Reversing revisited

In my last post, I talked about the ability to walk backwards, with the following conclusions: kangaroos – no ability to walk backwards; emus – ability to walk backwards unverified. Apparently, in the book that I mentioned (“Emus can’t walk backwards: Another round of dubious pub facts”) I have been told that the author describes experiments done in Australia to demonstrate that emus can, in fact, walk backwards. I’d be interested to read it, learn the evidence for myself, and also to know whether it describes the origin of this fable. (Really, emus are not all that popular an animal to discuss in everyday conversation! So who started the idea that they can only walk forwards?)

Anyways, I’ll see if I can check it out from the library. This is good - this could save me a long time sitting in front of the emu exhibit at the zoo, waiting for one of them to back up.

Ready, set, reverse!

Our cats really love to sit on the counters in our bathrooms. Every morning, as I’m getting ready for work, our older cat will come and sit on the counter for a few minutes – until I pull out the hair dryer, that is. The noise of this machine always scares her, and she inevitably jumps down off the counter and scampers away. A few days ago, however, she tried a new technique for getting off the counter. Instead of turning around and jumping down, she simply backed herself right off the edge. Not surprisingly, this didn’t work very well – she misjudged where the counter ended, and wound up with her rear legs in the trash can and her front legs on top of the toilet seat! (I guess I should be glad she didn’t wind up with her back legs in the toilet bowl.)

Now, I must admit, I laughed quite a bit at her predicament. (After making sure she as unhurt, of course.) But it sparked a question in my mind. She can back up quite well, but apparently she has to be level ground. And I wondered if that was a trait that all animals share. Can any creature that walks forwards also walk backwards? Or are there animals in the world that are physically unable to back up?

For the most part, animals that can walk forwards can also walk backwards. However, it is not universally true.

The one mammal that I came across that is unable to back up is the kangaroo. Kangaroos are marsupials that belong to the family Macropodidae, which means big feet. Other macropods include wallabies, quokkas, pademelons, honey possums, and wallaroos – in fact, there are over 50 different species of macropods. The most obvious difference between kangaroos and other species like wallabies and wallaroos is size. The 6 largest marsupial species are all referred to as kangaroos. In addition to really big feet, kangaroos have very powerful leg muscles, a strong tail for balancing, and a skeletal structure that makes them very efficient hoppers. But it also means that they can’t really walk. If a kangaroo has to move slowly, it forms a tripod between its tail and two forelimbs. You might see a kangaroo in this position if it’s eating something from the ground. But for general locomotion, hopping is much more efficient. And apparently if a kangaroo wants to retrace its steps (its hops?) it must turn around to do so. They cannot hop backwards, nor can they mince backwards in their tripod walk.

It has also been reported that certain birds are unable to walk backwards – in particular, ostriches and emus. These are the two largest birds on the planet; they are both members of the most primitive of modern bird families (including kiwis, cassowaries, and rheas). Both flightless, these guys rely on good old-fashioned leg power to get themselves around. Emus, in particular, can be quite speedy – they can sprint upwards of 30 miles an hour! They have a unique structure to their pelvic bones and muscles that allow them to move so quickly. They also have extremely powerful legs - in fact, emus are also the only birds that have calf muscles. Not only can emus run really quickly, their strong legs make them incredible jumpers. If startled, they can jump straight up almost 7 feet – which, considering that the bird itself is over 6 feet tall, is quite impressive. So they can move really well going forwards – but can they reverse? Unfortunately, though that statement is often thrown around as fact (and is even the title of a book – “Emus can’t walk backwards: Another round of dubious pub facts”), I wasn’t able to find any reliable source to tell me whether or not it was true. The evidence is mostly anecdotal. I guess the next option to me to verify this fact would be to camp out at the emu section of the local zoo and watch them for a few days to see if I can see any of them go backwards!

