Female Turkeys Can Produce Male Offspring Without Sperm

Female turkeys can sometimes develop offspring from unfertilized eggs, a process called parthenogenesis, but the surviving offspring are male.

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Some female turkeys can do something that sounds impossible at first: produce offspring without sperm. The process is called parthenogenesis, meaning an unfertilized egg begins developing as an embryo. It has been documented in domestic turkeys for decades and is also known in other animals, including some bees, lizards, and sharks. In turkeys, however, successful development is extremely uncommon. Most embryos formed this way fail early, and the offspring that reach hatching have been observed to be male. This connects to the unusual sex chromosome system found in birds. Female birds generally have ZW chromosomes, while males have ZZ. During parthenogenesis, the egg can combine with a matching cell produced during egg formation, allowing development to continue without sperm. A combination producing ZZ can develop as a male, while a WW combination is not viable. Older turkey breeding experiments found that only a small fraction of parthenogenetic embryos survived to hatching, with one study reporting about 1 percent survival and selective breeding increasing the rate to roughly 8 percent in a particular turkey line. The phenomenon is therefore a real reproductive pathway, but it is not a normal or reliable way for turkeys to reproduce. Later genetic work also distinguished true parthenogenetic embryos from other forms of abnormal early development in turkey eggs, reinforcing that the phenomenon is biologically unusual rather than a routine alternative to fertilization.

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