LSM1303 Animal Behaviour Student Blog : communication

Turning Green! Or grey? Or yellow?

CHUAN YELI — Fri, 21 Mar 2008 05:31:00 GMT

"Ahhhhhh! Oh my god!! That stupid chameleon gave me a fright!"

"Huh? Where, where?"

"It just ran past us! It's on the tree trunk now!"

"Huh? I can't see it!"

Have you ever had such an experience before? Personally, I had, many times. As we know, chameleons are well-known for their ability to display different colours within a short time. I always thought that they are really smart to be able to adopt this kind of colour-changing mechanism to blend into their surroundings so as to ward off possible predators, until I started surfing the internet for information about the reptile.

(image from http://news.softpedia.com/news/Why-Do-Chameleons-Change-Color-47360.shtml)

The chameleon is able to change colours via specialized cells, which are called chromatophores, under its outer skin layer. The top layers of the chromatophores consists of red and yellow pigments, while the lower layers consists of blue or white pigments. The messages sent to the chameleon's brain will inform it to alterits pigment cells to suit the current situation. It has a chemical called melanin as well, which primarily darkens it when released.

So, when do chameleons send messages to change their colour pigmentation?
Some researchers still believe that camouflage is one of the main reasons, which is similar in the cases of other animals such as the Golden Tortoise Beetle and the Flounder. However, other studies illustrate, contrary to common beliefs, that it is not true and quite the opposite in the case of the chameleon!

"Because these signals are quick--chameleons can change color in a matter of milliseconds--the animal can afford to make it obvious, as the risk that a predator will notice is limited.This finding means that the evolution of color change serves to make chameleons more noticeable, the complete opposite of the camouflage hypothesis."

- http://www.sciencedaily.com/releases/2008/01/080129125524.htm

Rather, it does so as a kind of communication as well as a form of response to changes in temperature. Although different species of chameleon can change into different colours or differ in the variation of colour change, the basic functions of this useful mechanism is quite consistent. The common situations when a chameleon displays colour changes are:

1) Temperature changes
For example, when it is cold, the chameleon might make itself darker, as darker colours trap more heat.

2) Light conditions
For example, when the chameleon is out in the sun for long, it might enlarge its yellow pigments so as to reflect the bright light away.

3) Mood changes/ Communication
    When two males want to compete with each other, this happens:

"If a male is challenged by another male they both begin by showing their brightest colours - until one figures out the other is going to win and changes to a submissive, dark, 'don't beat me up colour,"

    - Dr Stuart-Fox

Also, when a male chameleon is interested in attracting a female one, it will display striking and bright colours. This kind of courtship technique displays how sexual selection of the chameleon works- the more flashy and colourful, the more attractive a male chameleon is!

Since the main communication tool of the chameleon is through visual cues, colour changes play a most significant role in conveying various messages to other chameleons, such as the desire to mate as mentioned above.

From the video:

Please view this link because I don't know how to embed the video here!

http://www.youtube.com/watch?v=cNPDvsWISx0

I was very amazed at how colourful the male chameleon can become to get to hook up with the female one!

All the information I managed to derive from online sources, I am glad to say, have changed my opinion and knowledge about these small eyed and long-tongued reptiles! And they are so lucky-- they do not have to spend a bundle on new coats!

(image from http://en.wikipedia.org/wiki/Chameleon)

References:

http://library.thinkquest.org/C0115747/

http://www.wildwatch.com/living_library/other-2/chameleon

http://www.youtube.com/watch?v=cNPDvsWISx0

"Chameleon colour not to blend in" by Anna-Marie Lever
BBC News, 29 January 2008.

"Chameleons" by Sharon Katz Cooper. National Geographic, October 2002. Retrieved from http://magma.nationalgeographic.com/ngexplorer/0210/articles/mainarticle.html

PLoS Biology (2008, February 3). Conspicuous Social Signaling Drives Evolution Of Chameleon Color Change. ScienceDaily. Retrieved from http://www.sciencedaily.com/releases/2008/01/080129125524.htm

"Why do chameleons change colour? - It's about mood, temperature and light" By Stefan Anitei.
Retrieved from http://news.softpedia.com/news/Why-Do-Chameleons-Change-Color-47360.shtml

Snap… Snap… BANG!!!

LIN YAOWEI — Fri, 21 Mar 2008 04:24:00 GMT

Just when you thought that pincers are just for picking items up, grabbing or crushing, think again!

