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Science and Footprints


Michael Dennett

Skeptical Inquirer Volume 32.6, November / December 2008

A recent article in a scientific journal argues that alleged footprints from the Patterson film site provide evidence for Bigfoot. A review of the circumstances suggests a different conclusion.

In 2007, D. Jeffrey Meldrum, a professor at Idaho State University, published a paper in a scientific journal1 arguing that footprints from the site where Roger Patterson filmed his infamous 1967 Bigfoot footage support the idea of a giant North American ape. He has even given it a scientific sounding name: Anthropoidipes ameriborealis. Crammed with scientific jargon, the paper repeatedly refers to casts of footprints located at the Smithsonian Institution. Meldrum, quoting the editor of Nature, notes that perhaps it is “time for cryptozoology [the study of unknown animals] to ‘come in from the cold.’” To complete the impression of scientific accountability, Meldrum writes, “Much of the more serious literature on the subject [of Bigfoot] has been written by bona fide scientists with anthropological or biological credentials from recognized institutions.”2

To understand the significance of the Meldrum paper, a little background is needed (for a good overview, see Benjamin Radford’s article “Bigfoot at 50,” SI March/April 2002).3 Among supporters of the idea that North America is home to a giant bipedal ape, known as Bigfoot or Sasquatch, almost all agree on the authenticity of the Patterson-Gimlin film. The 952 motion-picture frames, allegedly shot by Patterson on October 20, 1967, and seen many times on television, is considered the most impressive evidence for the existence of the giant creature—the star “proof” in almost every book making a case that Bigfoot is a real animal. Unfortunately, the distance of the “ape” figure from the camera and the resolution of the film (the original transparencies are only 16mm) limit the film’s practical value.

The image is striking; even some skeptics are impressed with the footage. But several issues, besides a complete lack of subsequent corroborative evidence, cast doubt on the film’s authenticity. Significant and troubling is the fact that the original film is missing. More importantly, three key issues cannot be resolved. According to Patterson and his partner that day, Bob Gimlin, the film was “mailed” from California on a Friday evening (approximately 9 p.m.) and arrived in Yakima, Washington, the next day. Supposedly processed on Saturday at an unidentified photography lab, the film was viewed by several Bigfoot buffs (including the late René Dahinden and John Green) on Sunday. The two surviving witnesses to these events, Bob Gimlin and Patterson’s brother-in-law and financial partner Al Detley, have been unable or unwilling to explain how the film got to Yakima so quickly (in an era before overnight couriers), how the film was processed so quickly (in a time when development normally took a week), or even where the processing took place.4

Patterson’s sketchy reputation looms over all of these issues. Most Bigfoot believers admit that Patterson was no one’s choice for a reliable witness. In his authoritative 1992 monograph on the film (“Bigfoot at Bluff Creek,” a Bigfoot Times special), Daniel Perez, perhaps the film’s strongest supporter, called Patterson “shady.” Other Bigfoot investigators have not been as complimentary.

A recent book by Greg Long, The Making of Bigfoot,5 cast further doubt on the film. Long establishes in his book that Patterson was shadier than even most of those familiar with the story imagined. Of course, just having an unseemly past does not make the man a hoaxer, but Long convincingly portrays Patterson as a man with the ability, aptitude, and motive to fake a Bigfoot film. Through multiple interviews with people, both friends and acquaintances of Patterson, Long creates an unflattering but believable image of the most important man to the Bigfoot story. Long bolsters his arguments with objective data such as court records, contracts, and photographs.

Meldrum claims that “both the [Patterson] film and the tracks [supposedly recovered at the site] have been intensively studied by numerous researchers.” But do the plaster casts really lend support to Patterson’s account?

A careful examination of the circumstances of the footage suggests instead that the footprints are a hoax.

