The Mass Effect Wiki says that krogan females can produce up to 1,000 fertilized eggs in a year. However, we also know that Tuchanka is an insanely dangerous place to live: between the thresher maws and the nuclear devastation and the other krogan that will no doubt be trying to kill you from the moment you're born, I think it's safe to say that not all 1,000 of those eggs will reach adulthood. In fact, the krogan birthrate is probably an adaptation to compensate for that exact problem.

Then, obviously, the Genophage dropped that number even further. However, there seems to be some confusion about how much: Wrex and the krogan keep insisting that their race is going extinct, but Mordin and the salarians are steadfast in their belief that they merely "stabilized" the krogan birthrate. I always understood that it was the krogan's warlike nature that pushed them from "stable" to "declining," but the females' inability to have even one child does seem excessive.

Do we ever get a good idea of how fast the krogan population actually grows, once you factor in all those variables? Are there any comments in the games or the books or the comics along the lines of "they could fill a whole world to capacity in ten years" or "the Patriarch has six thousand children"? And then once the Genophage started, do we ever get an effectiveness rate (like "prevented 96% of all births" or "dropped female fertility to one viable birth every four years")?

  • 1
    it doesn't give actual numbers, but the Krogan managed to produce an army big enough to defeat the rachni in just 2 generations; also, note that the female's large litter was an adaptation to Tuchanka before the salarians helped make it safe; after that, I suspect a much larger % of that 1000 actually survived.
    – KutuluMike
    Commented Jan 10, 2014 at 21:35

2 Answers 2


I believe that after the genophage it was very rare for any Krogans to reproduce successfully... according to the Mass Effect Wikia for the Genophage

The genophage's modus operandi is not to reduce the fertility of krogan females, but rather the probability of viable pregnancies: many krogan die in stillbirth, with most fetuses never even reaching this stage of development.

It's also stated that Krogan females who can carry children to term, aka Birth were rare..

Any female krogan who could carry young to term became a prize of war who was viciously fought over. Taking advantage of this, a female warlord named Shiagur used her fertility as a bargaining chip to attract the strongest males to her army.

With this information we can gather that the Genophage was indeed one of the main reasons for the declining Krogan population.. but it's not to say that their War like nature and the fact that they are a doomed race could be a factor as well..

After several hundred years of living with the genophage, the knowledge their species will soon be extinct has created a kind of fatalism amongst the krogan that makes them dangerous opponents—they are indifferent to who they attack or kill, or what risks they take, as their species is doomed. A few individuals, such as Wrex, have attempted to rebuild the species, or at least curtail its decline, by focusing on breeding, but the inherent belligerence of the krogan usually frustrates their efforts.

I don't remember seeing any sort of actual data related to how often they reproduce after the Genophage though.

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    I want to say that Mordin mentions that the genophage set viability rates for pregnancies to 1:1000. Also, the Krogan are dying out because of their fatalistic attitude. That was Wrex's goal in ME2~ME3. He was trying to get the males to stop dying for credits and start living for the future. Because of how long Krogan live 1:1000 would still allow for "normal" growth.
    – Xantec
    Commented Mar 25, 2014 at 4:31

If you speak to EDI after completing Tuchanka: Bomb but before Priority: Tuchanka she will say to Shepard "Females are known to produce clutches of up to 1,000 fertilized eggs over the course of a [Galactic] year" she goes on to tell you if only 1% of the Krogan females are cured of the genophage 10 million children will be born in the coming year.

  • The question seems to be asking about the numbers when they are not cured of the Genophage. Beyond speculation, or the removal of variables, how quickly do they successfully reproduce? Commented Mar 25, 2014 at 4:54

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