Permanent liberation from cycle of birth and death is possible only in human form, never lower forms of life including animals.
Moksha cannot be attained in animal form. Every soul atman has to further evolve from animal state to human form.
In the evolution timeline every soul atman passes 7.3 million manifestations in insect plant and animal life. In the remaining 1.1 million manifestations in human form a soul atman is expected to reach state of moksha salvation, a state of absolute purity.
Human form is the highest manifest stage in cosmic life cycle and it was only in human form one could reach state of moksha salvation.
When human beings indulging in spirituality succeeded gaining enlightenment then state of moksha salvation is not far behind. The moment an enlightened one left mortal frame one attains moksha salvation forever.
Moksha salvation is a state reached when the soul atman liberated from cycle of birth and death forever. Only a pure soul atman could reach state of moksha salvation. As long as dross impurities existed within a soul atman, it keeps rotating endlessly in the cycle of birth and death manifesting form after another.
Enlightenment was all about indulging in spirituality which was not possible in animal form or lower forms of life.