A little background is necessary. Purported Sasquatch footprints, in most instances, lack a chain of custody. The impressions are not normally associated with a specific individual, nor are the environmental conditions or context of the time the prints were made usually known. The moisture content of the soil, soil mineralogy, organic content, grain size, or the mode of traverse by the animal (was it bounding across the terrain or tiptoeing) are seldom reported. In the case of the Patterson film, we need not speculate on any of these parameters, because the film site is available and we know the alleged creature’s gait, the conditions at the time, and many other factors.

Although Patterson is now dead, his filming partner Bob Gimlin (who supposedly stood nearby with his rifle ready) gave a detailed account of the events on several occasions.

Author John Green interviewed Gimlin in 1992 and videotaped the session. In 1997, the interview was transcribed and published on Bobbie Short’s Bigfoot Web page6 and through this interview we get Gimlin’s story.

“I rode the big horse,” he tells Green. “The horse that I was riding was around 1,200–1,300 pounds. I rode him along side the [Bigfoot] tracks with this new film in the camera [and] Roger took pictures of how deep the horse’s prints were in the soil compared to the creature’s tracks. Then I got up on a stump, which was approximately three to four feet, you know? We didn’t measure it, probably should have. Anyway, I jumped off with a high heel boot as close to the track as we could. Then we took pictures of that to illustrate the depth that my footprint went into the same dirt with a high heel cowboy boot, and at that time I weighed 165 pounds. These were all things that we did prior to leaving the scene.”

Were the plaster casts of the creature’s alleged tracks made on the same day? Gimlin answers, “Yes we did, in fact right that afternoon. By the time we got the tracks cast . . . it was getting late.”

Green asks, “[Do you] remember how deep the horse tracks were compared to that of the Sasquatch tracks?”

Gimlin replies, “The horse tracks were not as deep as the Sasquatch tracks of course. I just walked the horse through. I walked him as slow as I could but you figure he is distributing his weight on four feet. The tracks were better than half as deep but they weren’t as deep as the tracks of the creature.”

At this point in the interview, Green notes a contradiction in Gimlin’s account and asks him, “You have estimated this thing [at 300 pounds] a great deal less than the horse and yet the footprints were deeper, what explanation could you think of?”

Gimlin replies, “there was no way of really knowing. We knew it had to be heavier than it appeared to be when we first saw it. Of course, we thought the horse’s weight was distributed on four feet, and I’m not good with the mathematics of such things, but . . . if you figure 1,400 pounds [for horse and rider] distributed on four feet would be about 350 to 400 pounds, so we figured it must have weighed much more than we originally figured.”

Figure 1. Copy of one of the casts of the “tracks” from the Patterson film site.

Figure 1. Copy of one of the casts of the “tracks” from the Patterson film site.

The fact that something is seriously wrong with Gimlin’s account should have been obvious to Bigfoot researchers. A horse is a big creature, and because its feet are relatively small in comparison to its weight, a horse makes deeper and more visible tracks than almost any other animal. The depth of an impression is not only based on the weight of an animal but also on weight distribution as a function of foot size and downward force at a given point, which is expressed in terms of pounds per square inch.

Is Gimlin’s account credible? Forest Service worker Lyle Laverty, who was on the scene the following Monday, said he “walked along the sand adjacent to the tracks and didn’t come anywhere close to sinking to that kind of depth.”7

Figure 2. Elevation view of the same cast showing a remarkably deep impression with the maximum depth just behind the ball of the foot.

Figure 2. Elevation view of the same cast showing a remarkably deep impression with the maximum depth just behind the ball of the foot.

Laverty also took photos of some of the impressions showing they were about one-inch deep in the substrate, something confirmed by duplicates of the original casts (see figures 1 and 2).8

Recently when I talked with Laverty, he confirmed his statement about the depth of the tracks. To clarify, I asked, “And the horse’s hoof prints were deeper than your foot prints?”

