Aelian
περὶ ζῴων ἰδιότητος – On the Characteristics of Animals [=NA]
Schofield's Loeb parallel translation is available from Attalus.org in a HTML version, and from 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.
Aelian, trans. Scholfield (1958–1959) On Animals (3 vols). Cambridge, Mass; London: Harvard University Press; Heinemann.
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. http://penelope.uchicago.edu/Thayer/E/Roman/Texts/Aelian/home.html.
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.
http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3atext%3a2008.01.0590
Ποικίλη Ἱστορία – Various History
There is no modern open-access translation of Aelian's Varia Historia; however, James Eason has made a HTML version of Stanley's 1665 translation available on his website (see link below).
Aelian, trans. Stanley (1665) Claudius Aelianus, His Various History. London: Thomas Dring. —Link is to a HTML version made available by James Eason. http://penelope.uchicago.edu/aelian/