Snowy Palms: An Omen of Death

Recently, parts of Southern California experienced some surprisingly cold weather, as falling snow graced the tops of the palm trees around Christmas time.  A White Christmas is nothing terribly surprising for folks like myself, born and raised in Colorado, but for California natives it was definitely more of a surprise.  People had pulled over on the side of the highway for an opportunity to play in the snow, throwing snowballs and taking selfies all over the place.

Wind turbines in the foreground, and snow capped mountains in the background in the middle of the desert just outside of Palm Desert in California.

A family stopped along Interstate-15 in Temecula, California to play in the snow, a scene that could easily have been lifted out of Colorado, if not for the trees adorned with green leaves, and especially the palm tree in the background.

A snow selfie on the side of the Interstate-15 in Temecula, California.

Although the winter freeze was very exciting for many of the residents, for the native residents of Southern California's deserts, the freeze would be much less welcome.  Over millions of years, the animals that call these seemingly barren slopes home have evolved to cope with extreme environmental stress typical of those experienced in the desert.  Aridity and extreme heat of course play major roles in any desert ecosystem, and many of the adaptations of desert animals are in response to these climatic factors.

The bobcat (Lynx rufus), one of the residents of the Southern California deserts.  This particular individual was at The Living Desert in Palm Desert.

A captive desert bighorn sheep (Ovis canadensis nelsoni) at The Living Desert.  This subspecies is native to the southern United States and Mexico.

A western diamondback rattlesnake (Crotalus atrox), also native to the southern United States and northern Mexico.

A wild greater roadrunner (Geococcyx californianus) that I chased through a Target parking lot.  

A wild California ground squirrel (Spermophilus beecheyi) that we saw foraging around at The Living Desert.

A hummingbird, possibly an Anna's hummingbird (Calypte anna).  Hummingbirds in Colorado will fly south for the winter, in order to avoid harsh weather like that seen in Southern California last week,

Of course, environmental conditions that fall well outside the norm are arguably equally important for animals native to a specific biome or region.  Even if a population of animals thrives in the harsh, arid landscape of Southern California, if all it takes is a single night of snow to wipe out the population, unusual weather (such as that seen in the area last week) can be extremely troublesome.  Extreme weather can also help control populations, and can be what keeps other animals from colonizing an area.  For example, if a population of desert rodent attempts to colonize the mountains around Palm Desert, but is unable to cope with the occasional snow storm, then that type of rodent would be much less likely to survive and thrive there.

Part of the mountains west of La Quinta and Rancho Mirage, prior to the snowstorm.

The same mountains, following the snowstorm.

Works Cited:

Hummingbirds found in California, USA. (n.d.). Retrieved January 4, 2015, from http://beautyofbirds.com/hummingbirdscalifornia.html

Rancho Mirage on Dwellable

Taima the Seattle Seahawk and the Genus Buteo

For those of you who watching the Broncos/Seahawks game right now, you might have noticed clips of a random bird of prey flying around which, if you're anything like me, that was the highlight of the entire game.  Named Taima, the bird is the mascot for the Seattle Seahawks football team, an augur hawk (Buteo rufofuscus).  Although sometimes referred to as the augur buzzard, I prefer the name augur hawk, as buzzard is sometimes a bit of a confusing name.*  According to the Seahawks website, Taima has been the "first one out of the tunnel" prior to every game.**  The augur hawk is one of the most common hawks in Africa, and inhabits an enormous portion of the eastern and central part of the continent.  Open plains, grasslands, and forests are the augur's preferred habitat, fairly similar to its close North American cousin, the red-tailed hawk (Buteo jaimaicensis).

The broad-winged hawk (Buteo platypterus) is one of the smallest members of the genus, and a hawk that's involved in a very interesting new project, the aptly named "Broad-Winged Hawk Project."  Similar in many ways to the OCEARCH shark tracking project, the BWHP is using satellite telemetry technology to track broad-winged hawks on their migration from Pennsylvania, all the way down to Central and South America.  You can join in the tracking fun by clicking on the link HERE!  Several of the nestling broad-wings were from pretty close to where my friend Zach Evens's cabin in Pennsylvania was that we visited in August!

There are a ton of other hawks in the genus Buteo besides the red-tail, augur, and broad-wing, several of which we've talked about here on the blog, such as the red-shouldered hawk (B. lineatus), rough-legged hawk (B. lagopus), and the Swainson's hawk (B. swainsoni).