“Of course,” he answered.9

John Green viewed a second film reportedly showing the making of the casts. In his 1978 book Green notes that “There was also some film taken later when they were making casts of the tracks. It seems to have shown that when the men walked beside the tracks their feet did not sink appreciably into the packed sand. The prints of the creature on the other hand, sank about an inch deep, indicating tremendous weight. Its feet measured fourteen inches in length, five inches in width at the ball, and four inches at the heel. The prints were flat10 [emphasis added], and there were five toes of fairly human pattern, except that there was less difference in size from largest to smallest. The men [Patterson and Gimlin] made beautiful casts of both left and right feet.”11,12

Gimlin is correct when he says he is not good with numbers; let us do the math. For an experimental comparison, I obtained tracings of the footprint of several horses,13 and their size, weight, and hoof measurements agree with Gimlin’s description of his horse. From the interview Gimlin tells us, “the hoof print area, if you’re familiar with sizes of horses’ hoof prints, well the horse wore a size one shoe, which is not quite six inches in diameter, probably more like five inches in diameter with a number one shoe on the front feet. The shoes were a little bit smaller on the back feet. They were size ones trimmed down is what they were.” At another point, he describes his horse as sixteen hands high.

The three horses in my sample were 15.3 to 16.1 hands high, and all had hooves approximately five inches in diameter. Asher, a 16.1-hands-high horse who weighs about 1,300 pounds and wears a size one shoe, was the closest fit. Asher’s hoof covers an area of 20.5 square inches. Of course, horses make the impressions as they walk or run, which means when they are walking they distribute their weight on two or three feet. The surface area of three of Asher’s hooves is 61.5 square inches. (The two other horses had a total area for three hooves as follows: Jasmine 63.6; Sonny 64.5 square inches.)

What about the surface area of the purported Sasquatch foot? With a copy of the figure’s alleged footprint, it is easy to compute its14 supposed displacement.

Figure 3. View of a horse’s hoof. This is a photo of one of Spencer’s hooves. Note most of the hoof area is recessed.

Figure 3. View of a horse’s hoof. This is a photo of one of Spencer’s hooves. Note most of the hoof area is recessed.

The figure in the film is placing its weight on one foot at a time, so we must compare a single foot with two or three from a horse. But, the fourteen-inch monster feet each cover 66.3 square inches of surface area! (The plaster casts from the film site and Green’s description confirm the entire foot made the impressions.) Using these simple calculations, one alleged Sasquatch foot roughly displaces about the same area as a horse does. So, if the figure made an impression the same depth as Gimlin’s horse, and using this simple reckoning, we could gauge its weight to be 1,400 pounds!

The true measure is more complex.15

Seldom will the entire surface area of the hoof actually come into contact with the ground, because the inner hoof is recessed, especially so once the hoof is shod (see figure 3). In reality, since the horse distributes its weight on two or three sharp-rimmed hooves, normally only the horse’s shoe touches the terrain. The figure in the film, however, distributes weight on one broad, padded, round-edged foot, allowing a maximum surface area to make contact with the ground. This means that the foot of the figure in the film will make less of an impression per more weight than a horse.

Figure 4. Full view of Spencer, a horse similar in size to the one descibed by Gimlin in his account.

Figure 4. Full view of Spencer, a horse similar in size to the one descibed by Gimlin in his account.

Even if we base our comparison on the entire area of three hooves, we get a measurement of about 22.7 pounds per square inch for Gimlin’s horse. If the figure in the film applied the same pounds per square inch, it would have weighed 1,505 pounds.16

This calculation works if the impressions were the same depth as a horse, but from all indications (photos, film, and testimony), they were not. We are told they were noticeably deeper. This means the creature in the film had to exert more downward force than the horse. If the force exerted by the figure in the film was 1.5 times our estimates, that would yield 34 pounds per square inch. This means the creature weighed 2,254 pounds if the earth compacted evenly. As sediment compacts, it causes more resistance to penetration in a nonlinear progression. In this case, we know the surface material compacted enough to support a horse hoof at a shallow depth, meaning the filmed subject would have needed to exert even more pressure on the sediment!

