How a dragon's lifespan affects Reproduction and Population

[Ewolf20]

in a setting i'm building from the ground up, dragons more or less exist. alike the common depictions of them being these horde sitting, cunning, vicious beast, they're more like a horse. flying, long-lived horse to be more exact. the average lifespan of a dragon is about 130 years but it mainly depends on several factors. Pergus and shiryan dragons are the longest-lived, while the dragons with the most shortest life spans are rogga and yelno dragons (which live to be about 40-70 years old). naturally, this has an effect on mating and how dragons court potential mates.

a dragon is considered ready for riding by the ripe age of 10 years with the average mating age being around 15. some dragons are ready to mate as early as 9 years. during their mating years, a dragon searches for a mate but sending off a signal of pheromones to attract a mate. this usually tends to be a female doing it but in some breeds, it's been observed to happen to males. most courtship happens in places called mating grounds, which also serves as a nursery during the rest of the seasons. for a rogga dragon, a male must prove his worth but getting involved in sparring with other males. the male that manages to pin down the opponent the longest is given the chance to mate. the male who loses is barred from the mating grounds until next spring.

the average clutch of eggs is around 2-10 eggs. again, this depends on breed. dragons with longer lifespans lay less eggs compared to dragons who have much shorter lifespans and lay larger clutches. shiryan dragons, for example, lay one egg once in their lives. never has there ever been reports of a shiryan dragon laying another egg in it's life. it helps that these dragons tend to mate for life. as a consequence for their mating habits, shiryan populations could barely recover when their numbers were reduced to 20 (and one hatchling) of them left. only one egg hatched recently, and the last remaining ot the shiryan people make sure none of their dragons escape the sanctuary.

if anyone has any questions about the setting or anything else, please fo ask.

 

[DragonOfTheAerie]

This sounds cool, but the Shiryan dragon populations would halve with every generation if females only ever laid one egg. Look at it this way: Obly females can lay eggs. Every female will produce one egg. Of those dragons, half are male and half are female. Only the females can lay eggs, so they each produce one offspring, and only half of THAT generation can lay eggs. They certainly wouldn't be able to increase in population.

This is assuming that no dragons die before reproducing or are infertile. In reality the population would break down a lot quicker than just by half each generation because there's no way every dragon would survive to reproduce successfully. Even if they were all females reproducing through parthenogenesis, they wouldn't be able to delay decline in population for long.

Other than that, cool stuff.

 

[Ewolf20]

This sounds cool, but the Shiryan dragon populations would halve with every generation if females only ever laid one egg. Look at it this way: Obly females can lay eggs. Every female will produce one egg. Of those dragons, half are male and half are female. Only the females can lay eggs, so they each produce one offspring, and only half of THAT generation can lay eggs. They certainly wouldn't be able to increase in population.

This is assuming that no dragons die before reproducing or are infertile. In reality the population would break down a lot quicker than just by half each generation because there's no way every dragon would survive to reproduce successfully. Even if they were all females reproducing through parthenogenesis, they wouldn't be able to delay decline in population for long.

Other than that, cool stuff.

I never would have thought of that. Though I should have clarified that the reason there 's 20 left is because of overhunting during the shiryan empire collapse.

 

[DragonOfTheAerie]

I never would have thought of that. Though I should have clarified that the reason there 's 20 left is because of overhunting during the shiryan empire collapse.

You could have them lay only one egg every nine years or something

 

[Night Gardener]

A way to side step some of the issues with shiryan dragons is simple: longer gestation times. Some whales and elephants are gestating for 18 months, sometimes up to almost 3 years. If their reproduction cycle is also expanded, lets say estrus is every 4 years... well, that is a long time between new generations. I like the idea of the one egg, though. I could see shiryan dragons viciously defending that singular egg to their deaths. One egg, ferociously defended and then the hatchling doted upon by its parents... I would deduce that the survival rate is fairly high for that dragon species. Have pair-bonded dragons stagger their breeding cycles within the greater population so there's always a new baby dragon somewhere being added to the general population, and therefore differently aged within said demographics... if all dragons are hatched exactly 3 years apart, that's a big problem. If some are born every year, throughout the year, not so much a problem overall. . . Survivors of fledgling would mature into the population at slightly different ages, and slightly different sexual maturities to help stabilize a population. Unlike cicadas that emerge en mass to mate and lay eggs every 17 years. It only works as a survival strategy for the species as a whole because there are BILLIONS of them to ensure some will procreate and even more will be added to the population. If you lose a million to predation or disease in a single region, there's still a ridiculous amounts of cicadas.

 

[CupofJoe]

And then there are animals [like Kangaroos?] that can mate at any time. The females hold the fertilised eggs until they are in a good/better position to bare young.

 

[The Ancient One]

I also noticed the "one egg for life" problem the others have mentioned, but the idea certainly has a very nice ring to it. I especially like the scenario that Night Gardener has painted, where these dragons will do anything for their one egg because it's the only chance they got. I believe that has a lot of potential and is an interesting characteristic.

To solve the population problem, without throwing the idea of a singular egg away, you could have these dragons lay one big egg with multiple babies inside. Three on average should be enough to stabilize the population, assuming the shiryans dragons have good life expectancies (which is a necessity in such a scenario).

 

[Night Gardener]

Multiple young, singular egg. That is very interesting solution. Add that to a very, very long gestation (as such an unusual complicated egg would probably demand). They may only get to lay one, two ...maybe 3 eggs in all of their fertile years. To an average human lifespan, it may certainly seem like a "once in a lifetime" event to see a those dragons lay and hatch and egg. Though, I imagine they'd have to observe through binoculars at a very safe distance, downwind, to stay clear of the egg's relentless guardians.