Little is known about Gervaise, other than that he is the author of a verse Bestiaire in a Norman dialect of French. He is thought to have lived around the end of the twelfth century to the beginning of the thirteenth, and was possibly a member of a Cistercian abbey at Barberie (or Barbery) in the diocese of Bayeux, established in 1176. Meyer notes that there were three men named Gervaise in the area at the time, and says that the most likely one was the priest Gervasius of Fontenai.
In the prologue to the Bestiaire, Gervaise names himself as author, and says he created the rhymed verses based on a manuscript in Latin that he found in a cupboard in "Barbarie". It is not known which Latin text Gervaise used, though he ascribes it to John Chrysostom, who was one of the many early Greek writers said to be the author of the Physiologus. Gervaise probably wrote his poem around the beginning of the thirteenth century. It does not seem to have been well known in his time; it appears in only a single manucript (British Library, Additional MS 28260), a late thirteenth century copy of Gervaise's original.
The 29 chapters of the Bestiaire are (from McCulloch, p. 56):