The snapping shrimps or pistol shrimps (Alpheidae) are famed for their asymmetrical pincers. It has an enlarged pincer that can grow as long as half its body length and is capable of producing a loud snapping sound. What is so fearful of its huge pincer is not in its ability to crush, but its ability to act like a “pistol”. When the snapper claw extends into position and follows up with an extremely rapid closure, a high-velocity water jet is emitted from the claw with a speed exceeding cavitation conditions. This high-velocity water jet hits its prey animals with extreme pressure and temperature, and effectively stuns or kills them. Amazing! It is also this very action that produces its characteristic loud snapping sound, which is loud enough to affect naval sonar systems in submarines.

Such behavior by the snapping shrimp does not confine to attacking only, but also employed for defence and communication. The loud snapping sound wards off predators and potential territorial rivals of its kind. Interestingly, there is no concrete research to show that snapping shrimps have hearing organs. Instead, they have dense sensory hairs on their claw to pick up the vibrations from an opposing snapping shrimp. Two opposing snapping shrimps would “shoot’ at each other while maintaining a safety distance because their “duel” is not to annihilate or injure the other party, but to show who is the stronger of the two. The bigger the pincer, the larger the jet of water fired, the more powerful the "fire arm" and the stronger its owner. Sometimes, it is also through such battles that the snapping shrimp gets to befriend a female.

In that case, why not more? Well… since snapping shrimps dwell on seabed, they need to have traits that allow it to maneuver in such a terrain. For example, in addition to the pincer, the next limb (second thoracic limb) after the pincer is much longer, thinner and flexible, which allows the snapping shrimp to probe and reach for food that are concealed below the substrate. The remaining limbs also allow the snapping shrimp to move and burrow around just like normal shrimps.

Then the next question to ask would be… What happens if the shrimp loses that weapon of his? The fascinating thing about nature is that the other smaller claw would grow and replace the huge claw while the damaged one just recovers as a normal pincer. So perhaps the only thing the shrimp would need to do subsequently is to conduct more target practices with the other arm. BANG!!!

Reference:

“Pistol crabs use cavitation as a Navy shock: High Noon on the sea bed!” by Tobias Micke. Articles Extra, 22 Oct 2001.

“Snapping Shrimp Stun Prey with Flashy Bang,” by John Roach. National Geographic News, 3 Oct 2001.

D. Lohse , B. Schmitz & M. Versluis, 2001. Snapping shrimp make flashing bubbles. Nature, 413(6855):477-478.

A. T. Read, J. A. McTeague & C. K. Govind, 1991. Morphology and Behavior of an Unusually Flexible Thoracic Limb in the Snapping Shrimp, Alpheus heterochelis. The Biological Bulletin, 181(1): 158-168.

D. Schmitz & J. Herberholz, 1998. Snapping behaviour in intraspecific agonistic encounters in the snapping shrimp (Alpheus heterochaelis). Journal of Biosciences, 23(5): 623-632.

M. Versluis, B. Schmitz, A. von der Heydt & D. Lohse, 2000. How Snapping Shrimp Snap: Through Cavitating Bubbles. Science, 289(5487): 2114 – 2117.

Fairy Penguins in red light district

TEOH YUE LING ELLEN — Thu, 20 Mar 2008 15:14:00 GMT

Granite Island has been specially designed to make it easier for the penguins to breed. They have ready-made burrows and taken special precaution to make the island penguin-safe. The penguin population is dwindling (ironically due to tourism) and they are trying to revive it. On a recent trip to Granite Island, Australia, we were fortunate enough to watch penguins as they were coming back from a day out at sea with their catch to feed their young. Apart from the usual guidelines of observing wild animals like not to feed, approach or disturb them with loud noises, there was a particularly interesting note of caution which caught my attention: “No flashlight, only RED light can be used.” to shine at the penguins. According to the guide, it is only under red light, that the penguins would behave normally. As a result, the pictures turned out like this:

note that it was pitch dark except for the stark red light obvious to us humans, but not the penguins

Vision

Fairy penguins (Eudyptula minor) breed and live on the island. They are also known as little penguins as they are the smallest known species of penguins. Penguins have a flat cornea that allows for clear vision underwater. They are, as many avian birds, able to see the ultra-violet range of the light spectrum. Since their receptors have higher sensitivity towards colours with shorter wavelength (UV light), sensitivity towards red light(with longer wavelength, at the other end of the spectrum of visible light) would decrease. [link] Hence, penguins would behave naturally under red light as they are unable to detect it. However, colours are in fact only perceived in the brain, penguins may not see additional UV colours and may perceive colours differently from us. In order to fully understand this phenomenon, we have to find out how penguins perceive colours. This would better our comprehension of their signals, and give us an insight to the function and evolution of the various colour vision systems that exist across different species.

