Wild Things

The weird and wonderful in the natural world

Sarah Zielinski

Wild Things

Wild Things

How bears engineer Japanese forests

Japanese black bears

Japanese black bears live in forested regions of Honshu and Shikoku. The bears are “ecosystem engineers,” a new study claims, because when they break tree branches, the gaps allow light to reach other plants.

Sponsor Message

If you were to look up when walking through a forest in Japan, you might see “Kuma-dana,” or “bear shelves,” high in the trees. These patches of broken branches and dead leaves are created by Japanese black bears when they climb high to find fruit. That’s why climbing a tree won’t save you from a Japanese black bear.

These bears are a subspecies of the Asian black bear (Ursus thibetanus), and they are quickly disappearing. Now found on only two islands — Honshu and Shikoku — they probably number fewer than 10,000. About two-thirds of Japan is forested, but much of the native forest has been replaced by managed groves where bears are not welcome.

Where the bears remain, though, the animals are “ecosystem engineers,” a new study finds. Their presence helps plants to fruit more, producing more seeds, and it’s because of those bear shelves.

bear shelvesKazuaki Takahashi of the University of Nagano in Japan and colleagues studied the effects of black bears on plants in the Nagakura-yama national park near Mount Asama in Nagano Prefecture, Japan. They focused on Mongolian oak trees, because the bears like to bulk up on the trees’ acorns in the fall. They measured light availability in the canopy below trees that had bear shelves and others that didn’t and quantified fleshy fruits produced by the plants in that canopy. The results of their study appear July 24 in PLOS ONE.

In the closed canopies, two species of trees bore fruit. But in those that had gaps, seven species fruited. Six shrub species bore fruit in closed canopies; 10 species had fruit when there were gaps. Similar results were seen with woody liana plants.

“Light conditions improved beneath bear-disturbed trees with large canopy gaps,” the researchers note, and “fruiting of fleshy-fruited plants was facilitated by the improvement of light conditions.” The plants create more flowers, more fruits and — most importantly — more seeds as a result.

The increase in the number of flowers on the plants that grew beneath the bear shelves may also help pollinators, the team notes, since a higher density of flowering plants can support a great number of pollinators, such as bees or other insects.

The creation of gaps that let in light and have a host of effects on other species in the ecosystem qualifies the bears as “ecosystem engineers,” the researchers say. These are species that “directly or indirectly modulate the availability of resources (other than themselves) to other species by causing physical state changes in biotic or abiotic materials.” Beavers are a classic example; others include African elephants and badgers. But this would be the first bear species to receive the label. 

Animals,, Plants

On the importance of elephant poop

By Sarah Zielinski 4:57pm, July 28, 2015
Asian elephants are key dispersers for tree seeds. A new study finds that buffalo and cattle can also disperse the seeds, but not nearly as well.
Animals,, Oceans,, Climate

Sea level rise threatens sea turtles

By Sarah Zielinski 4:00pm, July 22, 2015
Sea level rise is causing coastal areas to be inundated with water. Even short periods of being wet can kill sea turtle eggs, a new study finds.
Animals,, Oceans

Eyewitness account of a dolphin birth takes a dark turn

By Sarah Zielinski 11:17am, July 21, 2015
Scientists witnessed the first wild birth of a bottlenose dolphin — and an attempt at infanticide.

Birds learn what danger sounds like

By Sarah Zielinski 12:00pm, July 16, 2015
In just two days, superb fairy-wrens learned to recognize an unfamiliar alarm call as a sign that a predator loomed.

Feeding seabirds may give declining populations a boost

By Sarah Zielinski 12:00pm, July 15, 2015
Supplementing the diets of kittiwakes with additional food might give fledglings a head start, a new study finds.

Children’s classic ‘Watership Down’ is based on real science

By Sarah Zielinski 10:34am, July 12, 2015
The novel ‘Watership Down’ is the tale of a bunch of anthropomorphized rabbits. Their language may be unreal, but the animals’ behavior was rooted in science.

Cuckoos may have a long-lasting impact on other birds

By Sarah Zielinski 1:02pm, July 8, 2015
Some birds that don’t have to worry about parasites like cuckoos reject eggs that aren’t their own. It might be a legacy of long-ago parasitism.

Seabirds may navigate by scent

By Sarah Zielinski 7:44am, July 3, 2015
Shearwaters may use olfactory cues to find islands far across the open ocean, a new study suggests.
Climate,, Animals

Pink salmon threatened by freshwater acidification

By Sarah Zielinski 6:00pm, June 30, 2015
Ocean acidification gets more attention, but freshwater systems are also acidifying. That’s a problem for young salmon, a new study finds.

For dwarf mongooses, handstands aren’t just good fun

By Sarah Zielinski 3:25pm, June 26, 2015
Dwarf mongooses may use marks laid down in handstand positions to gather information on rivals, a new study shows.
Subscribe to RSS - Wild Things