In The Galapagos, Penguin Gender Can Be Told by Beak Size

A Galapagos penguin prepares to take the plunge. A thicker beak indicates a male.

IN CASE YOU EVER WANT TO ASK A PENGUIN FOR A DATE, researchers studying Galapagos penguins have found an easy way to tell males from females: Penguin gender can be judged by the fact that males have bigger beaks than females.

I’m not sure what practical use this information has for most of us but it’s important for scientists doing field research on the little guys. And, it gives me a chance to post one of my photos of Galapagos penguins.


 “Beak size points to sex of Galapagos penguins,” an article published by, focuses on work by scientists at the University of Washington. They sought a fast and reliable means of determining Galapagos penguin gender to aid them in studying the birds, particularly as to how changing climate conditions might affect them. Previously, figuring it out meant getting blood samples from the penguins and sending them off for DNA testing.

Galapagos penguins make their livings off the small-schooling fish brought to the Galapagos by the upwelling of Pacific Ocean currents. But this food web can be disrupted by El Nino events, leaving the birds facing the threat of starvation. In some hard-hit years, the birds stop breeding altogether.

A concern is that it’s suspected that males are more likely to survive extreme conditions than females, although the reasons are unclear. The population varies between 2,000 and 5,000 birds.


Galapagos penguins (Spheniscus mendiculus) are the only penguins to live north of the Equator and within tropical regions. Just over one foot/35 cm tall, they’re the third-smallest of the 18 species of penguins worldwide.

Until now, it’s been hard to tell males and females apart. They lack external genitalia, look very similar to each other and share parental duties like incubating eggs.


The telling sign is that male Galapagos penguins have somewhat thicker beaks. Relying on this schnazolla standard, the researchers were able to correctly determine penguin gender more that 95 percent of the time.

The beak factor characteristic has been identified in several other species but this study is the first to demonstrate in Galapagos penguins.

PRINCIPAL SOURCES: “Beak size points to sex of Galapagos penguins,”; Galapagos – A Natural History, Michael H. Jackson.

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