Researchers at Nagoya University in Japan, including Professors Hanami Suzuki and Hisashi Kajimura, have revealed new insights into the relationship between the red bamboo plant (Sasabamboo) and the animals that eat its seeds. Their research focused on the behavior of voles interacting with red bamboo seeds.
Various Factors Affecting Seed Utilization by Rats
The researchers found that vole seed utilization patterns differed depending on species (Japanese giant vole Apodemus speciosus and Japanese small vole A. argenteus), presence or absence of understory vegetation, forest tree species (broadleaf or coniferous) and season (summer or autumn).
Their findings highlight the importance of understanding the needs of plants and animals to ensure the health of local ecosystems. They also overturned previous ideas about how mice store seeds.
Baiting behavior of red bamboo
Sasaborealis exhibits cyclical widespread flowering and seeding behavior, a group of plants that collectively flower and set seeds at regular intervals to overwhelm predators and maximize pollination rates.
However, this behavior occurs rarely, with intervals as long as 120 years. But once it does, the abundance of seeds in the forest provides plenty of food for a variety of animals, especially rodents like voles.
Experimental Observations on the Behavior of Wild Voles
To further understand how wild mice behave during seeding, the researchers placed seeds in shallow mesh baskets to simulate mass flowering and seeding. They then used automated cameras to record the foraging behavior of voles in different forest environments and during different seasons.
Initially, as one would expect, some mice ate the seeds they found on the spot. However, other mice engage in "dispersal behavior", carrying away the seeds and burying them for later feeding. This is an example of "remove and hide" behavior.
Species-specific behavior and environmental impacts
The two species of voles also behave differently. Large Japanese voles eat seeds directly from places where plants and shrubs protect them from predators, and they also carry seeds from places where they are more vulnerable, such as areas without vegetation.
And small Japanese voles are more likely to carry seeds to another location, even in areas protected by vegetation. The researchers believe that differences in the mice's size may be responsible for this behavior. Simply put, larger rats are less worried about other rodents stealing their food.
Impact on seed dispersal and ecosystem health
Seasonality and tree species also appear to influence how often mice eat seeds, with these animals being more likely to eat seeds immediately in the summer than in the fall, possibly due to food availability.
Rodents in coniferous forests are also more likely to eat seeds on the spot than rodents in broadleaf forests, which may also be due to the presence of other food stores. Because alternative foods for later consumption, especially acorns, are more abundant in hardwood forests, mice have the ability to consume these foods immediately.
In fall hardwood forests, mice are more likely to eat food immediately. This behavior plays an important role in ensuring that seeds are dispersed throughout the forest. "Forest-dwelling voles play an important role in the distribution and regeneration of trees because they are seed dispersers and are responsible for transporting and storing seeds," Suzuki said. "This suggests that we need to reevaluate the relationship between co-seeding by Hokkaido voles and voles. It may also spread to food choices for seeds from other trees and predictions of forest regeneration and vegetation succession associated with them."
Challenging established theories
Suzuki explains: "It is known throughout the world that the massive flowering and seeding behavior of bamboo causes large outbreaks of the typical seed-eating vole. This is a striking example of the impact of plants on animals. As seed predators, vole choices and behaviors, such as feeding or 'removing and hiding', can lead to the suppression of certain plants or enhance their regeneration capacity. When I learned about this, I became keenly interested in vole, a species important to the future of forest ecosystems".
"There has been a lot of research on the relationship between voles and seeds, and the existing theory is that larger seeds, such as chestnuts and acorns, are scavenged and hidden, while smaller seeds are consumed more quickly. However, our results show that even much smaller seeds, such as red bamboo seeds, which weigh only about 0.025 grams each, are storage targets for mice. Therefore, the dispersal and storage behavior of voles on seeds as small as sassafras suggests that the established theory needs revision."
Kajimura concludes: "Our experiments show that voles consider their surroundings and use sassafras seeds flexibly. Since this behavior affects tree regeneration as well as understory vegetation, our results demonstrate the impact of mice in creating complex forest ecosystems."