some species might only be male-male and other female-female, with(obviously) others being both sexes.

This behavior tends to happen more in males in species that are polygamous and that form leks. Apparently they are so polygamous they tend to mount any bird of their species that will get close enough to them to allow it to happen…. Watch your back, literally. It occurs more frequently in females in species that are monogamous. An example of a situation where this occurs in monogamous bird species is when the ’mother bird’ is left to care for the chicks on her own and the chicks don’t learn what its like to have a father, they essentially rebel against their single mother and deserting father and refuse to spread either of their genes by exhibiting homosexual behavior. Even though most birds that behave homosexually will at one point or another behave heterosexually as well, you can call it their ‘experimental period’ I guess.

Not all of the information the researchers would like to understand about the issue is clear to them at the moment, but it was mentioned that some benefits of this behavior are seen in the form of indirect fitness and social interactions.

If you’d like to know more about the homosexual birds ... Here

Also, because I am one of the last posters to this blog this semester, if not the last, I leave you with some humor and a song. One of Engelbert Humperdinck’s greatest hits…..

Over rocks and trees and sand

Soaring over cliffs

And gently floating down to land

She proudly lifts her voice To sound her mating call

And soon her mate responds by singing

Caw Caw Caw

Come with me

Lesbian Seagull

Settle down and rest with me

Fly with me lesbian seagull

To my little nest by the sea

With me that's where you belong with me

I know I can be strong when you're with me

She skims the water

At the new time to seek

Her fish and she emerges

With one squirming in her beak

She plays among the waves

And hides between the swells

She walks the beach at twilight

Searching for some shells

Come with me

Lesbian Seagull

Settle down and rest with me

Oh fly with me lesbian seagull

To my little nest by the sea

With me that's where you belong with me

I know I can be strong when you're -- you're with me

And in the evening

As they watch the setting sun

She loooks at her as if to say

The day is done

It's time to find their shelter

Hidden in the dunes

And fall asleep the

Music of the moon

You and me

Lesbian seagull

You just watch the world oh my

Just you and me lesbian seagull

Side by side with me 'till we die

('Till we die)

You and I

We can make it if we try

Our love will keep us flyin' high

Until we die...

Posted by: DarkStarSpace (14)

It took me a really long time to format the song that way, please don't delete it. Plus it's hilarious.

Talking with the Fishes

Most people know that certain animal species have ways to communicate through sound. Elephants, primates and birds all have auditory communication capabilities and now fish. A recent discovery in Japan has proven that a certain tropical reef fish can use auditory communication to “speak” to one another.

New research, reported Wednesday at a meeting of the Acoustical Society of America and Acoustical Society of Japan sates that butterfly fish can communicate by making numerous sounds to “talk” to its mate. Butterfly fish have internal ears called swim bladders that can detect sound and lateral lines that sense movements in the water. Only butterfly fish have both organs connected. It has been speculated that they are capable of more sophisticated means of hearing.

An experiment was performed in the tropical waters of Hawaii by marine biologist Tim Tricas of the University of Hawaii, Manoa, and his colleagues. They found three or four pairs of butterfly fish in feeding territories. In numerous experiments the researchers enclosed a pair of fish in a glass bottle and put the bottle in the middle of another pairs territory. They discovered that the owners of the territory would perform sound-generating behaviors such as erecting and flickering fins. The bottled fish would respond by grunting at the opposition. Interestingly only paired fish would communicate which would conclude that they are talking to one another. They also performed another experiment were they injected petroleum jelly into a fishes swim bladder. This caused interference in the sound traveling from the swim bladder to lateral lines. Fish that were injected swam closer together which would lead to believe that the butterfly fishes sense of “hearing” was disrupted.

The sense of hearing in butterfly fish my have developed because of their highly social nature. This would help in detecting food, predators and intruders. This new finding may lead to other social fish being experimented on to find whether or no they can communicate.

Posted by AZA (14)

Drinking Macaques?

Apparantly, we are not the only species that drink hard alcohol to feel good. Surprisingly, you would never expect a monkey to display similar drinking patterns and behavior as humans. In a study done by a researcher, Scott Chen from the National Institutes of Health Animal Center, 10 female rhesus macaques were given free acces to a sweetened ethanol concoction. In a follow-up experiment, Chen and his team separated 10 monkeys into individual cells. The monkeys in the cells ended up drinking less than their "social" counterparts. Lower level members and males were recorded as having consumed the most alcohol. In simal experiments, it was noted that monkeys were more likely to drink during stressful periods, just like humans!

Perhaps the reasons for drinking were most interesting. When the working hours in the facility increased, lets say an increased amount of testing or after a longer period of testing than usual, the monkeys responded by drinking a great deal more than usual. Most amazingly is that Chen reported that some monkeys even have preferences for alcoholic behverages and that alcohol affects different monkeys depending on their genetic background. Monkeys even had withdrawal symptoms after losing access to alcoholic beverages.

Using studies like these, Chan hopes to create a drug that lessens the intensity of withdrwal symptoms. It is hard to believe how closely related alcohol tendencies are between humans and monkeys. Perhaps alcohol can be so addicting that even monkeys show the same symtoms of alcoholism as we do.

posted by AMG (14)

Singing in the City

Everyone knows that city people are loud and in a rush, but do we ever think that city life can apply to the animal world. Now it can, recent research from Europe states, birds that live in the city change the frequency and length of their songs to over come the loud sounds of the city.

Ecologist Hans Slabbekoorn and his colleagues from Leiden University in the Netherlands researched bird songs in urban and rural environments throughout Europe, they focused their research on the male Great Tit, which lives in the surrounding forests and flourishes in European cities. The team studied 213 urban and 252 rural birds from 10 different cities and their surrounding forests. They found that the city bird’s songs were higher in frequency and shorter in length than their rural counterparts.

Slabbekoorn claims the change make sense because cities are full of low-frequency sounds made by the hustle and bustle of human city life, for example construction equipment. Making the change to a high-frequency sound allows it to stand out to the female birds over the sound of the city. This is why the Great Tit can easily breed and survive in the city better than other birds.

Posted by JLW (14)