The Animal Realm:

“Their classification is fourfold: those who have many legs, four legs, two legs, and those who are without legs. Where are they located? Ocean, plain, or forest. For most of them, the ocean is the place they abide.

What type of suffering do they experience?

The suffering of being used, the suffering of slaughter, and the suffering of being eaten by one another. The first is accorded to the domestic animals under the power of humans. As is stated:

«Powerless, they are tortured. Hands, feet, whips, and iron hooks enslave them.»

The second suffering is accorded to wild animals. As is stated:

«Some die for pearls, wool, bone, blood, meat, and skin.»

The third suffering is accorded to the majority, who abide in the big oceans. As is said:

«They eat whatever falls into their mouths.»

What is the life span of the animals? This is indefinite. The longest is one-quarter kalpa. As is said:

«Among the animals, the longest life span is one antahkalpa at the most.»”

Gampopa, The Jewel Ornament of Liberation, Kagyu Lamrim