The exact reason for the decline in the 1950s is unknown as well. The Fish & Wildlife Services states that the eagles declined in the 1950s because of DDT. The problem with that statement is the fact that the bald eagle was recovering for many years before the nation banned DDT.
Elephants in the wild live to a range of 50 to 70 years. For well kept and fed animals in captivity, the oldest recorded is 82 years.
Horses live on the average to 20 years but can live as long as 30 - 40 ...i once heard the oldest horse ever lived to 62 or something in like the 1700s.