In none of these cases is there any indication that acclimatization was necessary or ever took place.
These instances, so well stated by Spruce, seem to demonstrate the complete acclimatization of Spaniards in some of the hottest parts of South America.
Amounting to a serious pest in Australasian colonies, it is also established in the Falklands and Kerguelen; its presence in much of Europe is attributed to early acclimatization, as it seems anciently to have been confined to the Iberian peninsula.
The modern presence of the black swan of Australia (Chenopis atrata) in New Zealand appears to be due to a natural irruption of the species about half a century ago as much as to acclimatization by man, if not more so.
The acclimatization of white men in tropical Africa generally is dependent largely on the successful treatment of tropical diseases.