Rabanus Maurus (ca. 780-856), abbot of Fulda and Archbishop of Mainz, was theological and pedagogical writer. He was born at Mainz about 776 (or possibly 784) and died near there in 856. His name, which is spelled in various ways (Hrabanus, Rabanus, Rhabanus, Reabanus, Raban, Rabano), is connected with Old High German hraban, "raven"; "Magnentius", which sometimes appears before his surname, Maurus, is probably related to his residence in Mainz. At an early age he became a Benedictine monk at Fulda. In 802 he went to Tours to study theology and the liberal arts, under the great scholar Alcuin, from who he received the surname Maurus after the favorite disciple of St. Benedict. After a year of study, he was recalled to Fulda, where he taught at the monastic school and eventually became head-master. In 814 he was ordained as a priest; in 822 he became abbot of the monastery. Under Abbot Hrabanus, the monastery flourished, becoming a renowned seat of learning in the Frankish kingdoms. Between 840 and 847 Hrabanus became embroiled in royal political struggles, resigned as abbot, and fled from Fulda. In 847, after a reconciliation with the king, he was appointed Archbishop of Mainz.

Hrabanus was said to be the most learned man of his age. His knowledge of scripture, patristics, canon law and liturgy was without compare. The scope of his writing extended over the entire field of sacred and profane learning as then understood. He wrote commentaries on nearly all the books of the Old Testament, as well as the Gospel of Matthew and the Pauline Epistles. He also wrote more secular works such as De computo, a treatise on numbers and the calendar; the Excerptio de arte grammatica Prisciani, a treatise on grammar and his famous encyclopedia, De rerum naturis.

De rerum naturis (On the Nature of Things), also known as De universo, is an encyclopedia in 22 books, covering a large range of subjects. It was written between 842 and 847. Hrabanus' stated intent was to compile an encyclopedic handbook for preachers. He drew on earlier sources for his information, particularly the Etymologiae of Isidore of Seville, but the organization of the material was his own invention.

Book 8 is on animals. It is divided into seven chapters: De bestiis ("beasts", mostly mammals); De minutis animantibus (small animals); De serpentibus (serpents, reptiles); De vermibus ("worms", mostly insects); De piscibus (fish); De avibus (birds); De minutis avibus (small birds). The chapters and the animals in them are (based on Schipper) (this list is preliminary and may not be entirely reliable):

Chapter 1: De bestiis - On beasts

• Leonis (lion)
• Tigris (tiger)
• Panter (panther)
• Pardus (pard)
• Rinocerota (monocerus and unicorn)
• Elefantem (elephant)
• Gripes (griffin)
• Camaeleon (chameleon)
• Linx (lynx)
• Castores (beaver)
• Ursus (bear)
• Lupus (wolf)
• Canis (dog)
• Vulpis (fox)
• Simiae (ape)
• Enidros (hydrus)
• Dracontius (dragon)
• Musio (cat)

Chapter 2: De minutis animantibus - On small animals

• Mus (mouse)
• Mustela (weasel)
• Talpa (mole)
• Glires (?)
• Hiritius (hedgehog)
• Grillus (?)
• Formica (ant)
• Ranae (frog)

Chapter 3: De serpentibus - On serpents

• Cerastes (cerastes)
• Draco major (dragon)
• Aspis (asp)
• Ipnalis (hypnalis, another kind of asp)
• Bailiscus (basilisk)
• Scorpio (scorpion)
• Vipera (viper)
• Enidris (hydros?)
• Celidros (?)
• Salamandra (salamander)

Chapter 4: De vermibus - On worms

• Areana (spider)
• Cantarida (?)
• Multipes (multiped)
• Limax (?)
• Bombices (?)
• Eruca (?)
• Teredonas (termite?)
• Tinea (?)
• Lumbricus (?)
• Ascaridae (?)
• Tarmus (?)
• Ricinus (?)
• Usia (?)

Chapter 5: De piscibus - On fish

• Crocodrillus (crocodile)
• Mullus (?)
• Mugilis (?)
• Anguillae (sea snake?)
• Draco marinus (sea dragon)
• Mure (?)
• Concae, Cocleae (?)
• Murice (?)

Chapter 6: De avibus - On birds

• Aquila (eagle)
• Vultur (vulture)
• Grues (crane)
• Ciconiae (stork)
• Olor (swan)
• Strutio (ostrich)
• Ardea (heron)
• Fenix (phoenix)
• Cinomolgus (cinnamologus)
• Psittacus (parrot)
• Alcion (kingfisher)
• Onacrotalus (bittern)
• Vespertilio (bat)
• Noctua (owl)
• Bubo (owl)
• Lucina (nightingale)
• Ulala (owl?)
• Graculus (jay)
• Picus (woodpecker)
• Pavo (peacock)
• Gallus (cock)
• Anser (goose)
• Mergis (merganser?)
• Fulica (coot)
• Turtur (turtledove)
• Columba (dove)
• Perdix (partridge)
• Coturnices (quail)
• Passer (sparrow)
• Pellicanus (pelican)
• Nocticorax (owl)
• Garrula (?)
• Hirundo (swallow)
• Corvus (raven)
• Cornix (crow)
• Milvus (kite)
• Accipiter (hawk)
• Uppupa (hoopoe)

Chapter 7: De minutis avibus - On small birds

• Apes (bee)
• Spines (?)
• Scrabrones (?)
• Locusta (locust)
• Musca (?)

The books and chapters of the De rerum naturis are listed below (based on Schipper).

1. On God and angels
2. On man, the patriarchs, the status of man
3. on people of the old testament
4. People of the New Testement, martyrs, clerics, monastics, heretics
5. On the scriptures
6. On man and the parts of man
7. ?
8. On animals
9. On astronomy - the world and the heavens
10. On time and the calendar
11. On water - oceans, rivers, floods
12. On geography - the regions of the Earth, the globe, paradise
13. On geography - mountains, valleys, deserts
14. On architecture and building
15. On the liberal arts
16. On language
17. On geology - stones, minerals, gems, metals
18. On number, music, medicine
19. On agriculture
20. ?
21. On textiles and clothing
22. ?

Other medieval encyclopedias:

• Bartholomeus Anglicus : De proprietatibus rerum
• Isidore of Seville : Etymologies
• Lambert of Saint-Omer : Liber floridus
• Brunetto Latini : Li Livres dou Tresor
• Jacob van Maerlant : Der Naturen Bloeme
• Konrad von Megenberg : Das Buch der Natur
• Thomas de Cantimpré : Liber de natura rerum