But this doesn't make sense. Gender is a social construct.
Because, you know, people were so dumb until social-constructivism landed on Earth like the Messiah no-one expected. And we need to be re-educated. Or else.
What baffles me most is the insistence that one can build any kind of objective distinction based on subjective experiences, that is, what one feels. We're all capable of sadness, joy, excitement, and what not. But we can not build any kind of categorization (read diversity) of people based on these concepts/states of mind. I don't identify as sad, although I'm sad from time to time. No one does. Companies can not be forced to hire more sad people, for the sake of diversity. Yet, now, it's compulsory to have more people hired because they report some sort of internal and inaccessible state of mind which they express using words used for categorizing people based on the shape of their genitalia.
The only thing that's funny is that on a thread about lab rats reacting differently to male or female lab workers, people feel the need to start a holy war about topics as pointless as this one.
But one assumes that in this case the cause might be that the pheromones that people all hopped up on testosterone give off is different those given off by people who aren't .... those people would likely be cis-males, trans-males who've transitioned, trans-females who haven't transitioned, and some trans people who are currently transitioning in either direction .... we don't really have one exact word that encompasses those categories
And the researchers can be taking drugs changing their smell, possibly changing the mice behaviour.
As for why rats may develop the ability to sequence XX vs XY - if rats with the ability to do so were killed far less than those without, then rats would quickly evolve the ability to do so. This could happen if males were the ones killing rats and not females. Actually, skip the 'probably not' I began with - it's a perfectly likely explanation that may or may not be true based on further study.