Friday 16 May 2014

The Carcass Problem (Part 2)

Having looked at some of the dubious carcass stories from years and even centuries past at Loch Ness (as exemplified by the front cover above), we now look at the basic question - "Why has no Loch Ness Monster carcass been found yet?".

This question may sometimes be framed as a statement by sceptics. To wit - "A Loch Ness Monster carcass should have been found by now!". However, this issue is better framed as a question as I have seen no detailed or logical argument by anyone as to why such a statement should be true.

Back in the 1930s, it seemed a given that if there was a creature in Loch Ness, it would eventually be captured, dead or alive. By the time the 1960s came around with the Loch Ness Investigation Bureau, this gave way to more cautious hope. Now in the 2010s, one wonders if any prospect of a DNA find is on the cards.

But back to the problem. There are only two answers to the question. The first is that there are no carcasses to find. However, that answer can itself be subdivided into four categories. The first of the four is the position that there is no carcass because there are no monsters and never has been. The second is that the creature is a boneless invertebrate and so any body will be scavenged away in short measure. The third is that the Loch Ness Monster is a paranormal phenomenon and hence no carcasses are to be expected. The fourth is that Nessie is a regular visitor to the loch but not a resident and hence we again should expect no carcasses.

I won't dwell on these categories any further and readers may wish to comment on them below. The second answer to the question is simply that nothing has been found because researchers have not looked hard enough. That answer requires further explanation and subdivides into the nature of the beast, its environment and the search.


There are two ways to find a corpse, by accident or by design. Millions have visited the shores of Loch Ness in the past eighty years and no one we know of has stumbled upon any body part of any mysterious creature. Meantime, a far smaller group of divers have ventured in those waters since the nineteenth century. I have been sniffing round the shores of Loch Ness for decades and have detected nothing I would seriously present as evidence. That tale can be repeated multiple times for all Loch Ness investigators, named and unnamed.

However, it has to be said that I don't often see much of anything around the shores of Loch Ness. I stumbled upon a sheep skeleton on my last visit and it is a matter of unimportant speculation as to how it got there. Polling the statements of others largely bears this out. I asked long term monster hunter, Steve Feltham, what he has encountered from his home on Dores beach. His reply was:

"Deer that drown trying to swim the loch occasionally. We dont generally get fish on the beach, in fact in twenty years I cant recall a fish. One or two eels on their backs in shallow water, thats about it."

Another on site investigator, Dick Raynor, said this of things floating around:

"I have seen dead fish on the surface - there's a Roach on my website, I saw a salmon or trout floating around the bay here last summer and there was a dead sheep near the castle about 4 years ago. My suspicion is that most of the floating dead things were dead and floating before they entered the loch. In the case of corpses, they are sometimes found floating a couple of weeks after dying and it is assumed that they were lying in the shallows until they resurfaced."

So not much of even what is known to exist in Loch Ness is readily found. Perhaps there is some truth in that old legend about the loch never giving up its dead, which brings us to the murky depths below. Dick Raynor makes another statement on the death process at Loch Ness:

"The only large creatures regularly shot on Loch Ness seem to sink immediately, and I'm not aware of one ever being washed up. I refer, of course, to the seals."

I recently spoke to Gordon Menzies, a veteran of Loch Ness cruise ships, who added that a seal could remain afloat for a time if it was shot after taking in a lungful of air. But, in general, they sink and then it is what happens after that which has an impact on the carcass problem.

This absence of floating corpses is explained in terms of the rate of decomposition. In that regard, I would like to quote leading Loch Ness researcher, Adrian Shine, on the problems inherent in locating carcasses. This is taken from the 1976 Loch Morar Expedition report.

There are very few records of unidentified carcasses being found by Scottish lochs. Factors which may account for this are that Lochs Ness and Morar are deep, steep sided and cold (about 5oC below the thermocline). The cold would slow decomposition and allow time for scavengers such as eels to dispose of the remains. Gases, which did result from decomposition, would have their volume and buoyancy reduced by water pressure at depth. One cubic foot of gas at the surface would have a buoyancy of about 621bs but at a depth of only 32ft this would be halved, while at 200ft the buoyancy would amount to only about 8lbs.

