Pufferfish, which are highly poisonous when eaten by the player, can be fed to tamed wolves since this snapshot. In real life, the effect of the pufferfish poison ("Tetrodotoxin") is not specific to humans, but is the pufferfish's last-line defense against all kinds of predators that ignore it puffing up into a spiky ball.

Observed Behavior

Pufferfish items can be fed to tamed wolves and will heal them the same way as tropical fish. The tamed wolf does not get affected by any status effects from this. Feeding pufferfish even works for breeding tamed wolves.

Expected Behavior

Pufferfish can either not be fed to tamed wolves or applies its negative effects.

(I guess a third option would be that the pufferfish is spit out again. That's supposedly how predators react to the taste of young pufferfish, who have not developed the size and spines as mechanical defense yet.)