Could the Bigfoot in the film realistically displace the weight needed to make the impressions? For this assessment, we must take into account that the figure is allegedly a female Sasquatch (some claim to see its furry breasts) about to winter in Northern California. The images suggest a thick coat of fur. Fur accounts for little weight. The creature would have to bulk up with a layer of fat, and fat accounts for far less weight than muscle. We don’t know how tall the figure is, but Roger Knights, an active Bigfoot booster, has recently taken a look at this issue. According to Knights, “we are probably looking at maybe six feet at most.” Gimlin’s original estimates were “six-feet one-inch or six-feet two inches.”17

Figure 5. The copy of the Patterson film site cast next to Spencer’s front hooves.

Figure 5. The copy of the Patterson film site cast next to Spencer’s front hooves.

Others envision the subject as taller. According to longtime Bigfoot enthusiast Peter Byrne, the creature’s height is somewhere between “Jim McClarin’s [another Bigfoot enthusiast] height estimate of eighty inches and mine of seventy-seven inches. This would give the figure in the footage [an average] height of six feet, six-and-a-half inches. This is the maximum that I would allow.”18

When one views the image, does it look like an animal, whatever the height, of such enormous weight? If we could accept that this figure made these incredibly deep tracks, shouldn’t there have been many more impressions found just before and after the event? According to Laverty, “there was some skepticism, because we had been up and down that same road all summer long and never saw anything . . . and then all of a sudden Mr. Patterson comes in for a couple of days and bang! Yeah, I think there was some skepticism.”19

Gimlin would have us believe the creature in the film is of enormous weight.

Isn’t a hoax more plausible? Is it possible Patterson and Gimlin conceived a way of making deep impressions before they left Yakima?20

Readers must draw their own conclusions, but this track depth analysis casts additional scientific doubt on the Patterson film. In view of the litany of discrepancies swirling around the film’s origin and circumstances, the revelations in the Long book, and this evidence of possibly faked tracks, we are exceptionally close to a judgment against the authenticity of the film.