A rough-legged hawk on the hand of Anne Price, the Curator of Raptors for the Raptor Education Foundation at one of the raptor shows at the Best Western Denver Southwest!

*In the Americas, a buzzard typically refers to a vulture, while in the Old World, buzzard is often attributed to members of the genus Buteo, of which the augur hawk is a member.  We Americans tend to refer to buteos simply as hawks, which is part of what can lead to this confusion.

**For those of you not in the know, the tunnel is not a metaphorical tunnel, and instead refers to a legit tunnel that leads from the locker room onto the stadium.

Works Cited:

Anoxic Conditions From Everest to Europa: Swamps, Fossils, Naked Mole Rats, and the Hunt for Extraterrestrial Life

Above elevations of 6500 meters (21,300 feet), most climbers tend to start using supplemental oxygen.  At altitudes higher than this, oxygen is spread so thin that humans can have a very tough time breathing.  Even people who come from sea level to my hometown of Boulder, Colorado at an elevation of 1,655 meters (5,430 feet) often get altitude sickness, and there's still a whole lot of altitude to go before you even get to Everest Base Camp.  Most birds don't fly as high as the summit of Mt. Everest, because most birds have no reason to fly that high.  However, for the bar-headed goose, the Himalayas form an unfortunate, but not impassable, barrier between their winter feeding grounds in India and their Tibetan nesting grounds.  These geese have been reported flying over some of the highest Himalayan peaks, and they're not the only ones that fly this high.  On November 29th, 1973, a Rüppell's griffon, a type of Old World vulture, collided with an airplane at an altitude of 11280 meters (37,000 feet).  By comparison, oxygen cylinders are recommended for sailplane pilots flying over 3660 meters (12,000 feet)!

Here we have a beautiful (and extraordinarily neat) size comparison and altitude chart of a number of things covered in the post, including the altitude of Denver, the summit of Mt. Everest, the upper extent of the range of the snow leopard, and the height at which the Rüppells griffon got sucked into the jet engine.  I've also thrown in some other helpful and fun things for comparison as well.

Part of what helps birds survive at altitudes that could kill a human is a series of air sacs that allow air to flow in one direction through the body of the bird.  In humans, the air we breath in and out travels back and forth along the same tubes.  In birds, as well as some of their close dinosaurian cousins, these air sacs would have have allowed the air to flow more efficiently through their bodies.  While this is simply one of many adaptations that can help birds fly at incredibly high altitudes, other animals have evolved other adaptations to assist in high altitude living.  Scientists have determined that changes in the genes EGLN1 and EPAS1 are linked with animals living in oxygen impoverished environments, such as the snow leopard, humans native to Tibet, and naked mole rats.  Naked mole rats live in underground colonies of 20-300 individuals, and are one of two species of mammal that can be classified as "eusocial," meaning that their colonies display a caste system (similar to the social structure seen in ant and termite colonies).  These underground colonies are poorly ventilated, which means that as the mole rats inhale oxygen and exhale carbon dioxide, CO2 concentrations can increase to levels that would be unsafe for humans.  Fortunately, naked mole rats are well adapted to breathing very little oxygen, and their brains seem incapable of registering pain upon contact with acids, which is thought to help them in these CO2 rich confines.  They also demonstrate similar changes in the aforementioned genes as snow leopards and the Tibetan people, indicating another adaptation to these low oxygen (or hypoxic) conditions.

A group of naked mole rats all huddled together at the Cheyenne Mountain Zoo in Colorado Springs, Colorado.  Look at all of that eusociality!

Although hypoxic conditions can bode ill for human climbers and gregarious colonial rodents, low oxygen conditions can be great for paleontologists.  When oxygen levels drop to nearly zero, anoxic conditions prevail, and bacterial decomposition of organic material is greatly reduced.  This can be a major factor when it comes to soft-tissue preservation, such as feathers and skin.  A FEW WEEKS AGO, we talked about several famous fossil sites called Lagerstätten (a German term meaning "mother lode"), that are set apart from other fossil deposits due to the quality and/or quantity of the fossils discovered there.  One of the most famous examples is the Cambrian-aged Burgess Shale in British Columbia, Canada.  Abrupt burial of the 500 million year old organisms, coupled with the anoxic conditions that prevailed at the bottom of this body of water, ensured that these soft-bodied organisms would be preserved in exquisite detail.

