Tame a Shrieker broodmother.
As a prerequisite, you'll need to research, craft, and equip a pacifier weapon on at least one survivor.
I got this during a shrieker attack on my base (military scenario on Saltu). I defended against the attack as normal until there was only a single broodmother and about a dozen hatchlings left. I micro'd my defenders to kill only the hatchlings (pausing to retarget), and as soon as the last hatchling was dead, undrafted everyone except the survivor with the pacifier and turned off defenses. I then ordered the survivor with the pacifier to attack the broodmother until the word Pacified popped up over its head. Then I undrafted that survivor too and had him tame the broodmother. It helped that the survivor was Hugo, who cannot fail a taming attempt.