Pradyumna: Sometimes love affairs between two persons culminate in ghastly murder scenes. Such rasas are displayed between man and man and between animal and animal. There is no possibility of an exchange or rasa between a man and an animal or between a man and any other species of living beings within the material world. The rasas are exchanged between members of the same species. But as far as the spirit souls are concerned,..."
Prabhupāda: You have seen sometimes the pigeons fighting. But a pigeon and crow does not fight. A pigeon and pigeon fights. So this is also another indirect way of love. You'll see the pigeons, they will fight and again sit down in the assembly of the pigeons, not that the pigeon is going to the assembly of crows. Go on.
Pradyumna: "The rasas are exchanged between members of the same species. But as far as the spirit souls are concerned, they are one qualitatively with the Supreme Lord. Therefore, the rasas were originally exchanged between the spiritual living being and the spiritual whole, the Supreme Personality of Godhead. The spiritual exchange, or rasa, is fully exhibited in spiritual existence between living beings and the Supreme Lord. The Supreme Personality of Godhead is therefore described in the śruti-mantras, Vedic hymns, as "the fountainhead of all rasas."
Prabhupāda: Raso vai saḥ.