It is likely that Tribbles are nothing more than equivalents of animals.
According to reference from Memory Alpha,
Tribbles were small, non-intelligent lifeforms originating from Iota Geminorum IV
and even the Star Fleet Medical Reference Manual, which lists life forms in four categories ("humanoid", "intelligent", "parasites", and "plants") lists Tribbles in the "parasites" category rather than in the "intelligent".
And if we take a descrpition of what a civilization is, i.e. if quoting from Wikipedia
A civilization is any complex society characterized by urban development, social stratification imposed by a cultural elite, symbolic systems of communication (for example, writing systems), and a perceived separation from and domination over the natural environment.
Civilizations are intimately associated with and often further defined by other socio-politico-economic characteristics, including centralization, the domestication of both humans and other organisms, specialization of labour, culturally ingrained ideologies of progress and supremacism, monumental architecture, taxation, societal dependence upon farming and expansionism.
it is clear that all these things require a biological complexity and especially intelligence, that Tribbles don't possess.
They also had a very rapid metabolism, being able to reproduce and give birth to a new generation in about twelve hours. Their lifespan is never explicitly stated, AFAIK, but given this accelerated biological course, it is likely that the don't live very long, and their life-cycle to be based on quantity rather than quality; under these circumstances, their evolutive strategy don't seem to even need more than the basic vital functions required for feeding and reproduction; and, in fact, always as reported by Memory Alpha,
An entire half of a tribble's metabolism was solely devoted to reproduction.
It is true that even animals can have some form of social structures, even complex (think about mammals but especially insects), but even in the cases of highly intelligent animals like in example other non-human primates, we don't define their social structures as "civilizations".
The fact that they have an homeworld, well, it simply means that there is a world where their species initially developed and that can be considered their place of origin, without implying nothing more than this. 350