The bodies of those drowned in Loch Ness are seldom recovered.  One would not expect the remains of fish living at depth to float. Many animals, which are secondarily aquatic, swallow stones, and it is believed that these may function as ballast. Plesiosaurs did this, as do crocodiles. Sea otters are examples of mammals with the same habit, as are seals, which may contain as much as twenty five pounds of stones. This may well cause a body to become negatively buoyant at depth when the air cavities are compressed. Cmdr. Cousteau has found "graveyards" of elephant seals and these bodies seem to have little tendency to float.

I would add my opinion that the scavenging task is increased by possible cannibalism amongst Loch Ness Monsters. I suspect this would be rare and confined to dead and dying animals. The Loch Ness Monster would certainly not be unique in this regard. Loch Ness Ferox Trout are well known for their predation of other ferox.

If these creatures are mainly benthic dwellers, then we should not expect any floating corpses. However, there are exceptions to the rule. If a creature died in the shallow shelf waters of the loch or a little deeper down amongst the clefts and the ridges of the littoral region, it is theoretically possible for them to remain there for a period of time and be more amenable to discovery. But since the behaviour of your typical dying monster is not known with any certainty, that must remain a matter of speculation.

For example, a dying, aquatic creature would have less energy to move itself up from the depths, let alone haul itself into shallow waters. To me, it seems more likely they would stay deep.


So what is it that prevents discovery of Loch Ness Monster bodies? In an answer, it is Loch Ness itself. I have already pointed out the decomposition problem, but what else hinders a search?

The most likely scenario for a discovery is that part of the creature which endures the longest. That would normally mean the skeleton. For the sake of argument, I will assume this would be an endo-skeleton. Now, there are two things that can happen to bones in Loch Ness. They can either be eventually broken down by the water's acidity or they can be buried in the silt. It is a matter of conjecture as to which process will claim the bones first.

In terms of acidity, Loch Ness researcher, Dick Raynor, had this to say:

"Exposed bones are not likely to survive for many years however as the calcium hungry loch water will cause them to dissolve and crumble in the slightly acid environment."

However, it is unclear how long it would actually take for a skeleton to be broken down. An experiment conducted by the Loch Ness Project in 1984 bears this out. A hessian sack containing beef bones was lowered to a depth of 200 metres and left there for a year. When it was brought back up, no discernible change in terms of bone dissolution was noticed. Clearly, this is a process that would take a number of years (depending on the thickness of the bones).

The question is further complicated if the creature has a cartilaginous skeleton. These bones are less dense than the bones we possess because in water they do not have to be so load bearing. You can find such bones in sharks, sturgeons and so on. As a consequence, these bones will break down faster than terrestrial ones. It is a bit of an irony that the sceptical idea that some sightings of the Loch Ness Monster may only be Atlantic Sturgeon also may suffer from lack of evidence due to the same problems!

The silt that blankets the sides and floor of Loch Ness also presents its own problems. A large number of rivers and smaller burns empty into the loch, bringing with them debris of varying sizes and composition (animal, vegetation and minerals). This continual flow of debris eventually settles into the sides or bottom of the loch where it will be further broken down into smaller particles over time. The higher water pressure of the bottom will also compress and compact the silt over the centuries.

Any larger object that gets caught in this process will get buried but how long that takes is variable. The rate of silt deposition depends on where you are in the loch and when. Clearly, the seasons of higher rainfall will drive debris into the loch at a faster rate and those areas nearest to water inflows will generally receive the greatest depositions.

Moreover, silt may accumulate on the higher ridges and shelves over the years but then cascade down into the deeps when a tipping point is reached. A study of sediment core samples taken in the 1990s by the Loch Ness Project suggest varying levels of sedimentation with a contemporary rate exceeding 1cm per year for the deeper waters of the North Basin.

Other core samples contained markers for the radioactive events of Chernobyl (1986) and the peak in atmospheric nuclear bomb tests (1963). These depths were given as 3cm and 9cm down respectively which suggest more recent depositions rates of 3 to 7 mm per year. A more historic core sample detected the 1868 great flood of Inverness at 30cm to 50cm depth which gives a deposition rate of about 4mm per year. Note that this one off event alone added up to 20cm of silt, probably enough to cover many carcasses.

