(image from: wikipedia)

Aren’t they adorable? Orcas are beautiful animals and people often try to portray them as nicer animals than they really are (most notably anyone who thinks it is a good idea to keep these animals in an aquarium). Really though, orcas are nasty. That’s not to judge, all predators are essentially nasty. They eat other animals (but then again, so do I).

Increasing evidence has been found however, that killer whales are more vicious than many would have expected.

In a recent paper in Marine Ecology Progress Series it was reported how Orcas hunt and kill Grey Whales calves on their annual migration around Alaska. The Orcas where observed to attack calves and yearlings in deeper waters. The whales only escape is water less than 3m deep where killer whales would not follow. The predation of Grey Whales by Orcas was first noticed when the scientists noticed that the Greys weren’t progressing along towards their feeding grounds through a narrow straight. Where, it turns out, the Orcas lay waiting. Aside from the impact on whale conservation, the predation of other whales by Orcas is interesting because the Orcas also displayed a caching behaviour. Caching is when a predator stores it’s prey somewhere to avoid other predators getting at it, such as leopards caching their kills in trees to prevent lions from scavenging. Orcas drag the dead whale down and presumably store them under rocky overhangs as they were seen returning over several days to feed off their kill. If the kill washes onto the shore, not only will it be scavenged by brown bears, it will be completely inaccessible to the whales. This is the first example of caching behaviour seen in marine mammals.

However, not all Orcas hunt whales. A while ago, there was a paper discussing how killer whales should be divided into several species based on their mitochondrial DNA and now another paper shows how Orcas can be divided into at least distinct populations based on habitat and tooth wear.

(from Ford et al, 2010)

The Orcas that prey on other whales are transients. Residents prey mainly on fish while offshore Orcas probably prey on sharks, as was described in the same papers. Orcas have also been described to prey on penguins, of all things. And even more interesting is how neat the Orcas managed to dissect out the pectoral girdle of one penguin while leaving the not-so-nice bits behind as seen in the picture below:

(from Pitman & Durban, 2010)

And if this wasn’t enough interesting whale information for you, check out Sci’s posts on whale threesomes and whale penises (obviously NSFW!).

Morell, V. (2011). Killer Whales Earn Their Name Science, 331 (6015), 274-276 DOI: 10.1126/science.331.6015.274

Barrett-Lennard, L., Matkin, C., Durban, J., Saulitis, E., & Ellifrit, D. (2010). Predation of gray whales and prolonged feeding on submerged carcasses by transient killer whales at Unimak Island, Alaska Marine Ecology Progress Series DOI: 10.3354/meps08906

Morin, P., Archer, F., Foote, A., Vilstrup, J., Allen, E., Wade, P., Durban, J., Parsons, K., Pitman, R., Li, L., Bouffard, P., Abel Nielsen, S., Rasmussen, M., Willerslev, E., Gilbert, M., & Harkins, T. (2010). Complete mitochondrial genome phylogeographic analysis of killer whales (Orcinus orca) indicates multiple species Genome Research, 20 (7), 908-916 DOI: 10.1101/gr.102954.109

Ford, J., Ellis, G., Matkin, C., Wetklo, M., Barrett-Lennard, L., & Withler, R. (2011). Shark predation and tooth wear in a population of northeastern Pacific killer whales Aquatic Biology, 11 (3), 213-224 DOI: 10.3354/ab00307

Pitman, R., & Durban, J. (2010). Killer whale predation on penguins in Antarctica Polar Biology, 33 (11), 1589-1594 DOI: 10.1007/s00300-010-0853-5

TED talks are cool. I remember seeing this guy’s book in a shop – and not buying it. I love his point, I draw out information myself for revision times.

One thing though … what if, what if all this where online complete with links to sources and further information? Now that’d be what I’d call sexy.

The Cost of Sexual Selection

Hummingbirds are amazing fliers. They’re fast and agile. Some species have extremely long tails such as the Red-billed Streamertail, Trochilus polytmus(image on left below).

In species where females investment into offspring is larger, they choose their mate. Thus in many bird species, males compete with each other to be the “prettiest” and in some birds this means having a long tail. This is called sexual selection. (That long tails are selected for by females has been shown in some bird species.)

However, it has also been shown that an overly long tail decreases fitness in some species because a long tail decreases flying ability. If a birds tail is so long that it will die from other causes, such as starvation or predation, because it cannot fly well enough, tails won’t get longer. An equilibrium is reached.

In hummingbirds, where flying seems such an exquisitely honed, perfectly executed skill with amazing accuracy and power, wouldn’t long tails be really in the way? Presumably not, since these animals have them. Therefore a team of researchers set out to do experiments on hummingbirds to work out what the cost of a long tail for flying is. Apart from the Red-billed Streamertail, they also used Anna’s hummingbird, Calypte anna (left image below).

