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 Americanfalcon 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).
As I mentioned in a post just a few days ago about the Harris hawk (which you can read by clicking HERE), the fantastic dinosaur-themed remodel at the Best Western Denver Southwest is well underway, and the folks over there are making the hotel even more fantastic by having weekly raptor (bird of prey) shows on Saturdays! Each Saturday, Anne Price, one of the folks over at the Raptor Education Foundation, brings over four birds of prey to show to the audience! Last week, they brought over a Harris hawk (which, like I already mentioned, I talked about in a previous post), a prairie falcon, a red-tailed hawk, and a great-horned owl! I have so much information I wanted to share with you...but how! How could I POSSIBLY share all of this information in a non-story like, brain-dumpy fashion? AH-HAH! Another 23-Fact Tuesday is upon us! But before you enjoy, make sure you check out the website for the Raptor Education Foundation by clicking HERE, and checking out the Facebook page for the Best Western Denver Southwest by clicking HERE!
1. This particular prairie falcon actually used to fly down at the Air Force Academy, where many of the cadets have the option of training a falcon!
2. The great-horned owl used to be the only member of the genus Bubo (what a fun name, right?), but around ten years ago, scientists reclassified the snowy owl to be the second member of the genus.
5. In response to this behavior on the part of the falcons, some prey species of bird have developed very tough feathers on their back and such to defend themselves against such attacks.
6. In nocturnal owls, like the great horned owl, the eyes are surrounded by a sort of sensory dish full of hyper-sensitive feathers that can actually detect sound, funneling it into the “dish.”
7. Diurnal owls, such as the burrowing owls, do not have this dish, or at least it is not as pronounced as other owls that are more active at night. The burrowing owl is actually most active at dawn and dusk, although it can function perfectly well at night.
8. Red-tailed hawks apparently love to nest in cottonwood trees. I think I might have actually found a red-tailed hawk nest in a cottonwood tree: hopefully, there will be more information on that in a later post!
A red-tailed hawk nest in what might or might not be a cottonwood tree....Photo Credit: gaiagarden.blogspot.com
9. The great-horned owl that Anne brought in for the presentation is DEFINITELY a survivor: he has survived being shot, hit by a car, West Nile Virus, and being attacked by another owl!
10. Here's the scoop: this particular great-horned owl first came to the sanctuary because it was hit by a car which, in the long run, probably saved its life. The reason why it hit the car in the first place was that it was flying drunkenly about due to the fact that it had West Nile Virus, which had caused its brain to go a little loopy. The owl received the medical treatment that it needed, and it wasn’t until a few years later, when it accidentally broke its leg, that a full X-Ray was ordered, and it was revealed that the owl had a few pellets lodged in its back. The skin had grown around it and completely healed, but yeah. Still. What a trooper!
11. You might have noticed on some of these great-horned owl pictures that the pupil of the left eye is MUCH more dilated than the pupil on the right eye. This is because this great-horned owl is blind is his left eye, due to the brush with West Nile Virus we were just talking about.
12. Later on, there was an enclosure that contained three great horned owls: two males that could fly and an older, grumpier female that couldn’t really fly that well. The two males could EASILY avoid the female by remaining up in the top of the enclosure, where the female simply could not reach them. However, one time, the people walked into the enclosure to find this particular male great horned owl perched next to the grumpy female. The female didn’t seem to be displaying any hostility towards him, so they left them together. After a few weeks, I believe, the female had decided that she had had enough, and attacked the male, and I believe broke his wing. He can fly today, but not terribly well, and not very far.
13. Not all red-tailed hawks have a red tail. There is a wide variety of coloric differences across its vast range, and sometimes even melanistic forms are seen. This DEFINITELY messes with birders!
A melanistic red-tailed hawk! Melanistic, FYI, would be just like a melanistic jaguar, where the coat of the animal is very, very dark, much darker than noraml, due to a pigment issue in its genes! Photo Credit: thenatureniche.com
14. As a matter of fact, none of them have red-tails their first year! At that point in their life, their tails are a darkish gray-brown: muddy and dull with darker brown stripes.
15. The juveniles don’t actually get their red tails until they molt, which, at the time this post is being written (early July) is happening now, in the spring and summer. Here, we have a video featuring the red-tailed hawk, as well as a brief appearance by a pooping Harris hawk (which unfortunately happens off screen)!
16. Besides the owls, only one other type of raptor is able to swivel one of it's toes to face backwards, so that it has two toes pointing forwards and two toes pointing backwards: the osprey! The osprey does this to allow for a more secure grip when catching fish, and the owls undoubtedly do it for much the same purpose when it comes to holding on to their prey.
An osprey, where you have a clear shot of its feet! Photo Credit: www.flickr.com
17. This particular prairie falcon has also survived a brush with West Nile Virus, just like the great horned owl! Anne was telling us that no one really but her would know it, but he far right tail feather on this bird has grown in weirdly ever since the birds dangerous brush with the virus. Here, we have a brief video where Anne talks a bit about this particular falcon's feather!
