Scatter-hoarding rodents play an important dispersal role for many large-seeded plants. Seed traits affect their foraging behavior; however, it is difficult to isolate their effects because of the covariance among traits. Dr. Wang Bo and his supervisor Prof. Chen Jin developed a series of experiments using artificial seeds to isolate the effects of seed size, nutrient and tannin content on rodent caching behavior distance.

With a careful design of the artificial seed, the authors tested the following predictions: (1) rodents would exhibit a significant and consistent response to each independently tested trait and (2) the seeds with the best combination of traits should have the highest removal rate or greatest dispersal distance.

 The results indicate that scatter-hoarding rodents choose which seeds to cache primarily based on an “ideal” seed size, and larger seeds were likely to be dispersed farther.

　 The study was carried out during September to November in 2006 and 2007 in a pine forest forest in Shangri-La Alpine Botanical Garden, Hengduan Mountains, Yunnan Province, Southwestern China (27°54'N, 99°38'E, altitude 3456 m). The study was funded by the National Basic Research Program of China (973 Program—2007CB411603).

　 Entitled with “Seed size, more than nutrient or tannin content affects seed caching behavior of a common genus of Old World rodents” has been published in the prestigious journal “Ecology” in November 2009.

Abstract

Scatter-hoarding rodents play an important dispersal role for many large-seeded plants. Seed traits affect their foraging behavior; however, it is difficult to isolate their effects because of the covariance among traits. Here, we used artificial seeds to partition the effects of seed size, tannin content, and nutrient content on scatter-hoarding rodents in a natural pine forest in Northwest Yunnan, China. Apodemus, a common genus of Old World rodents, consistently consumed small seeds in situ but removed medium-sized seeds (1.2–2.5cm in diameter) and transported bigger seeds farther. Seed nutrient and tannin contents also significantly influenced rodents’ behavior, but response varied substantially between years.

Rodent behavior did involve some aspects of multivariate optimization. Our results strongly indicate that seed size is a decisive factor for scatter-hoarding rodents in the choice between seed predation and dispersal, while nutrient and tannin content played a less consistent role, possibly responding to confounding factors in the community. This result also has important implications for seed production by trees, which can improve the probability of long-distance dispersal of high-quality offspring by simply making them larger. The ability to tease apart the relative influence of different seed traits on the behavior of predators provides powerful insight into this important coevolutionary dynamic.

Key words: Apodemus; artificial seed; condensed tannin; foraging behavior; hydrolyzable tannin; nutrient content; scatter-hoarding; seed dispersal; seed predation; seed size.