The transmission and use of bestiary material in medieval Portugal, as in Castile, confronts us with an immediate problem: although there are extant Catalan bestiary texts (translated from Italian; Panunzio), the rest of the Peninsula has nothing in the vernacular or in Latin – either extant texts or records of lost ones – that can be described as a bestiary in the accepted sense of the word. We do, it is true, possess Castilian, Aragonese, and Catalan translations of Brunetto Latini's encyclopedic Livres dou Tresor (Baldwin 1982 and 1989, Prince, and Wittlin, respectively), a work that incorporates a version of the bestiary's immediate ancestor, the Physiologus, but without the Christian moralizations that are central to the purpose of the bestiary. Any Peninsular work that makes use of a bestiary animal with its moralization cannot, therefore, have relied on one of the translations of Brunetto Latini. It is also true that the Aviarium, the first book of the twelfth-century De bestiis et aliis rebus (wrongly attributed to Hugh of St Victor), sometimes copied independently, appears to have made a greater impression in Portugal than in the rest of the Peninsula. Both a Latin and a vernacular text survive, the latter only in part but the former in full, in three manuscripts.

Neither the Latin nor the vernacular aviary seems to have influenced Portuguese or any other Peninsular literature of the Middle Ages. How, then, can we account for the frequent appearance of bestiary animals – that is to say, creatures such as the phoenix and the unicorn, ordinary animals with their bestiary attributes, and animals with bestiary moralizations attached – in medieval Castilian and Portuguese works? The answer is to be found partly in the pervasive influence of the bestiaries in the church culture of the Middle Ages (notably in sermons and in ecclesiastical architecture), and partly in intergeneric borrowings between bestiaries and encylopedias, bestiaries and Aesopic fable collections, etc. It is, therefore, not surprising that bestiary animals play a substantial part in the exempla and comparisons of the Orto do Esposo, a doctrinal and devotional work of the late fourteenth century.