LSM1303 Animal Behaviour Student Blog : adaptation

Raccoons - Rascals or Ninjas?

Lee Wan Jing — Fri, 21 Mar 2008 15:39:00 GMT

Raccoons - are they cheeky grinning rascals or skillful ninjas of the night?

Image by OCPetPhotos and Sara Heinrichs

First and foremost, racoons (procyon lotor) are noctural animals, and increasingly abundant inhabitants of suburbans areas and cities as humans have destroyed their natural habitats. They are extremely adaptable and can be found in many different kinds of habitats such as wooded areas near water bodies, trees, to woodchuck burrows, caves, sewers, garages and houses, and so on.

Image by k e v i n, kjdrill, dazed81 and secretsamba

The raccoons are omnivorous and their diet consists of a wide range of food, from berries, corns, walnuts, to fish, insects, rodents and in suburban areas, foraging leftovers in garbarge cans and even stealing food from houses, and at times, "begging" for food from passerbys (watch videos below). An interesting note on the raccoon's eating habit (no, they don't sing before they eat nor say grace, nor wipe their hands before they eat)

Image by OCPetPhotos

is that if water bodies are near, they dabble their food in the water as if washing their food in order to clean it, but it is not. The raccoon is simply just softening the food and perhaps at the same time looking for foreign objects/particles on the food (survival skills).

Video 1 - The Night Raiders
note* their eyes - being nocturnal creatures, they have excellent night vision, and they are also especially alert (fine sense of hearing)

Video 2 - Adaption to urban habitat (and humans)
note* they have adapted to the city, and learned to associate humans with food!

Video 3 - More raiding

note* how they used their paws to grab food! using their grasping hand-like paws, they have learned to open garbage cans and gates as well as getting hold of food

Video 4 - a closer view of their paws
note* their paws have five toes that looks a little like our hands and it is flexible and very good, not only at grabbing things, but as pulling things apart and holding things. Very handy indeed! That makes them excellent climbers too, climbing up trees, houses, fences and gates with great agility!

Given their physical appearance, a black mask around its eyes, it gives them the mischievious look of a burglar/ninja indeed.

References

1. http://animaldiversity.ummz.umich.edu/site/accounts/information/Procyon_lotor.html
2. http://teacher.scholastic.com/dirtrep/animal/raccoons.htm
3. http://www.massaudubon.org/Nature_Connection/wildlife/index.php?subject=Mammals&id=26
4. http://www.nhptv.org/natureworks/raccoon.htm
5. http://www.raccoonlearningzone.com/index.php
6. http://www.backyardnature.net/raccoons.htm

Is that a cookie I see floating on the water?

CHNG WEI LING JOANNA — Tue, 18 Mar 2008 17:05:00 GMT

What is this strange looking brownish-disc like thing floating on the water in the image below? Floating algae? Frogs' eggs? A big brown cookie? Truth be told, you already knew that whenever this type of question is asked, the answer is some absurb truth that you could never imagine possible.

photo: http://bugguide.net/node/view/30113/bgpage?take2

Red Imported Fire Ants (scientific name: Solenopsis invicta), or simply RIFA, is one of the 280 species of ants in the world. Although it is native to South American, it is common in the United States, Australia, Taiwan and other South Asian countries as well. The bodies of these fire ants, like all insects, consist of 3 parts - the head, the thorax and the abdomen. They also have 3 pairs of legs, and 1 pair of antennae. RIFA are more aggressive than most ants species, and have been known to "kill newborn calves if the calves do not get on their feet quickly enough. They attack en masse, responding to pheromones that are released by the first ant to attack. They then swarm and immediately sting when any movement is sensed."¹

They nest near moist areas, like rivers and ponds, and their nest is usually not visible as it will be hidden under logs, rocks and bricks. Unlike other species of ants which bite to inflict a deadly wound, these fire ants bite to get a grip, then sting their prey by injecting a toxic venom, the sensation of which is "similar to what one feels when burned by fire"².

photo: http://entomology.lsu.edu/faculty/hooper_files/RedImportedFireAnt.jpg

RIFA are able to survive floods by clinging together to form rafts. They have adaptations to contend with both flooding and drought conditions. Their nest structure includes a network of underground foraging tunnels that extends down to underground water supplies, ensuring a steady supply of food and water in winter. The more intriguing behaviour exhibits in times of increased water levels; these ants will gather and begin to form a huge raft, with the queen on the inside. The raft will flow with the current until the floodwaters recede, then they will get on to anything that they come into contact with to build their new nest. If the raft hits a solid object, the ants would swarm onto it and wait for the water level to fall.

