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Free-ranging Red Deer Had Male Antlers, Female-like External Genitalia and Y-linked DNA

Wild adult red deer stag standing among rocks and larch trees
Research · Anatomy & morphology

A free-ranging red deer of the nominate subspecies (Cervus elaphus elaphus) from Poland combined well-developed antlers and otherwise male-typical morphology with female-like external genitalia. The case was investigated as a rare disorder of sex development in a wild cervid.

The animal had a hypertrophied clitoris or penis-like protrusion and no scrotum. Microscopic examination of the available external genital tissue showed structures typical of penile tissue, including cavernous tissue and urethral-like epithelium.

Y-linked DNA showed a genetically male individual

The researchers also tested genetic sex using the Y-linked markers SRY and ZFY, together with ZFX. SRY is a key mammalian sex-determining gene that normally initiates testis development, while ZFY provided an additional marker of Y-chromosome material. Both SRY and ZFY were detected, demonstrating the presence of Y-linked sequences without by itself establishing a complete XY karyotype — a chromosome profile showing the full chromosome complement. Because the preserved DNA was degraded, the team redesigned the genetic test to target a shorter ZFY fragment.

The authors could not determine the exact cause or classify the disorder more precisely. Internal reproductive organs were unavailable, and no complete chromosome profile or hormone measurements could be obtained. Chromosomal mosaicism — the presence of cell populations with different chromosome complements in the same individual — and other Y-chromosome abnormalities therefore could not be excluded.

Sources and image credit

  1. Zacharski, M., Pieczka, K., & Dzimira, S. (2026). A case of disorder of sex development in red deer (Cervus elaphus elaphus). Sexual Development, 20(1–6), 75–81.Primary case report, published online 10 April 2026. The free-ranging Polish red deer had antlers and male-typical morphology but female-like external genitalia; penile-type tissue was found histologically and Y-linked SRY and ZFY sequences were detected. The precise DSD category could not be determined.

Image: Giles Laurent / gileslaurent.com — wild male red deer (Cervus elaphus elaphus) in Aletsch Forest Nature Reserve, Switzerland, 2 October 2021; representative image, not the Polish case animal. Source: Wikimedia Commons. · CC BY-SA 4.0 · Source

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