Figure 1: Domesticated cat demonstrating the "tail up" position

          

        Most species of felines live the majority of their lives in solitude and do not engage in social interactions, with the exception of mating and raising offspring. The only two  feline species that are exceptions to this are lions and domesticated cats. Both species often live in social groups. Living in a social group requires that individuals be able to communicate with one another. An example of such behavior in domesticated cats is the placing of the tail in a vertical position, bent at the end towards the individual with whom it is interacting. This action is referred to as “tail up” (Cafazzo and Natoli, 2009).          

Figure 2: Domesticated cats greeting one another

        “Tail up” is not observed in any adult feline species other than domesticated cats. It is believed this behavior has developed in domesticated cats as a method to communicate with humans and other cats. Upon observing cat behavior amongst a wide variety of cats in Rome, scientists Cafazzo and Natoli have determined that “tail up” is used as a greeting and a sign of submission amongst domesticated cats.  Cats of high social ranking within a social group, often the most aggressive male, received the most greetings from cats with their tails’ held up. They also tended to greet cats with their tails in a horizontal position. Cats with their tails held up were approached by other cats with less aggression and meetings were followed with other greeting behavior, including sniffing each others noses and rubbing one another. Amongst neutered males, females were most likely to initiate greetings with males. However, in non-neutered males, males were most likely to initiate greetings with females. It is hypothesized this occurs because males who are neutered produce less testosterone, making them less aggressive and competitive (Cafazzo and Natoli, 2009).   

Figure 3: Wildcat kitten greeting its mother

            Most scientists are in agreement that domesticated cats hold their tails up as a form of social interaction, and that this trait evolved as cats shifted from a solitary outdoor existence to an urban life. However, the origins of this trait are largely debated. One theory suggests that the trait of “tail up” evolved from an action observed in other cat species, in which kittens hold their tails up when greeting their mothers. Kittens loose this trait when they mature into adults and go their separate ways. However, as domesticated cats often stay in frequent contact with other cats, they may have evolved to maintain the behavior into adulthood (Cafazzo and Natoli, 2009)          

       Another theory suggests that the behavior of “tail up” evolved as method for domesticated cats to communicate with humans. Cats often great their owners with their tail up.  This behavior is believed to be an opening and welcoming jester, inviting human interaction (Cafazzo and Natoli, 2009).  

Figure 4: Cat greeting a human

            A third theory suggests that the “tail up” behavior evolved from sexual interactions between cats. When courted by a male, female cats respond by turning in circles, rubbing the male, and holding her tail up to present herself to the male. The greeting that was originally used for mating may have evolved into the general greeting observed in cats today (Cafazzo and Natoli, 2009). 

            Similar behavior to “tail up” has been observed in lions, the only other social species of cat. When lions greet one another, they do not hold their tail up in a vertical position, but instead tip the end of their tail towards the individual they are greeting. Like in domesticated cats, this is believed to signal submission. The greetings behavior of lions and cats is an example of parallel evolution (Cafazzo and Natoli, 2009). 

Figure 5: Lions greeting one another

Works Cited:

Cafazzo, S, and Natoli, E, 2009, ‘The Social Function of Tail up in the Domesticate Cat (Felis silvestris catus), Behavioral Process, Vol. 80 (1), pp. 60-66.

Figure 1: Available from: http://cdn.shopify.com/s/files/1/0601/4169/files/Cat_signs_4_large.jpg?12373879695195808162

Figure 2: Available from: http://lifeonfourlegs.com.au/wp-content/uploads/2015/03/cats-greeting-with-tail-up.jpg 

Figure 3: Available from: http://upload.wikimedia.org/wikipedia/commons/thumb/b/b6/Scottish_wildcat_%26_kitten.jpg/220px-Scottish_wildcat_%26_kitten.jpg

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Figure 5: Available from: http://www.earthrangers.com/content/wildwire/lions_greeting1.jpg