Physical body parameters of red-crowned cranes Grus japonensis by sex and life stage in eastern Hokkaido, Japan

Middle upper beak fracture in a Red-crowned crane that completely recovered with external skeletal fixation

An adult Red-crowned crane in captivity that had a displaced compound fracture of the middle upper beak caused by an accident was treated by using Type I-a external skeletal fixator (ESF). The ESF that was equipped with a unilateral epoxy putty fixator and with five half-pins was fixed on the premaxilla bone. The crane with the ESF on the beak was able to feed smoothly by itself. The ESF was removed 49 days after the first surgery. Beak malocclusion, which was observed in the latter half period of fixing, spontaneously improved within one month after removal of the ESF. This is the first successful case of repair of an upper beak fracture in a Red-crowned crane.

Contamination Status of Seven Elements in Hooded Cranes Wintering in South-West Kyushu, Japan: Comparison with Red-Crowned Cranes in Hokkaido, Japan

The hooded crane is designated as an endangered species. The cranes breed primarily in wetlands in southeast Russia and China in summer. Most of the hooded crane population winters in the Izumi plain in Japan. It is difficult to know the contamination status of their habitat because of their vast breeding area. We determined the levels of Cd, Pb, As, (total) Hg, Se, Zn, and Cu in the liver, kidney, and muscle of hooded cranes that were found dead in Izumi in the periods 2003-2006 and 2014-2015 compared with the levels in red-crowned cranes in Hokkaido, Japan, as the only cranes in which these elements had been studied extensively. There were no notable differences between levels of the seven elements in the two periods. Overall, tissue levels of the elements examined in hooded cranes were comparable to those in red-crowned cranes except for Hg and Se. Tissue levels of Hg and Se were clearly lower in hooded cranes than in red-crowned cranes that were found dead from 2000. One lead poisoning case was confirmed. The results suggest that Hooded cranes wintering in Izumi are not extensively contaminated with the seven elements examined.

Persistent organic pollutants in red-crowned cranes (Grus japonensis) from Hokkaido, Japan

The red-crowned crane (Grus japonensis) from eastern Hokkaido is classified as a Special Natural Monument in Japan. In this study, we determined the concentrations of persistent organic pollutants (POPs) in red-crowned crane muscle tissues (n = 47). Polychlorinated biphenyls (PCBs) had the highest median concentration (240ng/g lipid weight), followed by dichlorodiphenyltrichloroethane and its metabolites (DDTs) (150ng/g lipid weight), chlordane-related compounds (CHLs) (36ng/g lipid weight), hexachlorobenzene (HCB) (16ng/g lipid weight), hexachlorocyclohexanes (HCHs) (4.4ng/g lipid weight), polybrominated diphenyl ethers (PBDEs) (1.8ng/g lipid weight), and finally, Mirex (1.5ng/g lipid weight). Additionally, a positive correlation was found among POP concentrations. No sex differences beyond body parameters were observed. Additionally, red-crowned cranes exhibited a high enantiomeric excess of (+)-alpha-HCH, with enantiomer fractions varying from 0.51 to 0.87 (average: 0.69).

Accumulation properties of inorganic mercury and organic mercury in the red-crowned crane Grus japonensis in east Hokkaido, Japan

The red-crowned (Japanese) crane Grus japonensis is native to east Hokkaido, Japan, in contrast to the East Asia mainland. Previously, we reported that red-crowned cranes in Hokkaido were highly contaminated with mercury in the 1990s and that the contamination rapidly decreased to a moderate level in the 2000s. In the present study, we determined levels of organic mercury (O-Hg) in the liver and kidney of cranes in east Hokkaido in comparison with levels of total mercury (T-Hg). T-Hg levels in the kidneys were higher than those in the livers in adults but not in subadults and juveniles; however, the reverse was the case for O-Hg even for adults. The ratio of O-Hg to T-Hg in both the liver and kidney decreased as T-Hg increased in the three developmental stages. While the ratios of O-Hg to T-Hg in the liver and kidney of adults were significantly lower than those of juveniles, the ratios were similar for adults and juveniles in a lower range of T-Hg. The ratio of selenium (Se) to T-Hg decreased as T-Hg increased in both the liver and kidney, irrespective of stages. Mercury burdens in feathers were about 59% and 67% of the total body burdens for juveniles and adults, respectively. Furthermore, ratios of carbon and nitrogen stable isotopes to T-Hg varied greatly, with no relation to mercury level in the liver. The results suggest slow accumulation of inorganic mercury in the kidney of red-crowned cranes in east Hokkaido, Japan.

Arch displays signal threat intentions in a fission–fusion flock of the red-crowned crane

Ritualised displays are used by group-living animals in various contexts, such as when individuals join a group or flock. Only a few quantitative studies of the function of displays in species with fission–fusion social dynamics have been conducted to date. Here, we examined the arch display in red-crowned cranes (Grus japonensis) immediately after joining a flock. Behavioural observations indicated that the arch functions as a signal of both threat motivation and individual strength. Singletons had disadvantages in terms of competition over resources and were, therefore, expected to have higher threat motivation than pairs or families. Indeed, singletons performed the arch more frequently than did pairs or families. Performance of the arch was related to dominance: males and adults were more likely to perform the arch than females and sub-adults. The likelihood of performing the arch was positively associated with local group density, indicating that joiners arched in more competitive situations. Contextual analyses indicated that subsequent behaviour by a joiner was more aggressive and that nearby individuals more frequently showed behavioural responses when a joiner arched than when it did not. Together, this study shows that cranes demonstrate functional displays to potential competitors, and represents a rare example of the functional analysis of ritualised signals in non-songbird species with fission–fusion social dynamics.