When it comes to probing the prowess of animal athletes, biologists could take a lesson from the frog jockeys of the Calaveras County Fair
THE Calaveras County Fair is much like any other rural country show; there are fairground rides, prizes for the best livestock and a children’s parade. Many come simply to sit around, drink beer and enjoy the early summer sunshine. But the undisputed highlight is the annual Jumping Frog Jubilee.
Inspired by the story that launched Mark Twain’s literary career, in May every year, the small town of Angels Camp in the foothills of the Sierra Nevada pays homage to the jumping prowess of the humble green bullfrog. It is a four-day tournament, but Sunday afternoon provides the climax when crowds from across California file on to makeshift seating around a central outdoor stage to witness the year’s top crop of “frog jockeys” do battle in a jump off. The goal of the competition is to see who can make their frog jump the furthest in three straight leaps. There’s a $750 prize at stake, although that’s not the main reason people compete. “It’s a historic tradition,” says Bob Lema, one of the competition’s organisers.
Advertisement
How come frogs at the Calaveras County fair jump so much further than those in biology labs? (Image: Jim Wilson/New York Times/Redux/eyevine)
Henry Astley had never heard of the Jumping Frog Jubilee, but in a university laboratory on the opposite side of the US, he was engaged in a similar pursuit. Astley has always been a critters kind of guy, with a particular interest in the slimy and scaly. His first research project found him in a snake biomechanics lab. Then when he was looking for a PhD, fortune led him to Providence, Rhode Island, and Brown University’s frog lab. There he had been persuading his menagerie of frogs and toads to jump as far as possible so as to study their capabilities.
Video: Under study: The frogs of Calaveras County
Biologists are fascinated by animals whose performance is at the extreme end of a spectrum – the animal Olympians. And when it comes to jumping, frogs are the vertebrate champions. They have long been used as the model system for understanding how muscles work, just as fruit flies are the model system for genetics. One mystery is how frogs generate the massive explosion of power that enables them to jump great distances. “Right now, we don’t have a great deal of understanding about how muscles power accelerations,” says Astley. Some frogs, including tree frogs, produce power well beyond what their muscles should be capable of. The belief is that their joints function as a kind of catapult, enabling them to slowly load energy and then release it in one powerful burst. However, it is not clear whether all frogs can do this, or precisely how the system works. To get to the bottom of it, you need to push frogs to their absolute physiological limit. But how do you make a frog jump?
Over the months, Astley had pioneered several creative ways of coaxing his amphibious charges to leap. Lightly touching them on the back legs was one; blowing on them another. Not every species was equally compliant, but he generally found a way, and was fairly confident of his coaching abilities – until the day his supervisor, Tom Roberts, walked into the lab clutching a Guinness Book of World Records. One of his children had stumbled across an entry, claiming that a bullfrog named Rosie the Ribeter had jumped more than 6.55 metres in three hops at the Calaveras Jumping Frog Jubilee. Astley was highly sceptical. This would make the average single jump 2.18 metres long – far in excess of the 1-metre leaps his bullfrogs had achieved. Neither, to his knowledge, had any other scientific study reported a bullfrog jumping more than about 1.3 metres. So he got hold of a documentary about the jubilee. “That’s when we decided to go there for ourselves and see,” Astley says. Six months later, he and his colleagues were packing up heavy boxes of recording equipment and heading west.
Angels Camp was at the heart of the gold rush during the 1800s, and Mark Twain is believed to have had a small cabin on nearby Jackass Hill, which he used when he wanted to do some gold prospecting of his own. The story goes that he was drinking in a tavern one night in 1865 when he heard a local tale about some miners betting on how far two frogs could jump. Inspired, Twain penned The Celebrated Jumping Frog of Calaveras County, which proved an instant hit, launching his literary career.
Rental frog
In 1928, Angels Camp had its streets paved and, to celebrate, its residents held the first Calaveras County Fair. By then, Twain’s story was well known, so they decided to include a frog jumping contest. Today, this spectacle of frog versus frog attracts up to 35,000 spectators and draws “professional” frog jockeys from across the state – although anyone can have a go with a rental frog captured from a local pond the week before.