Red-billed Streamertail and Anna’s hummingbirds (images from wikipedia)

What they did is illustrated in the figure below. They cut off the tails of red-billed streamertails and grafted them on to Anna’s hummingbirds. The figures labelled d-h are the actual experimental birds.

• D: normal, unaltered

E: tails stuck to bird as shown in A-C

F: tails stuck to bird but cut to normal length

G: normal tail trimmed

H: normal tail completely removed

Then the birds where put in a flight chamber and their maximum speed as well as their metabolic cost at different speeds.

As expected the metabolic cost of flight increased, especially at high speeds. Also, the lack of the entire tail, increased metabolic cost while the lack of the rectices (part of the tail as shown in G) did not significantly affect forward flight. However, hummingbirds spend only 1-7% of their day flying forwards while spending a significantly large part of their time hovering or flying slowly while feeding. Here, a longer tail has a smaller loss and thus impacts fitness only to a smaller extend.

The red-billed streamertail has the longest tail feathers of any hummingbird. In those with shorter tails, the effect on performance would be lower.

The issue I have with this study is why they did the experiments on Anna’s hummingbirds on not on red-billed streamertails as well. It would be interesting to so, if they have adapted in some way so that the cost of a long tail in them is even lower (e.g. flight muscles etc).

As such, the study only shows that if you suddenly put a long tail on a bird not used to it, there’s a (small) decrease in “flight-ability”. However, long tails don’t appear suddenly and the bird can adapt to it. It would be interesting to see if the red-billed streamertail has minimized cost of a long tail further.

Clark CJ, & Dudley R (2009). Flight costs of long, sexually selected tails in hummingbirds. Proceedings. Biological sciences / The Royal Society, 276 (1664), 2109-15 PMID: 19324747

Hummingbirds in slow motion

Check out this awesome "behind the scenes” video of hummingbirds. Contains some awesome footage. The full length video is located here but unfortunately I cannot watch it where I am so I don’t know how awesome it actually is.

Use this video to get in the mood for some more exciting info on hummingbirds coming up (hopefully) soon!

But this is not only about some pretty cool images but also about the technique. There’s a paper in Science that’s all about taking images of embryos and measuring them. It’s all very technical but it comes with some cool computer generated images made from these measurements.

Olivier N, Luengo-Oroz MA, Duloquin L, Faure E, Savy T, Veilleux I, Solinas X, Débarre D, Bourgine P, Santos A, Peyriéras N, & Beaurepaire E (2010). Cell lineage reconstruction of early zebrafish embryos using label-free nonlinear microscopy. Science (New York, N.Y.), 329 (5994), 967-71 PMID: 20724640

How hard does a penguin push?

Remember to read the newest and indeed first edition of the Carnal Carnival featuring many other stories about poop!

I’ll admit, I didn’t get the idea to post about penguin poop from the cool and well popularised study on tracking them from space. I got it from a very cool talk by Nathan Myhrvold. This is a guy who got rich working for Microsoft and then quit in 1999 do do random stuff with his money. Like take pictures of whale sex, buy T.Rex skeletons and laser mosquitos to help prevent Malaria. However, he’s not an author on this study so no more shall be said about  him now. For more information check out this TED talk.

What’s this all to do with penguin poop? Well, he mentions a paper on the forces involved in penguin pooping. Because penguins are protected you cannot just go and measure the forces on a wild penguin. Instead, the authors relied in photographs. They used the previously mentioned Adelie penguin and the closely related Chinstrap penguin (picture below from wikipedia) again both of the genus Pygoscelis.

When these penguin poop on land (via a cloaca) they stand one the edge of their nest, slightly bend forward and lift their tail and then spray whatever needs to go as far as possible. They reach first around 40cm away and then, as pressure drops, form streaks towards the nest. These streaks go out in every direction from the nest, possibly the penguin chooses the direction based on wind-direction (but no one really knows).

Based on photographs they made the following estimates:

And based on these estimates, they did some fancy calculations. The one further value they needed was the viscosity of penguin poop. They tried taking samples to measure it but because of various fragments of solids such has scales and fish bones in the faeces, they could only estimate that the viscosity is somewhat like that of olive oil.

Now on to the results. The pressures produced by penguins lie between 77mmHG and 450 mmHg. For comparison, the human rectum muscles can withstand pressures up to 55mmHg, any higher and the contents are expelled. When straining, pressures up to 100mmHg can be reached. So no matter how hard you try to poop, a penguin can do it harder.

The authors call these “Cautionary Conclusions” seeing as all values are based on estimates. Still, I find it a fascinating topic, probably because it’s such a random thing to think about. And the drawing of the penguin is kind of cute if you forget that it’s pooping.

