LSM1303 Animal Behaviour Student Blog : diet

Who packed a juicy dragonfly for lunch on campus?

TEO SHU WAN JILLYN — Thu, 20 Mar 2008 17:00:00 GMT

Caught on camera were ants carrying a dragonfly many times their size. Cooperation speaks out loud here! Also find out how these tiny but mighty creatures communicate and help each other out at work.

I took this video by chance in the toilet of the NUS arts campus. You can see many ants (House ants if I'm right) carrying a dead dragonfly significantly bigger than them and performing a turn as though they knew they were caught on camera. I found out that house ants run about in an erratic fashion when alarmed. I was grossed out but also amazed by the strength of the tiny creatures and decided to read up on how ants work together to transport food etc. I found an interesting article named “From Ants to People, an Instinct to Swarm”.

Army ants, which Dr. Couzin has spent much time observing in Panama, are particularly good at moving in swarms. If they have to travel over a depression in the ground, they erect bridges so that they can proceed as quickly as possible.

"They build the bridges with their living bodies," said Dr. Couzin, a mathematical biologist at Princeton University and the University of Oxford. "They build them up if they're required, and they dissolve if they're not being used."

Dr Couzin spent much time observing Army ants in Panama and found out that they are proficient in moving in swarms and if they had to travel over a depression in the ground, they form bridges with their bodies so that they can proceed with their “work” as quickly as they can. An interesting fact I read about was that army ants return to their nest with food travel in a dense column and a three-lane highway of army ants can stretch up to 140 meters from the ant nest, comprising hundreds of thousands of insects!

In another article “'Living plugs' smooth ant journey”, scientists from the University of Bristol investigate how ants used their own bodies to plug potholes to provide a faster route between their prey and nest. Not only did the ants plug the hole, they would size-match themselves to a hole which fits best. And amazingly, the ant could remain in place for hours, while the rest move back and forth across the trail.

Dr Powell said: "Broadly, our research demonstrates that a simple but highly specialised behaviour performed by a minority of ant workers can improve the performance of the majority, resulting in a clear benefit for the society as a whole."

He was referring to how speeding up the route by covering the holes with their bodies could increase the ant’s daily prey intake.

The communication between ants is something amazing because in my impression, they are so tiny! They communicate with each other through chemicals called pheromones and when one of them find food, they mark a trail on the way back to the colony, which is reinforced by other ants when they head back to the colony. Ants can carry up to twenty times their weight!

Besides chemical communication, I found out that another communication method used more commonly by ants who occupy wooden nest is accoustical communication. For example, carpenter ants communicate through drumming in times of danger. A drummer ant strikes the substrate with its mandibles and gaster while rocking its body back and forth. Signals would be transmitted through the nest. Another way which they produce a high pitched sound like a “chirp” is through rubbing together the organs at the rear of their bodies!

"The more ants are studied the more they reveal capabilities that exceed their small size." - Whit Gibbons

References

From Ants to People, an Instinct to Swarm by Carl Zimmer. The New York Times, 13 Nov 2007.

'Living plugs' smooth ant journey BBC News, 26 May 2007.

Sheppard software

The Miracle In The Ant

Pictures

http://www.alexanderwild.com/gallery/1455585/1/70631814#70631814

http://thinkorthwim.com/2007/05/28/ants-using-themselves-as-living-bridges/

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