LSM1303 Animal Behaviour Student Blog : cost-benefit analysis

The Stinging Sailor

LIAU QINGYE EILEEN — Fri, 21 Mar 2008 06:10:00 GMT

Now, what could this be?

a) An inflatable float.

b) A breathing apparatus.

c) A Jellyfish.

Answer: d) None of the above.

What this inflatable jellyfish like animal is an invertebrate, the Man- of –war. It does have a rather impressive name, but IS IT impressive?

As I have found out from this article, it is indeed extraordinary.

The Man- of – war is not exactly ONE animal, but is actually a floating hydrozoan, which consists of four types of polyps. The four different simple animals that form the Man- of – war are the float, the tentacles, the feeding zooids and the gonozooids which produce gametes for reproduction.

Click here for more information on polyps.

These different polyps work together to form an intelligence system that functions as a whole. Each polyp has a different function, which helps in the survival of the Man- of – war. For example, the float polyp helps in the locomotion of the Man- of – war. It is like a sac filled with nitrogen, and acts as a “sail” to drift the animal in the direction of the wind and tide. This is also where the Man- of – war derived its name from, as it resembles an olden day battle ship.

With all these different animals living “under the same roof”, one must wonder why they do so and how they do not feel a competition for resources.

Each polyp has different needs and functions. Other than the “sail”, one other part is for reproduction, while the remaining two parts function as the hunting and digesting tool.

Man- of – wars are hermaphrodites; each individual gonozooid consists of male and female parts. The fertilised egg develops into a planktonic larva which then reproduce in large quantity by asexual budding.

The most powerful part of this combined animal is the tentacles, not only do they contain a painful sting which can be fatal, they are also used to catch and trap small sea creatures which will then be slowly dissolved by enzymes secreted from the underside of the float.

As you can see, these four simple animals coexist as “one organism” because the benefit of doing so greatly outweighs the cost involved. Although a single animal has a function by itself, it will never be able to survive alone, as it lacks other necessary functions for survival.

I find this animal really amazing because it has managed to survive even without doing much. There’s no need to swim as the “sail” helps in drifting. Eating for this animal is also like a simple task as it simply traps and dissolves its prey; absolutely no need for foraging or stalking. In addition, there is no need for MATE- SELECTION, a process which many other animals spend alot of time and energy engaging in.

At this point, we wonder what could possibly lead any fish to swim through the deadly tentacles of the Man-of –war.

The answer?

The Nomeus gronovii.

This fish shares a symbiotic life with the Man-of-war.

Want to see the Man- of- war in action?

Man-Of-War Podcast!

Remember to look out for the Man-of –war fish, as well as the enemies of the Man-of-war.

Here's some trivia:

As compared to a jellyfish, the man-of-war is a giant.

As compared to a grown man...

it STILL is a giant!!

See also:
Man Of War Fact-file
Team Transformation Rule 2: Cultivate Team Intelligence
What to do when you get stung by a Man-Of-War??

Reference:
Websites:
Kurlansky, Mindy B. (2002). Physalia physalis. Retrieved March 20, 2008, from Animal Diversity Web Web site: http://animaldiversity.ummz.umich.edu/site/accounts/information/Physalia_physalis.html

Polyp. (2008, March 17). In Wikipedia, The Free Encyclopedia. Retrieved March 21, 2008, from http://en.wikipedia.org/w/index.php?title=Polyp&oldid=198944134

Portuguese Man-of-war. In National Geographic. Retrieved March 20, 2008, from http://animals.nationalgeographic.com/animals/invertebrates/portuguese-man-of-war.html

Pictures:
Man-of-War Fish - Nomeus gronovii. In thejump.net. Retrieved March 20, 2008, from http://www.thejump.net/id/man-of-war-fish.htm

Portuguese Man-of-war. In aloha.com. Retrieved March 21, 2008, from www.aloha.com/~lifeguards/portugue.html

Nomeus gronovii- Man-of-war fish. In FishBase. Retrieved March 21, 2008, from http://filaman.ifm-geomar.de/Summary/SpeciesSummary.php?id=2461

Video:
Portuguese man-of-war. In National Geographic. Retrieved March 20, 2008, from http://podcastmedia.nationalgeographic.com/ngvideos/pc62_PortugueseManowar.mp4

Little Penguins at the World Famous Penguin Parade --->> Little Penguins Going HOME!!!

U0601181 — Thu, 20 Mar 2008 14:43:00 GMT

Little Penguins heading back to their burrows after a day's out at sea

Few months ago, I made a trip down to Philip Island to view the world famous Penguin Parade and it left a truly memorable natural wildlife experience, a treat never forgotten to me, and I felt I should share this wonderful experience with you.

So what is this Penguin Parade am I talking about?

