Strato of Lampsacus

Strato (~335 – ~269 BCE) was a Peripatetic philosopher, and the third director of the Lyceum after the death of Theophrastus. He devoted himself especially to the study of natural science, and increased the naturalistic elements in Aristotle’s thought to such an extent that he denied the need for an active god to construct the universe preferring to place the government of the universe in the unconscious force of nature alone. He wrote three books relating to animals but his stance on the moral salience of sentience is unclear. He may well have been vegetarian/vegan given the philosophy of Theophrastus, his predecessor, and others in the Peripatetic and Pythagorean traditions.
Strato of Lampsacus on Wikipedia