A drawing of Opabinia, one of the many creatures that inhabited the Cambrian aged Burgess Shale in British Columbia, Canada.  Photo Credit: Sam Lippincott

Why do swamps often have that rotten egg smell?  Believe it or not, the answer is closely related to what we've already been talking about!  Under hypoxic or anoxic conditions, bacteria that use oxygen (O2) sometimes have to make do with sulfur (S).  If you look at a periodic table, you can see that sulfur (element #16) is directly below oxygen (element #8).  In the periodic table, each group (or column) of elements has very similar chemical properties, which means each element will react in a similar fashion.*  For the bacteria that can't get enough oxygen, they will sometimes turn to its close cousin sulfur instead.  Below is the chemical formula for cellular respiration, which is what these bacteria do, as well as some of the cells in humans.  On the left, we have the inputs: glucose (C6H12O6), and oxygen (O2).  When we breath in air, we are bringing oxygen into our lungs, and we can get glucose from the foods we eat.  On the right of the arrow, we have the outputs: water (H20), carbon dioxide (CO2), and energy.  Remember how we talked about the CO2 concentrations in naked mole rat burrows?  CO2 is one of the products of respiration, and one that can be harmful in large doses.  Energy is another product of respiration, which is the fuel that cells need to do their job.  In places where there is less oxygen input (such as at the top of Mt. Everest or in a naked mole rat burrow), the cells don't get as much energy output, and they can't do their job as well.

Now, instead of having oxygen as one of the inputs of cellular respiration, let's try sticking oxygen's close cousin, sulfur, into the equation to see what will happen.  As you can see below, the glucose on the left of the equation remains unaffected, as does the carbon dioxide output on the right of the equation.  But instead of having water (H2O) as another one of the outputs, we now see a molecule with the formula H2S.  Instead of forming water (hydrogen oxide), we have now formed a closely related molecule, hydrogen sulfide.  In swamps, large amounts of organic material leads to lots of bacteria and bacterial decomposition, which in turn can lead to lots of the oxygen being used up in the water.  That's when these bacteria start using sulfur to make their energy, producing hydrogen sulfide, with that characteristic rotten egg smell.  Even with this sulfur replacement, sometimes the bacteria just can't keep up with the amount of vegetation that is deposited in the swamp, and the organic material builds up.  If the rate at which the vegetation accumulates exceeds the rate which the bacteria can decompose the vegetation, then you have coal formation potential sometime in the future.

Let's take this one step further.  In normal respiration, where oxygen is one of the inputs and water (H2O) is one of the outputs, carbon dioxide (CO2) is another one of the outputs.  If animals and bacteria keep using up oxygen and turning it into carbon dioxide, why haven't we run out of oxygen?  Will we run out one day?  Fortunately, for the time being, plants have got our back, by undergoing a process called photosynthesis.  Photosynthesis is almost the exact opposite of respiration: carbon dioxide and water are the inputs, and glucose and oxygen are the outputs.  However, unlike respiration, light is one of the inputs of photosynthesis.  In the 1700s, a man named Joseph Priestly did experiments in which he sealed a mouse in a jar, and waited to see what happened.  The mouse, as you could probably predict, suffocated and died.  It used up its oxygen to create energy (as well as carbon dioxide), and eventually ran out of oxygen.  (This is why it's important not to put animals into completely sealed jars with no airflow, as they will suffocate.)  However, if he put a plant into the same jar as the mouse, the mouse didn't suffocate.  We now know that is because, as the mouse used up the oxygen, creating carbon dioxide, the plant would use the carbon dioxide, ultimately creating more oxygen.

As you probably know, plants need light to survive, and as we mentioned before, that's because light is one of the inputs of photosynthesis.  No light, no photosynthesis.  No photosynthesis, your plant dies.  For many years, scientists assumed that all life on Earth was directly dependent on the Sun for its energy.  That is, until 1977, when scientists discovered entire communities of biological organisms living thousands of meters beneath the surface of the ocean, too far from any sunlight to undergo photosynthesis.  So what was going on?  How were these communities able to survive without access to the sunlight?

