LSM1303 Animal Behaviour

An Adelie penguin choosing its pebbles

While prostitution has been around for many years, it was thought to be something that humans engage in. That does not seem to be the case. Adelie Penguins, a species found along the coasts of Antartica, were discovered to engage in extra-pair copulations, sex with other penguins other than their partners. This is rare as penguins are known to be monogamous.

So how does prostitution happen in the penguin world? The female Adelie penguin will look for a single male Adelie penguin. The female will offer herself by showing courtship moves and then lying prone for the male to mount her. This action tricks the single male penguin into thinking that this female could be a possible partner and the male penguin will copulate with the female penguin. After copulation, the female will then be able to take a pebble from the single male’s nest. Permission is needed in order for the female to get the pebble as the male usually attacks other penguins who tries to steal his pebbles. After getting a pebble, the female would then return to her ‘husband’ with a new found pebble.

The next burning question in everybody’s mind would be, why pebbles? Why don’t the penguins exchange sexual favours for something more practical, like fishes? This is because pebbles are very precious to female penguins as they are the main materials to build a large good nest. Because the Adelie penguins live  near the coasts, flood waters from melted ice during spring might wash away the egg if the nest was not large enough. Larger nests built with enough pebbles will keep the egg in place and also elevate the egg so that it would not be immersed in floodwaters, which might stop it from hatching . Because pebbles are so precious to these penguins, thefts of pebbles often happen and agression will occur when pebble stealing is involved. Thus, in order to be able to build decent nests without being attacked, the females , instead of stealing pebbles, exchange sexual favours from sexually frustrated single males in exchange for pebbles.

While some behaviorist speculate that this behaviour could be something the penguins are doing in order to test for a future change in mates, but there are not enough evidence to support this claims yet. Currently, what is known is the exchange for pebbles using sex. Interestingly, beneath all this promiscuity, female Adelie penguins can still be considered monogamous. After all, all this exchange of sexual favours was in exchange of materials for a safer nest in order to increase reproductive success. Let’s salute the female Adelie penguins for their selfless behavior for their families!

Sources:

Female Adélie Penguins Acquire Nest Material from Extrapair Males after Engaging in Extrapair Copulations
F. M. Hunter and L. S. Davis
The Auk, Vol. 115, No. 2 (Apr., 1998), pp. 526-528

Mating in a Material World
Maggie McKee
URL: http://www.nwf.org/nationalwildlife/article.cfm?issueID=73&articleID=1039

Pick a Penguin
URL: http://news.bbc.co.uk/2/hi/asia-pacific/60302.stm

Here I present to you: the Basilisks.

Credits to Edgley Cesar on flickr

They are lizards that live in tropical and sub-tropical forests. It spends most of their time on ground and near water areas. The green or brown colours on their bodies allow them to camouflage easily on forest grounds. They can be easily recognized by the crest above their heads. Because of their crests, they are thought to related with dinosaurs.

The amazing part: They can walk on water.

Okay, maybe they don’t “walk”. They do that at a faster speed. Basilisks actually cycle or run on water. This is the reason why they are called the Jesus Christ Lizard. I am guessing that another reason could be there will be people who will say “Oh Jesus Christ!” when they see this.

They perform this stunt when they are fleeing from predators. The trick behind this is the presence of fringes at the sides of their hind toes. As they dash across water surface, the surface area of their feet are able to support their weight. For this to succeed, the momentum of the run is crucial for the escape. Of course, they can’t run across oceans. They can only achieve records for short distances. Sometimes, when they cannot make it in time to land, they will just disappear into the rivers, leaving predators at banks to wander where they have gone.

Just another interesting fact:

Juveniles and adults have different water-running abilities. According to Glasheen and McMahon, juveniles are able to run farther and faster than the adult Basilisks due to their size differences.

My advice is PLEASE DO NOT TRY THIS AT HOME!! You’ve been warned.

Credits to Joachim S. Müller on flickr

Reference:

Journal Article

Glasheen J.W. and McMhon T.A. (1996). Size-dependence of water-running ability in Basilisk Lizards (Basiliscus Basiliscus). The Journal of Experimental Biology 199, pp. 2611–2618

Book

Jonathan A. Campbell (1998). Amphibians and reptiles of Northern Guatemala, the Yucatán, and Belize. Pp. 148-150. http://books.google.com/books?hl=en&lr=&id=GhoqxyLETKcC&oi=fnd&pg=PA148&dq=basilisks&ots=FnJYlbVG3Y&sig=l1RV_hePnAxpZW5zOAv4nJGjbwQ#

One of my favourite things to watch on the Discovery Channel is Mike Rowe on Dirty Jobs, where he bravely (or insanely) takes on tasks that would make your stomach churn. In one particular episode, Mike heads to Ohio’s West Sister Island to help bird conservation workers band and count young herons and egrets on the island. Amongst the bird populations on the island are species such as the Great Blue Herons, Great Egrets, Black-crowned Night Herons and Double-crested Cormorants.

