Tuskless bulls in Asian elephant Elephas maximus. History and population genetics of a man-made phenomenon

In Asian elephant Elephas maximus Linnaeus, 1758 tuskless bulls or maknas are generally rare. Only in Sri Lanka 93% of subadult and adult bulls have been reported to be maknas. Using historical records and computer simulations we demonstrate that this situation is man-made. The following mechanisms were identified to be associated with a loss of tuskers: (1) When using elephants, man has always preferred tuskers. (2) Selective hunting and capturing frequently led to a decrease of tuskers in wildliving populations. (3) The impact of selective hunting and capturing was highest in isolated populations, such as Sri Lanka. (4) Selective removal of tuskers for protecting a maximum wild-living male population resulted in an increase of maknas. The rate of increase in the frequencies of maknas in particular populations with known history could be best explained by a dominant mode of inheritance of tusks in combination with a slight advantage of tuskers in reproduction. For the mainland populations it can be predicted that even in those where tuskers are already largely lacking the allele responsible for the expression of tusks should often be sufficiently abundant to allow the recovery of tusk bearing males.