LSM1303 Animal Behaviour

An Imperator Angelfish (left) being cleaned by a Cleaner Wrasse (the smaller fish on the right)

Symbiosis is common in nature - clownfish and anemone, bees and flowers, fish and fishes - and it has always been a fascinating topic to me. So in this post, I will discuss about a particular symbiotic relationship that mesmerizes me whenever I see it, whether on tv, youtube or in the ocean: the cleaning service provided by the Cleaner Wrasse (Labroides dimidiatus).

Basically when a Cleaner Wrasse “cleans”, it is removing and eating, among many things, parasites from other fishes (which are usually called “host fish”) (Dennis 1987). The interesting thing about Cleaner Wrasse, and most other cleaner fishes, is that they will stay at a particular place (usually called “cleaning stations”) to wait for host fishes to come for their service, and usually the cost of visiting these cleaning stations is high because of the need to travel long distances and battle aggression from other marine lives (Bshary 2002).

So intuitively one might think that both parties, the one that cleans and the one being cleaned, benefit from this relationship, because the former gets food, while the latter reduces its parasite load. However, there is no sufficient empirical evidence to support the claim that host fishes have a reduction in their parasite loads after being cleaned by Cleaner Wrasses (Dennis 1987, Alexander 1996). Dennis and his team did, nonetheless, observe a change in the structure of the parasite population, but they were unable to explain conclusively how this could have benefit the host fish. On the other hand, they did explain why “cleaning” doesn’t reduce parasite load in the host fish – one of the reasons they gave was that immunity of the host fish plays a vital role too. Such a counter-intuitive research outcome is perhaps an illustration on how experiments are still necessary to confirm so-called intuitively obvious “facts”.

And what makes everything even more frustrating is that, as mentioned in the previous paragraph, the cost of visiting those cleaning stations is high, and so the desire to receive cleaning services from the Cleaner Wrasse makes no sense from the cost-benefit point of view. So I believe that more research in this area will give us yet another new theory, or could help us understand deeper results which baffles us at present. Either way, the possibility of learning something new, or even exciting is high. As a note, the articles cited are relatively old, so if anyone has found new articles on this subject (in particular on Labroides dimidiatus), please post it under the comments. Thanks! And finally, just in case the first picture wasn’t clear, below is another photograph of the cleaner wrasse, and a youtube video which shows several Cleaner Wrasses cleaning the gills of a big fish (according to the title of the video, the big fish is called a Midnight Snapper)::

Labroides dimidiatus

Midnight Snapper with Cleaner Wrasse (Coral Garden, Bali) by tennam01

References:

Alexander S. Grutter, 1996. Experimental demonstration of no effect by the cleaner wrasse Labroides dimidiatus (Cuvier and Valenciennes) on the host fish Pomacentrus moluccensis (Bleeker). Journal of Experimental Marine Biology and Ecology 196 (1996) 285-298

Bshary R., 2002. Building up relationships in asymmetric co-operation games between the cleaner wrasse Labroides dimidiatus and client reef fish. Behav Ecol Sociobiol (2002) 52 365-371

Dennis L. Gorlick, Paul D. Atkins & George S. Losey, 1987. Effect of Cleaning by Labroides dimidiatus (Labridae) on an Ectoparasite Population Infecting Pomacentrus Vaiuli (Pomacentridae) at Enewetak Atoll. Copeia, 1987(1) 41-45

Predator-prey relationship is extremely crucial in upholding the delicate balance among different animal species. Prey and predators alike are constantly undergoing adaptive changes to aid in their survival. To avoid falling prey to a predator, animals have developed various types of defense mechanisms and methods of accessing predator risk factor. For the red-eyed treefrogs, Agalychnis callidryas, it appears that even their embryos are able to respond to predator threat.

I look cute but my bite definitely will kill.

The Komodo dragon (Varanus komodoensis) is an endangered species of monitor lizard (Varanidae) that inhabits the Indonesian islands of Komodo, Gili Motang, Flores, and Rinca. It is the largest and one of the deadliest living species of lizard in the world. Growing at times to over 3 meters in length and weighing over 150 kilograms, they hunt anything and everything that they can overpower. Despite having a diet consisting mainly of carrion, komodo dragons dominate the ecosystems that they live in as a result of their size and the lack of other carnivorous predator. In addition, they have a long lifespan of up to 50 years. They have a low metabolism rate and require as little as 12 meals annually.