When Astley and his colleagues arrived at the fair they set to work filming the frogs and analysing their jumps. “The biggest thing we found is that our prior lab estimates were way, way off,” he says. “Around 58 per cent of the jumps were above the previous maximum recorded in the scientific literature.” How could this be? Intrigued, the team set about interviewing frog jockeys and observing some of the tactics they used. “Generally, the professionals are very secretive about their methods,” says Astley. So finding out what makes a champion frog wasn’t easy.
John and Laura Kitchell have been jumping frogs since the early 1980s, though it wasn’t until 2012 that either of them produced a winner. That year, Laura’s frog, Hillbilly Hopper, jumped a total of 5.93 metres in its three leaps. The following year, their son Riley won with his frog, Shhh: Don’t Tell Morgan, who jumped 6.35 metres – although Laura’s frog had come close to beating the world record in the preliminaries. Even within this loving family, when it comes to frog jumping the rivalries run strong. “I was pissed,” Laura says.
The Kitchells’ successes have been achieved mostly by a process of trial and error. John learned a basic lesson in year one. Frog jockeys usually capture the bullfrogs themselves, going out after dark and shining a torch over local ponds and lakes to light up the frogs’ reflective eyes. “The light blinds them for a few seconds, and then you just swoop in and grab them with a net – or with your bare hands if you get close enough,” he says. In 1983, John and his friend Mike Nash went out and caught six frogs. “We put them in an ice chest with our beer, and then went right up there and bought our entry tickets to jump them,” he says. “We learned very quickly that when you put frogs on ice they go into hibernation. They were sound asleep.” Lesson number one: a frog’s performance is crucially affected by temperature.
Motivational methods
Astley already knew that. Frogs are cold-blooded, and the chemical reactions that enable them to contract and release their muscles are temperature-dependent. They typically jump best at around 29 °C, and his lab frogs were generally quite warm before he jumped them. He noted that professional jockeys stored their frogs in warm environments, although he was not allowed to manually inspect any of the animals. Rental frogs, by contrast, were kept in cooler conditions and had a mean body temperature of between 20 °C and 23 °C – instantly putting them at a disadvantage.
What other tactics do the jockeys employ? Astley found no evidence that any of them trained their animals. In fact, the Kitchells say they keep interactions with their frogs to an absolute minimum after catching them. But, speaking to jockeys, Astley discovered that most did screen frogs before the competition. This might entail running a trial hop to weed out bad jumpers or, like the Kitchells, selecting the best jumpers by eye. “Essentially you’re looking for the same things as you look for in an athlete: big, long legs, a skinny waist and small upper body,” says John. “You sure don’t want a short, fat frog with short, skinny legs.”
But physical attributes alone are not enough; frogs also need motivation. Whereas the amateurs employed a wide range of techniques to persuade their frogs to jump, Astley noticed the tactics used by professional frog jockeys were fairly consistent. They included rubbing the frogs’ hind legs, dropping them on to the launch pad from a short height, and lunging at them head first. The lunge is a crucial method, says John, and to be most effective you need to come up at the frog from low down and behind, imitating one of their key predators, a large fish. “Frogs want to do few things in life: they want to eat, not be eaten, and procreate. We try to trick them into thinking we’re going to eat them.”
“The tactics used by jockeys include dropping frogs on to the launch pad from a short height”
Despite their best efforts, the Kitchells believe that winning the competition is 90 per cent in the hands of the frog. “It’s a silly competition and we work our butts off at it, but at the end of the day if you’ve got a good frog you’re in business,” says John.
In all, Astley’s team recorded 3124 bullfrog jumps over the course of the four day event in 2009. The longest single jump was 2.2 metres, but the winning frog’s three jump tally was still 14.6 centimetres short of Rosie the Ribeter’s record, set in 1986. Overall, there was a sharp drop-off at 1.9 metres, with few jumps exceeding this length, a distribution pattern that suggests Rosie’s record comes close to the true maximal jumping ability of bullfrogs.
