Creatures Caves

Glycotoxin

Is this as confusing to anyone else as much as it is to me?
Ok, here's how it started...
I was trying to train Grendels to be sweet, loving, and not hit Norns... Long story.
Anyways, my first Grendel died of old age, so I waited for the "Grendel Mother" to hatch another.
I taught him his words and pretty soon, he was a child, and I got to thinking:
"Are Grendels more resistant to illness and toxins than Norns and Ettins?" So I tested.
After being amazed because he fought off a few Antigens with no problem whatsoever, I decided to check if he was immune to Glycotoxin.
I first injected a tiny little bit of it in him, he fought it off like it was nothing. So I injected a bit more, again, he seemed to resist it fine.
So then I injected 50% into him, he was still fighting it off.
So, as you can imagine, I was a happy.
Trying my luck, I injected 100% of Glycotoxin into my Grendel, I checked the "Biochem" page and the Glycotoxin bar hadn't even gone to 100% and it was slowly going away.
My Grendel had only 2 health bars left, but I healed him, gave him some ATP and Life, with some Oxygen and when the Glycotoxin was gone, my Grendel was all fine again.

So what I'm wondering is... Do Grendels have a stronger immune systems than other Creatures, or did I discover something extraordinary?