Aelian: περὶ ζῴων ἰδιότητος – On the Characteristics of Animals [=NA]
The Loeb parallel English translation is available at the Internet Archive as a scanned copy. Also at the Internet Archive is a scanned copy of Hercher's 1858 Greek text with parallel Latin translation, while a HTML version of the Latin translation from Jacobs' 1832 edition is available from LacusCurtius. Hercher's Greek text is available in HTML version from Perseus., trans. Scholfield (1958–1959) On Animals (3 vols). Cambridge, Mass; London: Harvard University Press; Heinemann. —Volume I: Books 1–5; Volume II: 6–11; Volume III: 12–17.

Aelian, ed. Jacobs (1832) Aeliani de natura animalium libri xvii. Jena: F. Frommann. —Text in Greek with translation, commentary and notes in Latin. URL links to HTML version made available by Bill Thayer. 

Book I   II   III   IV   V   VI   VII   VIII   IX   X   XI   XII   XIII   XIV   XV   XVI   XVII

Aelian, Porphyry, and Philo of Byzantium, ed. Hercher (1858) Aeliani: de natura animalium; varia historia; epistolae et fragmenta. Porphyrii philosophi: de abstinentia; de antro nympharum. Philonis Byzantii: de septem orbis spectaculis. Paris: A.F. Didot.