Why is it always males that get eaten during sex?

Scientific concepts / nature phenomena

• Sexual cannibalism: animals eating a mate or potential mate before, during, or right after mating.
• Observed pattern in mantises: female praying mantises more often eat the male (commonly by biting the male’s head) during mating.

Evolutionary / fitness explanation (reproductive payoff constraint)

In many species, if a male eats a female before/during/right after mating, the pair produces no offspring, because the female carries eggs/developing young. Therefore, a male who practices such behavior would likely fail to reproduce, making the behavior hard for males to persist evolutionarily.

For females, eating the mate can be advantageous because:

• It removes a future “baby daddy” that might help care for offspring in species where males would otherwise contribute (less beneficial where males don’t help).
• In species where males don’t help with raising young, females bear most/all parental energy costs; a high-protein meal can directly boost reproductive success.

Quantitative evidence mentioned

• A study cited reports that mantis females who ate their mates laid more than twice as many eggs as females that did not.

Potential genetic / offspring tradeoffs

The video notes that while mate-eating might seem like it could benefit both sexes’ genetic legacy, the male dies, so his future mating opportunities end. If the male were not eaten, he could potentially mate again and produce more offspring.

When self-sacrifice may benefit males (redback spiders)

• After mating, male redback spiders may somersault into the female’s fangs and are eaten.
• Proposed evolutionary reason: in this species, most males are eaten by predators before mating, so successful mating is rare. Males may therefore “cash in” by sacrificing themselves to improve provisioning and offspring survival.

Sexual cannibalism before mating (fishing spiders)

In some species, female aggression and strong intrasexual/partner competition can cause aggression to be misdirected toward a potential mate, leading to pre-mating cannibalism.

---

Methodology / list-like reasoning presented

Why females are more likely to eat mates (general logic)

• If males eat females → zero offspring → male behavior is less evolutionarily stable.
• If females eat males → the male dies, but the female often gains energy/protein at a time of high reproductive demand.

Why male self-sacrifice can occur (redback spiders)

• Most males fail to mate at all due to predators.
• When mating happens, self-sacrifice can maximize the odds of successful reproduction/provisioning.

Why pre-mating cannibalism happens (fishing spiders)

• High female aggression/competition.
• Aggression can unintentionally target mates.

---

Researchers / sources featured

• Arcadi: speaker/participant in the video (name appears in subtitles): Arcadi
• A mantis study: referenced, but no specific researcher names or publication details are provided in the subtitles.