Paul Michael Kielstra

A friend of mine and I recently decided that it would be a good use of our time to determine how many dragons the USA could support. While exact numbers are obviously hard to come by, it turns out that the answer is about 4500. Here’s how we got there.

First of all, we need to know what a dragon is. Since this is the USA we’re talking about, we’ll use a more European/Western-influenced dragon biology: large, intelligent, quadrupedal, carnivorous flying reptiles, who are willing to deal with humans but never primarily for those humans’ benefit. The most important word right now for us is “large.” We know from various sources that they’re big enough to lay waste to towns and small armies pretty much solo, which puts them outside the range of anything that exists on land (or, for that matter, in the air). Instead, we look at an environment which does support such huge animals: the sea.

Mainly because the sizes vaguely look right, we’ll say that your average dragon is about the size of a humpback whale. That means, in particular, that they weigh about 36 metric tons. This only gets us so far, though, because in all other respects dragons and whales are nothing alike. Dragons are carnivorous, airborne apex predators, which puts them more in the territory of birds of prey. According to the National Eagle Center, a large eagle weighs on the order of ten pounds, possibly a bit more and will eat between one-half and one pound of fish and meat a day. In short, an eagle eats between five and ten per cent of its body mass per day. Given that dragons are able to cook their food, thereby extracting more nutrients from it, we’ll use the five per cent figure rather than the ten per cent, meaning that a dragon would eat about 1.8 metric tons of food a day.

Dragons eat cows, which they pick up and carry off on their own. According to Beef Magazine, the average weight of an American beef cow at slaughter is currently about 1.4 metric tons. (Some of that, especially the skeleton, is inedible to humans, but dragons will occasionally swallow knights in armour, so we can assume that they have better digestive systems than we do.) A dragon would therefore need to eat pretty much exactly nine cows per week, were he or she to survive on nothing else, or about 470 cows per year. According to a 2005 University of Iowa study reproduced by Penn State, 87.5% of breeding cows end up with a calf every year in Iowa. So, to produce 470 cows, we would need about 540 breeding cattle. The United Nations argues that the best age for slaughtering beef cattle is three years or thereabouts, so triple that to get 1620 cows, of which two-thirds are being reared to be eaten by the dragon and one-third are breeding. It takes a herd of 1620 cows to sustainably feed a dragon.

That’s a lot. The USDA’s 2017 census says that the average American beef herd size is 43.5, but that number is skewed slightly low by the number of people who own a few cows along with other crops or animals, or supplement their income by working off the farm. Furthermore, looking at modern American herds isn’t going to give a great idea of what a dragon herd would look like, as the vast majority of them are factory-farmed to some degree and we would imagine that a dragon, designed to hunt and kill in the wild, would vastly prefer and be willing to pay a premium for entirely free-range cattle. This is especially true since dragons’ method of eating bypasses the meatpacking industry entirely, making it much more obvious if the cow in question were intensively farmed or not. Once again, we’ll have to do some food calculations.

Rick Rasby, a professor of animal science and beef specialist at the University of Nebraska, says that beef cattle eat about 2% of their weight in dry matter each day. For our 1400kg cows, that would be 28kg of forage per day. A herd of 1620 cows, over a year, would eat 16,600 tons. An undated USDA document claims that the most productive forage grasses produce between 6 and 8 dry tons per acre – I would imagine that these measurements are per year. The document, however, probably uses short tons, since it later measures something else in hundredweight. Converting to metric, forage pasture realistically tops out at 7.25 tons per acre per year. We’d therefore require 2300 acres of top-quality pastureland to feed a dragon.

2300 acres is between three and four square miles. That’s the size of a medium to large town, or a small village with surrounding fields, which is about what fairy tales tell us is a dragon’s natural territory. I’d call this a sanity check, but I’m calculating the number of dragons that the USA could support, so maybe we should stay away from that word.

Across the contigouous 48 states, there are about 528 million acres of pasture. Even with the diverse benefits dragons bring to the economy, Americans will not want to stop eating and exporting cows and other grazing animals, so let’s say that one per cent of these lands are turned over to the feeding and care of dragons. This gives us 5.28 million acres, or just under 2300 dragon territories.

Dragons will often hibernate for years at a time, but once awake they can remain so for years more. In the absence of any decent figures, we can wildly guess that a dragon spends half of his or her life in hibernation, so each territory can support two dragons, for between 4500 and 4600 dragons total.

This is, it turns out, enough to sustain a population. Dragon reproduction works similarly to that of humans: it involves two dragons, it’s done by choice rather than on a yearly schedule, and it takes a lot of time and energy. Ecology has a concept called the minimum viable population, the smallest population of a species that can survive in the wild sustainably. The MVP for humans is probably about 98, and that for elephants is between 100 in the medium term and 3000 in the very long term. Humans, elephants, and dragons all reproduce similarly, so 4500 would be more than enough.

The final question to answer is how common, in general, dragons would be in the USA. 4500 is just a number. Excluding Sam’s Club, which isn’t Walmart-branded, but including everything else, there are 4753 Walmart locations in the USA as of 4/30/20. If dragons were to come to the States, they’d be about as common as Walmarts.