Skill caps on pets. The cap on a skill is either 100 or what the skill ended up at after taming, which ever is higher. In this case, your poisoning being 117,4 is the cap and it will keep that even if it dies. If it dies, it will be at 117,3/117,4 and can regain the skill if it still has poisoning on it's lore gump. Skill caps can be increased by scrolling during training, but only if there are scrolls for it(poisoning being an exception).