[I was thinking, since penguins and birds can see UV light, are they able to detect the female UV jumping spiders]

Communication

A full grown penguin is only about 40cm tall. They live in groups by the coast in burrows.

penguin at the mouth of the burrow

The penguins would venture out to sea in the day in search of small fish and squid for food and return just after dark, using the absence of light as a camouflage from predators. While we were there, we observed that penguins used a mixture of something like a cackling/quacking sound for communication. There are three main types of penguin calls. There’s contact call for maintaining communication among the colony, display call to be used between couples and threat call to warn the colony of intruders. I would suppose that threat call is the easiest to recognise because of the urgency and loudness of the call which makes it effective Click here or here to listen to a sample of penguin sounds.

Penguins’ interesting mating selection behaviour is also noteworthy. The male penguins would walk along the shore in search of the nicest and shiniest pebble to present to a female penguin. They may walk the shore for the whole day and drop the pebble at the feet of the female. If she picks up the pebble, they would become mates for life. Penguins practise monogamy. And for communication between partners, penguins use the display call. As penguins live in large colonies and their tuxedos look pretty much the same, it is each others’ call which they recognise and respond to.

I'll end off with a video of fairy penguins

References:

http://www.indianchild.com/what_do_animals_see.htm, What do animals see. Retrieved 17 March 2008

http://www.bio.bris.ac.uk/research/vision/4d.htm, Ultraviolet Vision, University of Bristol 2007. Retrieved 17 March 2008

http://www.usbyte.com/common/approximate_wavelength.htm, Color Wavelength. Retrieved 17 March 2008

http://www.seaworld.org/animal-info/info-books/penguin/communication.htm, Penguins – Communication, SeaWorld. Retrieved 17 March 2008

http://www.aad.gov.au/default.asp?casid=229, Australian Antarctic Division - Sounds of Antarctica. Australian Government. Retrieved 17 March 2008

http://www.bio.davidson.edu/people/vecase/Behavior/Spring2005/Harshaw/MatSys.html, Mating System. Retrieved 17 March 2008

http://www.canongate.net/Lists/Animals/11ExamplesofUnusualMatingHabits, 11 Examples of Unusual Mating Habits, Canongate. Retrieved 17 March 2008

Lyrebird or “Liar” bird?

GOH HUI SHAN AMANDA — Thu, 20 Mar 2008 13:41:00 GMT

Mention a bird so skillful at imitating sounds and the parrot always comes to mind right away. However, the ability to mimic sounds is definitely not exclusive to parrots.

As it turns out, renowned vocal mimics in the bird world include “mockingbirds, starlings, mynahs, marsh warbler, lyrebirds, bowerbirds, scrub-birds and African robin-chats”. Read more...

The Superb Lyrebird flaunts its incredible adeptness towards mimicry, imitating a Kookaburra, a camera shutter, a car alarm, and a chainsaw!

Watch "Lyrebird”, Youtube.

The Superb Lyrebird (Menura superba, or M. novaehollandiae) is an Australian ground-dweller “named for the shape of their tail when spread in courtship display. The name also aptly suggests a musician”. Read more...

So what inspires the Lyrebird to become such a successful impersonator?

As David Attenborough clearly describes, the male Lyrebird “incorporates other sounds he hears in the forest into a complex song in attempt to out-sing rivals in his courtship display”. As if copying the songs of other bird species lacks some kind of star performance, it extends its repertoire to include the reproduction of man-made sounds.

The Lyrebird goes this extra mile so as to win the attention of the female bird, drawing her into his territory to admire not just his elaborate song, but also his attractive plumes.

The level of mimicry mastered by the Lyrebird is a fascinating illustration of the role of learnt behaviours in social communication.

But what mechanism underlies this ability to produce such complex sounds?

“The muscles of the syrinx (sound-producing organ in birds) control the details of song production; birds with more elaborate system of vocal muscles produce more complex songs”.The Life of Birds by David Attenborough. As it turns out, the lyrebird's syrinx is the most complexly-muscled of all songbirds. Read more...

In addition to its impersonations of other species’ songs, it learns and incorporates the new sounds it is exposed to such as the camera shutter and the car alarm. So while the Lyrebird’s instinctive loud bird song is a product of nature, its integration of other interesting sounds into its song are inspired and nurtured by sounds it hears in the forest environment.

And the adaptive significance of this learnt behaviour in Lyrebirds is clear – to increase its attractiveness and, the chances of mating and reproduction. Large song repertoires increase a male's attractiveness to females.