Of course, the remaining question is WHY do penguins do this. The obvious answer is to keep their feathers clean. Many birds actually poop like this, though I don’t know of another study about pressures. Because of a penguin’s posture, they cannot bend forward as much as other birds to increase their range. It has been estimated that eagles poop at an angle between 15° and 30° which would need lower pressures to achieve the same distance.

Obviously, further studies are needed. Who doesn’t want to study eagle poop?

Meyer-Rochow, V., & Gal, J. (2003). Pressures produced when penguins pooh?calculations on avian defaecation Polar Biology, 27 (1), 56-58 DOI: 10.1007/s00300-003-0563-3

Tracking penguins in time

Having established where these awesome, possibly cuddly, penguins are, it is time to turn out attention to their history. This is going to be a relatively short post based on a very short article.  

Gentoo penguins (from Encyclopaedia Britannica) 

Historical records are limited especially concerning animals in remote habitats. If we want to know how many of them there where at a specific point in time, we’re going to have to resort to different measures. That’s what some researchers from the University of Science and Technology in China did.

The location they investigated is the Ardley Penisula in Antarctica. This is actually an island with a lake on it. Penguins roost around the lake and their droppings can be found on the surrounding rocks as well as in the lake where they are either deposited directly or indirectly by water flow into the lake. The map below (from the Australian Antarctic Data Centre) shows the location.

I have mentioned previously that penguin guano is high in phosphorous, nitrogen and other elements not regularly found in the environment in these concentrations. So these are the elements to test for. The researchers took a sediment core sample spanning around 3 000 years according to C13 dating. Then they measured that concentrations of certain elements in different sections:

We found that the concentration of elements such as sulphur, phosphorus (represented by P₂O₅), calcium (represented by CaO), copper, zinc, selenium, strontium, barium and fluorine in Y2 was much higher than in other lake sediments in the maritime Antarctic.

The relative concentrations of the elements stayed the same, indicating a common source – penguin droppings from the nearby colony. The concentrations in this lake where significantly higher than in surrounding lakes (that are presumably without penguin colonies).

The total concentrations varied however. They peaked between 1800 and 2300 years BP (before present = before 1950). This was a period with higher rainfall.

One thing I noticed was that the article does not mention penguin species. Of course, I would assume that it is relatively difficult if not impossible to distinguish between the droppings of different species, especially if they are all mixed up in the sediment! Still, it shouldn’t be a problem to mention the species currently living there.

Despite this being relatively unimportant to the point made by this study, I looked up the species living on the Ardley Penisula today at the Australian Antarctic Data Centre and they are Gentoo Penguin (depicted above), Chinstrap Penguin, Adelie Penguin and Macaroni Penguin. The first three are members of the Pygoscelis genus meaning they are presumably quite similar, especially in their droppings. The Macaroni Penguin is distinctively marked and warrants an extra image for this post (‘cause they’re cool!):

Macaroni Penguin (image from Wikipedia)

Now that we’ve established that penguin droppings can alter the sediment in the long run, keep your eyes peeled for the next instalment of The many (scientific) uses of penguin poop.

Links to the other parts: (further links to be edited)

Part I – Tracking penguins in (& from) space
Part III – How hard to penguins push? (20/8/2010)

Other links of possible interest:

March of the fossil penguins – a blog on fossil penguins for those interested in fossils and/or the history of penguins

Sun L, Xie Z, & Zhao J (2000). A 3,000-year record of penguin populations. Nature, 407 (6806) PMID: 11057656

Penguins are charismatic animals with a large role in popular culture. They are seen as cuddly (though personally, I think that penguins are from the dark side). Regardless of personal inclination regarding cuddliness, it is easy to see that penguins are unique animals. Something your average penguin fan will think of less often are penguin droppings. These are sometimes also referred to as guano, meaning they have a high concentration of certain elements such as nitrates and phosphates making it useful as a fertilizer (e.g. bat guano is often mined though this practice is controversial). However, penguin droppings, especially those from flagship-species such as the Emperor penguins are hard to harvest. However, penguin droppings have other uses which inspired this series of posts, here’s part I on tracking penguins in (& from space).

Emperor penguins, adult among chicks (from Telegraph.co.uk)

You will have to excuse the little joke in the title – I do so enjoy playing with words. But let’s get down to business. Now that we have agreed that penguins are unique, it seems pretty obvious to want to protect them. One of the things you need to know when protecting a species is where they are. In the Antarctic, getting to a penguin colony is difficult especially as they breed in winter when conditions are even harder.

Recently some clever people realised that they could see penguin droppings from space. Emperor penguin droppings tend to be a brownish-reddish colour so they stand out against the white of the ice. So instead of trekking around in the cold, dark arctic winter, scientists can view some picture while sitting in their warm office sipping coffee. Below is such an image showing a brown stain in creek. That’s what a penguin colony looks like from space.