There may be other animals that cannot reverse their locomotion. One other suggestion my husband came up with was the centipede. With that many legs, I can imagine that it might very well be difficult for organize them all to go in reverse!

Anyone have any other ideas?

Yikes! Brain Freeze!

Here in the Seattle area, we are going through a rather disappointing spring. With the exception of 1 very notable day, our weather has been much colder and wetter than usual. Now, I love warm weather. Give me sun, sun, sun! So I’ve been having a hard time being patient for the nice weather to return. When I think about warm weather, I think about lots of things associated with summer time – barbeques, running through the grass in my bare feet, seeing our cats sunning themselves in the windows, listening to the birds outside, and, of course, all the yummy summer food. Especially ice cream. I really like ice cream. The only downside to eating ice cream on a warm summer day, unfortunately, is the chance of developing brain freeze.

Have you ever had brain freeze - that feeling when you’re eating something really cold (could be ice cream, or a slurpee, or some ice cubes in a drink) and all of a sudden you get a horribly painful ache in the front of your skull? Fortunately, it only lasts a few seconds, which is a very good thing since it hurts so badly. Have you ever wondered what causes it?

Brain freeze occurs when your palate gets a little confused over the temperature. Your palate is, basically, the roof of your mouth. If you run your tongue over the roof of your mouth, everything from the ridge behind your teeth to the farthest back you can reach is the palate. It is made of both bone and muscle, and is covered by a layer of skin. It serves several important purposes, including separating your nose and nasal cavity from your mouth. There are many nerves and blood vessels situated in this region, which are all sensitive to the things you eat. When you eat something very cold very quickly, the nerves in your palate get a strong message that there’s something freezing here! These nerves then get a little confused – they think that your brain is in danger of freezing from the cold. And since a frozen brain would be very bad for your health, these nerves send an immediate message to increase the blood flow to your head. Increased blood flow would mean extra warmth for your brain, keeping it safe from freezing. However, the blood vessels holding this extra blood in your head expand so quickly that they cause pain. The pain is very short-lived – the increased blood flow stops as soon as your palate warms up a little, your blood vessels contract again, and the headache stops.

One thing that surprised me is that not everyone suffers from brain freeze. Apparently, it only happens in 30-40% of the population. (The American population, that is.) I guess that makes me one of the unlucky ones, since I definitely get them! I did learn one new way of getting the brain freeze to go away faster, though. When you feel it start to develop, press your tongue against the roof of your mouth. This will warm your palate up faster than it would otherwise, and stop the headache faster.

Or you could just eat your ice cream a little bit slower.

The Oregon earthquake swarm

I live in western Washington, an area not as well-known as California for being earthquake-prone but which is nevertheless earthquake territory. That's because we're right on the edge of the North American tectonic plate, which runs almost directly up the western coast of North America. When you think about the fault lines created by this boundary, you might think first of arguably the most famous fault line in the US – the San Andreas fault. The San Andreas fault stretches approximately 800 miles up the coast of California; here, the passage of the North American plate (which moves southeast) and the Pacific plate (which moves northwest) generates the most memorable earthquakes of the region. This includes the devastating 1906 San Francisco quake, which was an estimated 7.8 on the Richter scale and responsible for some 3000 deaths.

Now, the San Andreas does not extend up into Washington state. However, being at the edge of the North American tectonic plate means that we also have fault lines capable of generating substantial earthquakes in the area. For us, however, the danger comes primarily from where the North American plate meets the Juan de Fuca plate. The Juan de Fuca plate is very small, extending from the southern border of Oregon to British Columbia, Canada; it was once part of a much large plate (the Farallon plate) that has largely subducted (meaning sunk) underneath the North American plate. There are three remnants of the Farallon plate still in existence - the Juan de Fuca plate off of the Washington coast, the Cocos plate off of Central America, and the Nazca plate along the western edge of South America. Subduction of the Juan de Fuca plate is responsible for the formation of the Cascade mountains which includes two volcanoes that you might be familiar with - Mount St. Helens and Mount Rainier.