Hydrothermal vents are essentially underwater hot springs that form along tectonic boundaries thousands of meters beneath the surface of the ocean.  These underwater vents spew different compounds containing sulfur into the surrounding water, just like aboveground geysers do, too.  (If you have ever been to Yellowstone National Park, then you might even remember the rotten egg smell.)  Some bacteria that surround these vents are actually able to use these sulfur-containing compounds to create the energy needed to undergo a process similar to photosynthesis, called chemosynthesis (consult the equation below).  Chemosynthesis is very similar to photosynthesis, with a few key differences, the biggest difference being the sulfur reactions vs. sunlight as one of the inputs.  You can also see that, instead of having water (H2O) as an input like in photosynthesis, chemosynthesis instead uses hydrogen sulfide (H2S) as an input.  Then, instead of producing oxygen, the chemosynthetic organisms produce water and sulfur.  You can compare it to the oxygen-poor respiration equation that we talked about with the swamps, and see that it is similar to that equation as well, simply flipped around.

But that's not all.  Scientists have taken this idea a step (or rather, one giant leap) further.  The search for life on other planets thus far has yielded nothing, but that doesn't mean it's not there.  It is now realized that some of the factors that were once thought to limit the development of life, such as sunlight, might not be as crucial as we once thought, and the hydrothermal vent communities have been crucial in the maturation of these ideas.  Some scientists suspect that life could exist on Mars by using chemosynthesis, but a new candidate has been receiving an increasing amount of attention: one of Jupiter's moons, Europa.  Icier than the planet Hoth, Europa is now thought to have an ocean of liquid water up to 160 km (100 miles) deep surrounding the solid, rocky mantle, following the discovery of a magnetic field surrounding the moon, similar to the magnetic field that surrounds the Earth.

What keeps the liquid ocean of Europa from freezing solid?  Jupiter is pretty far from the Sun, and even Mars, which is much closer to both the Sun and the Earth than Jupiter is, has had its water frozen for millennia.  It's thought that the gravity exerted by the enormous mass of Jupiter continually pushes and pulls, or tidal stresses, on its moons, which keep the planets from becoming tectonically inactive, like Mars.  Io, another of Jupiter's moons slightly larger than our Moon, is the most geologically active body in our Solar System.  The tidal stresses from Jupiter exerted on Io apparently make Io's ground itself buckle up and down, similar to the tides we experience here on Earth, except that instead of water moving up and down 18 meters (60 feet), its solid ground moving up and down up to 100 meters (330 feet!)  It's these same tidal stresses that make Io so geologically and volcanically active that help keep Europa from freezing solid.  It has been hypothesized that the tidal flexing might also create hydrothermal vents on the bottom of Europa's oceans, and it shouldn't take too much thinking to realize what that might mean: the potential for extraterrestrial life!

*For example, we humans, as well as all known lifeforms, are carbon-based.  In science fiction, such as Star Trek and Transformers, you will often hear about "silicon-based lifeforms."  Why silicon, as opposed to any other element?  If you look at the periodic table, silicon is in the same group as carbon, and situated right beneath it, and therefore has very similar chemical properties as carbon.



Works Cited:

Baby Prairie Dogs and Birdwatching on the Bird of Prey Route!

Today, with the summer weather and the lack of school, I decided to take my car over to what I like to call the "Bird of Prey Route," a little dirt road in between Superior and Boulder about ten minutes from my house here in Colorado.  You can usually see at least one or two different types of raptors there, and there are a number of other awesome animals that I have spotted there, as well!  Today, I saw a lot of really cool birds, as well as some baby prairie dogs, as you can see below!

This particular species of prairie dog is the black-tailed prairie dog (Cynomys ludovicianus).  Like the other species of prairie dog, the black-tail is a highly social little rodent.  Below you can see two pups "kissing" each other, a type of interaction that members of the same family group will employ.  I think this is just to help solidify familial bonds, but I'm not sure if anybody knows for certain.

Today, the bird of prey route did not disappoint!  Perched in the tree in the picture below is the red-tailed hawk (Buteo jamaicensis), definitely the raptor that I see most often when on the route.

I also saw a pair of American kestrels (Falco sparverius), the species of raptor that I see second most often.  I don't usually see the kestrels so close together, however, so perhaps this was a mated pair.  I did see one of them fly into a hollow in a tree, which might be where a nest is hidden away!

As I was watching the hollow in the tree where the American kestrel swooped off into, I noticed several European starlings (Sturnus vulgaris) flying into other hollows on the tree.  Then I realized that the angle of one of the hollows was just right, and that I could actually see the adult starling feed its young!  If you zoom in on the picture, you can see that the baby already looks pretty big, maybe even as big as the parent!

