Lord Krishna in Bhagavad Gita advocates practicing samatva (equanimity) that relates not only to human form but all lower forms of life.
As per doctrine of samatva all living forms must be treated equally. This does not mean we go near a hungry lion. The reason is apparent. We understand the language of samatva, not the lion.
What Lord Krishna intends to say is, if we need one duck for our dinner and we land killing three for the sake of pleasure then for the extra two killings we shall be punished by god!
Humankind is the highest manifest form on mother earth. It is only as human beings one could reach state of enlightenment, become a pure soul atman forever. Path of spirituality can be indulged only in human form, never lower forms of life.
For this very reason it becomes a duty of mankind to protect the lower species from indiscriminate elimination at the hands of human beings.
We are lucky to be born a human being, so says Lord Krishna in Bhagavad Gita. We are equally lucky if we indulge in spirituality to reach God in our lifetime. Indulging in religion (rituals) one gains nothing in life. Going to temples churches and mosques is just a pastime.
As per Lord Krishna in Bhagavad Gita, God Almighty himself existed in all human beings in miniscule form as the spirit, consciousness existing in our heart as soul atman. As we are part of God Almighty, a spiritual traveler it becomes our duty to indulge in spirituality to reach cosmic end of life.
From spirituality point of view all the lower species are our brethren in the evolutionary cycle. All human beings evolved from stage of amoeba. As per Bhagavad Gita a soul atman initially manifests form of amoeba (single cell formation), the first manifestation in cosmic life cycle. It further evolves into multi-cell formation, insect life, plant life, animal life and finally the human form.
Lord Krishna in Bhagavad Gita says every single species on mother earth had equal right in all the natural resources available absolutely free of all costs.