photo: http://www.tarleton.edu/~physci/Envir/FireAnts.jpg

These scary little buggers have honed survival skills. They are able to avoid drowning while rafting by "rotating from the underwater side to the above water side with the queen staying in the middle. Enough air bubbles adhere to their spiracles that they have no problem being underwater for a period of a couple minutes"³

Also, as a precautionary measure, "colonies would compensate for their elevated vulnerability by increasing their defensiveness"⁴ through adjusting the amount of venom that they delivered per sting. As the ants are more susceptible to predatory attacks while rafting, they have to protect themselves by increasing venom doses in the event of an attack. Any encounters with an ant-raft would be potentionally more dangerous than if on land.
(for a more detailed explanation of the experiment, please refer to K.L. Haight's research article, 2006, an abstract of which can be found here)

photo: http://www.angryflower.com/ants.gif

Citations:
(1) http://en.wikipedia.org/wiki/Red_imported_fire_ant
(2) http://en.wikipedia.org/wiki/Fire_ants
(3) http://bugguide.net/node/view/30113/bgpage?take2
(4) Haight K.L., 2006. Defensiveness of the fire ant, Solenopsis invicta, is increased during colony rafting. Insectes Sociaux (Vol. 53, No. 1, Pg. 32-36)

References:
1. http://www.springerlink.com/content/x362362m5708212v/
2. http://www.chron.com/disp/story.mpl/storm2001/943267.html
3. http://bugguide.net/node/view/30113/bgpage?take2
4. http://en.wikipedia.org/wiki/Ant
5. http://en.wikipedia.org/wiki/Fire_ants
6. http://en.wikipedia.org/wiki/Spiracle
7. http://www.independent.co.uk/news/science/wild-things-the-weirdest-facts-from-the-animal-kingdom-418659.html

"Airborne Geckos take a Little Trip, YEAH!"

TAN YU-YANG KENNETH — Tue, 18 Mar 2008 14:03:00 GMT

'Airborne' geckos! Now that must be a real good sight. Imagine, a gecko trying to keep itself up on a slippery, vertical surface when suddenly, *Slip*, and it falls off!

(Credit: Robert Full/UC Berkeley, copyright PNAS/NAS 2008)
Watch It

Now isn't that a cool sight?

But what happens next? Surely the gecko does not fall flat on its face does it?

The gecko in question, Cosymbotus platyurus, or the flat-tailed house gecko of Southeast Asia lands perfectly feet-down in an awesome display of aerial acrobatics with only a flick of its tail!

According to Robert J. Full, "Initially, we thought the gecko's climbing ability was all in the feet, but now we know that this is clearly not true and the tail is critical." With the knowledge that geckos' tails are imperative in their climbing ability, researchers also found out that these tails come into use during perilous falls. Specifically, they rotate their fat-filled tail to counter-rotate their body and spread their legs and toes to parachute and glide to safety in a Superman posture! Read more here...

Watch It

Researchers have acknowledged the use of tails in other species of animals: Kangaroos lean on theirs, New World monkeys use their prehensile tails to grasp, but these are relatively static uses compared to the gecko in terms of high-speed climbing and gliding.

In my opinion, the gecko's active use of its tail is another functional explanation for its climbing and gliding ability. These abilities are essential for the gecko's survival, both in foraging for food and escaping from predators. I'm simply astounded that a simple mechanism of flicking its tail allows the gecko to reorient itself in mid-air, which can be akin to cats (which involves a more complex spine-twisting behaviour)! The instinctual nature of such tail use in climbing and gliding behaviour is perhaps an evolutionary adaptation that would enable them to use these 'acrobatic skills' in their natural habitat of the forest!

Furthermore, what is even more interesting is that researchers believe that this new discovery could inspire engineers in applications such as "new climbing and gliding robots as well as highly manoeuvarable unmanned aerial vehicles." Imagine the wonderful applications that humans can apply to their own lives drawing on research about animal behaviour and functions!

For an appreciation of how other species use their tails:

"Anna's Hummingbird Chirps with Its Tail During Display Dives" (Feb 5, 2008)

"New World Monkeys and their Gadgets" (Feb, 2003)

For a look at other interesting applications from gecko research:

"Scientists Prove How Geckos Stick, Unlock Secret to Making Articial Gecko Glue" (Aug 28, 2002)

"Engineers Create Gecko-inspired, High friction Micro-fibers" (Aug 23, 2006)

"Sticky Questions tackled in Gecko Research" (Jan 2, 2008)

Citation:

University of California - Berkeley (2008, March 18). Gecko's 'Active' Tail Key To Preventing Falls And Aerial Maneuvers. ScienceDaily. Retrieved March 18, 2008, from http://www.sciencedaily.com /releases/2008/03/080317171030.htm

Tail 'key' for gecko acrobatics, By Rebecca Morelle. BBC News. 18 March 2008

Green Anaconda Devours The Spectacled Caiman Alligator!!! (Warning: Not for the faint-hearted)

CHUA CHING HOCK — Mon, 17 Mar 2008 19:16:00 GMT

Never thought that an adult Spectacled Caiman alligator (Caiman crocodilus) can be eaten alive by another predator? Well, think again!! Especially when you have this chap around:

(Image Source: http://animals.nationalgeographic.com/animals/reptiles/green-anaconda.html)

Introducing.... The Green Anaconda (Eunectes murinus) !!!

