Analysis of Data over time?


I am investigating animal social networks and I have long term data set spanning 15 years. I have looked at each animals 'network position' called betweeness, and this is given a score, the higher the score, the more "important" the animal is in the conectivity of the network. I want to look at the relationship between age and betweeness. My animals are long lived (living up to 95 years) and the population size ranges from 84-99. My data are non parametric, and are also not independent (as each animals betweeness score and age were recorded every year). I want to compare the ages (maybe by age classes with 10 year intervals?), but i also want to do some sort of randomisation (I think). My data are arranged in 4 columns, the first is year, the second is individual ID, the next is age class and the last is betweeness. The stats packages i have are SPSS and R (although I am not confident writing scripts in R).

I have been told that I need some sort or model to look at the each animal between and within years, however, I have no idea where to even start! Can you offer any guidance please?

Thank-you in advance!