The thing to remember here is that evolution does not necessarily do "what makes the most sense" to a human mind. It just goes with whatever accident happens to work at the time and place in which it occurred. A lot of people here are acting like it's an open and shut case on the basis that females are the ones that gestate offspring, but that's operating under the potentially erroneous assumption that you WANT a lot more offspring in the first place, (it all depends on the ecological niche that organism fills and how many offspring the environment can even support and with just about any predator species, the answer is often "not many") and frankly, that's not entirely relevant anyway considering how many species die in childbirth yet still manage to exist.
For example: Let's look at the giant panda. It survives on nutrient-poor food that it can't digest well and so it needs a ton of it to survive. Pandas have 1-2 cubs and if there's a second, the mother usually lets it die. Why? She can't meet the nutritional needs of two cubs. She's already starving herself in a cave, living off fat reserves just to protect the one. The point is: their survival strategy isn't efficient and wouldn't make any sense to a hypothetical designer, but it works because of the panda's environment (adapting to an easy-to-obtain and abundant food source even though they're bears and their digestive systems weren't well adapted to it). If pandas reproduced more or had more offspring at a time, there may no longer be enough food to support the entire population because they need to eat so much of it. They evolved to do things in a very specific and, in some ways inefficient way, and they were fine until mankind came along and began ravaging their environment and actively killing them.
Now there are also plenty of animals out there that frequently, or in some cases always, die in childbirth, including humans in the former category. From BBC Earth: "The World Health Organization estimates that about 830 women die every day because of complications during pregnancy and childbirth – and that statistic is actually a 44% reduction on the 1990 level." (Source:
http://www.bbc.com/earth/story/20161221 ... -dangerous ) It's only recently and only in developed countries that women do any better and yet we're still overpopulated as all hell. Then there are animals like the giant octopus which lay their eggs and guard them until they hatch, thus starving to death in the process. There are also a handful of species of animals that go a step further and eat their mothers as they're born (
https://en.wikipedia.org/wiki/Matriphagy ). My point is that despite these practices, the species survive just fine and their populations aren't threatened by guaranteed maternal death upon mating.
So given such precedent in nature, I don't see why it's implausible to have a species in which the males evolve to be cannibalistic. There are multiple ways it could go down:
In a hypothetical species we'll call "alpha," the males eat each other during mating season. Why? To ensure that there are more females for them to breed with, of course! Less competition means more females can carry one supremely powerful individual's genes to ensure a stronger next generation than what the weaker males currently resting in the king's belly could create. They're basically just a vore themed version of other animals that actively try to kill off their mating competition, like Dawson's bees for example:
http://news.bbc.co.uk/earth/hi/earth_ne ... 354788.stmIn another hypothetical species we'll call "beta," the males eat the females after they give birth. The female is weak and her body is irreparably damaged from gestation and birth and the male is hungry from guarding her nest at all times. Once she has completed her job and given birth, he devours her to regain his strength and, fully rejuvenated, he goes out to hunt to bring back food for his newly born offspring who are tiny and well-camouflaged enough to survive while he's away. There are, afterall, numerous precedents in the animal kingdom for the male doing the child-rearing as is the case with seahorses, certain penguins, and, in an especially vore-tinged example, paternal mouthbrooding fish like arowana and some cichlids.
Species "gamma" is similar to mouthbrooders, but is more extreme. Like species beta, gestation is very taxing for gammas and their environment doesn't provide them with a lot of food. The male hunts and builds up his fat reserves while the females gestate their young. Before a female can give birth, the male swallows her whole. She provides him with one last meal before his long fast. As her body breaks down and feeds him, the offspring survive in his stomach due to their as of yet, still malleable skeletal structure and a thick coating a mucus they secrete to protect themselves from their father's digestive juices. From here on, the male will not eat for months lest he risk harming his children and for his efforts, they are protected from any would-be predators or nest invaders by having the father serve as a mobile fortress of sorts until the children are mature enough. At such a time, he will regurgitate them and leave them to fend for themselves.
My point with all of these examples isn't to try and disprove what anyone else said about the possibilities of females adapting to be predators in this scenario. That's plausible too. I'm only here to provide a counterargument against those who say "This is the only way it makes sense," because that just isn't true. Nature doesn't care what you think is the best way to do things. Evolution is random and sometimes borderline nonsensical. Any solution to the problems of life doesn't need to be brilliant or ideal, it only has to work just well enough to ensure a continuous population.