Among all the species of life we souls may inhabit, human life is the best because it affords us the higher intelligence with which to make spiritual progress. In plant or animal bodies, our consciousness is too undeveloped.
With the higher awareness of human life comes greater responsibility. Animal life comprises only four activities: eating, sleeping, mating, and defending. Human beings are no better than animals if they spend their lives in similar pursuits and don't try for self-realization.
When we observe the vast numbers of plants and animals in this world, we can understand just how rare is a human birth. That should inspire us to make the best use of our short time in these bodies by diligently following the authorized spiritual practices of Bhakti yoga, which can lead to perfection.