A team of researchers has discovered a link between the length of rat fingers and their sexual activity and preferences. The study, published in Experimental Animals, found that rats with shorter second digits were more sexually active and showed a clear preference for female scent.
The 2D:4D digit ratio, which measures the length of a rat’s second to fourth digits, has been studied in humans before, where it is linked to sex-typical traits. The researchers used this ratio as a biological marker to predict sexual activity in rats.
In their study, the team confirmed that male rats had shorter second digits than females. They then ran a series of mating tests and found that males with shorter second digits ejaculated more frequently and displayed higher levels of sexual vigor.
When it came to exploring preferences, the researchers offered male rats a choice between bedding soiled by females or males. The males with shorter second digits showed a clear preference for female-scented bedding, spending more time investigating it than those with longer second digits.
The study’s findings have implications beyond just understanding rat behavior. They also suggest that biology can subtly influence an individual’s actions, even in complex behaviors like sexuality. This could potentially inform research into conditions like autism, depression, or attachment disorders, which show varying prevalence between males and females.
The discovery of this link between finger length and sex preferences in rats offers a valuable animal model for investigating questions that are ethically and practically inaccessible in human research.
Source: https://phys.org/news/2025-07-clues-claws-finger-length-reveal.html