User blog comment:Kogath/Monster Hunter 4 Ultimate for the Nintendo 3DS/@comment-6050823-20150306225752

After doing some research I finally found what Furious Rajang is or might be...

It turns out that not even the Guild are exactly sure what Furious Rajang is, however, its true that the tail controls a Rajang's power. Its theorized by them that the Furious Rajang's power is unstable due to the lost of its tail though something interesting was said. Some hunters reported that even after destroying the tail of a Rajang they were hunting, apparently it was still able to into Rage Mode without its tail.

I thought about this long and hard and finally came up with a possible explanation. In Dragon Ball Z, Low-Level Saiyans can easily be stopped at their tracks by getting a hold of their tail while Saiyan Elites have done special training to avoid such a pitiful weakness. What I'm going with is that maybe this also applies to some experienced Rajang to a degree.