  1. New Mexico Museum of Natural History and Science, Bulletin 42, 2007. Lucas, Spielmann, and Lockley, editors.
  2. In the paper, Meldrum makes bold statements about the Patterson film, such as “several footprints were clearly filmed.” Because Meldrum does not mention the “second film” allegedly made later in the day, the readers of the paper would assume this statement refers to the film including the figure. He labels a clear photo from the second film simply as “from the Patterson-Gimlin film clip . . .” leaving the uninformed reader to believe this still is from the film showing the figure.
  3. The best book-length account of the legend of Sasquatch is Bigfoot Exposed by David J. Daegling, 2004, AltaMira Press, Walnut Creek, CA.
  4. These issues are the result of troubling questions raised by Bigfoot believers.
  5. The Making of Bigfoot by Greg Long, Prometheus Books, Amherst, New York, 2004.
  6. For the complete interview go to
  7. Bigfoot Times, October 20, 1992, page 22, and personal conversations with Lyle Laverty.
  8. I am indebted to Don Ryan for the loan of his copy of one of the Patterson film scene casts as well as for many other favors concerning this investigation.
  9. Subsequent telephone conversation with Lyle Laverty on February 16, 2007.
  10. In his paper, Meldrum confirms: “the footprint is notably flat . . . presumably to maximize distribution of the plantar pressures at the onset of touchdown.” N.M. Museum Bulletin 42, 2007, Page 228.
  11. Sasquatch: The Apes Among Us, by John Green, Hancock House, Saanichton, B.C. Canada, 1978, page 118.
  12. Elise Kirk, an associate producer with National Geographic Television, asked several questions about the footprints associated with the Patterson film when she interviewed me while making a film on Bigfoot. Her insightful questions caused me to reexamine the way I viewed the impressions.
  13. I had help from two horse aficionados: Nancy Stutzman and Christy Sanders-Meena. The horses cooperating in my initial survey were Sonny, Jasmine, and Asher. Asher weighs about 1,300 pounds; Sonny, the smallest horse, weighs about 900 pounds, and Jasmine about 1,100 pounds. Later, for photos, a four-year-old named Spencer posed for comparison with a copy of the Patterson cast. Spencer is almost sixteen hands high and weighs about 1,100 pounds.
  14. For those readers who have not examined the film image in detail, the figure in the film has large, fur-covered breasts. It is the consensus of the Bigfoot community that the creature is allegedly female, one of the few issues skeptics do not dispute.
  15. Not factored into the calculations is the body shape of a horse. Unlike a primate who displaces all of its weight evenly but alternately on each foot, approximately 60 percent of the body mass of a horse is distributed over the front legs, due to the size of the head and neck. Of course, this means the weight per surface area is even greater than the number given in my calculation, making the case even stronger against the authenticity of the Patterson tracks.
  16. I am indebted to Anton Wroblewski for comments about the details related to the mechanics of human and horse footprints and many other helpful suggestions.
  17. Big Foot-Prints by Grover Krantz, Johnson Books, Boulder, Colorado, 1992, page 96.
  18. The Search for Bigfoot Monster, Myth or Man? by Peter Byrne, Acropolis Books Ltd., Washington D.C., 1975, page 141. To be fair, there are many other height estimates. The late Grover Krantz, using film speed as a measure of height (a most unimpressive argument), calculated the image between 5-feet-9.3-inches and 8-feet-6-inches tall (see Big Foot-Prints, page 96). Patterson claimed the creature was 7-feet-4-inches tall and in the 1992 interview Gimlin revised his estimate of the creature to “about 9-feet high.”
  19. Bigfoot Times, October 20, 1992, page 21, and telephone conversations with Robert Lyle Laverty.
  20. Gimlin says that in the night it began to rain. “Around 5:30 a.m. or so it started raining and it was just a pouring down rain. I told Roger we better get up and do something about the tracks or they’d wash out, and he said no, it would stop raining after a while. I went ahead and got up, put the saddle on my horse and decided I would ride up there while it was raining really hard and Roger says ‘ah it’ll quit, don’t ride up there.’ I said ‘no I’m going to go ahead and ride on up there.’ I had gotten a couple of cardboard boxes from Mr. Hodgson’s to cover these tracks the night before. So when I went outside to get a couple of these boxes that were folded up out there, they were just soggy old pieces of cardboard. I disregarded [sic] taking those back up there—so I rode back up to the scene, pulled some bark off some trees and covered up the tracks as best I could and went back to camp.” Is it possible that after spending the day making fake tracks showing unusual weight Gimlin wanted to protect his work? When I showed this quote to Anton Wroblewski, he commented: “Isn’t it curious Gimlin uses the word ‘scene’ as if from a movie.”

Michael Dennett

Michael Dennett, who headed the Seattle area skeptics group Society for Sensible Explanations for over two decades, died May 2, 2009; he was fifty-nine years old. He had been diagnosed with leukemia and hospitalized for several months.

Mike was an investigative writer perhaps best known to Skeptical Inquirer readers for his research into Bigfoot, on which his first feature-length article was published in 1981. He was one of the first skeptical investigators to challenge Bigfoot claims, doing research into claims of dermal ridges (“Bigfoot fingerprints”) and hoaxed tracks. He was a meticulous researcher, a careful investigator, and a true skeptic who called out fakery and pseudoscience when he saw it but was careful not to belittle or criticize people for their beliefs.

Dennett’s research went far beyond Bigfoot, and he wrote about topics as varied as fire-walking, the Bermuda Triangle, UFOs, the Salem witch trials, and psychics. He also contributed to Psychic Sleuths, The Encyclopedia of the Paranormal, The Outer Edge, and other books. Born June 20, 1949, Mike was a 1971 graduate of Norwich University and a former Army Captain, paratrooper, and Ranger. Though his day job was selling municipal water systems, his academic loves were history, skepticism, and writing alternative-history science fiction. He is survived by his wife, Lois. His final article, “Science and Footprints” (about contradictions in accounts of the 1967 Patterson/Gimlin film, the “best evidence” for Bigfoot), was published in the November/December 2008 Skeptical Inquirer.