Temporal diet changes recorded by stable isotopes in Asiatic black bear (Ursus thibetanus) hair

Abstract

Carbon and nitrogen stable isotope ratios were measured in hair samples of the Asiatic black bear (Ursus thibetanus) inhabiting the Northern Japanese Alps (NJA) (n = 20) and the periphery of Nagano City (NC) (n = 6), in Nagano Prefecture, Japan. The hair of NJA bears, which did not have access to anthropogenic foods, showed lower values of d13C and d15N than that of NC bears which had access to garbage and corn fields, especially during the summer. These results reflect somewhat differing diets between the NJA and NC bears. We attempted to assess the feeding history during the hair growth cycle using the growth section analysis method. Each hair sample had been cut into 3?mm lengths from root to tip, labeled, and analyzed along the hair growth. We measured the carbon and nitrogen stable isotope ratios of each 3?mm length of hair sample from one NC bear which had been killed while raiding a corn field. The sections showed wide ranges of isotope ratios, from -23.2% to -14.6% for delta13C, and from 0.3% to 4.6% for delta15N. It was shown that the diet of this bear shifted dramatically from principally C3 plants to more C4 plants and to foods of animal origin. An analysis of the whole hair reflects just the average feeding habit during hair growth, but the present method can trace its diet history. This method can contribute to obtain precise ecological information of wildlife.

Using stable isotopes to assess dietary changes of American black bears from 1980 to 2001

“…First, similar to Mizukami et al [24], examination of the intra-annual variation of diets may be considered. Second, an extensive food items collection should be completed to examine the proportional contribution of food sources using mixing model analysis.…”

“…However, the majority of previous wildlife stable isotope studies have been conducted only over short time periods (2-7 years; [1,11,20,21]). Mizukami et al [24] used stable carbon and nitrogen isotope analysis to examine the temporal diet changes of Asiatic black bears and found that stable carbon and nitrogen isotope values changed significantly over a time period of one year. We used a similar approach to examine temporal diet changes over a 20-year time period.…”

Inflated population density of island antechinus: a case of allochthonous marine inputs leading to increased food availability?

“…Metabolically inactive tissues such as hair do not reabsorb or turnover nutrients. Therefore, their stable isotope ratios reflect the diet of individuals during the limited period when the tissue was formed (Roth 2002;Mizukami et al 2005). Therefore, the d 13 C and d 15 N of the fur of the swamp antechinus collected from the island in early spring and in the autumn were compared to determine whether a dietary shift to include seabird products occurred.…”

Assessing dual hair sampling for isotopic studies of grizzly bears

“…It further preserves temporal dietary information as hair forms incrementally over time in a cyclic pattern . Thus, the isotopic ratios of carbon ( δ 13 C values), nitrogen ( δ 15 N values) and sulfur ( δ 34 S values) in bear hair can give an indication of food and water sources …”

“…9,10 Thus, the isotopic ratios of carbon (δ 13 C values), nitrogen (δ 15 N values) and sulfur (δ 34 S values) in bear hair can give an indication of food and water sources. 6,11 δ 13 C values provide information on the relative contribution of C 3 and C 4 plants consumed, where higher consumption of C 4 plants, or indirect consumption of human foods, results in higher δ 13 C values. 12 δ 15 N values provide information pertaining to primarily protein consumption and secondarily trophic level, where a higher δ 15 N value signifies feeding of a marine or meat-based diet.…”