You must learn a special skill to tame Lesser Dragonkin. For pets of this family other than cloud serpents, the skill is taught by the tome, How to Train a Dragonkin. This is awarded by Kaestrasz in Valdrakken at renown level 23 with the Valdrakken Accord. It is only awarded to hunter characters with the appropriate renown, you cannot achieve the renown on a non-hunter alt.
Level scaling: Most NPCs will scale with the Hunter's level, within the constraints of their level range. Hunters can tame regular NPCs up to 2 levels higher than them, but can only tame elite NPCs of the hunter's level or below.