Well, basically these penguins are called Little Penguins (known by their scientific name as Eudyptula Minor), or other common name such as Fairy Penguin or Little Blue Penguin, and they are the world’s smallest species of penguins.

Each night at sunset, these Little Penguins would emerge from the sea after a day’s fishing at sea, and will waddle ashore to their sand dune burrows. And at Philip Island, visitors like me, would be able to watch this event unfold right before you.

Sounds interesting isn’t it? Well to me it was, watching these Little Penguins coming ashore at dusk really fascinate me, not too sure about you but I hope you do.

Little Penguins coming ashore after a day's out at sea

First, let me give you a brief overview about these Little Penguins, basically they live in burrow unlike their largest Antarctic cousins, the Emperor Penguin, who live in the cold. They are 30 – 35 cm tall and weight 1 kg, unlike the Emperor Penguin which is 1 -1.3 m high with adult males weighting up to 38 kg. They are mostly found along the southern edge of mainland Australia, as well as Tasmania, New Zealand and the Chatham Islands.

Little Penguins is a social bird, and it is the most nocturnal of all penguin species. During the day, they are either hunting at sea or in its nest sleeping. They live in loose colonies, composed of birds of all age. They form small, very vocal groups when coming ashore at night, but then disperse to their respective territories to call it a day.

These Little Penguins usually leave their burrows 1 – 2 hours before sunrise each morning, they travel 15 – 50 km at sea each day and swim at a speed of 2 – 4 km/hr on average (maximum 6.4 km/hr). They forage only in daylight returning ashore at sunset.

From what I heard from one of the ranger who was on duty that day and through some research, these Little Penguins display group behaviour when arriving at the colony or departing to sea. At dusk, small groups of penguins appear in the shallows before making their way to their burrows, and similarly, in the hours leading to sunrise, they congregate in groups within the colony before making their way across the beach towards the ocean.

Having no prior knowledge about penguins or seabirds before my trip to Philip Island, this causes me to wonder why they have to enter and leave the beach in groups and in the darkness. And from the information I found, Little Penguins exhibit such behaviour as a form of predator avoidance strategy because their small stature and limited terrestrial mobility makes them particularly vulnerable to predation during their beach crossing. Both safety in numbers from grouping and moving under the cover of darkness help counteract these threat. Also, Little Penguins will linger within the safety of the vegetation or the ocean until there are enough numbers of penguins for a safe crossing. In the hours before sunset, they will congregate in groups at sea before making their way across the beach in darkness after sunset, towards the colony in groups of 10 – 100.

Again, it makes me wonder whether the groups that these penguins formed when they crossed the beach were composed of the same individual from day to day, or were formed randomly. After some research, I found that these Little Penguins can seek to form groups with the same individuals when arriving or departing from the colony. They display a nonrandom association or sought to parade with the same individuals when forming groups to cross the beach to and from the sea. In years of high breeding success, small groups of penguins form nonrandom groups and studies have shown that up to 25% of the arrivals were with the same individuals, but not in years of low breeding success.

While observing the penguins, I was wondering to myself, do they always enter and leave their nesting area at the same time everyday or do they enter and leave as and when they feel like to. From what I have found, the Little Penguins have the most predictable colony attendance among penguin species with mean arrival and departure times around 75 min after sunset and before sunrise, respectively. In years of low breeding success, Little Penguins tend to arrive on average 30 min later, suggesting a rigorous arrival schedule which could only be delayed if penguins are unable to return home because they are further away or impeded from doing so.

What was interesting was there was a dramatic change in the arrival time of Little Penguins at their breeding colony when a heavy low-level fog that blanket Philip Island on a particular evening. It was noted that, only 5% of penguins arrived at the expected time (compared to other days where it is 88%), and the peak time at arrival was 2 hours behind the usual peak arrival times (the maximum interval in the mean arrival time on normal days was 26 min). It is shown that these Little Penguins were unable or unwilling to return to the colony under the low visibility caused by the fog. It is reported that only half (52%) of the average number of penguins returned to the colony on the evening of the fog. This unusual environmental condition that affects the behaviour of the penguins can provide an insight into their behavioral response to limited depth vision. So why was there a dramatic changed in their arrival time? Several reasons include: the Little Penguins did not come ashore with poor visibility to avoid predation (their inability to detect predators could have kept them at sea) or their visual senses were impaired and were probably unable to find their way back home; or a combination of both.

However, it was noted that 5% of the penguins crossed the beach at the expected arrival time and a further 7% arrived later under thick fog. This can be analyzed using the cost-benefit analysis: as it was the breeding period at the time of the fog, the benefit gained from coming ashore to feed their chicks outweighs the risk of predation.

