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A stochastic simulation model for Asian elephant Elephas maximus populations and the inheritance of tusks

100%

Tiedemann R., Kurt F.

Acta Theriologica. Supplement

1995

nr 03

In the framework of available historical data on population size and human impact on the Asian elephant Elephas maximus Linnaeus, 1758, we developed a stochastic simulation model for elephant populations, which simulates individual elephants and includes their geno- and phenotype regarding the tusk character. The model omits density dependence of reproduction parameters and mortality rates. The model predicts female mortality and mean calving interval to be the paramount factors determining the long-term population trend. For simulated female mortality rates of 5% and 5.5% a mean calving interval of 5.2 years and 4.4-4.5 years, respectively, leads to stable populations, which is in accordance with values derived from field observations. Taking into account a higher mortality of tuskers due to human impact, frequencies of the tusk allele were simulated both for dominant and recessive inheritance of the tusk character. The best accordance with census data was achieved, when the tusk allele was assumed to be dominant, combined with a slight reproductive advantage for tuskers. Since the model simulates population dynamics and tusk allele frequencies under various mortality schedules, it can be used to predict the effect of conservation efforts on populations of the Asian elephant.

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

100%

Kurt F., Hartl G. B., Tiedemann R.

Acta Theriologica. Supplement

1995

nr 03

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.

Ograniczanie wyników

2 Acta Theriologica. Supplement

2 Kurt F.

2 Tiedemann R.

1 Hartl G. B.

2 1995

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A stochastic simulation model for Asian elephant Elephas maximus populations and the inheritance of tusks

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