FSD 2010 - Bear

5th International Symposium-Workshop on Frugivores and Seed Dispersal (1985-2010)

The Frugivores of the Month are Bears

There are 8 species of Bears in 5 genera : Ursus (photo : Asian black bear U. thibetanus) , Tremarctos, Melursus, Helarctos, and Ailuropoda. Bears are found on all continents except Antarctica and Australia, but are primarily found throughout the northern hemisphere, historically occurring as far south as the Atlas Mountains of northwestern Africa, the Andes of South America, and the Sunda shelf region. Bears are omnivorous and opportunistic. Specific food types may vary by habitat or season. For example, North American brown bears (Ursus arctos) may rely extensively on fruits and insect larvae throughout the year, or may prey extensively on calves during ungulate breeding seasons and on migrating fish. Most species eat primarily fruits and insect larvae but will include vertebrates when they can, carrion, honey, forbs and grasses, seeds, nuts, tubers, fish, and eggs. Bear species may help to disperse seeds from the fruits they eat. Bears have been hunted and persecuted throughout human history. Most bear populations continue to face hunting pressure and have become fragmented as a result of human habitat destruction and hunting (Dewey & Myers. 2005).

Carnivores as seed dispersers

Koike, S et al. (2008) found that Asiatic black bear, Japanese marten, badger, red fox, and raccoon dog act as seed dispersers for some fleshy-fruited plants (N = 17 spp.) in cool-temperate deciduous forest of central Japan. More precisely, Koike et al. (2008) investigated the relationship between the fruit phenology of Prunus jamasakura and the fruit-feeding period of the Asiatic black bear (Ursus thibetanus) that appeared to be potentially effective dispersers. Takahashi et al. (2008) studied fruit use seed dispersal by the Japanese black bear (Ursus thibetanus japonicus) in central Japan. They concluded that Japanese black bears seldom digest ingested seeds, thereby contributing to the seed dispersal of their food plants, including species with fruits that are too large to be swallowed by frugivorous birds.

Bear may also consume and predate on seeds as shown by Kuhn and Vander Wall (2007) who documented seeed comsumption of Jeffrey pine (Pinus jeffreyi) by black bears (Ursus americamus) in the eastern Sierra Nevada, USA. See also mention of seed predation of acorn by black bears (photo © Phil Myers).

In southeastern Alaska, Willson and Gende (2004) observed that the abundant Brown Bears (Ursus arctos) are among the most important dispersers of seeds for the numerous plant species producing fleshy fruits often eating large quantities of fruit, and commonly excreting seeds in germinable condition.

In the tropical rainforest, frugivores bear are also seed dispersers. Kitamura et al. (2002) (cited in Forget et al. 2007). In Southern india, Sreekumar and Balakrishnan (2002) demonstrated that scat of the sloth bear (Melursus ursinus) contained fruits, seeds collected from scats germinating faster than seeds not passing through bears. McConkey and Galetti (1999) studied seed dispersal by the sun bear Helarctos malayanus in Central Borneo, and found that one sample of these bear feces contain 309 seeds of a given species.

Nonetheless, question remains whether bear are legitimate dispersers if the consumed fruit species. For instance, Auger et al. (2002) wonder whether black bears (Ursus americanus, Photo © Phil Myers) are legitimate seed dispersers for fleshy-fruited shrubs since ingestion treatments suggest that the digestive process of black bears may simulate prewarming of seeds. Ultimately, Bernejo et al. (1998) compared the fate of "clean" seeds of (Rubus spectabilis, Oplopanax horridus, and Streptopus amplexifolius) with seeds embedded in feces of bears, important dispersers in Alaska showing that seed removal was significantly higher for clean seeds than for seeds within bear feces.

References (abstracts)

Auger J, Meyer SE & Black HL. 2002. Are American black bears (Ursus americanus) legitimate seed dispersers for fleshy-fruited shrubs? American Midland Naturalist 147 (2): 352-367.

Bermejo T, Traveset A, & Willson MF. 1998. Post-dispersal seed predation in the temperate rainforest of southeast Alaska. Canadian Field-Naturalist 112 (3): 510-512.

Kitamura S, Yumoto T, Poonswad P, Chuailua P, Plongmai K, Maruhashi T & Noma N. 2002. Interactions between fleshy fruits and frugivores in a tropical seasonal forest in Thailand. Oecologica 133 (4): 559-572.

Koike S, Kasai S, Yamazaki K, & Furubayashi K. 2008. Fruit phenology of Prunus jamasakura and the feeding habit of the Asiatic black bear as a seed disperser. Ecological Research 23 (2): 385-392.

Koike S, Morimoto H, Goto Y, Kozakai C, & Yamazaki, K. 2008. Frugivory of carnivores and seed dispersal of fleshy fruits in cool-temperate deciduous forests. Journal of Forest Research 13 (4): 215-222.

Kuhn KM, & Vander Wall SB. 2007. Black bears (Ursus americanus) harvest Jeffrey pine (Pinus jeffreyi) seeds from tree canopies. Western North American Naturalist 67 (3): 384-388. (photo © Phil Myers).

McConkey, K; Galetti, M. 1999. Seed dispersal by the sun bear Helarctos malayanus in Central Borneo. Journal of Tropical Ecology 15: 237-241, Part 2.

Sreekumar PG, Balakrishnan M. 2002. Seed dispersal by the sloth bear (Melursus ursinus) in South India. Biotropica 34 (3): 474-477.

Takahashi, K; Shiota, T; Tamatani, H; Koyama, M; Washitani, I. 2008. Seasonal variation in fleshy fruit use and seed dispersal by the Japanese black bear (Ursus thibetanus japonicus). Ecological Research 23 (2): 471-478.

Willson MF & Gende SM. 2004. Seed dispersal by Brown Bears, Ursus arctos, in southeastern Alaska. Canadian Field-Naturalist 118 (4): 499-503.

Sources

Animal Diversity Web

Dewey, T. and P. Myers. 2005. "Ursidae" (On-line), Animal Diversity Web. Accessed February 04, 2010.

Contributor : Phil Myers (photographer, copyright holder), Museum of Zoology, University of Michigan. Schoolcraft Co., Michigan. Caption : acorns chewed by a bear ; Caption : black bear scat ; Glacier Park, Montana: Caption : black bear.

Mongabay. com

Educational resources on Malayan Sun Bear

Sun Bear

Presentation about Bears at FSD2010

Shinsuke Koike et al. Estimate of the seed shadow created by the Asiatic black bear (Ursus thibetanus) and its characteristics as a seed disperser in Japanese cool-temperate forest.

Ami Nakajima et al. Difference in foraging patterns of fruits by Asiatic black bears in relation with abundance, timing and duration of various fruit production.

Kazuaki Takahashi et al. The Japanese black bear (Ursus thibetanus japonicus) as seed dispersers and ecosystem engineers.

Mark Enders & Stephen Vander W. Black bears (Ursus americanus) are effective seed dispersers, with a little help from their friends.