LSM1303 Animal Behaviour Student Blog : natural selection

Ignorant pig, Silly cow, Bird brained?

QUEK QING LIAN ADELINE — Fri, 21 Mar 2008 15:03:00 GMT

Don’t we tend to assume farm animals to be one of, if not the most stupid creatures in the animal kingdom, since they are most likely to end up as breakfast, lunch and dinner for us humans? Well, don’t belittle these animals as the video below will illustrate what they are capable of. Look out for the high IQ hens and the acrobatic heroics of the pigs in the video, suddenly “Chicken little” and “Babe” doesn’t appear so fictional anymore.

If you detect some form of moralistic slant on the video, well, not to worry, after all it was produced by the Compassion in World Farming Organization. FYI, I am in no way advocating anyone to go become a vegetarian/vegan… I am a happy carnivore and nothing can come between me and my meat!

For me, what’s more interesting about this video is that it highlights the notion of duality in the interpretation of animal behaviours. “Are animals capable of intelligent behaviour?” That is, “Do they actually know what they are doing?” Well, according to the Darwin’s theory of evolution by natural selection, an instinctive behaviour will be selected if it serves the best interest of the animal, in a particular environment or context. However, what then is the selective value that would enable a pig to swim and rescue an entirely different species?

Gadagkar R. actually proposes that intelligence is possible in animals. However, there is a prerequisite before animals can possess such “intelligence”. Animals have to first have “instinctive behaviour before it can have any flexible, intelligent behaviour”. Therefore, it can be said that intelligence evolved from instinct.

Well, as I mentioned before, I will not be forgoing my meat. But, before I pop a wanton into my mouth, maybe I'll think, hmm… perhaps the pork came from a smart pig! Hopefully, some of its intelligence will rub onto me ;-)

References:

Gadagkar R., “Observational Study of Animal Behaviour – From Instinct to Intelligence”, Current Science 68, 2 (January 25 1995), pp. 185-196

http://en.wikipedia.org/wiki/Instinct

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

Mummy, who's Daddy? And why is my cousin white?

LIN HUIYUAN — Fri, 21 Mar 2008 09:25:00 GMT

Dialogue One

Kid: Mummy, who is my daddy?

Mummy: Forget about daddy, dear child. You have to learn how to be strong and independent, and I am going to teach you how.

Kid: But all the other animals have their daddies… (looks sad)

Mummy: Listen kid, daddy doesn’t really know and care who you are. He has left us to fend for ourselves. One day, you might even have to fight against him...

Kid: But why would daddy want to fight me? Doesn’t he love us anymore...? (tears start to well up in his eyes)

******

Fig. 1 Tiger Cubs at Amersfoort Zoo ¹

Tigers are generally solitary animals. They live alone, hunt alone, do everything alone (there are however two exceptions), and only come together during mating seasons. After they mate, they go their separate ways (of course they don't in the zoo :P), and the female, who becomes impregnated (not 100% but highly probable) with a child/children, will have to hunt for food all on her own, for herself as well as her future little cubs.

So when are tigers seen together? The first is pretty obvious - it is during the mating season. According to the website Tiger Territory ², there is "temporary fidelity in tigers" ³; the tigers are seen hunting together and they remain monogamous to each other. However, this only lasts through the mating season.

The second scenario in which tigers are seen together is when a tigress hunts for food together with her children. As the tigress is solely responsible for the upbringing of her children (due to the extreme irresponsibility of the father of the cubs, in my opinion that is :X), she has to teach her cubs how to hunt for food, so that they would not die of hunger once they mature and become independent.

Usually the tigress will move to a new area when impregnated, if she is unsuccessful in driving away juveniles from her range. She does this to seek a "solitary and safe area for the cubs" ⁴. This reduces the threat to her cubs and it also reduces competition for food.

What I think:

Here, I believe, is a result of natural selection. Over time, the tigress realises that there will be less food for everyone in the same territory if more tiger cubs joined in. In addition, the territory of a tigress is three times smaller than that of a tiger ⁴.

