Appendix S1. Uninformative priors used to model the abundance of rabbits and cats across pastoral regions in Otago and the Mackenzie Basin (Southern Canterbury), South Island, New Zealand. Uninformative priors in the observation model relating the observed counts of cats and rabbits at transect i, survey j and season k, to their abundances and detection probability, through a binomial process are: πΌππππππ‘,π ~πππππππ(0,1). πΌπππ‘,π ~πππππππ(0,1). π½ππππππ‘ ~ππππππ(0,100). π½πππ‘ ~ππππππ(0,100). 2 πΏππππππ‘,π,π,π ~ππππππ(0, 1/πΎππππππ‘ ). 2 πΏπππ‘,π,π,π ~ππππππ(0, 1/πΎπππ‘ ). πΎππππππ‘ ~πππππππ(0,3). πΎπππ‘ ~πππππππ(0,3). Uninformative priors in the Gompertz-type model describing the seasonal population dynamics of rabbits and cats are: πππππππ‘ ~πππππππ(0,3), ππππ‘ ~πππππππ(0,3), πππππππ‘,π πππ ππ ~πππππππ(−5,5), ππππ‘,π πππ ππ ~πππππππ(−5,5) , πππππππ‘ ~πππππππ(−1,1), ππππ‘ ~πππππππ(−1,1), ππ πππ ππ ~ππππππ(0,100), πππππππ‘,π,1 ~πππππππ(πππ₯π π , (πππ₯π π + 1000)) , ππππ‘,π,1 ~πππππππ(πππ₯πΆπ , (πππ₯πΆπ + 100)). The πππ₯π π and πππ₯πΆπ values are the counts of rabbits and cats known to be alive on transect i. Because rabbits have persisted throughout the Mackenzie Basin and Otago since the 1870s [1], we limited πππ₯π π and πππ₯πΆπ to ≥ 2, that is, a minimum abundance of two individuals. References 1. Norbury G, Reddiex B (2005) European rabbit Oryctolagus cuniculus (Linnaeus, 1758). In: King CM, editor. The Handbook of New Zealand Mammals 2nd Edition. Melbourne: Oxford University Press. pp. 131-150.