The last major earthquake to occur off a fault from the Juan de Fuca plate was around 1700, with a magnitude of somewhere around 9.0 on the Richter scale. However, in the last 2 weeks, scientists have detected a rash of earthquakes off the Oregon coast – over 600 of them, up to a magnitude of 5.4. But here’s the odd thing – these earthquakes do not appear to be coming from any of the fault lines from the Juan de Fuca plate. Instead, they are centered in the middle of the plate – about 40 miles from its edge.

There are actually several odd things about these earthquakes. First, of course, is that they do not correspond to a fault line. But second, they do not follow the typical earthquake swarm pattern of a major shock followed by steadily decreasing aftershocks. It has been a steady stream of earthquakes of mostly equal size. That means this is unlikely to be caused by a fault internal to the plate itself. In fact, scientists really have no firm idea what’s causing these tremors to occur.

One of the major researchers studying this swarm is Dr. Robert Dziak, marine geologist from Oregon State University. Though he says that nothing like this has been detected in this region ever since monitoring has begun, he has a couple of suggestions as to what’s causing the swarm. It’s possible that a new fault is opening in the middle of the Juann de Fuca plate. Or it could be that the entire plate is under stress, being squeezed by the plates around it, which could cause it to crumple a little in the middle. Or there could be new volcano activity in the area immediately beneath this spot, injecting new magma into the middle of the plate and pushing the plate much faster than it has previously moved.

I should mention that these earthquakes do not appear to be any danger to the inhabitants of the Oregon coast. The quakes are too far away, too deep and too small to even be felt on the mainland. They are detectable by a system of hydrophones set up on the ocean floor – which were actually originally set up to detect submarine activity off the Pacific coast during the cold war. But they’ve been put to a more peaceful use as of late.

Not a lizard, and not a snake - but some of both

Did you know that there is still a species alive on earth that roamed the planet alongside the dinosaurs?

It’s called the Tuatara. The tuatara is the last surviving species of the Sphenodontians, a group of animals that developed and thrived during the upper Triassic – nearly 220 million years ago. If you were to look at it, you might think the tuatara is a lizard – a triangular head, four squat legs with long spiny toes, leathery skin, and a long tail. However, while the tuatara is a reptile, it is equally closely related to both lizards and snakes. It is the only surviving species on earth that fits this description. Other relatives of the tuatara were the beak-headed reptiles (also known as Rhinocephalia), but the rest of them died out 100 million years ago.

The tuatara is sometimes referred to as a living fossil. Despite its ancient origins, the appearance of these animals has not changed very much in the last 200 million years. This means that they can be used to study what their ancient relatives looked liked. Because of this, they are of great interest to scientists who study the evolution of lizards, snakes, and diaspids (the group that includes both birds and crocodiles).

Interestingly, though the overall appearance of the tuatara has remained unchanged for millions of years, it now seems that they undergo relatively rapid molecular changes. By comparing DNA extracted from tuatara bones approximately 8000 years old to modern tuatara DNA, scientists now believe that this animal has the fastest rate of DNA changes ever measured. At an average rate of change of slightly over 1.5 subsitutions per nucleotide per million years, it beats out the previous record-holding fast molecular evolver, the Adelie penguin. The fact that the DNA of the tuatara changes so rapidly, while its overall body hasn’t changed in millions of years, is remarkable.

