So, for an obligate carnivore + ambush predator species, what could necessitate their babies being born precocial?

IRL, big cats' babies are fairly altricial, but I need a reason for them to be the opposite. I figure a more extended gestation period would have something to do with this?

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    $\begingroup$ The best reason is a bigger and hungrier carnivore. (And as a counter example, spotted hyena cubs are born with their eyes open and functional teeth.) $\endgroup$
    – AlexP
    Oct 4, 2023 at 21:36
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    $\begingroup$ Part (A): I was going suggest the last point in the answer below. It's harder to give a good answer BTW without knowing at least a little about the world and environment your imagine your predators living in but environmental factors as suggested below could definitely drive a species to develop the traits you desire. $\endgroup$
    – Mon
    Oct 4, 2023 at 22:53
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    $\begingroup$ Part (B): So if for example you assume your predators exist on a continent or world with strong seasonal temperature & weather shifts (Perhaps greater axial tilt than Earth?) you could end up with an ecosystem built around two broad evolutionary paths. Animals either have to migrate in tune with the growing season or hibernate and wait for it to return. Your species went down the first path and has to follow it's prey. $\endgroup$
    – Mon
    Oct 4, 2023 at 22:57
  • $\begingroup$ Tigers ("approximately 100 days, and females give birth to between one and seven offspring at a time") ween for 18~24 months. That's too short? That's plenty of time to get eaten by a pack of hyenas. - Baby elephants ("which are born with complex cognitive skills and are immediately able to sense how to survive in their environment") take 2y, can stand in 20m, and can keep up with the heard in 2d. $\endgroup$
    – Mazura
    Oct 5, 2023 at 13:19

2 Answers 2


First, it would be a good idea to figure out why some species are born precocial and some are born altricially. It helps to look at several well-known examples of both: Most Ungulates are born precocial because they are on the move prey animals, who can’t afford to stay for an extended period and raise young. Humans are born altricially due to the continued growth of our brains becoming a danger to the mother.

Using this as a basis for a new species you can come up with several reasons why some species are born precocial such as the threat of predators, the threat of its ecosystem (most aquatic species are precocial due to the danger of the water), or the search for food; like for example a predator species having to follow a constantly moving prey source.

Here is an article talking about the precocial-altricial spectrum for extra research


I'd offer intra-species conflict. Male bears kill young bears all the time. Not that much, but bear cubs are first protected by being born in the mother's den, then by the mother that can probably physically compete with most males. Take away opportunities for seclusion and tough and strong mothers, then you can make a need for precocious cubs. Alternatively, make the intra-species competition group based. Basically, they "war" a lot. The hard part in having trouble with is making mothers less competitive with males. If pressures encourage the cubs to fight, we should expect that to encourage strong-fighting mothers too. I'm not sure what to offer for this.

But... maybe a handwave is fine. A sexual dimorphism that has petite and attractive females and strong brutish males is a trope people seem to like. "Males come out swinging" adds to that. There's something to be said that this is only an exaggeration of humanity, not a total fantasy. That's probably why people like it.


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