A new study by researchers at Azabu University in Japan suggests that the intestinal microbiomes and hormones of domestic cats, such as Cortisol, oxytocin and testosterone, could explain why some cats get along well and others are more distant.
“Cats are solitary and territorial, but they have evolved to acquire the skills and abilities necessary to live in groups,” lead author Hikari Koyasu, from Azabu University, told Tara Yarlagadda from Inverse.
The researchers divided 15 protective cats into groups and placed five random cats in three 13-by-25-foot spaces for two weeks. During this time, they used video cameras to observe the behavior of the cats and collect urine and feces to measure the hormones and microbial species present.
They found that cats with higher Cortisol and testosterone concentrations showed fewer social behaviors such as grooming, sharing food or sniffing, while cats with lower Cortisol and testosterone levels were more social. In addition, cats with similar microbiomes were more likely to be in contact with each other, and cats with higher testosterone levels were more likely to try to escape, according to the study. The results were published in the journal PLOS ONE.
Unexpectedly, Oxytocin-often called the “love hormone”-was lower in cats that exhibited more social behaviors.
“We were surprised by the results,” Koyasu told NBC News’ Sarah Sloat. “Although a positive correlation in the middle of Oxytocin and associative behavior has been reported in animals living in groups, the results were reversed in [these] cats. Cats with high oxytocin levels had less associative behaviors with other cats.”
These results show that hormones can work differently in different species, Maren Huck, a cat expert at The University of Derby who was not involved in the study, tells NBC News. Carlo Siracusa, professor of clinical behavior and animal welfare at the University of Pennsylvania, told the publication that cats can show affection differently from other animals.
“Cats use closeness, but not necessarily body contact, to show how much they love another person — the closer they are, the kinder they are,” he told NBC News. “It would have been interesting to know if the cats [in the study] with higher levels of oxytocin spend more time with other cats, but do not necessarily interact bodyly with other cats.”
Since the cats were of different or not known ages and origins, “we do not consider our results to be applicable to all groups of cats,” Koyasu told Inverse. Future research should examine how factors such as spending time together as adolescents and changing environmental conditions influence social behavior. And although the study showed correlations in the middle of hormones and behaviors, the causality is not known. The authors conclude in the study that the research may need to be conducted over a longer period of time to “provide more complete information.”