An interesting question to ponder on: How does the female Lyrebird is able to differentiate the male's "performance" from the actual production of these sounds sounds (e.g. camera shutter, car alarm going off). To the regular hiker making his way through the forest, what may sound like a whole range of birds singing and the sounds of foresters working close by may well be just one "liar" bird's deceptive song.

One wonders, what else does this “liar” have up his sleeves?

Of course, we will always remain intrigued at the ability parrots have to imitate human voices.

Michael Schindlinger’s article “Why do parrots have the ability to mimic?”, lends insight into this amazing ability.

“When parrots are kept as pets, they learn their calls from their adoptive human social partners. Part of their appeal as pets is their ability to sing lower notes than smaller birds and so better reproduce human voices. In the wild, though, their calls may go much higher in pitch and much faster in tempo than any human tutor's voice.”

Once again, the role of environment in learnt behaviours demonstrated.

The benefits of birds’ reliance on learning for vocal development are also described in this account. Read more...

“Some benefits of learning may include development of context-specific calls. Imitative vocal learning is also a reliable social display of neural functions—requiring good hearing, memory…” - qualities even females humans seek out in her mate!

References

“Bird Songs”, by Gareth Huw Davies. The Life of Birds by David Attenborough. Retrieved 14 Mar 2008.

“Lyrebird”, Encyclopedia Britannica - the Online Encyclopedia. Retrieved 17 Mar 2008.

“Lyrebird, From Wikipedia, the free encyclopedia”. Retrieved 17 Mar 2008.

“Why do parrots have the ability to mimic?”, by Michael Schindlinger. Scientific American, 5 Dec 2007.

Can’t do Maths? The Honeybee shows you how!

ER WAN LING — Wed, 19 Mar 2008 06:04:00 GMT

If you think that only humans have the knack for Mathematics, the Honeybees will prove you wrong. Do you know that one of the channels of communication between Honeybees is through the use of visual cues? I will show how Honeybees exhibit Mathematical techniques in their visual communication, the “Waggle dance”.

(Extracted from http://animals.nationalgeographic.com/animals/bugs/honeybee.html)

It is no secret that Honeybees have been the main provider of honey for us through the collection of nectar from flowers. But how do the bees ensure a consistent and steady flow of nectar to the beehive with the varying amount of nectar that could be extracted from flowers with the changing season and climate?

The interesting waggle dance performed by Honeybees is the main communication means to inform worker bees about the location of nectar from their beehive. A few scout bees will fly around in search for food. When it finds a promising site, it will fly back to the beehive doing the waggle dance to inform about the location.

Click on the bee to find out how it works

The waggle dance consists of straight runs, during which the bee waggles its abdomen from side to side, forming wavy lines followed by semicircular returns to form a figure-8 pattern. The angle the bee waggles indicates the angle of the food from the sun.

(Extracted from http://neurophilosophy.files.wordpress.com/2006/04/300px-Bee_dance1.png?w=300&h=239)

Besides indicating the direction of nectar to other fellow bees, the waggle runs also indicates the distance of the beehive to the source of food. How long the bee goes forward wagging signifies the distance. Also, as shown in the video above, “depending on how plentiful the nectar is, the figure-8 pattern may be repeated a few times”. As long as there is still nectar to be found, the waggle dance continues and the dance will slowly taper off with the diminishing amount of nectar around that area. After which, a new scout bee will come back with a more “appealing dance routine” when it finds a more promising spot for nectar collection.

The unique way of visual communication amongst the Honeybees is part of their cooperative effort in working to sustain the inflow of nectar. What is interesting about the mode of communication of the Honeybee is the parallel of their dance to the mathematical skills we learn in class. The Honeybee uses vector calculus to inform about the direction of nectar location, and uses the forward wagging to inform about the distance. For those people who are bad at direction, the Honeybee beats you hands down!

It is also interesting to note that the bee’s dance has inspired development of communication system by the Georgia Institute of Technology to improve Internet servers. For more details click here!

Such an impressive way of communication among Honeybees is unique to the bee family. What lies behind what we have always taken for granted – the collection of nectar – actually engages a special mechanism which the ingenious bees employ.

References

Georgia Institute of Technology (2007). Bee Strategy Helps Servers Run More Sweetly. ScienceDaily. Retrieved 19th March 2008 from http://www.sciencedaily.com/releases/2007/11/071116133551.htm

James L. Gould & William F. Towne. (1987). Evolution of the Dance Language. The American Naturalist. 130, No. 3. pp. 317-338.

The University of Arizona. Honey Bee Dances. Africanized Honey Bee Education Project. Retrieved 19th March 2008 from http://ag.arizona.edu/pubs/insects/ahb/inf7.html