LSM1303 Animal Behaviour Student Blog : evolution

Inhuman Doctors: Zoopharmacognosy and Self Medicating Animals

Vigneshwaran Shunmugam — Fri, 21 Mar 2008 15:15:00 GMT

Many major cultures around the globe have developed some form of medical science. The Indians have Ayurveda, the Chinese have TCM and of course there is Western medicine. What these fields have in common is that they are derived from the process of observing the effects of certain herbs or foods on the health of the imbiber and thus correlating cause and effect. While medical science and its practitioners have long been held to be at the forefront of human intellectual pursuits, we now realise that this was no great achievement at all. In fact, even monkeys do it.

Observe this Orang Utan for example.

Right. This is just a monkey opening a packet of powder. Nothing fancy. However, monkeys DO develop their own medical techniques to deal with their own health issues. This is known as Zoopharmacognosy which is basically the animal form of Medical Science. Many species of animals use various techniques to deal with their maladies.

If you have seen your dog or cat eating grass you may have been puzzled at their sudden vegetarianism. They do have good reason for doing so. Eating grass "stimulates either retching or the rapid expulsion of worms in diarrhea" (Hart and Hart 1985). Compare this with the Tamil proverb which claims that a Tiger would not eat grass, no matter how hungry.

Medicine is not a purely mammalian pursuit either.Snakes too have herbological knowledge! "According to Chinese folklore, many centuries ago a farmer in the Yunnan district found a snake near his hut. Fearful for his life, he beat it senseless with a hoe and left it for dead. A few days later, the same snake returned. Again he tried to kill it, but again it returned. After he had beaten it a third time, the farmer followed the severely wounded snake as it crawled into a clump of weeds, started feeding on them, and thereby rapidly cured the worst of its injuries. The plant in the story was Panex notoginseng, which now forms the main ingredient in the herbal formulation 'Yunnan bai yao', a white powder that cauterizes cuts and stems external bleeding immediately. It was standard issue in the Vietnam War, for use when soldiers were wounded far from conventional medical treatment. "(Reid 1987).

Our closest cousins, the Great Apes have various methods by which they keep themselves in the pink of health.

Above we see a chimpanzee(Pan troglodytes) chewing on the bitter pith of the Vernonia Amygdalina plant. Chewing on the pith allows the chimp to extract the bitter juice that is within. THe chimpanzees use this method to kill parasites in their intestinal tracts. Interestingly, chimps do not usually eat this leaf due to it being slightly toxic to them. Thus, they only eat this leaf for medicinal purposes! This paper has extensive information on this phenomenon, complete with graphs. The author Michael Huffman is an eminent figure in the field of Zoopharmacognosy.

Chimps sometimes consume the leaves of the Aspilia plant, which they got to great lengths to obtain. The leaves are covered in stiff hairs and are swallowed whole, despite the difficulty of doing so. "Huffman doesn't doubt that there is a medicative function behind leaf swallowing behavior. His theory about how it gets rid of worms revolves around the hairiness of the leaves. Huffman found live worms in chimp *** stuck "like Velcro" to leaf hairs and trapped within the folds. He speculates that worms may become attached to the leaves or somehow enticed into the folds during digestion, taking a "magic carpet ride" through the gastrointestinal tract, eventually to be excreted from the body. Chemicals in the plant may also decrease the ability of the parasites to adhere to the intestine, making it easier for them to be swept out by the leaves."

Perhaps the animal use of medicines to treat themselves is not such a surprising phenomenon. In fact post-Darwinists should have predicted it regardless of evidence. Using medical methods enables an animal to prevent its death,prolong its life, to heal faster and have a survival advantage. This is an advantage that would allow those animals who use it to be more successful than those who dont. In the abscence of a consequent negative selection pressure, animals who self-medicate would definitely outsurvive those who do not. Thus, Zoopharmacognosy is not surprisingly prevalent in the animal kingdom.

Not only do animals consume herbs and plants as medicines, but they also consume certain types of soil(geophagy) and insects for the same purpose.

Even more interesting than the fact that animals employ medical science is the fact that many of the herbs and techniques employed by animals are similarly employed by humans. This highlights the cross pollination of medical knowledge from the animal kingdom to ours.