Komodo dragons are perfect hunting machines, attacking with brutal efficiency. They do not stalk their preys, instead, they are opportunistic hunters. They lie and wait for their victims in tall grass. When a victim approaches the ambush site, the dragon charges and goes for the victim’s throat, underside, or legs to bring it down. It then feeds by tearing chunks of flesh out of the victim and swallowing them whole. Sometimes, for smaller sized preys – up to the size of a goat, the dragon swallows them whole by loosening its jaws and expanding its stomach.

They are able to reach speeds of 20 kilometers an hour in short sprints, diving up to 4.5 meters in depth, and are capable of standing on their hind legs, using their tail as support, to attack prey that are out of reach. In addition, it has 3 weapons that are highly efficient in doing what they are meant to do – hunting and killing.

Firstly of all, a long, yellow and deeply forked tongue. As with all reptiles, komodo dragons rely on their tongue to capture airborne scent molecules to smell and taste stimuli. They are able to smell the aroma of meat as far as 9.5 kilometers away. Secondly, razor sharp claws coupled with powerful forelimbs. This allows komodo dragons to effortlessly tear their preys’ flesh or hold them down while feeding. Lastly, their teeth. Komodo dragons have 60 serrated gagged edged teeth, each measuring up to 2.5 centimeters, enabling them to tear through their preys’ flesh, teeth, claws, hoofs and bones, leaving nothing of their preys behind. To make matters worst, the mouth of komodo dragons contain more than 50 strains of virulent bacteria. A single bite will cause blood poisoning, leaving the victim dead in less than a week. With that said, a small nibble from the dragon will most probably leave a human dead without immediate antibiotics.

However, despite the strength and efficiency of such a killing machine, they are no match for an even greater opponent – man. Only 4,000 to 5,000 dragons are left living in the wild due to poaching, loss of prey and loss of habitat. Therefore, please preserve these wonderful creatures created by nature and perfected through evolution. Do not support products made of their skin or trading of their specimens. They are natures living reminder of her brutal force.

References

Trooper Walsh; Murphy, James Jerome; Claudio Ciofi; Colomba De LA Panouse. Komodo Dragons: Biology and Conservation (Zoo and Aquarium Biology and Conservation Series). Washington, D.C.: Smithsonian Books. ISBN 1-58834-073-2.

Burness G, Diamond J, Flannery T (2001). “Dinosaurs, dragons, and dwarfs: the evolution of maximal body size”. Proc Natl Acad Sci USA 98 (25): 14518–23. PMID 11724953.

Tim Halliday (Editor), Kraig Adler (Editor). Firefly Encyclopedia of Reptiles and Amphibians. Hove: Firefly Books Ltd. pp. 112, 113, 144, 147, 168, 169. ISBN 1-55297-613-0.

Ciofi, Claudio. “The Komodo Dragon”. Scientific American. http://www.sciam.com/article.cfm?id=the-komodo-dragon

Burnie, David; Don E. Wilson (2001). Animal. New York, New York: DK Publishing, Inc.. pp. 417, 420. ISBN 0-7894-7764-5.

“Komodo Dragon”. Singapore Zoological Gardens. Archived from the original on 2006-11-27. http://web.archive.org/web/20061127173608/http://www.szgdocent.org/resource/rr/c-komodo.htm.

Chris Mattison, (1989 & 1992). Lizards of the World. New York: Facts on File. pp. 16, 57, 99, 175. ISBN 0-8160-5716-8.

Tara Darling (Illustrator). Komodo Dragon: On Location (Darling, Kathy. on Location.). Lothrop, Lee and Shepard Books. ISBN 0-688-13777-6.

“Zipcodezoo: Varanus komodoensis (Komodo Dragon, Komodo Island Monitor, Komodo Monitor)”. BayScience Foundation, Inc.. Archived from the original on 2007-09-27. http://web.archive.org/web/20070927190225/http://zipcodezoo.com/animals/v/varanus_komodoensis.asp.

Feldman, Ruth Tenzer (February 2007). “Dragon Drool!”. Odyssey 16.2: 49.

Fence lizard trying to camouflage (Credit: Tracy Langkilde, Penn State)

In the past, fire-ants had been attacking fence lizards by slowly getting under the hard scales of an unsuspecting lizard. Once they had reached the flesh, they will inject toxic to paralyse the lizard. They will then tear out the flesh of this poor lizard to pieces before moving their “prized” possesion to their nest. An astonishing fact of this attack is that it takes just 12 fire ants to kill a three-inch long fence lizard in less than a minute.

