Notes on Animal Health, June 2024: Can You Really Outrun a Horse?

With the Paris 2024 Olympics rapidly approaching, many of us are looking forward to watching the best human athletes in the world compete for their home countries. As amazing as many of these athletes are, one wonders how other animals, specifically other land mammals, might compare.

When it comes to speed, humans do not rank very high. Currently, Usain Bolt holds the world record for the 100-meter dash at a time of 9.58 seconds, which translates to a speed of over 25 mph.  As impressive as this record is, it pales in comparison to the fastest land mammal, the Cheetah. Under ideal conditions, captive Cheetahs have been clocked at speeds approaching 65 mph, but their wild brethren routinely exceed 50 mph, and can exhibit acceleration power up to 120 watts/kg, which is more than four times what Usain Bolt produced during his world record setting run. There is evidence that Pronghorn Antelope can also run at speeds over 50 mph for short periods of time, and they have been observed running at an average speed of 40 mph for ten minutes or more.

It is not just wild animals that are capable of exceptional speed. Horses routinely run 25-30 mph and top racehorses can reach 40 mph or more. The top speed of our canine companions is much more variable due to differences in their body structure; no one expects a Bassett Hound or a Bulldog to set any speed records. However, breeds that have been bred specifically to run, including Greyhounds, Salukis, and Ibizan Hounds, can attain speeds of 40 mph or faster. So, in terms of speed, humans are nowhere near the front of the pack.

What about endurance? In the popular literature humans are often referred to as the best endurance athletes among all mammals, but it is difficult to find objective data supporting this. Supposedly, at longer distances humans have biomechanical and thermoregulatory advantages over other mammals. At what distance and what temperature these evolutionary advantages become apparent, however, has not actually been determined. Evidently, a mile is not far enough. A typical racehorse, for example, can gallop a mile in around one minute and 50 seconds, and the world record at that distance is held by a horse called Mandurah, who in 2010 ran a mile in one minute and 31.23 seconds. By contrast, in 1999, Hicham El Guerrouj ran the fastest mile by a human in three minutes and 43.13 seconds. What about a marathon? While there are no 26.2-mile races typically run by other species, the Man versus Horse race has been staged regularly in Wales since 1980. The rugged 22-mile cross country race has only been won by a human four times in forty-two years.

What about ultramarathons? According to Runner’s World, Lithuania’s Aleksandr Sorokin holds the world record for running 100 miles in ten hours, 51 minutes and 39 seconds. By contrast, the world record for a horse completing a 100-mile race is under 6 hours. The fastest completion of The Tevis Cup, which is considered one of the most grueling 100-mile equine endurance competitions because of its mountainous course in Northern California, was accomplished in 1981 in ten hours and 46 mins by Boyd Zontelli on Rushcreek Hans. So, even at ultramarathon distances, humans are not the super endurance athletes some claim them to be.

So, how did we come to believe that we are such better endurance athletes than other land mammals? Mostly by relying on hypothetical speculation rather than objective data. For example, it was hypothesized that the human’s ability to run at moderate speeds for long periods of time without overheating was unique and provided a distinct advantage in athletic endurance. Specifically, it was proposed that while humans can run at 4 to 9 mph for long periods of time, quadrupeds, such as horses, can only gallop or canter (a slower, modified form of a gallop), for around twelve to fifteen miles before becoming fatigued. However, quadrupeds don’t have to gallop or canter, they can also trot, a metabolically efficient gate that typically covers 5 to 10 mph. During endurance competitions, horses typically use a combination of gaits, depending on the terrain and environmental conditions, maximizing their endurance capabilities.

Horses and other equids also sweat like humans, allowing them to dissipate heat through evaporative cooling. This makes them less prone to hyperthermia than other quadrupeds. That said, horses are large and have a relatively low surface area-to-volume ratio and greater thermal inertia, so they lose heat more slowly than humans. In addition, their sweat contains more electrolytes than humans, which makes them vulnerable to electrolyte imbalances during intense exercise in hot climates. Therefore, theoretically, it is possible that a human could beat a horse in a 100-mile race run in a hot, humid environment, but based on actual race results, horse are generally far superior endurance athletes than humans.