To learn more on the exciting field of Zoopharmacognosy, this book might help.

"Really Wild Remedies—Medicinal Plant Use by Animals" by Jennifer A. Biser. Zoogoer, January/February 1998

Huffman, M.A. 2001. Self-Medicative Behavior in the African Great Apes: An Evolutionary Perspective into the Origins of Human Traditional Medicine. Bioscience, 51(8):651-661.

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Otters in love?

TAN WEI ZHEN MELISSA — Fri, 21 Mar 2008 07:33:00 GMT

Sea Otters (Enhydra lutris kenyoni ) belong to the weasel family and are one of the smallest marine mammals in the animal kingdom. They spend their mornings foraging and feeding on shellfish and afternoons resting by floating on their backs. Sea otters are coastal, shallow water dwellers. Their habitat consists of two areas in these waters- the ocean floor where they find their food, and the ocean surface where they eat, groom, rest and social interactions occur.

In this video, a pair of sea otters in Vancouver Aquarium, Nyac and Milo, share a lazy afternoon nap oblivious to the stares and chatterings of humans around their enclosure. Watch the video to see why it is the most popular youtube video having had 10,229,379 views to date. Make sure you watch it till the end where the good part is!

As sea otters are social creatures, they often live in groups although they do occasionally engage in solitary behavior such as foraging for food alone. When resting, sea otters often gather and hold hands. This is known as rafting. Rafting ensures that no sea otter drifts away during one of their afternoon naps. Sea otters usually raft with otters of the same sex with male otters forming the larger rafts. In this video however, the sea otters are a male-female pair. This could be due to the small otter population at the Vancouver Aquarium.

Rafting might also have an evolutionary purpose. "Garshelis et al. (1984) provided evidence that a historic land predator, perhaps aboriginal man, may have influenced the social behavior of sea otters. The tendency to rest away from the shore would also have provided protection from a land-based predator. "

So is the video clip above true love or just an evolutionary behavior? That's for you to decide.

References

1. The Alaska Sea Otter and Steller Sea Lion Commission , accessed on 20th March 2008

2.Garshelis, D.L. and J.A. Garshelis. 1984. Movements and management of sea otters in Alaska.Journal of Wildlife Management 48: 665-678.

3. Loughlin, T.R (1980) Home Range and Territoriality of Sea Otters Near Monterey, California. The Journal of Wildlife Management, Vol. 44, No. 3 , pp. 576-582

4. http://www.vanaqua.org/home/SeaOtterRafting.html, accessed on 20th March 2008

5. http://www.youtube.com/watch?v=epUk3T2Kfno, accessed on 20th March 2008

"It's a bird! It's a plane! No! It's a frog???!!!"

GAN ZHI-WEI — Tue, 18 Mar 2008 14:11:00 GMT

We always think of frogs as being amphibians whose existence is restricted only to land and water. This is largely true, given the fact that frogs have evolved over time to develop specific physical characteristics – lungs for breathing on land, webbed feet for swimming – that maximize their ability to survive in both these environments.

However, for some frogs, being masters of both land and water just isn’t enough… read on to find out more…

Wallace's Flying Frog. Photograph by Tim Laman

The ‘frog-ject’ of interest…
The particular frog being examined in this blog post would be Wallace’s Flying Frog, also known by its scientific name as Rhacophorus nigropalmatus. Named after the biologist, A R Wallace, who was the first person to collect the species for official identification, the frog has an overall length of between 90 and 100 mm. Its large eyes, tympanum and limbs are particularly distinct, and the large size and unique structure of its limbs will be the central discussion point in this blog post.

What’s so interesting about this?
Simple! These frogs can fly!!! Unlike the majority of its fellow cousins, Wallace’s Flying Frogs spend almost the whole of their lives living in trees, and only come down to the jungle surface to mate and spawn.

“When threatened or in search of prey, they will leap from a branch and splay their four webbed feet. The membranes between their toes and loose skin flaps on their sides catch the air as they fall, helping them to glide, sometimes 50 feet (15 meters) or more, to a neighboring tree branch or even all the way to the ground. They also have oversized toe pads to help them land softly and stick to tree trunks.”

