Trap distance affects the efficiency and robustness in monitoring the abundance and composition of forest-floor rodents

Abstract

Intensive monitoring of multiple taxonomic groups is essential to understand ecosystem structure and function. In such studies, plant ecologists desire to monitor animal communities as efficiently as possible. We examined the efficiency of two trapping methods with different trap distances and total trapping areas for monitoring forest-floor rodent communities. We especially targeted two endemic, terrestrial, and semi-arboreal species dominating in forests throughout Japan. The long-distance (25 m) and the short-distance (10 m) methods assumed less than and more than one trap per female territory, respectively. Irrespective of species, capture efficiency tended to be higher in the long-distance than in the short-distance method. Recapture probabilities of two species were more similar in the short-distance than in the long-distance method in 2013. Observed densities for both species in the short-distance method were relatively similar to the estimated densities based on the long-distance method in 2011. In contrast, observed densities were lower than the estimated densities in the short-distance method in 2013. Observed densities of semi-arboreal species tended to be underestimated when only terrestrial traps were used. From these results, we propose that the short-distance method can efficiently estimate densities and community composition when researchers plan a small-effort study for a short time with a small area. In contrast, the long-distance method will allow researchers to estimate population densities robustly, when taking a large effort of a 3- to 4-day session with a large area. Our results also suggest that using both terrestrial and arboreal traps will improve the estimation.

Keywords:

• Apodemus argenteus
• Apodemus speciosus
• Arboreal
• Community ecology
• Terrestrial

Acknowledgments

We acknowledge the Sugadaira Montane Research Center, University of Tsukuba, for permission to conduct research within the site. We also thank Takahiro Ogai, Shigekazu Tomizuka, Kouji Nagaoka, and Mariko Katsuyama for their research assistance and a member of SMRC for valuable advice on the field research. This work was supported by Grant-in-Aid for Challenging Exploratory Research from JSPS (Grant Numbers 24657018 to Shinsuke H. Sakamoto; 23650236 to Chihiro Koshimoto), and by grants from the University of Miyazaki (Support Program for Integrated Research Project for Human and Veterinary Medicine).

Notes

S. H. Sakamoto, S. N. Suzuki, and R. O. Suzuki equally contributing authors.