“Rosy the Ribeter’s record must come close to the maximal jumping ability of bullfrogs”
Further evidence for this came from the historical records. Since the first recorded jump in 1930, the winning jump distance increased consistently for 50 years, finally plateauing in the early 1980s (see diagram). “This pattern is strikingly similar to the curves of maximum recorded running speed over time for humans, greyhounds and thoroughbred horses,” Astley says. Just as the increase in human running performance can be explained by improved coaching and training techniques, the historical improvement in frog jumping may largely be due to a growing appreciation of frog psychology and physiology, including strategies such as warming the frog before it jumps. It is also possible that over time, competitors have hit upon subpopulations of frogs genetically predisposed to jump well.
The finding that bullfrogs can leap so far has convinced Astley that they employ a catapult mechanism within their limbs, like tree frogs (). “The jumps in Calaveras required more than twice the power the muscle can provide,” he says. This discovery is one small hop in a grander intellectual endeavour to understand the mysteries of the frog’s musculoskeletal system. But as frogs are the model system for muscular activity, studies like this provide wider insights into how our own bodies work. Ultimately, they could have important practical applications – in the design of prostheses and more agile robots, for example.
Astley’s research also has implications for anyone studying maximal performance in animals, whether they be interested in human physiology, the evolution of species or animal health. “The big lesson would be to try to spend time refining the motivational techniques you’re using,” says Astley. In his own lab he developed new scaring tactics – including lunging at a frog with an inflated glove attached to a large stick – and diligently ensured his frogs were at the optimal body temperature for jumping. Researchers should also ensure they test enough animals by checking that when they plot the curve of performance it forms a plateau with a sharp drop off. “If they get curves that are gentle slopes, it probably means they need more data to capture the true maximum,” says Astley, who is now at the Georgia Institute of Technology in Atlanta studying snakes again.
Back in Calaveras County, Sunday 18 May will see the final of this year’s . When it is over, all the frogs will be released back into the ponds whence they came. That has always been the way – which means that somewhere in the San Joaquin valley, the spawn of Rosie the Ribeter are practising their leaps. One day they might be plucked from the water and offered the chance to out-jump their feted ancestor. But, as this story shows, their destiny also lies in the hands of the jockeys that jump them. Because if you want to see how far a frog can leap, you’ve got to offer it some really powerful motivation.
Meet the contenders
Today, frog jockeys at the Calaveras Jumping Frog Jubilee compete using American bullfrogs. Females are larger than males and can be as long as about 15 centimetres from nose to tail and weigh 175 grams. They are not native west of the Rockies, but were introduced a century ago during the gold rush to satisfy the miners’ appetite for frogs’ legs.
Mark Twain’s original “Celebrated Jumping Frog” was probably a California red-legged frog, which is now rare and protected by federal and Californian law. Current jubilee rules would prohibit most from competing anyway, as entrants must be 4 inches (10.2 centimetres) long at the minimum and red-legged frogs average about 8 centimetres.
The minimum length rule was introduced after the 1952 competition when enterprising frog jockeys entered several tree frogs. Usually far smaller than their terrestrial cousins, arboreal dwellers have leg joints that act like catapults giving them a much more powerful jump than their muscles alone could achieve. In the 1952 preliminaries one tree frog leaped 7.62 metres in three hops.
In 1990s, an animal importer from Seattle tried to enter goliath frogs from Cameroon. These can measure 33 centimetres and weigh in at 3 kilograms, so only his smallest frog was able to comply with the rule that contestants put all four feet within the 20-centimetre-wide jumping pad. During the preliminary sessions it did beat the existing bullfrog world record. But in the final, when the pressure was on, it just stood up, waddled about a metre and sat down again.
This article appeared in print under the headline “Hop-a-long strategy”
