Varren are omnivorous and have a preference for living prey. They are pack hunters when vulnerable prey is readily available and become scavengers when outnumbered or outclassed. Their supreme adaptability, vicious demeanour and rapid breeding cycle have made them ubiquitous and dangerous pests on many worlds. Virtually everywhere the Krogan have been, varren infestations have followed, wreaking havoc with the native ecology.
The Krogan have had a love-hate relationship with varren for millennia, alternately fighting them for territory and embracing them as treasured companions. To this day, Krogan—and some other species, including Batarians—raise them as beasts of war. A common subgenus of varren has metallic silver scales, leading to the rather unusual nickname 'fishdogs'.