During his time with the Taensa, de Montigny prevented them from performing acts of ritual human sacrifice as part of the funeral rites for a deceased chief. Because of this, the Taensa later blamed de Montigny when lightning struck their wattle and daub temple and burned it down. He left to join the Natchez in 1790, and his mission to the Taensa was taken over by Jean-François Buisson de Saint-Cosme. Along with other native peoples of the lower Mississippi River, the Taensa were subject to slave raids and epidemics of European diseases such as smallpox during this time period. As the population of the Taensa steadily decreased, de Saint-Cosme in 1700 endeavored in vain to have them join with the much larger Natchez and consolidate the two missions. De Saint-Cosme settled among the Taensa and the Natchez for less than a year before leaving.