It is a common cause of arguments – but next time you bicker over the heating, you can use evolution to back you up.
Scientists have discovered female members of species are naturally drawn to warmer temperatures because of an in-built 'evolutionary difference'.
Researchers in Israel studied 13 bird and 18 bat species to determine if the animals displayed geographical separation between the sexes.
The study by Tel Aviv University found the males preferred lower temperatures than females. This led to physical distance between them at certain times of year.
Research in humans has previously suggested that the sexes experience temperature differently, with women feeling the cold more because of variations in metabolism and the production of body heat.
Turning up the heat: Scientists have discovered that female members of species are naturally drawn to warmer temperatures because of an in-built 'evolutionary difference' (stock image)
Study co-author Dr Eran Levin, from the university's School of Zoology, said: 'We have hypothesised that what we are dealing with is a difference between the females' and males' heat-sensing mechanisms, which developed over the course of evolution.'
In previous research Dr Levin found that during the breeding season males and females tend to segregate, with the males inhabiting cooler areas.
For example, entire colonies in caves on the slopes of Mount Hermon, on the Lebanon-Syria border, are composed of only males during the breeding season, while in the warmer area of the Sea of Galilee there are mainly females, who give birth and raise their pups there.
It was this phenomenon that aroused Dr Levin's curiosity.
Among many mammals, even in species that live in pairs or in mixed groups all their lives, the males prefer shade whereas the females prefer sunlight, or the males ascend to the peaks of mountains while the females remain in the valleys, the researchers said.
Their study included around 11,000 birds and bats using data collected over 40 years.
These species were chosen because they fly and are therefore highly mobile, so researchers believed spatial separation between the sexes – sometimes extending to different climatic zones – would be particularly clear in such groups.
Israel's significant climate diversity also allowed them to study individual animals of the same species that live in very different climatic conditions.
The researchers found that males prefer a lower temperature than females, and that this preference leads to a separation between the sexes at certain periods during the breeding cycles, when the males and females do not need, and may even interfere, with each other.
Dr Levin said: 'Our study has shown that the phenomenon is not unique to humans; among many species of birds and mammals, females prefer a warmer environment than males, and at certain times these preferences cause segregation between the two species.
It is a common cause of arguments – but next time you bicker over the heating, you can use evolution to back you up (stock image)
'This difference is similar in its essence to the known differences between the pain sensations experienced by the two sexes, and is impacted by differences in the neural mechanisms responsible for the sensation and also by hormonal differences between males and females.'
Co-author Dr Tali Magory Cohen said the separation may be explained by a desire for offspring to be kept away from aggressive males and to reduce competition for food.
'The bottom line is, going back to the human realm, we can say that this difference in thermal sensation did not come about so that we could argue with our partners over the air conditioning, but rather the opposite: it is meant to make the couple take some distance from each other so that each individual can enjoy some peace and quiet,' the researchers concluded.
'The phenomenon can also be linked to sociological phenomena observed in many animals and even in humans, in a mixed environment of females and males: females tend to have much more physical contact between themselves, whereas males maintain more distance and shy away from contact with each other.'
The research has been published in the journal Global Ecology and Biography journal.
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