Black-billed magpies (Pica hudsonia) are especially abundant in the area, and I saw several of them as well.

This magpie looks like it is molting!

Now this particular tree presents a particularly provocative puzzle, as it is almost completely covered in some very sharp looking thorns.  A few weeks ago, I saw another tree, much larger than this one, along the banks of Boulder Creek that had some enormous thorns on its branches as well, some of them easily six inches long, and super sharp on the end!  I don't know for certain what kind of tree this, or the Boulder Creek tree, is, but a good candidate I think is the honey locust (Gleditsia triacanthos), or some other tree closely related to the honey locust.  Below is the picture of the tree that I took on the Bird of Prey Route.

Here is a picture of the thorns of the honey locust tree.

And here is the picture that I took on my iPhone at Boulder Creek of this tree.  The thorns look pretty similar to those of the honey locust, and I think that the trunk of the tree looks pretty similar, too.

Now why do these trees have such huge thorns?  That's a really good question.  I started answering (or at least trying to answer) the question here in this blog post, but everything rapidly started spiraling out of control and off focus as I started talking about giraffes, tiny squirrels, cheetahs, and extinct North American elephants.  For those of you who know me, it should come as no surprise that I spiraled so quickly off topic.  But regardless, what I had written ended up having enough material for at least three or more posts, so I have moved the answer to a different post, which I will hopefully be publishing soon.  Keep an eye out for that!  In the meantime, back to the future birds!  Here, we see a pair of barn swallows (Hirundo rustica) perched on a wire.

I'm not quite as sure about the identity of this particular bird.  Also a swallow, I am thinking that it might be a violet-green swallow (Tachycineta thalassina).

I believe this to be a vesper sparrow (Pooecetes gramineus).

A western kingbird (Tyrannus verticalis), another bird that I see all the time here, at least in the summer!

At last, we have one of the most exciting birds that I saw on the route today, the blue grosbeak (Passerina caerulea), a bird that I don't remember ever seeing before!

Remember to check back soon to learn all about those massively spiky trees!

Works Cited:

Robbins, C. S., Bruun, B., & Zim, H. S. (1983). Birds of North America. New York: Golden Press.

Stokes, D. W., & Stokes, L. Q. (2010). The Stokes field guide to the birds of North America. New York: Little, Brown.

Birdwatching at the Morrison Natural History Museum!

Last Monday, a snow storm hit Colorado....in the middle of May.  Although it snowed even as much as sixteen inches in some places, it melted pretty quickly afterwards, leaving an excellent opportunity for many birds that rely on insects for their meals.  After a rain, you can often see birds like the American robin or flicker foraging around (click HERE to read more), using the soft ground to their advantage to try and catch insects that were washed up out of the ground.  After the snow, it seems like a number of birds were attempting to do the same thing.  As I was closing up, I looked out behind the Morrison Natural History Museum, and noticed a bonanza of birds!  I ran downstairs and grabbed my camera, and tried to get some good shots.  Here, we have a male western bluebird (Sialia mexicana), perching on one of the blocks of sandstone from the historic Quarry 5 in Morrison.  This block contains dinosaur bone, making it ironic that the bluebird, a dinosaurian descendant itself, perched upon the block.

There were plenty of American robin (Turdus migratorius) running around, and got a few shots of them!

As we talked about in a PREVIOUS POST, winter causes many birds, including the American robin, to decrease their territoriality, and flock together.

There were several lark bunting (Calamospiza melanocorys) hopping around.  The lark bunting is actually the state bird of Colorado!

A European starling (Sturnus vulgaris) probes the ground.

There were several more male and female western bluebirds flitting around, and I got some pictures of them that I really like!  Below is a female perched on the fence next to the Jurassic Garden!

A male perched on a fence.  Notice the sexual dimorphism displayed here; the male displays much more vibrant plumage than does the female.

A female perched near my car!

Sometimes, I am really, really bad at identifying birds.  Below are two pictures of birds that I think I have identified correctly, but am not positive.  The first I think is a picture of a pair of chipping sparrows (Spizella passerina).

This one gave me a bit more trouble.  I think this bird is either a western wood-pewee (Contopus sordidulus) or a least flycatcher (Empidonax minimus).

