Mātā yathā niyaṁ puttam
Even as a mother would protect her own child,
Āyusā eka-puttam-anu-rakkhe;
her only child, at the risk of her own life,
Evam-pi sabba-bhūtesu,
so too towards all creatures [, for their safety and happiness, ]
Mānasaṁ bhāvaye aparimāṇaṁ.
[You] should develop [and protect your] unlimited heart.
If it's talking about all animals, the element of 'protect' is even more clear.
Crows nesting get ultra aggressive protecting eggs and young from any approaching beings,
Mama bears mauling any humans that get anywhere near a baby bear, etc.