This is one of the classic studies of predator-prey interactions, the 90-year data set is the number, in thousands, of lynx pelts purchased by the Hudson's Bay Company (HBC) of Canada. While this is an indirect measure of predation, the assumption is that there is a direct relationship between the number of pelts collected and the number of hare and lynx in the wild.
If you are interested in the brutal story of HBC, see the video https://www.nfb.ca/film/other_side_of_the_ledger or read the article https://canadiangeographic.ca/articles/the-untold-story-of-the-hudsons-bay-company.
The format is: Time-Series [1:91] from 1845 to 1935: 30.1 45.1 49.1 39.5 21.2 ...
You can find demonstrations of astsa capabilities at FUN WITH ASTSA.
The most recent version of the package can be found at https://github.com/nickpoison/astsa/.
In addition, the News and ChangeLog files are at https://github.com/nickpoison/astsa/blob/master/NEWS.md.
The webpages for the texts and some help on using R for time series analysis can be found at https://nickpoison.github.io/.
Hare