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From Citizendium, the Citizens' Compendium
Unlike surgical desexing, contraception in animals is a reversible means of population control.
- Large animals
Behavioral abnormalities have been noted in female elephants treated with estrogen implants(reference:Fayrer-Hosken, R. A., Grobler, D., Van Altena, J. J., Bertschinger, H. J. & Kirkpatrick, J. F. Nature 407, 149 (2000)).