Persistence of wild rabbit (Oryctolagus cuniculus) latrines and its implication for monitoring programs

Counting latrines is a standard method to estimate European wild rabbits (Oryctolagus cuniculus) abundance. This method plays an important role in endangered predators’ conservation programs in the Iberian Peninsula, especially in potential reintroduction areas for the Iberian lynx (Lynx pardinus). However, since the last half-century, rabbit populations have declined dramatically within their native range, mainly due to the effect of two viral diseases, which have caused even local extinctions of natural populations. Hence, we raise the question regarding how reliable the method of counting latrines may be in ensuring the abundance of rabbit populations after an event of sudden decline or even local extinction. To answer this question, we carry out a simple experiment where we set ten lines with rabbit latrines with two different sizes each (small and large) and simulated low- and high-abundant rabbit population scenarios on five latrine lines each, respectively. Then, we calculated the pellets decay rate and latrines persistence rate through monthly surveys. Our results showed that the daily persistence rate varied little among the different scenarios. However, generally, latrines do not persist long (78 days on average) regardless of the size of the latrines or rabbit population abundance. The longest time to extinction for pellets (c. 469 days, 97.5 quantile) was longer than the time until no more latrines were identified (c. 191 days, 97.5 quantile). We conclude that, although we did not consider other factors that could affect pellets decay, counting latrines seems to be sensible to a hypothetical dramatic decline event of a wild rabbit population. Therefore, if there is evidence of an epidemiological outbreak event, we suggest managers carry out latrines census at least between 140–220 days after an outbreak detection to reduce bias on the determination of rabbit abundance.