One could take the contemporary rate of 1cm for further calculations, but it is acknowledged that not all parts of the loch are equal, so I will use the 4mm rate from the 124 year old flood example. So how long would it take the silt to normally bury a Nessie skeleton?

Not knowing what species the Loch Ness Monster may belong to, I will stick with a candidate whose skeleton is well known, the plesiosaur. The largest bone would be one of the main vertebrae and I doubt any of its dimensions would exceed 20cm. At a deposition rate of 4mm per annum, this, the last bone of the carcass would disappear after 50 years.

At our faster rate of greater than 1cm per annum, it is gone in 20 years. If an event akin to the 1868 flood occurs, it is probably covered in a matter of days. You perhaps begin to see how greater a problem this is on closer analysis.


But you may retort that there is more than one Loch Ness Monster and they must die on a regular basis, thus making them more amenable to a search. I would agree with you on that matter. Nobody knows when this creature entered the loch, but in the estimated 20 metres or more of deposits laid on the loch floor since the last Ice Age, there must be a good number of bones in varying stages of decomposition. Indeed, it is hoped that if the bones are encased in the clay quick enough before the slightly acidic waters totally breaks them down, there is a good chance of many examinable bones being found. I say that with a degree of optimism since I am not even sure if bones of known animals have been found in the various core samples collected over the last 20 years.

So let me indulge in some arithmetical speculation. If the loch contains a population of thirty monsters of varying sizes with an average lifespan of thirty years, then one carcass gets deposited every year. If it takes 50 years to completely silt over one carcass then this suggests there are fifty carcasses on the loch bed with varying degrees of exposure.

Concentrating on the floor of the loch and not the sides, the loch is 26 miles or 42 kilometres long and the width of the loch floor is at least half a mile or 0.8 kilometres. This gives an approximates floor area of 33.6 million square metres.

If we assume the area of the floor bed covered by a carcass is 10m by 1m, we get a carcass surface area of 10 square metres. Total up our fifty carcasses and we get no more than 500 square metres. This means the carcasses cover 0.0015% of the total floor of the loch. The probability of a ROV or diver submerging and alighting on one of these carcasses by chance is therefore about 1 in 67000.

Even if a ROV started at one end of the loch with a lit up search area radius of two metres and went to the other end of the loch, the odds of seeing anything is still 200 to 1 against. I am not aware of any such vehicle coming close to achieving this task in practise.

I am not saying this is the most accurate calculation, but in terms of showing the magnitude of the task, I think it has done its job. The bottom line is that it could be one, ten or a hundred carcasses lying on the loch floor or even none. It all depends on the population and its birth and death rates, though one would assume the two rates are nearly equivalent for a stable population.

However, since you or I do not know what this creature is, then it is not the Loch Ness Monster we are critiquing, but the various models put forward to explain it, and there are plenty of them! Indeed, there are monster theories that predict zero or next to zero carcasses. If anyone tells there "should be carcasses", ask what model they are using and why.


Of course, the odds could be improved by dredging up tonnes of the loch floor and panning for bone debris like gold prospectors. Sticking to our one a year carcass assumption, that gives an upper limit of 1000 carcasses buried in the sediment over the last one thousand years. If 1000 years of silt deposition gives us 2 metres of clay then the search volume is about 67 million cubic metres.

If a typical carcass takes up 10 cubic metres then the probability that a dredged up volume of 10 cubic metres contains anything is 6700 to 1 against. Of course, it is possible that the bones may generally be scattered over a wider area. Readers may wish to comment on whether that makes any difference whatsoever to the search.

Now some kind of dredging was attempted by the Loch Ness Investigation Bureau in the 1960s or 1970s. I have no idea how deep or wide that experiment went, but based on these odds, I doubt they had much chance of success.

Today, the sediments of Loch Ness are regarded as something of a scientific treasure trove for other reasons. The lack of water movement on the loch floor means sediment is laid in an orderly chronological fashion and hence provides a valuable natural journal of local and global events stretching back at least to the last glaciation and possibly beyond. In that light, it is unlikely we are going to see any serious dredging operations.

Attempts to search the loch for carcass material has been ongoing for decades, though it has tended to be haphazard, sporadic and limited to the shallower side regions. Anyone who goes down 200 metres to the floor of the loch for a sustained search is going to be susceptible to the bends without careful decompression procedures.

