Repeat the experiment with other scents. Did all of your scents diffuse through the balloon? The balloon has tiny pores or openings on its skin.
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A molecular analysis of recovered Miracinonyx DNA published in by Ross Barnett and colleagues confirmed this relationship. Regardless of their ancestry, though, the sleek form of Miracinonyx has inspired paleontologists to envision the carnivore as a cheetah copycat. The long legs and enlarged nasal openings — for better oxygen intake while running — appear to indicate that Miracinonyx sprinted to chase down prey.
Pronghorn expert John Byers took this assumption to propose that pronghorn co-evolved with the false cheetahs and other fast carnivores, making the speed of the herbivores a trace of an evolutionary arms race that ended 10, years ago. Advocates of Pleistocene Rewilding — the controversial notion that Old World species should be introduced to New World parks to kickstart evolutionary interactions that have gone dormant since the loss of American megafauana — have even suggested that African cheetah be brought to North America to reinvigorate the evolutionary competition that gave pronghorn reason to run.
I can only wonder what pronghorn would say to this misguided idea. The logic is simple — fast predator, faster prey. The problem is that visions of false cheetahs running down pronghorn are based on the appearance of speed rather than hard evidence. In fact, the ecological context of Miracinonyx bones hints that these cats were not simply speedy specialists who prowled open grasslands.
In their study, Van Valkenburgh and collaborators noted that later Miracinonyx bones have been found from Nebraska to Pennsylvania and Florida in deposits which accumulated under varying conditions. These cats were apparently just as at home among coastal savannahs as mountain stream valleys.
More recently, at the Society of Vertebrate Paleontology meeting, John-Paul Hodnett and coauthors presented a poster about Miracinonyx that frequented caves in prehistoric Grand Canyon, Arizona.
There was a distinct lack of fast-running, open-savannah prey animals during the same time period — the researchers noted that the extinct mountain goat Oreamos harringtoni was the most common possibly prey animal in the area. Rather than speeding over the grasslands, Hodnett and colleagues reported, the Grand Canyon Miracinonyx may have lived like snow leopards, bounding down sheer rock faces in pursuit of mountain goats.
There are a few ways we could find out a bit more, though. And while such a find is a longshot, perhaps a trackway made by a Miracinonyx running or launching itself into pursuit could tell us about how these cats actually moved. Both lines of evidence suffer from the complexities of accurately attributing a particular trace fossil to a trace-maker, though. Another route may be to compare the isotopic clues in the teeth of Miracinonyx to those of their potential prey, as was recently done for two sabercats and a bear dog found in Spain.
By ascertaining where herbivores were feeding, and how geochemical signatures of prey became locked in carnivore teeth, paleontologists could narrow down the preferred habitats and prey of Miracinonyx. Furthermore, a poster presented by Natalia Kennedy and coauthors at the SVP meeting outlined a new attempt to compare the spine of the modern cheetah to that of Miracinonyx and other extinct cats to see how skeletal anatomy influenced flexibility and lifestyle.
Miracinonyx might have been the reason for the swiftness of pronghorn. False cheetahs and archaic pronghorn overlapped in time, if not habitat, for as much as three million years. But saying Miracinonyx was certainly a speed demon that gave pronghorn a reason to run is only supported by the barest amount of evidence. The Just-So story of how the pronghorn got its speed has yet to be tested by the evidence which resides in the fossil record.
Adams, D. The Cheetah: Native American. Barnett, R. Evolution of the extinct sabretooths and the American cheetah-like cat. Current Biology. There is no magic. There are no tricks. No one adaptation by itself makes the difference. Pronghorns are just better at everything that affects sustained running speed. That is as expected. There is no use in having any one link in the system with extra capacity relative to any other—there is no point, for example, to have an oxygen delivery system to the muscles that greatly exceeds the capacity of those muscles to utilize the oxygen.
As Gary Turbak says in his loving treatment of this magnificent creature:. History is full of accounts of antelope apparently choosing to race a steed, car, train, or whatever just for the sport of it…. Is it too much to think when the prairie air hangs cool and crisp that pronghorns do not rise from their beds, stretch, and race off across the dewy morning grass at top speed…just because it feels good?
Why would a sleek pronghorn in its prime not want the wind to whistle by its ears as it flies along at fifty or sixty miles per hour? Or want to hear the rhythmic pounding of its hooves on the prairie sod?
Or to burst with bestial pride at being the best there is? Biologists may scoff at this, but as surely as sunrise, this happens. It has to. Most biologists would not scoff at the message in this quote at all. Play serves a vital function in many animals. It serves the ultimate function of practice, and it is motivated by pleasure.
Pleasure is a proximate mechanism for achieving many ultimate benefits. Byers, who has made a detailed study of play, has found that to the fawns of pronghorn antelopes and other ungulates that require speed to survive, play is fast running that may be interspersed with twists and leaps. It has long been argued that such exorbitant, apparently useless expenditure of energy is a survival cost.
Contrary to this supposition, Byers found that those pronghorn fawns who played more had a greater chance of surviving the first month of life than those who played less. We may hunt by choice using less effective weapons, such as antique guns and even bows and arrows, when we could use high-powered rifles with telescope sights instead. For us, hunting is not now always a necessity. It is also play. The answer evolutionary biologists usually give to this question is that everything has a cost.
One potential cost of a high O2 max could be that it results in an elevated basal metabolic rate. That is, having a large muscle mass packed with mitochondria might mean that as in a car with eight cylinders that can never be shut off and must always at least idle, when compared to a car with only four cylinders more is squandered in the long run.
However, goats are not known to be picky or finicky eaters, and it turns out that antelopes at rest eat less food than similar-sized goats. It makes them vulnerable to periods of cold and snow, when energy expenditure must rise for heat production but food may be scarce.
In the harsh winter of , thousands of antelopes died in Wyoming. And fences. The animals were unable to escape the weather by migration, and piled up dead in droves behind fences. They have powerful jumping capability, but they have not evolved, like forest-dwelling deer, the behavior of making vertical jumps. Although the task would be trivial for its body, its mind does not reach that high.
The mind leads, the body follows. No studies are available, but I suspect that the antelopes may be more compromised than is assumed with respect to ultrarunning endurance as well, and for the same basic reason that they are susceptible to periods of cold and snow. Pronghorn antelopes reduce body weight not only by having little fat but also by having a very small stomach—about half the size of comparable slower grazers.
They are therefore compromised for endurance, because to continue to run fast for long durations they are forced to refuel at frequent intervals, and on high-energy-containing food at that. Pronghorns are picky eaters, choosing broad-leafed plants generally growing best where herds of bison have grazed off the grass. Although the pronghorn antelopes, because of their exceptionally high aerobic capacity, have been touted as the ultimate mammalian endurance athletes, nobody has yet put the endurance of the pronghorn antelope to a serious scientific test.
At least two human runners have tried. Dave Carrier, who works on the biomechanics of locomotion at the University of Utah biology department, and his brother, Scott Carrier, had heard tales of how in the old days Navajos and Paiute hunters had chased antelopes to exhaustion.
By joining others who were still fresh, these animals were essentially using relays to outrun their pursuers. As part of a herd, an antelope also uses the others as a shield. Then it no longer needs to be able to outrun the predator, only the slowest member of its group.
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