Finally, a yellow-rumped warbler (Dendroica coronata)!

Works Cited:

Robbins, C. S., Bruun, B., & Zim, H. S. (1983). Birds of North America. New York: Golden Press.

Stokes, D. W., & Stokes, L. Q. (2010). The Stokes field guide to the birds of North America. New York: Little, Brown.

Eye Black: What Works for Football Players Works for the Cheetah

I remember when I was younger I would always wonder why baseball and football players wore black paint under their eyes.  My dad told me that the "eye black" was to help to reduce the glare that their eyes received from the sun.  Although some people seem to disagree whether or not this is effective for human sports players, it seems that several animals have evolved a similar pattern on their face!  But before we dive in, a very special thanks to Anne Price for her help with this post!

I imagine that there are a number of stories told by native peoples of Africa that explain the tear marks of the cheetah, which you can see in the picture above.  The one that I have heard before (which you can read by clicking HERE) tells of the cheetah being told by lions that she was not a cat, and instead was a dog.  The cheetah then went to talk with the wild dogs.  But the wild dogs also kicked the cheetah out, saying that she was a cat and not a dog.  The cheetah, sad with the fact that she did not seem to belong to either group, cried so much that the tear marks were burned into her face.

Some scientists believe that these black marks, which they called "malar stripes" or "malar marks," actually evolved to help the cheetah see in sunny conditions, by reducing glare and keeping the sun out of its eyes.  This would have been the original "eye black," a phenomenon whose roots extend back much further than the origins of baseball or football.  I was surprised when I was researching this natural eye black, as I thought it was a commonly cited fact that cheetahs had this eye black to reduce glare.  However, many of the sources just mentioned the malar stripes, and didn't actually address their function.  

In the book "Big Cat Diary: Cheetah," Jonathan and Angela Scott propose an alternative hypothesis.  Though they do mention the anti-glare hypothesis, the Scotts suspect that a more likely alternative is that the tear-marks serve to "accentuate facial expressions," which they say would be an "important consideration in social interactions with other cheetahs."  The tear marks, "along with the growls and hisses that are an important part of a cheetah's defensive repertoire," might "deter competitors from approaching."  While this is well and good for the cheetah, and is likely at least part of the reason why the cheetah has the malar stripes, I have a difficult time believing that this is the only reason why some animals evolved the stripes.  We will get to my reasoning in a second.

What I find really interesting about these stripes is that they are unique to the cheetah in the cat world.  The cheetah, as is mentioned in the African story above, is a very unique cat, different in many ways from others felines.  One way in which the cheetah is different is that it hunts primarily during the day, and is much less a nocturnal animal than most cats.  If you look at the eye of your house cat, look for two things.  The first is the size of the eye.  Though the cat is quite small compared to you, Mr. Whiskers has eyes that are only a bit smaller than yours!  Second, look at the pupils.  Unlike the pupils of humans that stay circular regardless of the level of dilation or constriction, cat pupils constrict to tiny diamond slits, but dilate to large circles.  This is because most cats are active at night and during the day, and in order to protect their eyes in a variety of light conditions, they have evolved very mobile pupils.  

My cat Chimney.  Notice her slit pupils.  And the One Direction pillow in the background.  Photo Credit: Dani Neher

The cheetah does not have diamond pupils, and instead has round pupils.  This stems from the fact that cheetahs are primarily diurnal, and usually hunt during the day.  According to the Scotts, "just like birds of prey," cheetahs have a "patch of highly light-sensitive cells on the retina known as the fovea."  These cells provide the cheetah with the "most precise visual perception," and enables them to "spot prey from as far away as 5 km (3 miles)."  I find this comparison to birds of prey interesting, as both the cheetah and the prairie falcon, another animal with malar stripes, would have the need to be able to spot prey from a great distance, and in sunny conditions.  This large North American falcon has very similar streaks of brown feathers beneath its eye, which flow down the face.  According to "The Prairie Falcon" by Stanley Anderson and John Squires, the "black mustachial stripes near the eyes...may further reduce glare."

This idea is supported by other bird of prey experts, such as Anne Price, the Curator of Raptors at the Raptor Education Foundation in Colorado.  Eager to learn more about the similar stripes on the face of the prairie falcon, I emailed Anne, and here's what she had to say:

It’s meant to reduce glare by having the sun strike or be concentrated in the area beneath the eye, leaving the area above in proper contrast.  The black lines under the eyes of cheetahs, most falcons (gyrfalcons and merlins being notable exceptions) and even flickers have malar stripes, though in flickers they serve as signals for courtship, not for better visibility of prey species!