A tigress' care for her cubs may seem to be unusual, as opposed to other big cats like the lions. It is known that the lion cubs are being cared for in a pride, and therefore the job of raising cubs does not fall on the lioness' shoulders alone. In addition, the lions will feed on their meal first before the cubs get to eat, and in fact, they are also known to feed on their own offspring at times. However, if we think about it, unlike the lions, a tigress is the sole breadwinner of her litter. If she does not care for her cubs, by natural selection, her cubs will certainly lose out to the other bigger cats out in the wild. It seems then, that her care for her cubs is probably to ensure a higher survival rate.

There are probably other times where the tigress reunites with her older cubs, as well as the tiger who mated with her, but this only occurs if they do not pose a threat to her offspring.

******

Dialogue Two

Kid: Mummy, why are my cousins white? Are they different from me?

Mummy: Why, no, dear. They just have different colouration.

Kid: But why? They have white coats, blue eyes, pink noses and pink paw pads... they look so different from me! (Looks puzzled with bright inquisitive eyes)

Mummy: Well you know, it's the same with the dark-haired and blonde humans out there. Having a white coat is coded for by a certain mutated gene ('allele' to be exact, but Mummy is trying to avoid being overly specific), and it is only expressed if the child gets this gene from both parents. That is, this is a recessive mutated gene. (Mummy tried her best to be less scientific but seems like it is not working)

Kid: Huh? (Looks even more puzzled than ever)

******

The limelight of this post is really on the Bengal Tigers, also known as Panthera Tigris Tigris in the scientific community.

Fig. 2 A "Golden Tabby" - another colour variation of Bengal Tigers. ⁶

Among the Bengal Tigers, the White Bengal Tigers are highly popular among visitors of zoos who house these tigers. Contrary to popular belief, these white tigers are not subspecies of tigers. They simply have slightly different genes but they still belong to the Bengal Tiger species. As illustrated in dialogue two above, the white colouration, blue eyes, pink noses and pink paw pads are results of a recessive mutated allele, and are only expressed if the child inherits this recessive allele from both parents. This means that both parents are carriers of this mutated gene, although they need not express this allele since it is recessive.

As these White Bengal Tigers are extremely rare, it is highly prized among humans. Whatever the reason is, some humans have been breeding these white tigers together to obtain yet more white tigers.

However, this is extremely cruel to these tigers. Inbreeding, over long periods of time, results in deformities of the digestive tract, organs, skeleton, as well as eyes. Such deformities include crossed eyes, twisted necks and cleft palates ⁷. In addition, there's limited variation to their gene pool, which makes them highly susceptible to environmental changes. There's also high infant mortality rate as a result of inbreeding.

Fig. 3 White Tiger Cubs ⁸

What I think:

Again, I believe that this is a rather good example of natural selection - of why it is better to have a diverse variation in one's gene pool.

One should note that in the wild, there's no preference for white tigers to mate with white tigers. In fact, the white colouration is very disadvantageous to the tiger as it is harder for white tigers to camouflage in a jungle setting. Tigers need camouflage for hunting, to get nearer to their prey in order to catch them. That's because their prey are usually fast in escaping, and the weight of tigers makes it impossible to sustain high speeds for long periods of time. It seems logical then that a white tiger would prefer mating with another tiger of a different colour, to ensure a higher survival rate of her offsprings. It is speculated that the rarity of a white tiger is not solely because of the rare frequency of the mutated allele for the white colouration, but rather, due to the white tiger's inability to hunt as effectively as its orange peers (due to its magnificent snow-white colour), resulting in starvation and ultimately, death in its early years (before maturing and mating, which is essential for passing down its genes).

******

Here's a poem for you to enjoy! :)

The Tiger

By William Blake

1757-1827

TIGER, tiger, burning bright
In the forests of the night,
What immortal hand or eye
Could frame thy fearful symmetry?

In what distant deeps or skies
Burnt the fire of thine eyes?
On what wings dare he aspire?
What the hand dare seize the fire?

And what shoulder and what art
Could twist the sinews of thy heart?
And when thy heart began to beat,
What dread hand and what dread feet?

What the hammer? what the chain?
In what furnace was thy brain?
What the anvil? What dread grasp
Dare its deadly terrors clasp?

When the stars threw down their spears,
And water'd heaven with their tears,
Did He smile His work to see?
Did He who made the lamb make thee?

