Why not try just to estimate it? If you take the log of the Ricker equation, you have lnN(t)=lnN(t-1)+r-r/k*N(t-1) or dlnN(t)=r-r/k*N(t-1) - an equation, which is easy to estimate. r would be the constnat, r/k the coefficient of N(t-1). Maybe that puristic econometricians critizise this approach,, but you can try different tests, whether the results are valid (significant).

Thank you for the answer, I tested the equation as you suggest. It seems that my population does not respond to the logistic equation density dependence. I am not sure if the Ricker equation can be tested in abscence of age structures in cases where the logistic equation does not fit . Does anyone have suggestions about it?

I think that N in the Ricker funcion refers to generations, not to age groups, because the carrying capacity k is valid for the whole population, i.e. the sum of all age groups. My knowledge of the way of life of guanacos is rather limited, but I assume that they live about 10-20 years on average. If you take all animals at a certain time as a generation, then the time span between t and t+1 would, at least, be 10 years. Therefore, I think, it is unlikely to get a good econometric estimate on the base of a time series with annual data (from which I do not know how reliable they are). Another problem is, that k cannot be treated as a constant, because many (agricultural, traffic) activities can influence the living space of wild animals. Finally, there is a probability that N has, for most of the time, been near k. In this case, there is no population growth model, which could sensfully be applied.