04/08/2020
Dear Readers. In this weeks musings, we explore the Population Density, Size, and probability of Loch Ness Monsters. However I must provide this WARNING: NERD ALERT. Do not read unless you are suitably nerdy.
This conversation is based on the article below.
Sheldon, R. W., and S. R. Kerr. 1972. The population density of monsters in Loch Ness. Limnology and Oceanography 17:796-798.
At mention of the Loch Ness monster, most people, and especially scientists, just roll their eyes. But a careful review of reported observations reveal some characteristic features about such creatures, which, for lack of a better term, we can call “Nessies”. According to the article by Sheldon and Kerr, these characteristics are: They are rarely seen; they are never caught; and “sightings” go back centuries. Sightings also suggest that Nessies are large bodied creatures, they are few in number, and relatively shy, and in fact share many of the same qualities with yetis (I’ll leave Bigfoot out of the conversation for now because his sightings are not historical). Known laws of trophic ecology indicate that, if their bodies are large, their population must be small. But to suggest that the paucity of sightings indicates they do not exist is both “irresponsible and illogical”.
A scientific approach to understanding Nessie populations would start by estimating the potential biological production of their habitat, which allows us to estimate their population size, even if we can’t see them. Based on some Ecological mumbo-jumbo (see Endnotes) we can conclude that, at a minimum, at least two Nessies would be required, to allow for reproduction to occur and maintain historical populations, and these would be really monstrous, on the order of 1500 to 8000 kg. The alternative is a population consisting of many small individuals (10-100 kg) which would total from 30 to 156 individuals. The most likely result is somewhere in between, as anything smaller is “not suitably monstrous”. Additional eco-logic (Endnotes) allows us to conclude that the population probably consists of a small number, say 10-20, of large monsters, on the order of 1500 kg each. A Nessie of that size would be about 24 m long, which agrees well with reported observations.
The fact that so few Nessies have been seen is not due to lack of diligence on the part of observers. Au contraire, it is most likely due to fear of ridicule by the sceptics. To counteract that, and increase the availability of useful data, “monster observers should be encouraged”.
It is also noteworthy that these estimates were made in 1972, before the advent of large scale salmon aquaculture. The excess nutrient inputs, and availability of escaped fish for consumption, suggest that current populations may be greater than the estimates presented here.
Nevertheless, existing data, and the speculations of Sheldon and Kerr, are not enough to prove the existence of Nessies. However, another approach to solving the problem is via a traditional hypothesis test. In this case we shall try to disprove the null hypothesis 1, which is that monsters do NOT exist. Based on the data collected to date, the probability of NOT seeing them = 1 (our p-value). Normally, we would only reject a null hypothesis if the p-value was