West Sister Island in Ohio

Photo by Michael Baird

How is banding birds particularly dirty, you ask?

Well, there is a reason why the island is affectionately nicknamed “Vomit Island”.

Photo by Lee Tiah Khee

It turns out that the island is infamous for birds vomiting and pooping from their high perch atop the trees. The fact that the island is mostly covered with tall hackberry trees certainly creates the right conditions for anyone walking through to fully experience and embrace the essence of “Vomit Island”.

…not that anyone would want to.

The question is, why do these birds vomit on intruders?

This strange phenomenon would seem like a counter-intuitive thing to do, throwing out all the food you’ve wasted energy gathering throughout the day. However, this defense vomiting actually does serve a few purposes.

Whenever the birds feel threatened or are in danger of predation, throwing up can be an efficient way to drop the extra weight and fly off faster. It is also very distracting to the predator when half-digested, foul smelling food is thrown their way. Sometimes, the predator may even give up chase to go for the undigested food that was thrown up. The birds of Vomit Island mainly use this tactic, similar to many other water birds such as pelicans, as well as Turkey vultures.

Photo by Michael Baird

Black-naped Terns also use a form of vomiting as defense. Their vomit is different from the unpleasant substances that Turkey vultures and herons chuck up. Instead, terns regurgitate “stomach oil that is made up of fatty acids, fatty alcohols, glyceryl and wax esters that are derived mainly from their food”. Besides distracting predators with the foul smell, these oils are difficult to remove from the feathers, hindering the predator’s flight ability (Deng, Lee & Wee, 2008).

It’s a completely disgusting method, but an extremely effective adaptation to deter and distract predators, don’t you think?

So the next time someone refuses to get off your back, maybe you should try a little defense vomiting.

References

“Dirty Jobs: Vomit Island Workers Recap“, from TV.com. Retrieved 13 April, 2009.

“West Sister Island National Wildlife Refuge – Wildlife and Habitat“, from U.S. Fish & Wildlife Service. Retrieved 13 April, 2009.

“Turkey Vulture Facts“, from Turkey Vulture Society. Retrieved 13 April, 2009.

“Banding Pelicans“, by Sharon Stiteler. Retrieved 13 April, 2009.

S. H. Deng, T. K. Lee & Y. C. Wee, 2008. Black-naped terns (Sterna sumatrana Raffles, 1822) mobbing a grey heron (Ardea cinerea Linnaeus, 1758). Nature in Singapore, 1: 117-127.

J. Warham, 1976. The incidence, function and ecological significance of petrel stomach oils. Proceedings of the New Zealand Ecological Society, 24: 84-93.

It’s that time of the semester once again where assignment deadlines are nearing and the stress levels are at an all time high. Like us humans, birds too respond to stress due to a variety of reasons such as the appearance of a predator or a change in their environment.  In a paper by Dr Thais Martins of the University of Exeter, a study based on Zebra Finches found that stressed birds were bolder and more likely to take risks in a new environment.

Picture credit: http://www.flickr.com/photos/mrdehoot/208908983/

When stressed, birds produced a hormone called ‘corticosterone’, where the higher the levels of corticosterone, the more stressed a bird is.  In this experiment, the zebra finches were bred to have three different corticosterone levels, with the laid-back birds having lower levels than the stressed ones. By placing the birds in a new environment which housed several unfamiliar objects such as new feeders, the stressed birds were the first to visit the new feeders and also returned to it more quickly than the other birds after being startled. Although the stressed birds approached more objects than their more relaxed peers, this risk taking behaviour has indirectly benefited the birds by discovering the source of food first.  Initially, this was a surprise to the researchers as the bold behaviour exhibited was seen as something associated with confidence. However, as mother nature had it, corticosterone is in fact released to help tackle stress by encouraging the animal to adopt key survival behaviours like seeking food.

Another study based on the American Redstart (Setophaga ruticilla),  which looked at psychological consequences arising from habitat segregation from its non-breeding grounds also measured concentrations of corticosterone levels. It was found that corticosterone concentration was negatively correlated with body mass indicating that with higher stress levels, birds were leaner as a result of more foraging efforts. This study was thus in line with the one done on Zebra Finches although 2 different types of birds are being compared.

 That being said, does stress in humans lead us to “forage” by snacking more on food too? Does stress drive risky behaviour in us too?

References: