Utilization of Sasa borealis seeds by Japanese field mouse: discovery of small-seed caching

Abstract

Bambusoideae are well-known for their large-scale flowering, seeding, and death events that occur after a vegetative phase that can often last for decades. These events are a valuable resource for many animals. Their mast seeding, in particular, affects rodent populations although the causal relationship between them is speculative. Moreover, the species of animals that utilize this resource also remains unclear. Therefore, this study aimed to examine the interaction between mast seeding plants and animals by conducting a feeding test using the seeds of a dwarf bamboo species (Sasa borealis) at different seasons and in different forest types. The results revealed that two mouse species, Apodemus speciosus and A. argenteus, utilized the seeds. They both predated as well as removed and sometimes buried the seeds, exhibiting small-seed caching behavior. Furthermore, A. speciosus was found to exhibit higher seed predation at covered sites and switching to removal behavior at the more exposed, open sites, while A. argenteus showed no distinguishable trends. Additionally, A. speciosus utilized the seeds less frequently in fall than in summer, suggesting a shift in diet towards acorns when available. Collectively, the results of this study provide novel insights into the interaction between mast seeding plants and the animals that utilize them.

How much do field mice prefer dwarf bamboo seeds? Two‐choice experiments between seeds of Sasa borealis and several tree species on the forest floor

“…For A. speciosus, the foraging of C. crenata was higher (71%) than that of (Kaneko, 2005). Then, foraging for S. borealis seeds was the same as that reported previously (Suzuki & Kajimura, 2023). These results support the hypothesis that the increase in their population after the mast seeding of S. borealis was due to increased food resources (Suzuki et al, 2022).…”

“…The results of the generalized linear model analysis for the foraging rate of S. borealis suggested that the factors affecting the foraging rate of S. borealis were the plot and the presence or absence of C. crenata. The higher foraging rate of S. borealis in Plot-CF aligns with that reported previously by Suzuki and Kajimura (2023), suggesting that Plot-CF may have fewer alternative food sources due to the specific characteristics of the forest area. The same plots…”

“…Similarly, N. procyonoides was newly found to feed upon S. borealis of Poaceae on some occasions. The observation that neither of these two species was seen foraging in a previous study (Suzuki & Kajimura, 2023) may be attributed to a low encounter rate. M. itatsi was seen sniffing the container, possibly lured by rodents, its primary food source (Kaneko et al, 2013).…”

“…For the tests of F. crenata or L. triloba, a set comprised 2.5 g of S. borealis seeds and two seeds of F. crenata or L. triloba. These ratios of masses and numbers were based on our evidence and observation of a previous study that exclusively used S. borealis (Suzuki & Kajimura, 2023). We determined the amount of S. borealis required for approximate seed consumption in one night and the number of tree seeds available on the forest floor.…”

“…To clarify this cycle, the apparent competition between the seeds must be determined. In a previous study (Suzuki & Kajimura, 2023) conducted at the same site, only S. borealis seeds were tested in the forest to identify the foraging species. The results showed that field mice, the large Japanese field mouse Apodemus speciosus (Temminck, 1844) (Figure 1a) and the small Japanese field mouse A. argenteus (Temminck, 1844) (Figure 1b) forage using predation and removal (including caching).…”