Ever heard of the saying “Once bitten, twice shy”? I think this applies here in the case of the fence lizards. Fence lizards from sites which had been invaded by fire ants had evolved to prevent themselves from being attacked by the fire ants. Now, what they will do is that they will twitch and shake to fling their attackers off their body before they flee. They are also evolving longer hind legs to make their defensive behavior even more effective.

According to this journal, it states that toxic cane toads are highly toxic to snakes as they attempt to eat them. Therefore, the arrival of these toads had exert selection on snake morphology, favoring an increase in mean body size and a decrease in relative head size. They would then not be able to eat these toxic toad and hence, prevent death. In the case of the fence lizard, it is also the same. They had adapt to the attack of the fire ants and again, prevent death for their species.

However, those lizards from sites that had not been invaded before has not evolve yet. When introduced to the fire ants, they will just sit still and hope that the fire ants will leave them alone. But this will surely not happen. Therefore, they will be killed by the ants.

Below is a video to show the difference technique used by the lizards.

Source: Lizards Show Evolution in Action on YouTube
http://www.youtube.com/watch?v=PoeIIZFApF4

From this article, we can see that the fence lizards are developing behaviors to increase their survival. Humans can also learn do the same and that is, to change and adapt to whatever difficulties we may faced. By doing so, we will then be able to survive.

Click here if you want to read more about the article.

References:

Evolution In Action: Native U.S. Lizards Are Adapting To Escape Attacks By Fire Ants , ScienceDaily (Jan. 24, 2009)

Lizards Evolved Quickly to Avoid Death by Ants, Emily Sohn, Discovery News (Jan. 28, 2009)

Adapting to an invasive species: Toxic cane toads induce morphological change in Australian snakes, Ben L. Phillips* and Richard Shine (October 27, 2004)

Invasive fire ants alter behavior and morphology of native lizards, Tracy Langkilde, Ecological Society of America (April 29, 2008)

Take a look at this photo

What will you do if you every come across this crocodile?

What about this ?

Will you run away if you ever see this toad?
Well, you should as you are looking at the very eyes of a creature that is rapidly killing off the Australian salt water crocodiles. A very fine example of how such a small animal is able to take down such a vicious killing machine.

Basically, this toxic cane toads were brought into Australia to control the population of the cane beetles. However, they managed to populate a large area of Australia and these salt water crocodiles, which originated in Australia, died after eating these toads.These toad has a certain defense mechanism whereby they are able to excrete Bufotenin, a Class 1 drug under Australia laws. These toads accounts for the deaths of over 77% of the salt water crocodiles population. The alarming rate of the death is due to the fact that the crocodile immune system are unable to cope with these toads poison as the toads do not originate here.

The toad mechanism of defense is not only useful against the crocodiles but also other animals living in Australia. By poisoning the animals that feasted on the toads, it sends out a message that they are deadly and should be refrained from eating upon. Most snakes in Australia have learn this valuable lesson. A study conducted by Ben L.Phillips and Richard Shine show that snakes have managed to adapt by reducing their jaw size. This prevents them from swallowing the frog whole and this helps to prevent them from choosing the toads as food. If you are interested as to how the snakes manage to adapt to these toxic toads, click here.

Although it is rather clear that introducing the toxic toads to the ecosystem is harmful to the native species, there is at least one type of animal that managed to adapt to these foreign animals.Hence, for these crocodiles, they are likely to go extinct unless the entire species is able to adapt to cope with these cane toads.

But there is still a sliver lining whereby it is reported that the cane toads have indirectly helped to increase in the number of crocodiles eggs. These toads wipe out the goannas which feast on the eggs. So, is nature way of balancing nature ?

Only time will tell…

References:

“Toxic Toads Killing Australian Crocs“, Discovery News (Nov. 18, 2008 ).

“Toxic Toads Evolving quickly” Discovery News (Apr . 02 2007 ).

“Cane Toads“, Wikipedia

“Adapting to an invasive species: Toxic cane toads induce morphological change in Australian snakes” , Ben L.Phillips and Richard Shine(Published October 27 2004)

“Invasion and Evolution of speed in frogs” , Benjamin L. Phillips, Gregory P. Brown, Jonathan K. Webb & Richard Shine , Nature (International Weekly Journal of Science) 439, 803 (16 February 2006)

Salt water Crocodile picture (Extracted from National  Geographic )

Cane toad picture ( Extracted from Discovery News )