scholarly journals Testing for a predicted decrease in body size in brown bears (Ursus arctos) based on a historical shift in diet

2016 ◽  
Vol 94 (7) ◽  
pp. 489-495 ◽  
Author(s):  
Jun Matsubayashi ◽  
Ichiro Tayasu ◽  
Junko O. Morimoto ◽  
Tsutomu Mano

A recent study found a historical decline in the proportion of meat in the diet of brown bears (Ursus arctos L., 1758) in the Hokkaido Islands, Japan. Because feeding habits are strongly correlated with the body size of animals, the shift in diet should have led to a decrease in the size of these bears. To predict the effects of this dietary shift on the skeletal size in bears, we correlated the femur length in Hokkaido brown bears with the carbon and nitrogen stable isotope values from bone samples and predicted the historical change in their body size. The variation in the femur lengths of the male and female subpopulations was positively correlated with their δ15N values, but not with their δ13C values, and the explanatory power of the constructed model was higher in males than in females. Based on the model and the δ15N values for historic and modern bears, the skeletal size of bear subpopulations in eastern Hokkaido was estimated to have decreased by 10%–18% for males and 8%–9% for females. Our results suggest that a historical dietary shift caused the decrease in the size of the Hokkaido brown bears.

2000 ◽  
Vol 78 (6) ◽  
pp. 974-981 ◽  
Author(s):  
Gregory T Ruggerone ◽  
Renn Hanson ◽  
Donald E Rogers

Selective predation by and predation rates of brown bears (Ursus arctos) foraging on spawning sockeye salmon (Oncorhynchus nerka) in a small shallow creek in the Wood River lake system near Bristol Bay, Alaska, were quantified during 1986 and 1990–1992. Bears killed a high proportion of spawning salmon when few salmon entered the creek (92% of 505 fish) and a much smaller proportion when the spawning population reached a historical high (16% of 15 631 fish). Selective predation on salmon that differed in length, sex, and spawning condition was measured by tagging salmon at the mouth of the creek immediately prior to upstream migration and then recovering dead tagged fish during daily surveys of the entire creek. The relative frequencies of large, medium-sized, and small salmon killed by bears indicated that the risk of predation was more than 150% greater for large than for small salmon. A higher proportion of the male salmon population was killed and a greater proportion of male bodies were consumed than female salmon. Selectivity for male salmon increased as the spawning season progressed, possibly because male salmon weakened earlier and lived longer in a weakened state than female salmon. Male salmon were attacked mostly along the dorsal hump area, whereas female salmon tended to be attacked along the abdomen, where eggs could be exposed. Bears selectively killed female salmon prior to spawning during 1 of the 3 years, but only 6.1–7.8% of the female spawning populations were killed prior to spawning. These data support the hypothesis that selective predation by bears may influence the body morphology of spawning salmon.


2019 ◽  
Author(s):  
Shotaro Shiratsuru ◽  
Andrea Friebe ◽  
Jon E. Swenson ◽  
Andreas Zedrosser

AbstractHibernation is an adaptive strategy to survive harsh winter conditions and food shortage. The use of well-insulated winter dens helps animals minimize energy loss during hibernation. Brown bears (Ursus arctos) commonly use excavated dens for hibernation. Physical properties of excavated dens, such as the amount of space between a bear and the inner wall, wall/roof thickness, and bedding materials, are expected to impact heat retention and energy conservation of bears. The objective of this study was to examine the impact of physical properties of excavated dens on energy conservation in hibernating bears. Our hypothesis was that bears excavate dens in a way to minimize heat loss and optimize energy conservation during hibernation. We predicted that physical properties of excavated dens would significantly affect the bears’ post-hibernation body condition. To test our hypothesis and prediction, we analyzed data collected from brown bears in Sweden with linear mixed effects models, examining (i) what factors affect den-excavation behavior and (ii) if physical properties of excavated dens affect post-hibernation body condition. We found that bears excavated a den cavity in relation to their body size, that older bears tended to excavate better-fitting den cavities compared to young bears, and that the physical properties of excavated dens did not significantly affect a bears’ post-hibernation body condition. Older bears excavated better-fitting den cavities, suggesting a potentially experience-based shift with age in den-excavation behavior and an optimum cavity size relative to a bear’s body size. The strong year effect shown by the most parsimonious model for post-hibernation body condition suggests that variations in physical properties of excavated dens are possibly negligible, compared to the large annual variations in biotic and abiotic factors affecting pre-hibernation body condition and heat loss during hibernation.


PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9982
Author(s):  
Yuri Shirane ◽  
Fumihiko Mori ◽  
Masami Yamanaka ◽  
Masanao Nakanishi ◽  
Tsuyoshi Ishinazaka ◽  
...  