The problem is further exacerbated by the fact that any activity on the bed of the loch may stir up the sediment into impenetrable clouds of silt. Any search would have to be careful to maintain a certain height above this volatile surface.

Underwater searches of the loch bottom certainly go as far back as Operation Deepscan in 1987 when Osprey low light video cameras were sent down to investigate sonar hits.  Hours of observation were achieved with no "monster" success. However, it is to be noted that next to nothing at all was observed on the fine silt surface. Only the occasional twig was observed, not even logs were seen. If your search can't even find a common log, how can you expect to find a Nessie skeleton?

That lack of observation of even presumed common objects was somewhat rectified in later expeditions. A number of visits to the loch with remotely operated vehicles (ROVs) have occurred in subsequent years (see clip below). If a sum of the total operational hours on the loch bed could be added up over the last 25 years, one may begin to get an idea of how close or far they have got to beating the long odds.

But note, operational hours does not equate to productive searches. Most forays into the loch have been primarily for the purposes of testing equipment, not monster hunting. If the ROV merely dropped to the bottom but did not move around much and focused on testing its robot arms, that is of little use.


In practise, the one expedition that caught my interest was the 2005 search by Robert Rines, his Academy of Applied Science team and others. A summary of their search was presented to the Oceans 07 conference in Aberdeen seven years ago. Armed with a side scan sonar, some ROVs and underwater video cameras, they towed the transducer down the loch at a depth of 150 feet looking for targets of interest as it mapped the bottom and sides. Presumably anything above the transducer was not recorded (hence it was not a whole loch scan as some aver).

From this, they identified over one hundred objects of interest, which brings us to the first point. Sonar does not distinguish between skeletons and known debris that litters the loch. The normal gas filled cavities that register strong signals with living animals are not present and even decomposition gases will be short lived and small at greater depth. Doubtless, there were other sonar features which were more numerous and deemed not of interest. There appears to be a high noise to signal ratio in what was essentially a loch contour inspection.

One sonar hit was described as resembling straight long neck vertebrae. When the ROV got there, it was nothing more than staggered layers of shale rock. Other hard signals from under the Horseshoe Scree proved to be massive rock cliffs and chasms dropping to 600 feet below. So the second point is that multiple echoes from the sides were causing so much ambiguity as to make interpretation of the images difficult.

It was not stated how many of the one hundred targets were located in this potentially ambiguous zone of interpretation. Perhaps they would have more luck on the flat bottom. Below is a sonar hit at 112 feet and the corresponding tree trunk that was found by the ROV. Admittedly, this was well off the maximum depth of the loch, but it demonstrates the sonar potential.

Does this surface mapping approach reduce the long odds mentioned above? Yes it does, depending on the resolution and interpretation of the images. Assuming the axes on the sonar image are in metres, that would suggest that objects down to our 20cm vertebrae would be on the borderline of resolution. The problem is our hypothetical bone would not be readily distinguished from a 20cm stone or lump of wood and so there would be a drain on resources investigating each one.

So, it appears that Robert Rines' strategy was to look for larger, whole carcasses where some degree of structure definition could guide precious ROV deployment time. This particular tree trunk arrangement covered a length of about 14 metres - a good monster sized target. Whether any of those one hundred or more targets was a carcass is a moot point. The point being that unless a diver or ROV is sent down and comes back with a sample, it is all conjecture.

As it turns out, one of the ROVs went AWOL and the other two had to be diverted into finding it. Because of this, only a few targets were investigated before they had to pack up and go. Some might say that the Loch Ness Hoodoo struck again but it would have been interesting to have seen what was made of these other targets. In fact, just seeing the candidate sonar images would be a start!

I would also liked to have known whether there was any targets in the deepest parts of the loch and how signal attenuation affected interpretation of sonar returns.  Also, as a control experiment, it would have been interesting to see if any seal, human, sheep, cow or deer bones were found. After all, if you can't find them, it is unlikely you will find rarer Nessie bones. All in all, this was an expedition which showed promise but events constrained them. Nevertheless, future ventures of this kind may yet be fruitful.


