(CNN)Researchers have found an unlikely but compelling example of sex bias in the natural history collections of museums around the world.
The fact is that visitors are more likely to find male than female specimens in the Natural History Museum in London or the Smithsonian in Washington.
Natalie Cooper, a researcher from the museum in London, and her colleagues looked at almost 2.5 million specimens from five international collections and concluded that there was a bias towards male specimens. in particular, 40% of the bird specimens and 48% of the mammals analyzed were females.
"We suspected we'd see a bias towards males because science is done by people and people have an inherent male bias," Cooper told CNN via e-mail. "This is especially true as many of our collections come from the Victorian era of macho hunters going out trying to shoot the biggest fiercest creatures for their collections."
More interesting, perhaps, is that the proportion of female specimens hasn't really changed in the past 130 years.
"We were quite surprised by this as we thought things would be getting better," Cooper said. "It could be unconscious bias where people don't even realize they're selecting males, it could be passive in that males are easier to catch or easier to see in the wild, or maybe conservation concerns leading collectors to avoid females."
Cooper said unconscious bias probably played a big role, as both men and women tend to be biased towards males.
Collection methods need also to be considered as a factor for the bias. Males can be showier or larger in the wild, thus easier to collect.
"One good example is the way we usually collect birds. You put up a mist net, then play male bird calls to attract other birds," Cooper said.
"These will mostly be males trying to defend their territories. Although it is studied far less frequently, female birds also call. So maybe using female calls too might help. "