We used male voices in our experiment as most wildlife crimes against gulls reported in the media are committed by men. Although we did not test this, it seems likely that gulls are more wary of men’s voices compared to women’s voices – as found in nestling jackdaws as well as in African elephants. Men are more likely to represent a threat to these animals than women or children.

I feel like it wouldn’t have been that much more effort to get female voices as well, as they were using recordings anyways. Could also help add support to the referenced paper as well.