High long-term survival of PIT-tagged pekapeka | lesser short-tailed bats (Mystacina tuberculata) through annual pest control operations

Control of introduced mammalian predators is important for the protection of pekapeka | lesser short-tailed bat (Mystacina tuberculata) populations, but toxins used to control these predators may also pose a risk to bats when they forage on invertebrates that have consumed toxic bait or if bats directly consume bait. We studied the survival of a population of lesser short-tailed bats at Pikiariki, Pureora Forest Park, between 2012 and 2024, over which time conservation managers varied the methods and timing of toxin application for rat control to reduce secondary poisoning risk to bats. Reducing the duration of rat control operations and timing them to occur prior to the bat breeding season successfully reduced exposure of the bats to toxins. Although rat control operations effectively reduced relative rat abundance in the short term, there was no relationship between duration of rat control operations and annual mean rat tracking rates (the mean tracking rate for each year). Neither annual mean rat tracking rates nor the amount of time toxin was present in bait stations explained very much variation in bat survival from year to year. With an overall mean rat tracking rate across all years of 27 %, mean annual survival of the adult female lesser short-tailed bat population across all years was high (0.86), resulting in growth of the population. More frequent rat tracking data could be collected to test whether relative rat abundance at specific times of the year can be used to set a more precise operational target for rat control to further benefit bats. We recommend continuing to monitor the bat population as well as the relative abundance of rats and other introduced mammalian predators to improve the understanding of factors influencing bat survival. While an overall mean rat tracking rate of 27 % may allow this lesser short-tailed bat population to grow, other, more vulnerable, forest species requiring lower residual relative rat abundance targets should be considered in future management plans.