Swooping in for the kill: Wallace's Flying Frog. Photograph by Tim Laman

"Look out! Here I come!!!" Photograph by Tim Laman

This behavior is particularly interesting because:

It illustrates how the environment can influence the ways in which animals develop and evolve: The dense jungle floor can be a dangerous place for frogs as predators can easily camouflage and ambush unsuspecting frogs. By eliminating the need to travel on the jungle floor with their ‘flying’ ability, Wallace’s Flying Frogs are able to increase their chances of survival as exposure to land-based predators is significantly minimized. Furthermore, this ability to ‘fly’ also increases their chances of capturing their prey. As highlighted earlier, Wallace’s Flying Frogs spend most of their lives living in trees. The sheer height of the trees provides these frogs with a significant ‘high ground advantage’ – from an elevated position, these frogs are far more able to spot their prey, and swoop down on their prey using the most direct route without warning, thereby increasing their chances of grabbing a meal.

It demonstrates the power of evolution: This ability to ‘fly’ represents a departure from how one would normally expect a frog to behave. Originally beginning their existence as water-borne creatures, frogs gradually evolved over thousands of years to conquer the land. This evolution of the frog species to include the ability to fly highlights the fact that evolution knows no boundaries – it is a process steeped in continuity, where unpredictable but necessary results often occur to enhance and prolong the existence of animal species, where only the fittest survive.

A few additional points…
How then does Wallace’s Flying Frog fly? Wallace’s Flying Frog doesn’t fly per se. Rather, it glides through the air by extending the thin membranes and skin flaps extended over their feet and toes. Linking this with the Lift Equation below, where F_L represents the lift force experienced by the lifting surface and A represents the surface area of the lifting surface, the amount of lift force generated by the lifting surface is directly proportional to the surface area of the lifting surface. By extending its membranes and skin flaps, Wallace’s Flying Frog is actually maximizing the surface area of its ‘flying surface’, thereby maximizing the amount of lift that can be generated, hence allowing it to glide over considerable distances.

F_L = C_L (1/2) pv² A

Other flyers…
Well, I'm sure you're now wondering, is Wallace's Flying Frog the only animal specie that uses such a 'flying' technique? The answer to this question would be no. Another example of a non-avian 'flyer' would be the Flying Squirrel. Scientifically known as Pteromyini or Petauristini, it also uses similar skin 'flaps' between its fore and hind limbs to glide through the air, as can be seen in the photographs below. Interested to find out more about how the Flying Squirrel, and hence Wallace's Flying Frog, glides? CLICK ME to find out more!

"Whee!!! I'm naked... and I'm flying!!!" Photograph by Michael Hays

Warning: Swooping streaker on the loose!!! Photograph by J. Ann Eldridge

While videos that show Wallace's Flying Frog in action are few and far between, the workings behind its flying technique can be understood after you view the following video of how the Flying Squirrel glides.

As seen in the video, the Flying Squirrel extends its legs outwards, stretching the flap of skin linking these legs together, providing a substantial lifting surface that enables it to glide from point to point. (Recall the lift equation I mentioned earlier...) It can be observed that both these animals utilize the same principle of flight to glide over distances - an interesting observation, considering how different these two animals are: one's an amphibian, one's a mammal. This then leads to another interesting question: Were they related to each other in pre-historic times but evolved separately to be so different yet so alike? Or is this shared technique just a pure coincidence, with each animal owing it to the shared circumstances of escape and predation?

References:

Sunny Shah and Rachna Tiwari. "Rhacophorus nigropalmatus, Wallace's Flying Frog." AmphibiaWeb. 18 March 2008.
http://amphibiaweb.org/cgi/amphib_query?query_src=aw_search_index&max=200&where-genus=Rhacophorus&where-species=nigropalmatus

The Lift Equation. National Aeronautics and Space Administration, Glenn Research Center. 15 June 2007.
http://www.grc.nasa.gov/WWW/K-12/airplane/lifteq.html

Wallace's Flying Frog. National Geographic Society. 18 March 2008.
http://animals.nationalgeographic.com/animals/amphibians/wallaces-flying-frog.html?nav=FEATURES

"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!

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