Well, I have always thought that anacondas' diet consist only of fishes, birds, rodents, mammals, and other small reptiles. But little did I expect to discover that this particular species, the Green Anaconda, actually feeds on full-grown Spectacled Caimans (which can grow up to 2.5m) as well!

Devouring a fellow fearsome predator? Wow.

My interest in inter-species conflict originally led me to stumble upon the incredible videos listed below. And upon closer research, I discovered that the Green Anaconda, located primarily in South America, is actually the largest snake in the world in terms of weight. They can grow up to 30 feet (9 meters) long, weigh 1,200 pounds (550 kilograms), and measure more than 12 inches (30 centimeters) in diameter.

Youtube Link:
http://www.youtube.com/watch?v=acVlIJeY9ws&feature=related

As illustrated in the video above, the Green Anaconda kills with power, not poison. By coiling its muscular body around its prey, the Green Anaconda can even crush the armoured Caiman until it can no longer breathe. This constriction tactic allows the Green Anaconda to take down other prey as large as adult capybaras (giant rodents), adult white-tailed deers, adult jaguars, and even humans of approximately 55kg or more.

At the same time, this brutal predator can be really covert and sleek in the water, with its dull colour and black blotches enhancing its camouflaging capabilities in the marshes and swamps. Its eyes and nasal openings are on top of its head, allowing it to wait and ambush its prey while remaining almost completely submerged.

Youtube Link:
http://www.youtube.com/watch?v=Xc06MVH6W98

Interestingly, while all the videos here highlight the Green Anaconda prevailing over the Spectacled Caiman, my research indicates that this is not always the case. In fact, renowned anaconda specialist Jesus Rivas once documented an intriguing event of the Spectacled Caiman preying on a green anaconda in return:

"On 25 of May 1996 we discovered a large caiman (>90 cm svl) firmly gripping the head of a radio-implanted female anaconda (494 cm TL, 29 kg), who in turn had wrapped herself around the caiman’s head and neck. After approximately 15 min the snake relaxed her coils, apparently losing the struggle with the caiman.

We interrupted the event to recover the transmitter when the snake stopped struggling. One of the teeth of the caiman had gone right through the skull and into the brain region, other tooth mark where present in the first fifth but did not look life threatening. The snake died two months later in captivity due to a generalized infection. As we had found this snake severely wounded from 2 months previous to being preyed on by the caiman, it is likely that she was not in top physical shape and this may have played some role in the attack."

Certainly, there appears to be a history of inter-species conflict between these two large predators. One possible reason could be due to the fact that both share very similar habitats in the seasonally flooded savannahs of South America and the Amazon Basin.

Youtube Link:
http://www.youtube.com/watch?v=KMwt_fEe3CY&feature=related
(Warning: Do not watch this if you just had a heavy meal.)

As seen in the fascinating video above, the Green Anaconda possesses jaws attached by pliable ligaments, which enables it to swallow the Caiman as a whole. Such a sizeable and yummy meal can allow it to go for weeks or even months without food.

At the same time, the Green Anaconda's unique adaptation and natural selection allow it to experience an incredible change in body size from birth to adulthood, as compared to other snakes. This explains how it can grow to such a massive bulk despite the occasional meal. Moreover, the role of nature has also dictated that baby Green Anacondas can almost immediately be able to swim and hunt once they are born. A top, ectothermic predator indeed.

Poor Caiman.

Finally, just to make you feel a little better, Green Anacondas are not known for being fond of attacking humans, despite their mythical reputation as man-eaters. Thankfully. =)

References:

BBC Science and Nature, Amazon Abyss (Apr 2005)
<http://www.bbc.co.uk/sn/tvradio/programmes/amazon/creatures.shtml> 16 Mar 2008

Isho, Fady D., AllExperts, Interspecies Conflict: Saltwater Crocodile vs Green Anaconda (26 Jan 2008)
<http://en.allexperts.com/q/Interspecies-Conflict-3754/2008/1/Saltwater-Crocodile-vs-Green.htm> 17 Mar 2008

Mayell, Hillary, National Geographic News, Anaconda Expert Wades Barefoot in Venezuela's Swamps (13 Mar 2003)
<http://news.nationalgeographic.com/news/2002/04/0430_020503_anacondaman.html> 16 Mar 2008