Tuataras live only in New Zealand. And though I refer to the tuatara as one species, there are actually 2 closely related subspecies of tuataras – S. punctatus and S. guntheri. S. guntheri is also know as the Brothers Island tuatara, and it is extremely rare, much more so than its S. punctatus relative. In reading up on these creatures, I came across a few interesting facts:
-They have the slowest growth rate of any reptile we know of. In fact, they keep growing until the reach about 35 years old, but only attain a final size of 20 inches.
-They can live to be over 100 years old, though their average life span is around 60 years.
-They can hold their breath for nearly an hour.
-They are nocturnal – for the most part. Adult tuatara hunt at night, but young tuatara will hunt during the day. This is because a really hungry adult will eat a young tuatara if it can catch it. In addition, because they are cold-blooded, they will bask in the sun during the day to regulate their body temperature.
-They have an extra eye besides the two in the front of the face. Called the parietal eye, it is found on the top of the head, and is visible only in the very young. After about 6 months of age, it becomes covered with opaque scales and pigment. Its function is unknown, though scientists have suggested it to play a role in circadian rhythms or the absorption of UV light to aid in the production of vitamin D.
-The hearing organs of the tuatara are very primitive, and look very similar to that of turtles. There is no eardrum, or even an earhole. The cells that respond to sound are relatively poorly specialized, and respond only to low frequency sounds.

If you have a few minutes, and want to see some pictures of these cool little creatures, you can check out the website of the Kiwi Conservation Club at:
http://www.kcc.org.nz/animals/tuatara.asp


The image of the tuatara was taken from:
http://www.wpclipart.com/imgpage.html?http:
//www.wpclipart.com/animals/T/Tuatara.png

A well-built skull

Why don’t woodpeckers hurt their heads when they bang them into trees?

That question popped to mind the other day as I was working outside in my garden. We have a woodpecker that has taken to visiting one of our neighbor’s trees. Stay outside long enough on a decent afternoon, and soon you will hear the distinctive “rat-a-tat-a-tat-a-tat” of the woodpecker’s beak, as it rams over and over again into the trunk. These birds are tenacious when it comes to drilling holes in things! Not only are they tenacious, they are powerful. In fact, North America’s largest woodpecker (the Pileated woodpecker) can hit a tree 20 times a second, up to 12,000 times a day, with forces as high as 1,200 times the force of gravity with each hit. That’s roughly the same as hitting a wall with your face at 16 miles an hour – over and over and over again. Ouch. That makes my head hurt just thinking about it!

So how come they don’t hurt themselves?

Woodpeckers are highly adapted to this punishing lifestyle based on the design of their skulls and brains. First, the skull: a woodpecker’s skull is very thick and bony, but the bone itself is fairly spongy. There is also a think layer of cartilage at the bottom of the lower jaw bone that serves as a cushion. This cartilage and bone structure enables to force of the blow to be distributed to the base and back of the skull, rather than the brain.

Next, the brain: a woodpecker’s brain actually has several features that protect it from impact. First, it is small and packaged very tightly inside the skull cavity. Because of its tight packing, the brain does not move much more than the skull does. When a human hits his head, the brain can jostle around within the skull cavity, actually bumping against the bones. That bump causes much of the brain injury associated with a head trauma, such as a concussion. But woodpecker’s brains don’t move that way, so they can’t knock themselves out, get concussions, or incur brain bleeding. Second, there is not a lot of cerebrospinal fluid, either, because there is simply no room for it. This fluid helps transmit shock waves from the skull to the brain, which can also cause injury to the brain. Little fluid – few shock waves. Third, a woodpecker’s brain has a smooth surface, with a high surface area to weight ratio. This is unlike a human brain, which has ridges, folds and bumps all over the surface. We actually have a lot of surface area on our brains! That’s good for thinking, but bad for a head trauma. It means that any impact to the brain is felt over a small surface area. For a woodpecker, a blow to the brain is spread out over a larger surface area, which means that the impact on any given spot is smaller.

Finally, there is another very important fact that helps explain why woodpeckers don’t hurt their heads when they peck – it has to do with their pecking technique. Woodpeckers will always peck at a surface in a straight line, with no side-to-side twisting or torque. This prevents a specific kind of stress on the nerve fibers of the brain called “diffuse axonal injury” or DAI. DAI is one of the most common and dangerous forms of traumatic brain injury. DAI occurs when a sudden deceleration is coupled with some form of rotation, which can twist nerves apart like a lid coming off a jar. A brain impact that occurs straight-on will not cause DAI, because there is no rotational stress being applied to the brain. So it is vital that a woodpecker hit its target dead center and straight on with every hit. And, from all indications, they do!

