User blog comment:Lord Loss/Monster Hunter Theory... Blog/@comment-4361439-20130325023732/@comment-4640052-20130608181829

Gameplay and Story Segregation probably. Not everything makes sense when it comes to drops, you can carve many tails from the same monster, they cry bones and parts of their bodies, it is just a way to get the drops.

If I had to come up with a crazy explanation I would guess the Monoblos has dry hearts of other Monoblos it killed in duel stuck on the horn, so when it hits a wall or is smacked hard enough the hearts drop =D