Nav: Home

Detection of arboreal feeding signs by Asiatic black bears

June 26, 2018

Detection of arboreal feeding signs by Asiatic black bears: effects of hard mast production at individual tree and regional scales

Kahoko Tochigi, Takashi Masaki, Ami Nakajima, Koji Yamazaki, Akino Inagaki & Shinsuke Koike

Feeding signs give us the information about feeding ecology of animals. Feeding signs also provide information on animal distribution, habitat selection, or abundance. But, feeding signs do not necessarily directly reflect the distribution or density of animals. In addition, it is difficult to recognize the presence of endangered species only from the presence of feeding signs. Thus, we need to understand the factors and environmental conditions that influence the formation of feeding signs.

Most habitat of the Asiatic black bear (Ursus thibetanus) in Japan are close to human settlements, so monitoring of bear densities will help predict bear intrusions and decrease conflict between humans and bears. Because bears live in forests in low densities, it is difficult to directly find them. Therefore as one of the estimating methods of bear densities, feeding signs may be efficient.

Arboreal feeding sign (AFS) is noticeable field sign made by Asiatic black bears. When bears feed on trees, they break branches in the tree crown to acquire the fruits or leaves that are attached to the branch tips, thus broken branches are piled in the tree tops and the branches (i.e. AFS) look like birds' nests. Some local governments in Japan have used observations of AFS as indicators of bear density. However, it is unknown whether AFS are related to bear density and what kinds of factors may influence AFS formation. For example, bears climb and eat hard mast (i.e. create AFS) before the fruits are ripened and quantity of hard mast do not reach maximum value.

Here, we researched the influence of fruit production of individual trees and at regional scale on the detection of arboreal feeding signs to clarify in what case bears climb to eat hard mast. For seven years, we counts the number of fruits for 374 to 481 trees each year of three dominant hard mast species (Quercus crispula, Quercus serrata, and Castanea crenata) in the Ashio-Nikko Mountains of central Japan and estimated individual tree energy values and regional mast energy values that is calculated by averaging energy values of all three species annually. We also checked for the presence or absence of AFS in these trees, and analyzed the influence of factors such as individual tree energy and regional mast energy on the detection probability of AFS.

As a result, AFS were more likely in individual trees with larger mast energy values. This indicates that climbing may be cost for bears, and so they climb only trees bearing many fruits to maximize feeding efficiency. Because bears cannot digest fiber efficiently, quantity may be especially important for feeding plant. Moreover, AFS were created more during poor mast years. In those years, the energy that bears can obtain when bears climb a tree is lower and there is much greater competition for the hard mast on the forest floor with other animals, such as mice. While, in good mast years, bears can eat a lot of mature hard mast without climbing, because many fruit will fall on the forest floor. There was little difference in tendency of factors among three hard mast species despite there are several kind of differences in characteristics among these species (e.g. fruit size or masting interval).

Additionally, there is interaction between the factors (individual tree energy and regional mast energy). In poorer mast years, AFS is likely to be created on trees that were not selected in greater mast years. It is probably because the number of trees bearing many fruits decrease. In greater mast years, bears may not climb trees to eat fruits regardless of amount of individual tree energy.

In conclusion, bears may maximize their feeding efficiency in various ways depending on fruit quantity of individual tree and across the region. In conclusion, AFS cannot be used as an indicator of bear density unless both individual tree energy and regional mast energy values are monitored. To make AFS be a reliable indicator of bear populations, comparative studies are essential at sites with similar tree species compositions to our study area and with obviously different bear densities.
-end-
This work was partially supported by a grant-in-aid for JSPS Fellows (22-7646) and by JSPS KAKENHI (grant nos. JP25850103, JP25241026, JP17H00797, and JP17H05971).

Tokyo University of Agriculture and Technology

Related Energy Articles:

Cellular energy audit reveals energy producers and consumers
Researchers at Gladstone Institutes have performed a massive and detailed cellular energy audit; they analyzed every gene in the human genome to identify those that drive energy production or energy consumption.
First measurement of electron energy distributions, could enable sustainable energy technologies
To answer a question crucial to technologies such as energy conversion, a team of researchers at the University of Michigan, Purdue University and the University of Liverpool in the UK have figured out a way to measure how many 'hot charge carriers' -- for example, electrons with extra energy -- are present in a metal nanostructure.
Mandatory building energy audits alone do not overcome barriers to energy efficiency
A pioneering law may be insufficient to incentivize significant energy use reductions in residential and office buildings, a new study finds.
Scientists: Estonia has the most energy efficient new nearly zero energy buildings
A recent study carried out by an international group of building scientists showed that Estonia is among the countries with the most energy efficient buildings in Europe.
Mapping the energy transport mechanism of chalcogenide perovskite for solar energy use
Researchers from Lehigh University have, for the first time, revealed first-hand knowledge about the fundamental energy carrier properties of chalcogenide perovskite CaZrSe3, important for potential solar energy use.
Harvesting energy from walking human body Lightweight smart materials-based energy harvester develop
A research team led by Professor Wei-Hsin Liao from the Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong (CUHK) has developed a lightweight smart materials-based energy harvester for scavenging energy from human motion, generating inexhaustible and sustainable power supply just from walking.
How much energy do we really need?
Two fundamental goals of humanity are to eradicate poverty and reduce climate change, and it is critical that the world knows whether achieving these goals will involve trade-offs.
New discipline proposed: Macro-energy systems -- the science of the energy transition
In a perspective published in Joule on Aug. 14, a group of researchers led by Stanford University propose a new academic discipline, 'macro-energy systems,' as the science of the energy transition.
How much energy storage costs must fall to reach renewable energy's full potential
The cost of energy storage will be critical in determining how much renewable energy can contribute to the decarbonization of electricity.
Energy from seawater
A new battery made from affordable and durable materials generates energy from places where salt and fresh waters mingle.
More Energy News and Energy Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: The Power Of Spaces
How do spaces shape the human experience? In what ways do our rooms, homes, and buildings give us meaning and purpose? This hour, TED speakers explore the power of the spaces we make and inhabit. Guests include architect Michael Murphy, musician David Byrne, artist Es Devlin, and architect Siamak Hariri.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

What If?
There's plenty of speculation about what Donald Trump might do in the wake of the election. Would he dispute the results if he loses? Would he simply refuse to leave office, or even try to use the military to maintain control? Last summer, Rosa Brooks got together a team of experts and political operatives from both sides of the aisle to ask a slightly different question. Rather than arguing about whether he'd do those things, they dug into what exactly would happen if he did. Part war game part choose your own adventure, Rosa's Transition Integrity Project doesn't give us any predictions, and it isn't a referendum on Trump. Instead, it's a deeply illuminating stress test on our laws, our institutions, and on the commitment to democracy written into the constitution. This episode was reported by Bethel Habte, with help from Tracie Hunte, and produced by Bethel Habte. Jeremy Bloom provided original music. Support Radiolab by becoming a member today at Radiolab.org/donate.     You can read The Transition Integrity Project's report here.