The efficacy and costing of termite (Blattodea: Termitoidae) survey methods in Australian tropical savannas

Termites are important ecosystem engineers in many ecosystems globally. Hence, surveys of termite species composition, abundance and activity can be important for understanding ecosystem function—especially in biomes where they tend to be abundant, such as tropical savannas. However, comprehensively surveying termites can be challenging due to their cryptic nature and varied feeding and nesting habits, which strongly influence the effectiveness of different survey methods. Baiting and active searches of reduced transects are two methods commonly used to sample termites, and while these methods have been evaluated in the savannas of South Africa, this has not occurred in the extensive tropical savannas of northern Australia. Thus, this study evaluated the effectiveness of baits and reduced transects to assess termite species richness and activity across 18 × 1 ha experimental plots in a tropical savanna near Darwin, Australia. Surveys in each plot consisted of two 60 × 2 m transects and a 9 × 3 baiting grid of alternating buried wood and paper baits and surface straw baits. Baits were checked three times: at 4-, 7- and 10-week intervals following placement. Upon survey completion, the sampling effort, efficacy and costs of each method were compared. Reduced transects detected all 32 species recorded in this study, representing four feeding groups (from undecayed wood to highly decayed organic material in the soil). Baiting detected 20 species, but failed to detect some of the species that fed on decayed materials. Paper baits, checked only twice (at 4 and 10 weeks following placement), were required to detect all species sampled at both wood and paper baits. Therefore, overall baiting costs could be reduced (without data loss) by using paper baits only and reducing the number of bait checks. Compared with baiting using all three bait types, reduced transects detected the most species and had the lowest per-species cost. Consequently, reduced transect surveys are the most effective method in these northern Australian savannas when assessing species composition. However, if the abundance of species that feed on undecayed wood or levels of termite activity are being assessed, then reduced baiting is a more appropriate method.