In a similar manner, some dogs, under the right environmental conditions, may be superior to humans at completing endurance runs. It is true that because dogs do not sweat, they are much more suspectable to over heating than humans or horses. However, under cold conditions, where heat dissipation is of limited concern, it is likely that the average sled dog, which can run up to one hundred kilometers per day for up to ten days, could outpace a human.

Comparisons quickly become much more difficult when we consider more complex movement. Which species’ acrobatics should we compare to the amazing twists, leaps, and tumbles exhibited by Olympic gymnasts? Squirrels for example, make split-second, potentially life-threatening decisions of biomechanical capability depending on their skillful practice and use of acrobatic maneuvers. And Gibbons exhibit an amazing form of locomotion called brachiating, swinging through the jungle from branch to branch at up to 35 mph, bridging gaps as wide as 50 feet with a single swinging leap.

There are many different athletic skills we could compare between humans and other mammals, and it is likely that if we only looked at a single skill, we could find an animal species that was superior. That said, few animals exhibit the diverse array of athleticism that human do. Humans, not only run, jump, tumble, swim and lift, we throw balls and spears, use poles to lever ourselves over bars, and ride on the backs of other species, while running and jumping. Perhaps the diverse array of skills exhibited by humans is one of the reasons we watch the Olympics with such rapt attention. Let the games begin.



First Five
First Five is our curated list of articles, studies, and publications for the month.

1/ Your dog may really be hungry all the time
In 2016, Eleanor Raffan’s laboratory at the University of Cambridge discovered that a mutation in the POMC gene was associated with body weight in Labradors. Recently, the lab published a follow on study, which demonstrated that dogs carrying a specific mutation in the pro-opiomelanocortin (POMC) gene displayed increased hunger and a 25 percent reduction in resting metabolic rate, and not surprisingly, given these effects, increased adiposity. By providing a natural model to explore the biology of different POMC-derived neuropeptides, these hungry pups may give us insights into human physiology and the role of these gene products in metabolism and obesity.

2/ Horses were part of the West long before there were cowboys
Horses have played a significant role in many indigenous cultures in North America, but understanding their integration and spread has relied primarily on observations from 18th and 19th century European and American settlers. For example, it has been assumed that horses first began to spread into the American Southwest after the Pueblo Revolt in 1680. However, a recent study showed that by the turn of the 17th century or the early 1600s, domestic horses were already deeply integrated into indigenous societies throughout the Great Plains and northern Rocky Mountains. Genetic testing of horse remains demonstrated that they were primarily of Spanish or Iberian heritage, which coincides with the types of horses Spaniards brought to the Americas. Later, British horses began contributing to the genes of horses on the Great Plains.

3/ Canine Companions may help with signs of Post-traumatic Stress Disorder (PTSD)
The results of a recent study of 156 service members and veterans found that compared to the standard of care, the presence of a trained psychiatric service dog lowered PTSD symptom severity and was associated with higher psychosocial functioning. Psychiatric service dogs may be an effective complementary intervention for military service–related PTSD.

4/ So that is why my dog does that?
Many of us may wonder why our dogs are so particular when it comes to where they poop. A study conducted on 70 dogs of 37 different breeds, over a two-year period, concluded that when earth’s magnetic field (MF) conditions were stable, dogs preferred to excrete with their body being aligned along the North-South axis. When MF conditions were unstable, no directional preference was exhibited. Since the MF is stable for only about 20% of the daylight period, these findings might provide an explanation for why many magnetoreception experiments are hard to replicable. They may also help us be a bit more patient with our dogs, after all they are just trying to follow the pull of the Earth.

5/ Sharing the biosphere, all of it
With the COVID-19 pandemic in our recent memory, and H5N1 avian influenza front and center, the spread of viruses from animals to humans is a real concern. However, a recent study found that when it comes to the spreading of disease, other animals have more reason to fear us than we them. Investigators leveraged the ~12 million viral sequences and associated host metadata hosted on National Center for Biotechnology Information databank to assess the current state of global viral genomic surveillance. Additionally, they analyzed ~59,000 viral sequences isolated from various vertebrate hosts using a bespoke approach agnostic to viral taxonomy to understand the evolutionary processes surrounding host jumps. The analysis found that when viruses move between humans and other animals, in 64 per cent of cases it is humans infecting other animals – rather than the reverse. While zoonotic disease spread is a serious problem, it is important to keep in mind that we can and often do spread viruses to other species.

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