Take the 2-minute tour ×
Role-playing Games Stack Exchange is a question and answer site for gamemasters and players of tabletop, paper-and-pencil role-playing games. It's 100% free, no registration required.

As per question in the title.

I recognise that there are numerous criteria that would affect this, however, I am looking for a baseline estimate that could be modified as per specific vampire (his humanity, feeding habits, discipline usage etc.) I would assume that the said vampire is drinking about 2-3 points of blood per night and never kills his victim. However, I struggle to estimate anything else than a herd size (which is composed of exclusively fit-for-purpose healthy people). Assuming that it takes about four months to recover from a loss of a point of blood without any detrimental health effects (implied by the facts that a point is about a pint, that is about a single blood donation and the medical recommendation is to donate blood at most three times a year), I propose the following calculation:

3 * 1 * 4 * 31 = 372 people required to every night feed on 3 different people, drawing 1 point of blood for four months of 31 days, so that no person is bitten twice in this period.

But that doesn't explain how many "real" people would be necessary to at all times have no less than 372 healthy specimens for an indefinite amount of time (self-sustaining population).

Could you explain how to get that number and what would be the major contributing factors?

If this question is not fit to appear here, I could possibly ask in some medical SE instead. Please comment if that's the case.

Some people ask me for purpose, let me explain. That's not supposed to be a tool to estimate the vampire population in a given city. Instead I'm thinking about a single vampire living in a remote area without a practical possibility of leaving (think Tzimisce in a settlement surrounded by werewolves in the middle of Siberian taiga). I am trying to establish how many people should such a vampire have around him to survive by purely local means. I want to take into consideration aspect like not everyone having being suitable to be fed upon, naturally occurring illnesses, necessity of children to replace the elderly etc. to create a situation where a trapped Cainite struggles to keep himself alive. There are some imminent dangers to him, hence his usage of disciplines (additional 2 points per night) but he is aware that overfeeding would steer the population to a decline. I would like that status quo to last for more than five decades. No, I don't want to factor in the social problems of people gradually noticing his presence, I'd rather think of superstitious community who treats it as a curse over a town that has no explanation and him being extra careful to influence mortals into having a lot of children and not leaving, as a local prince could in the medieval times - only in contemporary setting.

Mortals are not supposed to be willing participants, if it were like that, I'd just go with Herd Background and assume no overhead of spouses, children and elders is needed.

share|improve this question
    
I'm having trouble understanding the problem being addressed here. Once you had this number, to what use would you put it? –  Jadasc Jul 11 at 15:00
    
@Jadasc Not the OP, but I've done calculations like this for other vampire games. It gives a sense of how many vampires you should be creating for a given setting during worldbuilding. Since some people have problems with the estbalished setting ratios, it gives an alternate ratio. See also rpg.stackexchange.com/a/2549/2556 –  Yamikuronue Jul 11 at 15:03
    
@Yamikuronue: Fair enough; I can see the merit in that. However, the OP is working with some assumptions I wouldn't consider universal in a vampire game -- 2-3 BP hunted for each night, making sure to not drink from the same person twice in a 31-day period, assumption of successful, safe, and healthy drinking. Basically, it's a weird sort of white room. Since addressing the math and the medicine behind it isn't my area of expertise, I thought I'd inquire what they were up to. –  Jadasc Jul 11 at 15:07
1  
Is this only about health issues, ie. the minimal size of the population to produce enough blood without endangering the food supply? Or would you also like to account for the fact that these are thinking beings who do not like to be fed on, and if everyone is getting bitten every 124 or so days, and, being a small population and they know each other well, perhaps they will flock together against the single vampire? Indeed, if you are an individual monster, victimizing a population works best if the victims don't get together, so 1 victim in a population of 1000 is a good start perhaps. –  Xabei Jul 11 at 15:10
1  
Explanation in amended question. Thanks for your interest :) –  eimyr Jul 11 at 15:35

2 Answers 2

up vote 3 down vote accepted

Like many things, it depends. Your calculations are quite reasonable and 372 should give your vampire enough, in fact it has a decent margin of error in it. It has a decent margin of error because a healthy person can give more than 1 BP in a night. I don't have the book handy, but I'm pretty sure they can give up to 3 BP before their life is endangered. Also a healthy person can give blood more often than the medical guidelines indicate. Also, the vampire can, at least to a degree, self regulate and avoid using unnecessary blood. You will still average well above 1BP a night, but a vampire that avoids fights and is deliberately conservative about blood use can probably come in under 2-3 BP a night on average.