Tiger, tiger, burning bright
In the forests of the night,
What immortal hand or eye
Dare frame thy fearful symmetry?
___________________________________________________________________________________________

Footnotes

¹ Courtesy of Dear Kitty. Some Blog http://dearkitty.blogsome.com/2006/05/19/tiger-cubs-born-see-video/

²Tiger Territory http://www.lairweb.org.nz/tiger/

³Tiger Territory - Habits of the Tiger - Mating - Copulation (page 4) http://www.lairweb.org.nz/tiger/mating4.html

⁴ Tiger Territory - Habits of the Tiger - Raising Cubs - Learning to Hunt (page 5) http://www.lairweb.org.nz/tiger/family5.html

⁵Tiger Territory - Habits of the Tiger - Mating - Fighting for a Female (page 2) http://www.lairweb.org.nz/tiger/mating2.html

⁶Courtesy of The Nature Sanctuary Gallery http://www.naturesanctuary.org/gallery.html

⁷ White Tigers - Inbreeding Depression & Genetic Anomalies http://www.messybeast.com/genetics/tigers-inbreeding.htm & Big Cat Rescue - White Tiger Fraud http://www.bigcatrescue.org/cats/wild/white_tigers.htm

⁸ Courtesy of Musings of the Hearth http://scv.bu.edu/~aarondf/hearth/archives/cat_links.html

References and Bibliography

1. Tiger Territory. http://www.lairweb.org.nz/tiger/mating4.html

2. Bengal Tigers. http://www.bengal-tigers.org/bengal-tigers-facts.htm

3. White Tigers. http://www.natureobservers.com/snowtiger/

4. White Tigers - Inbreeding Depression & Genetic Anomalies. http://www.messybeast.com/genetics/tigers-inbreeding.htm

5. Big Cat Rescue. White Tiger Fraud. http://www.bigcatrescue.org/cats/wild/white_tigers.htm

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

Who needs males for reproduction! Apparently dragons don't...

IVAN KWEK KENG LIANG — Sun, 16 Mar 2008 13:56:00 GMT

Maybe it's time to rethink the concept that reproduction involves two individuals of different sexes, especially after what happen to a Komodo dragon at Wichita's zoo in Kansas. Fertile embryos were found, but the surprising thing is - The female who produce them had no males in close proximity for over 10 years!

Komodo dragons (Varanus komodoensis), in short Komodos, are
big rapacious lizards naturally found in Indonesia. With only a few thousand left in the wild, the danger of extinction is a possibility. Komodos, like most reptiles and amphibians, have several reproductive tricks e.g. storing sperm as 'backup' in case of poor reproduction conditions in future. However an alternative explanation was offered for the case of the Kansas dragons. In
the last 2 years in Britain, there were similar occurrences to the discovery at Wichita Zoo, and analysis has proven that every
bit of the embryos' DNA originates from the female. The answer
to this? Virgin Birth (Parthenogenesis)

   The Komodo is believed to have used a form of virgin birth which involves
   no   fertilization and the embryos produced were genetic clones of the mother. This
   raises several interesting issues to think about:

Firstly, If males are not needed for reproduction, what's the purpose of having them in the ecosystem?
Secondly, cloning, often lauded as the invention of scientists, is actually an ancient ability among certain species like sharks and fish. Why is cloning so important to these species then?

This brings us to one of the most fascinating aspect of animal behaviour - Natural Selection proposed by Charles Darwin. Firstly, virgin birth results in genetic clones of the mother. Over time, there will not be enough variation within the population, limiting natural selection and evolution. Virgin birth should be seen as an emergency measure to ensure the survival of the species. In the long run, normal reproduction with males is still the key to ensure variation. Secondly, cloning is one of the means used by these species for survival. There are many different ways that species can develop, grow and form sexes, according to different environment conditions and behavioural cues. Natural selection also plays a major role in the sexual dimorphism between males and females.

"Biology is about variation. Without it, the world would be static and unchangeable, and species would gradually disappear."

I thought the quote sums up the article pretty well. Variation and natural selection allow the desirable traits to survive the selection process or even create new traits as a result of mutation. Both of these processes facilitate greater relative reproductive success. In the case of the female Komodo, being kept in a compound with no males deprives it of the chance to mate. Hence it resorted to cloning to produce offspring. Whatever measures used, ensuring the survival of the species is still the ultimate goal.