Incidentally, an Ig Nobel prize was awarded in 2006 in opthamology to Dr. Ivan Schwab and Dr. Phillip R.A. May, for their work on woodpecker head trauma. In particular, they studied why woodpeckers are immune to retinal detachments, brain damage and spinal cord injuries with their repeated head banging. And in addition to the stuff I’ve talked about above, they did learn one additional thing. Woodpeckers always close their eyes with every bang of their beak.

Dr. Schwab did admit, however, that whether they do it to keep their eyeballs in or the wood chips out was an open question.

Roadrunners

My husband and I were fortunate to be able to spend a few days last week visiting family in Palm Desert, California. Palm Desert is a beautiful oasis in Riverside County, a few hours east of Los Angeles. The weather there this time of year is gorgeous – 80 degrees, sunny, light breezes pretty much every day. Perfect weather for sitting out by a pool in the afternoon, which is mostly what we did! One afternoon, while engaged in this extremely pleasant activity, I looked over to the edge of the pool patio, and saw a funny little bird running underneath the shrubs. Lo and behold, it turned out to be a roadrunner.

I’ve never really thought about roadrunners that much (except, of course, for road runner in the Loony Tunes cartoon who always managed to get the best of Wile E. Coyote). But this was a neat looking bird. He had a long neck, a tuft on top of his head, and a very long tail. When he (or maybe a she, I don’t know exactly know what gender it was) walked or ran, his whole body went horizontal – head down, tail stretched out behind him. But when he stopped, his head came up, his tuft poofed out, and his tail rose up behind him. All in all, it was a very cute sight. I decided to investigate roadrunners a little bit more to see what I could find out about them.

A roadrunner is actually a kind of ground cuckoo. It is found in all of the southwestern states, but predominantly in the Mojave, Sonoran, Chihuahuan and south Great Basin deserts. Its prominent features include its tail and head (which I mentioned above), as well as its feet – it has 4 toes, 2 of which point forwards and 2 of which point backwards. The roadrunner can fly, and will do so if threatened or (apparently) if traveling downhill. But because it has a large body and weak wings, it can’t fly very well, so it usually prefers to walk or run. In fact, this little guy can run as fast as 17 to 19 miles per hour. (The fastest human in the world, incidentally, clocks in at around 22 miles per hour. But that’s for a distance of only 100 meters.)

The speed of this bird makes him well adapted to catching and eating other animals. Its diet consists almost exclusively of insects, scorpions, lizards, rodents, and other birds. They have been seen snatching dragonflies or hummingbirds out of air in mid-flight! They will eat fruit that they find on the ground, though, especially in the winter when prey becomes scarce. Roadrunners will even eat rattlesnakes – they are one of the few animals that can do this, actually. To catch this very dangerous snake without getting bit, the roadrunner will dart around, snatch the snake up by the tail, and whip it repeatedly against the ground until it’s dead. And here’s a funny tidbit that I happened across. A roadrunner will eat its prey whole; however, they have been know to catch snakes too big to eat in one sitting. So they will swallow as much as they can, then run around for a while with the rest of the snake dangling out of their mouths until the eaten bit has digested enough to make room for the rest of it! (Yuck.)

Interestingly enough, as long as the food that the roadrunner eats is high enough in moisture, the bird does not even need to drink any additional water. They also have special glands around their eyes that secrete extra salt from their bodies. This makes them very well adapted to living in the desert.

And no, they do not really say “beep beep” whenever they stop. Their vocalizations consist of a much more normal, bird-like cooing or whirring. The "beep beep" is, unfortunately, only in the cartoons.