18. Just like dogs, birds don't sweat. Also just like dogs, birds will sometimes pant to help keep cool! Below, we have a video of the great-horned owl thermoregulating via something we like to call "gular fluttering!"
19. As you can see in this video below, the prairie falcon is being assisted in its thermoregulation by the presenter Anne, who is misting him with some water!
21. The two brown streaks under its eyes help keep some of the light from reflecting into its eyes, just like the black paint worn under the eyes by football and baseball players. Another fascinating example of convergent evolution at its finest!
22. A lot of the time when people think a hawk has gotten in and killed their chickens, its actually an owl.
A fox in the henhouse! I couldn't find a picture of a hawk in a henhouse, and besides, I really liked this picture. Photo Credit: www.hyscience.com
23. For reasons that Anne couldn’t fully explain, other than maybe panic or opportunity, often when an owl finds itself in a pigeon loft, the owl will only pull out and eat one or two of the pigeons, but it will pull off the heads of almost all of them, and leave them there. An interesting and gruesome way to end yet another fun-filled and fascinating 23-Fact Tuesday!
Make sure you check out the website for the Raptor Education Foundation by clicking HERE, and checking out the Facebook page for the Best Western Denver Southwest by clicking HERE!
Today was quite an eventful day, for many reasons! Went to the Zoo Lights at the Denver Zoo with some good friends of ours; learned that Ray Wise is not in X-Men Origins: Wolverine, but is actually in X-Men: First Class; and learned that the building off the highway called "Quaker Steak and Lube" is actually a restaurant, and not a car repair place. Also, on my way to the Morrison Museum this morning, I saw what I am pretty sure was a peregrine falcon, as well as a number of red-tailed hawks and kestrels, and the great-horned owl that I have seen a few times recently perched on the "speed limit" sign on the highway! It was pretty awesome! Oh, and did I mention that one of my fossils might be radioactive?
One of the Zoo Lights was this tiger, but I'm pretty sure he's supposed to go around something a little thicker....
I was talking to Dr. Bob today at the museum, and we were talking about fossil hunting in Texas, chiefly the fossils that I got down there when we went to visit my gramma last Christmas, as well as the fossil dig-site that he has down there. As we were talking, I thought back to the fossilized wood (top picture, the thing with the penny on it and everything to the right and above that piece) that I had picked up in Santa Rosa, New Mexico, on one of the first nights of our trip. I had never been able to figure out what formation or what geologic time period it came from, so I asked Dr. Bob. He said that there are a lot of different aged rocks from throughout the Mesozoic Era (the time of the dinosaurs), from the Triassic to the Cretaceous. Then, as a sidenote, he mentioned that some of the fossilized wood down there tends to be radioactive, sometimes dangerously so. Well then! I am currently sorting this out, but I feel like I don't really have enough to worry about. Famous last words, right?
Today's animal was easier for many of you, and we had a number of good guesses! We had a few close guesses (like the American Kestrel, another North American bird of prey, but we had one totally right answer. This weeks winner is Julie N., who guessed the Peregrine Falcon!
Peregrine Falcon
The Peregrine Falcon is one of my favorite birds, mainly because of how it hunts. It dives at medium-sized birds from up to 3,000 feet in the air, and often dives towards the birds with the sun at its back; that way, its prey has a difficult time of seeing them through the sun's glare. In its dive, speeds of 175 - 200 mph have been recorded, placing it at the terminal velocity able to be achieved by the bird. Some people have reported that the peregrine can exceed terminal velocity but, despite being taken in by this theory for a time, I believe that this not, in fact, true. (I am not that into the math or physics, but I believe it might even be impossible, but I'm sure some of you know that better than me!) Click on the link below to learn a little more, and to see the bird in action!
Although their population numbers suffered tremendous, pesticide-induced blows during the 20th century, they have made quite a comeback throughout the United States. However, it was a close call. Use of pesticides like DDT (commonly known as DEET, used to be common in mosquito repellent before its negative impacts on the environment became fully known) caused the Peregrine Falcon's eggshells to become weak, and they were easily broken. The result of this was very few baby falcons surviving to breed themselves. In fact, at one point it got so bad that the Peregrine Falcon was listed as "Endangered" by the IUCN in the 1950's through the 1970's. It became extirpated, or locally extinct, in both Belgium and the eastern United States. However, now it is labeled as "Least Concern;" an amazing comeback, for an amazing bird.
This picture of the Peregrine Falcon was taken by me, last week at the Reptile Day at Dinosaur Ridge, near Golden. My friend Masaki Kleinkopf and I went and were able to see a few pretty cool things, the Peregrine Falcon being just one of them. I highly recommend going to check out the Ridge, as well as the museum they have there, it is really quire interesting!
Don't forget to check in later in the day for this week's challenge!