Reference:
"Birds Do It. Bees Do It. Dragons Don’t Need To," by Neil Shubin. The New York Times, 24 Feb 2008.

Other Cases of Virgin Birth:
"Virgin Birth Expected at Christmas -- By Komodo Dragon," by James Owen. National Geographic News, 20 Dec 2006.
"Shark Gives "Virgin Birth" in Detroit," by Hillary Mayell. National Geographic News, 26 Sep 2002.

Source of Images:
Komodo Dragon
Virgin Birth (Komodo)

In the shoes of an elephant!

Benjamin Christine Stephanie — Sun, 16 Mar 2008 12:09:00 GMT

As the title suggests, this post has to do with one of my personal favourite animals, the elephants! Having worked at the Night Safari for over a year now, the plastered look of awe as visitors lay their eyes on our majestic Asian elephants, never gets old. I love watching these gentle giants consume crazy amounts of vegetation, then produce crazy amounts of dung, roll in the mud, and interact with each other. I mostly understand why they do these abovementioned acts, however one thing I recently learnt, was why they are often spotted pacing back and forth. As mentioned early on in lectures, most seemingly random animal behaviours usually serve a greater function, and are induced by internal and external factors. Well, having no scientific academic background unfortunately, I used to think how the pacing and swaying was in a way, the ‘elephant dance’.

Then last December, as Christmas drew near, a newspaper clipping pinned up at work caught my eye. Our very own Singapore Zoo had come up with an elaborate and innovative Christmas gift plan for a couple of our own female elephants. (Hint: Think along the lines of feet, and a favourite amongst most girls)

Now stop guessing and read the captivating article HERE!

The article explains that, “as the world’s largest land animal, elephants naturally place an enormous amount of stress on their feet. Tun, the younger of the two elephants, has one front leg longer than the others. Her leg was injured some years ago when Chawang, a male elephant at the Night Safari, mounted her and caused her to buckle. She has a noticeable limp and the extra pressure she places on the other shorter front leg has created lesions on the sole of this foot. Meanwhile, 30-year-old Jamilah has lesions on the soles of both her front feet because she places extra pressure on her the two feet during her walks.”

The veterinarians at the Zoo said that “many things were done in the past to help both elephants. This included hot compresses, acupuncture, joint supplements such as glucosamine and pain killers” however treatment has not been easy.

“The vet team began thinking about ways to protect Jamilah’s bandages so that the lesions had time to heal. Tun’s unbalanced walk also had to be addressed if she was to have a chance of full recovery.”

Click HERE and HERE to read more about common issues with the elephant’s foot.

And so the clever team came up with the idea of GORE-TEX® shoes for this lucky pair! Meet Tun & Jamilah!

In my opinion, it is an extremely creative way of treating the elephant’s problems in this day and age. Who would have thought tailor-made shoes would have been an option to cure an elephant’s foot problem! It was also important to cure Jamilah as she is afterall the matriarch of the herd, and as mentioned in lecture, the role of the matriarch is vital to the elephants in many aspects, even in captivity as I have often watched her interact with Sang Wira, the calf at the Night Safari.

Kick off your shoes and catch a video of Tun & Jamilah HERE!

An interesting fact I picked up from the video about these elephants is that bad feet is not an inherited trait but rather, a common ailment amongst many captive elephants in zoos due to the lack of exercise and rough surfaces.

‘Natural’ Selection from Chawang’s Traits?

Read about CHAWANG!

From the above site, in a sense I believe that the Night Safari is using the process of natural selection too. Chawang has already sired 3 elephants and as quoted,

“The Night Safari hopes that Chawang can be involved in breeding more of the endangered Asian elephants.”
This is probably in hopes of giving his offspring favourable traits such as his criss-crossed tusks that now measures about 1.2 metres long!

Now aren't elephants your favourite animals too! Say no to the trade of ivory :)

References:

Night Safari Press Release, 12 December 2007.

Gore-Tex Fabrics Press Release, December 2007.

Video: Jumbo-sized X'mas gift - shoes fit for an elephant, Reported by Jermyn Chow. StraitsTimes.Com, Dec 12, 2007.

Elephants Foot Ailments:
The Elephants Feet
Elephant Feet and Nail Problems