Dolphins and ethical theories

In an interesting book (Dependent Rational Animals: Why Human Beings Need the Virtues), Alasdair C. McIntyre develops a sort of "ethics" for dolphins. He chooses dolphins insofar as they are intelligent, though non-human, beings. They can, thus, act because of reasons. His whole theory is based on the idea that a reason to act is "something good in itself that it realises or serves or […] something bad that it avoids". This definition is surprisingly similar to Maṇḍana Miśra's idea that what has to be done is only either something pleasant, or the avoidance of something unpleasant or a means thereto. (Interestingly enough, Maṇḍana develops the same thought as the above one, but starting the other way round, possibly because of his Mīmāṃsā background, which inclines him to take into consideration even authorless exhortations and to stress the importance of the final result).

It is possible that one can build a consistent theory of action upon that, but it is hardly the case that a theory of exhortation can work on these presuppositions. Maybe Maṇḍana just did not want to explain that? Maybe his primary focus was action, not exhortation?