Does size really matter?
According to a new study, the answer is 'yes' -- at least when it comes to a certain species of mole.
The study, published in the journal Mammalian Biology last month, found that female Hottentot golden moles judge potential mates based on the size of their penises: The longer, the better, researchers concluded.
Hottentot golden moles, according to the International Union for Conservation of Nature, are widely found in South Africa and Swaziland. Described as small, blind, underground creatures, the moles are polygamous animals who mate all year round.
Researchers say that the animals' blindness may be a contributing factor behind the female's desire for longer penises.
"We think that penis size matters for these essentially solitary, more or less blind, underground dwellers. Judging penis size when mating may be one of the only criteria they have available to them," Bateman, one of the researchers, told the BBC. "The mating is probably pretty rough and ready, and unromantic to say the least, so a physical assessment of a penis in situ, as it were, may allow females to reject males."
Bateman added that for evolutionary purposes, big or long penises can often make sense for animals that want to most effectively deliver sperm for the sake of procreation and to best their rivals. In the case of the golden moles, researchers said that there is strong evidence to show that penis length is a sexually selected trait.
For more on this study, read BBC.com's report here.
Scientists have long known that sexual selection influences the sex organs of some animals. In a 2004 paper, researchers David Hosken and Paula Stockley asserted that "new studies [have provided] ever more compelling evidence that sexual selection is important in driving genital divergence."
Some animals, including ducks, pythons and this very weird fish from Vietnam, have evolved complex and often strangely shaped penises for reproductive purposes.
Case in point: According to a 2012 study, scientists discovered that size also matters for the male bruchid beetle, known for its menacing, many-spined penis. The bruchid beetle is believed to have evolved such a "terrifying" sex organ to promote more efficient sperm delivery and to improve the chances of having offspring.
Science Nordic wrote at the time that the researchers had "found that the males with the longest spines on their penises get the most offspring, independent of other factors such as body size."
“The reproductive organs of animals with internal fertilization change more rapidly than all other morphological features during evolution,” said Michal Polak, one of the co-authors of the study, according to an October news release on the University of Cincinnati website.
"In virtually all groups of animals, from roundworms and molluscs to reptiles and mammals, the male sex organs differ markedly among even closely related species, with female genital traits remaining relatively unchanged," he continued.