So, as you say 372 will provide enough, and even give some safety margin. But that is 372 adults that are at least healthy enough to "contribute" three times a year. You are asking how many would be in a community to give you those 372 healthy adults.

And that depends. You want the birth rate to be equal to or greater than the death rate, but death rates are highly variable in different time periods and different parts of the world depending on circumstances. In the United States, for instances the crude death rate is 8 per 1,000 people per year. Going with that number and ignoring the fact that that is per 1,000 in the entire population and we are only looking at health adults in our 372, he can expect to lose around 3 of his herd each year. That means to be sustainable he needs 3 that are about to become old enough waiting in the wings. If we say they are "adult enough" at 16 and we want this to be indefinite we need 3 children at each age between newborn and 15 waiting around. So, in addition to our 372 adults, we need 48 children waiting around.

Incidentally, the crude birth rate in the US is 14 per 1000 people, so for our 372 adults we could expect an average birth rate (if comparable to US) of 5, easily more than the 3 we need.

Currently, this brings us to 420 to be sustainable. But, you also won't be able to usethose with chronic infirmaties that prevent them from being used, like the very elderly. But how many elderly you have also depends. If the death rate is high, you probably won't have many. If you have customs of senicide (killing or suicide of the elders), then again you won't have many. If the vampire has a firm hold and wants to keep the population to a minimum, he might well create such a custom or else "cull" his herd of any not of use to him. If he does this ruthlessly, than 420 is enough with a decent safety margin. But, if he doesn't do this then he will have some additional people. In the US our population over 65 is 13% of total. 13% of 420 is 54.6, so if this is a rough estimate of the number in his population he can't eat than we are up to 475.

I'm ignoring the temporarily sick because (unless there is an epidemic hitting a large percentage of the population) he can easily bypass them for a week and just come back. In short, they are absorbed into the safety margin.

So, I've played rather loose with a lot of the estimates and erred on the side of the vampire being cautious, but a population of 475 could sustain a vampire forever. This of course adds in the assumption that there won't be any huge deviations from average. If there is a war or plague or famine that wipes out a large portion of the population, he will have trouble.

share|improve this answer
1  
Brilliant! Just what I needed. Thank you very much. Would you happen to know what is an average rate of humans that are adult, but unfit to give blood for some reasons? I'm pretty sure about half of people who come to blood donation campaigns are turned down, but I don't know if that would concern a vampire. –  eimyr Jul 11 at 21:49
1  
Most of it won't concern a vampire. I for instance am not eligible to give blood in the US due to some of the foreign travel I've done, but a vampire won't care. Recent tattoos also exclude some people temporarily. Things like being too frail to do it without risk of death or some disease will concern the vampire. I don't have handy statistics for those though. –  TimothyAWiseman Jul 12 at 3:08

It depends on what quality of life you want for the victims. You can routinely take much more blood from the humans than medical guidelines suggest, though the humans will not like it very much. And is the vampire going to provide his victims with a healthy and iron rich diet? Or are the poor buggers foraging for moss to survive? that affects the quality of blood. In general it's better to have a larger v:h ratio, hundreds to one, so freak mischance or evening binging doesn't wipe out the herd. Minimiums are fragile things.

Does the vampire want to throw an occasional party for his vamp friends? Better lay in some extra humans; those warm blood fountains and blood puddings take a lot of raw materials. It's simpler if he just wants to subsist.

But the larger the population, more likely it is that someone gets born who gets fed up, so to speak, with being bitten every few months to years, and eliminates the vampire. That puts downward pressure on the ratio.

Thje simplest solution is a wandering vampire who can bite and move on; the world is wide and rich in blood, and the same scenery gets old after a thousand years, anyway. A wandering vampire never has to worry about running low on humans, or uppity local heroes catching him, so the population question is safely moot.

If you insist on a non-travelling vampire, I'd probably handwave up a 500:1 ratio, because it's a little less than double your minimium number and gives a safety margin; and then you're on the hook to explain why the population puts up with him. Dracula, in the end, travelled.

share|improve this answer
    
There are some good points in here, but it doesn't really address the scenario as posited by the OP. –  Bobson Jul 11 at 20:31

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.