Thus the visit to Philip Island was indeed a memorable experience as not only do I have a wonderful time watching them but I gain more insights into the lives of these Little Penguins, and managed to find out why they exhibit the various behaviours that I have just mentioned above. And I hope you too, have gain more insights into the lives of these Little Penguins like I do and hopefully have an urge to visit Philip Island some day to watch these Little Penguins waddle ashore to their burrows.

References:

Chiaradia, A., McBride, J., Murray, T., et al., (2007). Effect of fog on the arrival time of little penguins Eudyptula minor: a clue for visual orientation? Journal of Ornithology, 148(2): 229-233.

Daniel TA, Chiaradia, A., Logan M, et al., (2007). Synchronized group association in little penguins, Eudyptula minor. The Association for the Study of Animal Behaviour, 74(5): 1241-1248.

Anderson’s Creek Primary School. (2007). Index of Birds – Fairy Penguins. Retrieved March 18, 2007, from http://teachit.acreekps.vic.edu.au/animals/fairypenguin.htm

Birds in Backyards. (2005). Bird Finder – Little Penguin. Retrieved March 18, 2007, from
http://www.birdsinbackyards.net/finder/display.cfm?id=76

Animal Diversity Web. (1995). Eudyptula minor. Retrieved March 18, 2007, from http://animaldiversity.ummz.umich.edu/site/accounts/information/Eudyptula_minor.html

Squirrels-Sneaky??

CHANG LI HUA CLARISSA — Sat, 15 Mar 2008 11:47:00 GMT

Squirrels! Cute, cuddly, fast, are a few words which come to mind when one mentions 'squirrel'. What we hardly hear of is how wily and cunning they are. I came across an article about squirrels burying their food in the ground. Sounds normal so far right? But get this, there is about 20% chance [The Daily Mail online article] that what the squirrels are burying is nothing more than thin air!

The species in question is the Sciurus carolinensis, or the free living eastern grey squirrels. Squirrels hoard their food, as well as pilferage others, and according to Steele et al. [2007], they have to weigh the benefits-being able to store food for later consumption, and the costs-risk of being 'stolen' by others. The eastern grey squirrels have increased their benefits through deceptive behaviour.

These squirrels, carrying the nuts they have collected, turn their backs on whoever is watching as they bury their nuts (be they rival squirrels, birds, or humans), dig a hole, drop in the nuts, and carry on digging other holes, but not burying anything. Alternatively, they may dig a few holes before selecting one to drop the nut into. They then proceed to cover it up with leaves and grass. Or they would even bury it under a bush, or climb a tree and put it in a nest. Visual cues and the sense of sight is imperative in deceptive behaviour [Steele et. al.]. Squirrels, with their keen sense of sight, will take note of potential 'thieves' and turn their backs to them while burying nuts.

Sneaky huh? So now we can add that to the list of characteristics one thinks of when someone mentions the word 'squirrel'.

According to Sylvia Halkins, a professor of biology from Central Connecticut state university, this deceptive behaviour observed in squirrels is relatively rare in animals [The Seattle Times online article]. It just goes to show how intelligent these furry creatures are.

Linking this to our lectures, I believe this is a form of adaptive behaviour, which squirrels have fashioned "to confuse any rival squirrels, birds or humans who might be watching" [The Daily Mail online article]. To take it one step further, squirrels are so sensitive to their environments, and so flexible, that they adapt on-the-spot.

Dr Michael Steele, of Wilkes University in Pennsylvania, together with a group of his students, conducted an experiment to test this deceptive behaviour of squirrels. The group watched squirrels as they buried their cache of nuts, and later, dug up these holes one by one. They did this a few times, and discovered that the percentage of bogus holes increased as their raids increased in number! [The Daily Mail online article] However, the increase was not very drastic [Steele et. al]

Even with their keen sense of smell, squirrels are unable to tell whether a covered up hole has a nut buried in it or not [Discovery Channel online news article]. Ironically, though squirrels perform such deceptive behaviour, they seem unable to believe other squirrels do it too. A squirrel watching another squirrel "bury" a nut, and goes to dig it up, will give up a search if it does not find a nut [Discovery Channel online news article].

So next time you see a squirrel, and luckier still, are able to watch it foraging and hiding its cache of food, do remember how sneaky and wily they can be!

Website references:

"Cunning squirrels make bogus burials of 'and seeds' to fool onlookers" by David Derbyshire, The Daily Mail, 16 January 2008

"Squirrels Fake Out would-be Nut Thieves" by Jennifer Vegas, Discovery News, no date. http://dsc.discovery.com/news/2008/02/21/squirrel-deception-02.html

"Squirrel behaviour is not so nutty" by Steve Grant, The Seattle Times, 22 November, 2004

Steele, M.A et. al., 2007, Cache Protection strategies of a scatter-hoarding rodents:do tree squirrels engage in behavioural deception?, Science Direct, 75: 705-714