Talk of finding Loch Ness Monster skeletons has always been a bit of a subjective affair. Critics tend to issue words like "should have" or "must have" without giving any solid reasons why. I hope the numbers above give a sense of the magnitude of the task. But looking to the future, the task of going to the bottom of the loch to conduct an intensive search is an unlikely event.

Past searches have always been thin and opportunistic due to lack of funds. If that was the way it was when the climate was more receptive to a monster in the loch, what will it be like in this more sceptical environment?  Let's just say I am not holding my breath.

Monster hunters such as myself, Gordon Holmes and others cannot carry the can on this. The loch bed is hundreds of feet below us and those that have influence are not going to help us in any attempt to dredge something up. If one invested in diving equipment, then side searches along the shallower regions offers some chance of finding something. But with over 50 miles of shoreline going down to a searchable depth of 70 feet, this could become a thankless task.

But perhaps there is another route in the search for traces of the Loch Ness Monster. I am referring to the recent advances in DNA analysis. A year or so back, it was revealed that a Dutch study had managed to discover the various species resident in a number of lakes by examining their DNA traces in a sample of water. To put it in their own words:

Freshwater ecosystems are among the most endangered habitats on Earth, with thousands of animal species known to be threatened or already extinct. Reliable monitoring of threatened organisms is crucial for data-driven conservation actions but remains a challenge owing to nonstandardized methods that depend on practical and taxonomic expertise, which is rapidly declining. Here, we show that a diversity of rare and threatened freshwater animals—representing amphibians, fish, mammals, insects and crustaceans—can be detected and quantified based on DNA obtained directly from small water samples of lakes, ponds and streams.

We successfully validate our findings in a controlled mesocosm experiment and show that DNA becomes undetectable within 2 weeks after removal of animals, indicating that DNA traces are near contemporary with presence of the species. We further demonstrate that entire faunas of amphibians and fish can be detected by high-throughput sequencing of DNA extracted from pond water. Our findings underpin the ubiquitous nature of DNA traces in the environment and establish environmental DNA as a tool for monitoring rare and threatened species across a wide range of taxonomic groups.

So how applicable is this technique to the mysterious animals of Loch Ness? The first problem is to decide what constitutes Nessie DNA. Since it is not known what this might be, the analysis of any sample would have to eliminate the known species and see what is left. Anything which is unknown would clearly be of great interest and could at least be compared to species with similar DNA sequences.

The second problem is whether the vastness of Loch Ness and the potential Nessie biomass makes sampling possible. Loch Ness may be more oligotrophic than the lakes tested for this sampling technique and hence less suitable. The way ahead here would be to first of all test whether all known species are indeed detectable using this procedure.

Finally, samples would have to be taken from various locations underwater since it is also not known where these creatures are most likely to frequent. So we are talking here about samples from the open pelagic regions, the littoral, abyssal and benthic regions.

Undoubtedly, this would cost thousands of pounds to process. Who would foot that bill? The ideal people, in my opinion, would be the owners of the exhibition centres who take in revenues of millions of pounds per annum because of this mystery. Will any of this happen? At this point in time, I have no confidence it will.

Depending on your preferred model of the Loch Ness Monster, there may be zero or more bodies awaiting discovery. If no bones are found after intensive searches, that certainly puts any vertebrate model of the Loch Ness Monster under pressure. To others who believe in no monsters, paranormal monsters, invertebrate monsters or travelling monsters, this will merely serve to strengthen their position.

Monday 12 May 2014

That Recent Sonar Image

Okay, so the recent sonar image from Jacobite Cruises was five years old. I updated the article to reflect that shortly after, but it seems the real image has been published in what was deemed a cock up. Original article here.

The image was taken off Urquhart Bay on the 27th April 2014. A zoom in of the screen grab is somewhat indistinct, but it seems to be showing a target hit at about 30 feet down which has a crescent shape that is reminiscent of the crescent shape we see for smaller fish all the time. Note that in the case of fish such as charr or salmon, it is the swim bladder that registers the strongest echo. The crescent shape is caused by the relative motion of the fish to the sonar.

This sonar image is not a small fish. What it is on an initial inspection is difficult to say and I have seen various strange sonar hits from nearly all the cruise companies now. The normal answer from them is to say it is anomalous and I guess that is where I will have to leave it myself!