The answer is corrosive health hazard.
The Pre-Columbian era incorporates all period subdivisions in the history and prehistory of the Americas before the appearance of significant European influences on the American continent, spanning the time of the original settlement in the Upper Paleolithic period to European colonization during the Early Modern period.
While the phrase "pre-Columbian era" literally refers only to the time preceding Christopher Columbus's voyages of 1492, in practice the phrase is usually used to denote the entire history of indigenous Americas cultures until those cultures were exterminated, diminished, or extensively altered by Europeans, even if this happened decades or centuries after Columbus's first landing. For this reason the alternative terms of Precontact Americas, Pre-Colonial Americas or Prehistoric Americas are also in use. In areas of Latin America the term usually used is Pre-Hispanic.
In a way, this is a double edged sword. On one hand, the animals are needed to best test the effects, but on the other hand it can be seen as very unethical. Honestly, I don't really see a way around using the animals. Unless you get human volunteers, but there is no way to fully make them understand what they are getting themselves into which can turn unethical very, very fast. If all of a sudden one of your human volunteers decides that they do not want to be a part of the test anymore, there is noting you can do to reverse what has already been done.