Body condition is an important determinant of health, and its evaluation has practical applications for the conservation and management of mammals. We developed a noninvasive method that uses photographs to assess the body condition of free-ranging brown bears (Ursus arctos) in the Shiretoko Peninsula, Hokkaido, Japan. First, we weighed and measured 476 bears captured during 1998–2017 and calculated their body condition index (BCI) based on residuals from the regression of body mass against body length. BCI showed seasonal changes and was lower in spring and summer than in autumn. The torso height:body length ratio was strongly correlated with BCI, which suggests that it can be used as an indicator of body condition. Second, we examined the precision of photograph-based measurements using an identifiable bear in the Rusha area, a special wildlife protection area on the peninsula. A total of 220 lateral photographs of this bear were taken September 24–26, 2017, and classified according to bear posture. The torso height:body/torso length ratio was calculated with four measurement methods and compared among bear postures in the photographs. The results showed torso height:horizontal torso length (TH:HTL) to be the indicator that could be applied to photographs of the most diverse postures, and its coefficient of variation for measurements was <5%. In addition, when analyzing photographs of this bear taken from June to October during 2016–2018, TH:HTL was significantly higher in autumn than in spring/summer, which indicates that this ratio reflects seasonal changes in body condition in wild bears. Third, we calculated BCI from actual measurements of seven females captured in the Rusha area and TH:HTL from photographs of the same individuals. We found a significant positive relationship between TH:HTL and BCI, which suggests that the body condition of brown bears can be estimated with high accuracy based on photographs. Our simple and accurate method is useful for monitoring bear body condition repeatedly over the years and contributes to further investigation of the relationships among body condition, food habits, and reproductive success.


2006 ◽  
Vol 269 (3) ◽  
pp. 273-283 ◽  
Author(s):  
B. Dahle ◽  
A. Zedrosser ◽  
J. E. Swenson
Keyword(s):  

2013 ◽  
Vol 43 (12) ◽  
pp. 2208-2214 ◽  
Author(s):  
Ana Paula Gottlieb Almeida ◽  
Everton Rodolfo Behr ◽  
Bernardo Baldisserotto

This study analyzed the structure of the gill rakers of Parapimelodus valenciennis and Parapimelodus nigribarbis (planktivorous), Serrasalmus maculatus and Hoplias malabaricus (piscivorous), Iheringichthys labrosus (benthophagous) and Hypostomus commersonii (detritivorous) and related it with the body size and feeding habits of these species. The species of Parapimelodus and H. commersonii showed long, filiform and closely spaced gill rakers, similar to those of species that use the gill rakers as a filter to assist in the retention of small particles. The widely spaced gill rakers of I. labrosus probably allow the retention of insect larvae, but not particles of inorganic matter. In H. malabaricus and S. maculatus the gill rakers are most likely related to prey capture and swallowing, as observed in other piscivorous species. In general, gill raker length and the distance between gill rakers have a positive relationship with fish length. The gill rakers show adaptations related to the diet of the fish, but morphological variation may occur even between species whose feeding habits are the same.


2019 ◽  
Vol 8 (1) ◽  
Author(s):  
Heru Winarko Junardi, Tri Rima Setyawati

Terebellobranchia sp. is a member of the Terebellidae family, which is known to have a high level of morphological variation. The aims of research was to know morphometric variations and the relationship of body size and uncini of Terebellobranchia sp. in Lemukutan Island. The measurements body and uncini were carried out on complete specimens with digital caliper, while uncini measuring under a microscope with eyepiece micrometer. Data analysis with t test in 64 individuals. The Terebellobranchia sp. found in station 2 had a significantly different size with Terebellobranchia sp. in other stations. The body length of Terebellobranchia sp. shows a strong correlation with the width, number of segments and body weight, meanwhile the width of the segment strongly correlated with size of uncini.


1991 ◽  
Vol 69 (9) ◽  
pp. 2404-2409 ◽  
Author(s):  
K. Elgmork ◽  
H. Riiser

Analysis of measurements of guard hairs from North American brown or grizzly bears and Scandinavian brown bears (Ursus arctos L.) showed variation over the body and along the hair shaft. Using the medullary index, i.e., the medullary diameter as a percentage of the hair diameter, comparisons were made among body areas, age groups, geographical areas, sexes, and seasons. Statistically significant differences were found among body areas. Hairs from the foreleg were shorter and wider, with a smaller medullary index than those from other body areas. There was a weak but statistically significant negative correlation between the medullary index and age of individuals. Medullary indices from Scandinavian bears were significantly greater than those from Alaskan bears, which in turn were greater than those from bears of the contiguous United States. There were no statistically significant differences between the medullary index and sex or season.


2017 ◽  
Vol 25 (2) ◽  
pp. 161
Author(s):  
Sławomir Mitrus ◽  
Bartłomiej Najbar ◽  
Adam Kotowicz ◽  
Anna Najbar
Keyword(s):  
The Body ◽  

2007 ◽  
Vol 8 (3) ◽  
pp. 105-120
Author(s):  
Bruce Williams

ABSTRACT Rendered a true fetish of stagnation by the death of Cuba's bourgeois regime, the body of the male protagonist of Tomás Gutiérrez Aléa's Memories of Underdevelopment becomes a locus onto which the sexual strategies of the film debunk the contradictions implicit in moments of historical change.


Author(s):  
Adrian Marciszak ◽  
Yuriy Semenov ◽  
Piotr Portnicki ◽  
Tamara Derkach

AbstractCranial material ofPachycrocuta brevirostrisfrom the late Early Pleistocene site of Nogaisk is the first record of this species in Ukraine. This large hyena was a representative of the Tamanian faunal complex and a single specialised scavenger in these faunas. The revisited European records list ofP.brevirostrisdocumented the presence of this species in 101 sites, dated in the range of 3.5–0.4 Ma. This species first disappeared in Africa, survived in Europe until ca. 0.8–0.7 Ma, and its last, relict occurrence was known from south-eastern Asia. The main reason of extinction ofP.brevirostrisprobably was the competition withCrocuta crocuta. The cave hyena was smaller, but its teeth were proportionally larger to the body size, better adapted to crushing bones and slicing meat, and could also hunt united in larger groups.


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