Of course, it’s not the same as actually going there and doing research on penguins. Reference colonies are needed to establish the number of individuals and breeding pairs etc. But this study does not claim to actually count penguins. This study confirms where penguins are and on top of that, finds a few new colonies. A lot of data about colonies is old. Because it is such a hassle to go to the Antarctic, you’re not going to do it regularly for all colonies. So if a colony has been found, it is not necessarily repeatedly checked upon.

However, if we want to know if climate change or perhaps something else is affecting penguins, we need to know if they’re still there. If numbers decline, eventually colonies are going to vanish. This study took previous data and compared it to satellite images from the early 2000s. The mapped the results and compared them to previously known colonies. Some colonies where newly discovered, some found again and some could not be found, either because they where no longer extant or because the images where unsuitable.

A lot of the colonies that are found again where previously found in the 80s which is a pretty long time ago and it is reassuring that while a handful of colonies apparently no longer exist, about just as many previously unknown ones where discovered in this study. The previously confirmed colonies that could not be found anymore all lie in the areas with slightly higher temperatures (temperatures at colony localities range from -4°C to -20°C). The fact that new colonies have been found in a previously colony-free area shows that emperor penguins are not restricted to some areas of the Antarctic as previously shown, a good thing as a widespread population is more resistant to change. Another fact worth noting is that of the 38 colonies found, 16 lie above 70° latitude. This is the area which has been stated to be most at risk if climate change causes temperatures to rise by 2°C.

Of course, it would be useful if colonies where confirmed on site but in the long run this is a useful and easier way of keeping track of colonies, especially if climate change pushes the ice back faster.

If you are a poop-fan in any sense of the word, please do come back to read about some more uses of penguin poop coming up. Coming soon: Tracking penguins in time.

Text edited: 20/08/2010 due to image problems.

Further links (edited 20/08/2010):

Part II – Tracking penguins in time
Part III – How hard to penguins push?

See also the press release.

Fretwell, P., & Trathan, P. (2009). Penguins from space: faecal stains reveal the location of emperor penguin colonies Global Ecology and Biogeography, 18 (5), 543-552 DOI: 10.1111/j.1466-8238.2009.00467.x

The NHM has lots of fantastic specimen. And I have previously mentioned that I really would like to see more on display. However, I feel that the Mammals Gallery is overdoing things a little. The room is full of specimen. There’s some fantastic skeletons, including the Steller’s Sea Cow and what I identified as the Irish Elk (Megaloceros giganteus). [For many of the specimen, I couldn’t actually get close enough to read the plaque as even I do not stoop as low as pushing children out of the way, so correct me if I get something wrong.] These specimen are great but I feel that the whole gallery is a) too crowded and b) directed far too much at children. On a quiet day I imagine it would be far easier to make the most of these exhibits.

Next I made my way to the red-zone, hoping that the crowds had not found their way there. The first exhibit you see is Lasting Impressions. This is a large and spacious hall with only few exhibits that most people will just make their way past without really seeing them. The exhibits are “evidence of a long-ago event”. For example there are some ram’s horns with each ridge corresponding to a year of growth, an ammonite and a dinosaur footprint. The exhibit seems to be put together a bit randomly and I suppose it serves as more of an introduction to the red-zone in general. However, it is nice to see one specimen in detail including a description.

The only other exhibit in the red-zone that I managed to view is From the Beginning. This exhibit is described as a journey from the big-bang to the present (obviously not at all to scale). It contains some very nice specimen including fossil bats  (from Messel) and fossil fish. My only grievance with the gallery was that it was so damn dark. In places, shadows obscured the labels making it (at least for me) impossible to identify the specimen. Other than that, this gallery is excellent and from passing through, I regret not taking more time to explore the rest of the red-zone. Of course, there just has to be one more thing slightly marring the experience, doesn’t there? The escalator through the Earth Hall was closed. Oh well.

Last but definitely not least came what was possible the best part of the visit, the Darwin Centre. A new and exciting feature where the visitor can digitally “collect” items is the NaturePlus card. These items correspond to a number you can enter online and then find out more about the item. Unfortunately I messed up my online registration so now I cannot actually access whatever I collected. Still, it’s an exciting idea that makes the visit a little more interactive.

The Darwin Centre is an interesting start that I believe could be expanded further. There are large empty spaces and a lack of seating arrangements in front of tv-screens. And the NaturePlus cards could be implemented more across the museum. You know that really really exciting specimen? The one you want to look up more about at home? Well, I resort to snapping a picture of the plaque but what if you could just scan your card and then get a list of things, possibly even with links to further information? Wouldn’t that be awesome? Probably too expensive though, eh?

The best part of the Darwin centre however, is the tour of the spirit collection where you get to see some of the specimen in jars that you don’t normally see, including the giant squid! Awesome!

Listening to: the news (I mean, how exciting is this whole Naomi Campbell/Charles Taylor/loads of other people court thing?)