Other falcons that have the malar stripe include the American kestrel....

....and the peregrine falcon.

Not all falcons have the malar stripe, however.  As Anne mentioned above, gyrfalcons and merlins are notable falcons that don't have the malar stripe, but here is another one: the African pygmy falcon, the smallest of the African raptors!  This is a picture that I took of one at the Denver Zoo.

Furthermore, the black streak under the eye is also seen on the face of many species that the cheetah preys upon.  According to the cheetah section in "Wild Cats of the World" by Mel and Fiona Sunquist, 91% of cheetah kills in the Serengeti are Thomson's gazelle.  In Kruger National Park, 68% of kills were the impala, and in other areas such as Botswana, springbok are an important part of the diet as well.  73.9% of the kills made by cheetahs in Nairobi National Park were Thomson's gazelle, Grant's gazelle, and impala.  As you can see in the pictures below, all of these antelope have that black streak under their eyes, though it is less pronounced in the Grant's gazelle and impala than it is in the Thomson's gazelle.  One of the biggest reasons for markings on an animal that don't aid in camouflage or sexual selection (i.e. differences between male and female that are used to attract a mate) is to help with species differentiation, so that they don't waste valuable time and resources attempting to breed with each other.  But since all of these antelope have the black tear marks, as well as both genders of the species, that's probably not the role that the tear marks were playing.*

A Cuvier's gazelle at the San Diego Zoo, which also has very similar malar stripes.

A Speke's gazelle at the San Diego Zoo, yet another gazelle that has the same sort of malar stripes.

It is these antelope that make me wonder whether the cheetah evolved the malar stripe to "accentuate facial expressions," as proposed by the Scotts.  In my experience, antelope such as the Thomson's gazelle don't really go around making faces at each other, at least nowhere near as much as cats do.  The fact that both the predator and prey in this scenario possess the same adaptation makes me wonder whether coevolution has occurred.

Coevolution is a biological phenomenon in which the evolution of one animal influences the evolution of another.  A classic example would be flowers and the insects that pollinate them.  Flowers need their pollen to be carried to other flowers in order for reproduction to occur.  Oftentimes, these flowers employ the use of bees and other insects to do the job for them.  But to make it worth their while, the flowers supply the insects with a delicious meal of nectar.  When the insects land to suck up the nectar, they also pick up some pollen.  Then, when they fly off to another flower to indulge in some more nectar, they unknowingly deposit some of the pollen, and simultaneously pick up some more!

I find it possible that coevolution has occurred in regards to the cheetah and its prey.  Imagine if a certain lineage of cheetah evolved that had the black tear marks beneath their eyes, while the rest of their cheetah brethren did not have this black streak.  If the black streak did help them see their prey a little better by reducing glare, then perhaps these cheetahs were more successful hunters, and produced more offspring because of it.  Suddenly, the gazelles and impala are faced with a formidable foe that can suddenly see farther than they used to be able to.  In order to compensate, it's possible that the antelope who also had black streaks under their eyes were able to see farther as well, and spot the approach of a predator from a greater distance.  Strangely enough, I haven't been able to find anything anywhere suggesting that coevolution might have occurred here, so who knows!  I'm just throwing this out there, I'm not saying that's definitely what happened, but it's a prospect which I find intriguing and thought worth sharing with all of you.

*To read more about species differentiation and the role it plays in the success of biological organisms and species diversity, click HERE to learn more about the effects of logging on a type of fish called cichlids.

Works Cited:



An interview with Anne Price.

Anderson, Stanley H., and John R. Squires. The Prairie Falcon. University of Texas Press, 1997. (accessed December 16, 2013).

"General Information About the Cheetah." Cheetah Conservation Fund. http://www.cheetah.org/?nd=general_info (accessed December 16, 2013).

"How The Cheetah Got Its Tears." Cheetah Conservation Fund. http://www.cheetah.org/?nd=story_cheetah_tears (accessed December 16, 2013).

Stokes, Donald, and Lillian Stokes. The Stokes Field Guide to the Birds of North America. New York: Little, Brown and Company, 2010. (accessed January 23, 2014).