National Geographic, Green Anaconda
<http://animals.nationalgeographic.com/animals/reptiles/green-anaconda.html> 16 Mar 2008

Peach, Natasha, BBC Oxford, New Arrivals and Happy Feet (7 Jan 2008)
<http://www.bbc.co.uk/oxford/content/articles/2008/01/07/happy_feet_feature.shtml> 16 Mar 2008

Rivas, Jesus A., The Life History of the Green Anaconda (Eunectes murinus), with emphasis on its reproductive biology, Introduction (2000)
<www.anacondas.org/diss/intro.pdf> 17 Mar 2008

Rivas, Jesus A., Life history and conservation of the green anaconda - Eunectes murinus (2000)
<http://pages.prodigy.net/anaconda/research.htm> 16 Mar 2008

Rivas, Jesus A., Herpetological Review, Eunectes murinus: caiman predation (1999)
<http://pages.prodigy.net/anaconda/fight.htm> 16 Mar 2008

Rivas, Jesus A., Herpetological Review, Eunectes murinus: Juvenile predation (2001)
<http://pages.prodigy.net/anaconda/juvpred.htm> 16 Mar 2008

Vancouver Aquarium Marine Science Centre, AquaFacts: Green Anaconda - Eunectes murinus
<http://www.vanaqua.org/education/aquafacts/anaconda.html> 16 Mar 2008

Wikipedia, Anaconda (16 Mar 2008)
<http://en.wikipedia.org/wiki/Anaconda> 16 Mar 2008

Wikipedia, Green Anaconda (4 Mar 2008)
<http://en.wikipedia.org/wiki/Green_Anaconda> 16 Mar 2008

Wikipedia, Alligatoridae (10 Mar 2008)
<http://en.wikipedia.org/wiki/Caiman> 16 Mar 2008

Wikipedia, Spectacled Caiman (11 Mar 2008)
<http://en.wikipedia.org/wiki/Spectacled_Caiman> 16 Mar 2008

Jesus Christ!

YEO WAN TING — Mon, 17 Mar 2008 17:48:00 GMT

Reptiles - the mere mention of the word will send shivers down the spines of many I know, and it's perhaps with little wonder. Oftentimes, the word 'reptiles' evoke the mental image of something slimy, aggressive, dangerous, and hence, repulsive. Despite their less than appealing appearance (though this is, of course, subjective), I find reptiles to be utterly fascinating creatures, at least in terms of the way they move and adapt to their environment.

One such reptile is the green basilisk lizard (basiliscus plumifrons), "also called a plumed or double-crested basilisk but its amazing ability to run on water gives this species its most recognizable moniker: the Jesus Christ lizard." (Green Basilisk Lizard, National Geographic.) Yes, you read it right - the green basilisk lizard can run on water!

It is said in the Bible that Jesus once walked on water, and it is after this that the green basilisk was named. Harry Potter fans will also recognize the word 'basilisk'. Sorry to disappoint you Harry Potter fans, but this lizard is not exactly the type of basilisks mentioned by Rowling in her books!

Instead, it is a lizard that is part of the iguana family. They are most commonly found on the trees of the Central American rainforests, and are never too far from a body of water. (Green Basilisk Lizard, National Geographic.) When threatened by predators, the basilisk lizards take off at lightning speed, often over water bodies.

Here's a picture of a green basilisk scrambling for its dear life:

Image source

On average, basilisk lizards weigh between 200 to 600 grams - sure, that is light, but it is also far from being light enough to stand on a water surface without breaking the water tension (ala the waterboat man insect). (How Lizards Walk on Water, BBC News.)

How then, do the basilisks achieve this amazing feat?

The basilisk lizard has large hind feet with flaps of skin between each toe. According to Harvard University's Dr Tonia Hsieh, a large upward force is produced each time the lizard slaps its feet on the water surface. It is this force that keeps the lizard's body above the water surface - that is, until the lizard tires and falls into the water, where it will swim and/or dive with ease. It also follows that younger basilisks can usually run further than older ones, with the former being capable of running about 10 to 20 meters on water without sinking. (Jesus Christ Lizard, World Wildlife News.)

I don't know about you, but I found this lizard to be amazing. Imagine being able to generate enough force with your feet to run on a water surface! Here's an awesome clip from YouTube (National Geographic channel) of the basilisk running on water, as well as a bit of information on the lizard's diet:

Watch it because:

1) it will amaze you to no end (well, it amazed me at least!), and
2) as can be seen from the photo above, it really is quite hilarious to watch.

Enjoy!

References:
Green Basilisk Lizard, National Geographic

How Lizards Walk on Water, BBC News

Jesus Christ Lizard, World Wildlife News