Intraspecific differences in the diet of Kuril harbor seals (Phoca vitulina stejnegeri) in Erimo, Hokkaido, using DNA barcoding diet analysis

Competition between Kuril harbor seals (Phoca vitulina stejnegeri) and salmon set-net fishing industries has become a serious problem with the recent increase in the number of seals in Erimo, Hokkaido, Japan. We aimed to understand the detailed dietary structure of Kuril harbor seals focusing on intraspecific differences and verify whether "problem seals" who habitually use salmon set-nets could be characterized by intrinsic factors such as sex and maturity. We estimated the diet of Kuril harbor seals in two fishing seasons using DNA barcoding diet analysis on colon contents and verified intraspecific differences in their diet. In spring, their diets showed different tendencies between maturity stage; each adult seal fed on different prey items, suggesting that they avoid the intraspecies competition over food during the breeding season. Additionally, it was implied that some adult females habitually stole from salmon set-nets. Our dietary analysis showed dietary changes of Kuril harbor seals with different tendencies depending on maturity or sex, suggesting that problem individuals who habitually use set-nets can be characterized by intrinsic factors. This detailed dietary information can offer an accurate assessment of seal predation effects on fishing targets and the selective management of Kuril harbor seals, especially in mitigating seal-commercial fishery conflicts

Seasonal variations in the call presence of bearded seals in relation to sea ice in the southern Chukchi Sea

The seasonal habitat use of bearded seals is important information in terms of conservation of this species. However, their distribution outside the breeding season has not been well documented. We investigated seasonal variations in the call occurrence of bearded seals by using passive acoustic monitoring in the southern Chukchi Sea, which has some of the greatest benthic biomass in the Pacific sector of the Arctic Ocean. Underwater sounds were recorded between 2012 and 2015. Calls of bearded seals were detected from mid-September or early October to the end of each recording period (mid-May 2013, early March 2014, and mid-June 2015). Two peaks in call occurrence were noted; the first peak occurred during the open-water periods in November, and the second peak occurred during ice-covered periods. This suggest that bearded seals utilize the southern Chukchi Sea not only for the breeding site but also for the autumn foraging site. We could complement the information about the southward autumn migration pattern of bearded seals, and the southern Chukchi Sea was suggested as the south limit of bearded seals' autumn distribution. Additionally, their vocal activity during autumn in this site was suggested to have some role in social interaction. Our results indicated that the southern Chukchi Sea would be an important monitoring site for understanding the habitat use and the vocal activity of bearded seals, especially outside the breeding season

Atmospheric CO_2 captured by biogenic polyamines is transferred as a possible substrate to Rubisco for the carboxylation reaction

Biogenic polyamines are involved in a wide range of plant cellular processes, including cell division, morphogenesis and stress responses. However, the exact roles of biogenic polyamines are not well understood. We recently reported that biogenic polyamines that have multiple amino groups can react with CO2 and accelerate calcium carbonate formation in seawater. The ability of biogenic polyamines to capture atmospheric CO2 prompted us to examine their roles in photosynthesis. Here, we demonstrated that atmospheric CO2 captured by biogenic polyamines is a candidate substrate for the carboxylation reaction of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), which is an enzyme involved in the first major step of carbon fixation during photosynthesis, and that biogenic polyamines can accelerate the carboxylation reaction of this enzyme because of their specific affinity for CO2. Moreover, the results of our nuclear magnetic resonance (NMR) analysis showed that putrescine, which is the most common biogenic polyamine, reacts with atmospheric CO2 and promotes the formation of carbamate derivatives and bicarbonate in aqueous environments. A sufficient amount of CO2 is well known to be produced by carbonic anhydrase from bicarbonate in vivo. The present study indicates that CO2 would be also produced by the equilibrium reaction from carbonate produced by biogenic polyamines and would be used as a substrate of Rubisco, too. Our results may suggest a new photosynthetic research strategy that involves CO2-concentrating mechanisms and also possibly constitutes a potential tool for reducing atmospheric CO2 levels and, consequently, global warming.rights This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Te images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

Atmospheric CO_2 captured by biogenic polyamines is transferred as a possible substrate to Rubisco for the carboxylation reaction.

Biogenic polyamines are involved in a wide range of plant cellular processes, including cell division, morphogenesis and stress responses. However, the exact roles of biogenic polyamines are not well understood. We recently reported that biogenic polyamines that have multiple amino groups can react with CO2 and accelerate calcium carbonate formation in seawater. The ability of biogenic polyamines to capture atmospheric CO2 prompted us to examine their roles in photosynthesis. Here, we demonstrated that atmospheric CO2 captured by biogenic polyamines is a candidate substrate for the carboxylation reaction of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), which is an enzyme involved in the first major step of carbon fixation during photosynthesis, and that biogenic polyamines can accelerate the carboxylation reaction of this enzyme because of their specific affinity for CO2. Moreover, the results of our nuclear magnetic resonance (NMR) analysis showed that putrescine, which is the most common biogenic polyamine, reacts with atmospheric CO2 and promotes the formation of carbamate derivatives and bicarbonate in aqueous environments. A sufficient amount of CO2 is well known to be produced by carbonic anhydrase from bicarbonate in vivo. The present study indicates that CO2 would be also produced by the equilibrium reaction from carbonate produced by biogenic polyamines and would be used as a substrate of Rubisco, too. Our results may suggest a new photosynthetic research strategy that involves CO2-concentrating mechanisms and also possibly constitutes a potential tool for reducing atmospheric CO2 levels and, consequently, global warming

Diet selection and asocial learning: Natal habitat influence on lifelong foraging strategies in solitary large mammals

Exploring the process of diet selection will contribute to improvement in our understanding of animal foraging strategies. The overwhelming majority of ecological research on animal learning and foraging concentrates on how social learning influences the feeding styles of animals living in groups. In solitary animals that live long after independence from their mothers, foraging experience after independence is expected to have a significant influence on diet selection, but few studies have addressed this point. We used brown bears (Ursus arctos), which spend 1-2 years with their mothers before foraging alone, as a model species and investigated how their diet changed later in life. We estimated the diets of bears at the individual level by using stable isotope analysis of guard hairs and examined the factors that drove dietary variation. We also quantified the extent to which the diets of bears shifted by comparing the diets of bears at the time of capture with the average diet in their natal habitat. Our results indicated that females retained the average diet of their natal habitat, whereas the diets of males significantly changed more than 6 years after becoming independent from their mothers, when they reached physical maturity. Males were dependent on energy-rich marine animals at older ages regardless of their natal habitats, which we attribute to several factors, including habitat exploration, acquisition of foraging experience, and social dominance. Our results provide the first evidence, suggesting that foraging experience after independence influences diet selection later in life in solitary large mammals

Dining from the coast to the summit : Salmon and pine nuts determine the summer body condition of female brown bears on the Shiretoko Peninsula

Body condition in mammals fluctuates depending on energy intake and expenditure. For brown bears (Ursus arctos), high-protein foods facilitate efficient mass gain, while lipids and carbohydrates play important roles in adjusting dietary protein content to optimal levels to maximize energy intake. On the Shiretoko Peninsula, Hokkaido, Japan, brown bears have seasonal access to high-lipid pine nuts and high-protein salmon. To assess seasonal and annual fluctuation in the body condition of adult female brown bears in relation to diet and reproductive status, we conducted a longitudinal study in a special wildlife protection area on the Shiretoko Peninsula during 2012-2018. First, analyses of 2,079 bear scats revealed that pine nuts accounted for 39.8% of energy intake in August and salmon accounted for 46.1% in September and that their consumption by bears varied annually. Second, we calculated the ratio of torso height to torso length as an index of body condition from 1,226 photographs of 12 adult females. Results indicated that body condition continued to decline until late August and started to increase in September when salmon consumption increased. In addition, body condition began to recover earlier in years when consumption of both pine nuts and salmon was high. Furthermore, females with offspring had poorer body condition than solitary females, in particular in late August in years with low salmon consumption. Our findings suggest that coastal and subalpine foods, which are unique to the Shiretoko Peninsula, determine the summer body condition of female brown bears, as well as their survival and reproductive success

Development of a noninvasive photograph-based method for the evaluation of body condition in free-ranging brown bears

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