High resting metabolic rates with low thermal dependence induce active dives in overwintering Pacific juvenile loggerhead turtles

UTokyo FOCUS Articles掲載「三陸のウミガメは寒冷地仕様 高い休止代謝速度と低い温度依存性によって冬季でも活動性を維持」https://www.u-tokyo.ac.jp/focus/ja/articles/a_00627.htmlUTokyo FOCUS Articles "Cold never bothered me anyway Pacific sea turtles\u27 metabolisms stay active over winter" https://www.u-tokyo.ac.jp/focus/en/articles/z0508_00003.htm

Movements and activities of male black-tailed gulls in breeding and sabbatical years

Long-lived animals sometimes skip one or more breeding seasons; however, little is known about their movements and activities during such ‘sabbatical’ periods. Here we present novel data on year-round movements and activities of two male black-tailed gulls Larus crassirostris during a sabbatical year. We compare the data with those in a year when they bred and with those of two other breeding males. The year-round migration routes of two sabbatical males were consistent with those of the breeding males: they returned to the breeding area but did not visit the colony in the sabbatical year. They landed more frequently on water (a potential index of foraging effort) during the non-breeding autumn and winter prior to the sabbatical year than before breeding. Sabbatical gulls may forage more intensively to recover body condition immediately after breeding

Migratory movements of rhinoceros auklets in the northwestern Pacific: connecting seasonal productivities

Spatial and temporal variability in marine biological productivity may drive heterogeneity in seasonal resources available for marine animals in temperate waters. Migratory seabirds are expected to adjust their annual cycle of breeding activities and migratory movements to exploit seasonally available resources efficiently. We studied the movement and trophic position of rhinoceros auklets Cerorhinca monocerata breeding at Teuri Island, Japan Sea, during the nonbreeding and early breeding periods over 2 yr. After breeding, the auklets moved northward from the colony to the Sea of Okhotsk, where phytoplankton blooms enhanced biological productivity in autumn. The birds then moved southward to the southwestern Japan Sea (~1470 km from the colony), where major epipelagic fish and squid concentrations have been reported in winter. Stable isotope analyses suggest that the auklets fed on higher-trophic level prey, including fish and/or squid during the autumn and winter nonbreeding periods. The auklets moved northward and returned to the colony in mid-March. During the early breeding period, the birds foraged close to the colony (~380 km) on lower-trophic level prey including fish and/or krill, which were available during the spring phytoplankton bloom. The timing of the return migration does not match with the northward migration of warm-water anchovy, a profitable prey during summer, but may be related to timing the chick-rearing period to correspond with anchovy arrival. We suggest that rhinoceros auklets follow spatial and seasonal changes in prey availability by a distinctive ‘3-step’ migration (first northward, second southward, third northward) in the temperate marine system of the northwestern Pacific

Mercury concentrations in primary feathers reflect pollutant exposure in discrete non-breeding grounds used by Short-tailed Shearwaters

We measured mercury concentrations ([Hg]) and nitrogen stable isotope ratios (δ15N) in the primary feathers of Short-tailed Shearwaters (Puffinus tenuirostris) that were tracked year-round. The [Hg] were highest in 14 birds that used the Okhotsk and northern Japan Seas during the non-breeding period (2.5 ± 1.4 μg/g), lowest in nine birds that used the eastern Bering Sea (0.8 ± 0.2 μg/g), and intermediate in five birds that used both regions (1.0 ± 0.5 μg/g), with no effects of δ15N. The results illustrate that samples from seabirds can provide a useful means of monitoring pollution at a large spatial scale

Consistent individual variations in aggressiveness and a behavioral syndrome across breeding contexts in different environments in the Black-tailed Gull

Individual behaviors of animals do not evolve separately but do so in association with other behaviors caused by single shared genetic or physiological constraints and/or favored by selection. Measuring behavioral syndromes which are suites of correlated behaviors across different contexts, therefore, provides better understanding of the adaptive significance of variations in behaviors. However, studies that have examined the behavioral syndrome in wild animal populations in changing environments are in the minority. We measured behavioral syndrome among anti-predator nest defense, territorial defense, chick-provisioning, and mating behavior of male Black-tailed Gulls Larus crassirostris in two successive years with different conspecific territorial intrusion risks and food conditions. Males with high levels of anti-predator nest defense (aggressive anti-predator defenders) against the decoy of crows (an egg-predator) defended their territory against conspecific intruders more frequently than did other males (non-aggressive anti-predator defenders) independently of the risk of intrusion. Aggressive anti-predator defenders also fed their chicks more frequently than non-aggressive males, but only in the year of lower food availability. Taken together, this indicates that males show consistent aggressiveness regardless of breeding context (anti-predator and territorial defense), but they can regulate food provisioning according to food availability

Factors affecting individual variation in nest-defense intensity in colonially breeding Black-tailed Gulls (Larus crassirostris)

The physiological state of parent birds combined with the value of their clutch may affect the intensity of their nest defense. In colonially breeding birds, nest defense intensity may also be affected by the behavior of neighbors. We investigated individual variation in the intensity of nest defense among colonial Black-tailed Gulls Larus crassirostris in two years. Only 30-40% of males attacked a decoy of an egg predator (crow), and the other males and females rarely attacked. Males attacking the decoy had higher levels of plasma testosterone than males that did not attack. Each male's, but not female's, nest defense intensity was consistent throughout the incubation period and also across years. The intensity was not related to egg-laying date, clutch size, or age of offspring. The intensity was likely to be higher when individuals had one or more neighbors, representing higher nest defense intensity in the year where gulls had larger number of adjacent neighboring nests (5.23 nests), but this trend was not observed in the year where they had smaller number of the neighboring nests (3.73 nests). Thus, in addition to testosterone levels, behavior of neighbors also influences the intensity of nest defense

Data from: How do growth and sibling competition affect telomere dynamics in the first month of life of long-lived seabird?

Telomeres are nucleotide sequences located at the ends of chromosomes that promote genome stability. Changes in telomere length (dynamics) are related to fitness or life expectancy, and telomere dynamics during the development phase are likely to be affected by growth and stress factors. Here, we examined telomere dynamics of black-tailed gull chicks (Larus crassirostris) in nests with and without siblings. We found that the initial telomere lengths of singletons at hatching were longer than those of siblings, indicating that singletons are higher-quality chicks than siblings in terms of telomere length. Other factors likely affecting individual quality (i.e., sex, laying date, laying order of eggs, and clutch size) were not related to telomere lengths. Within broods, initial telomere lengths were longer in older chicks than in younger chicks, suggesting that maternal effects, which vary with laying sequence, influence the initial lengths. Additionally, telomeres of chicks with a sibling showed more attrition between hatching and fledging than those of singleton chicks, suggesting that being raised with siblings can cause a sustained competitive environment that leads to telomere loss. High growth rates were associated with a low degree of telomere shortening observed in older siblings, perhaps because slower growth reflects higher food stress and/or higher aerobic metabolism from increased begging effort. Our results show that developmental telomere attrition was an inevitable consequence in two-chick nests in the pre- and post-hatching microenvironments due to the combination of social stress within the nest and maternal effects. The results of our study shed light on telomere dynamics in early life, which may represent an important physiological undercurrent of life-history traits

Data from: How do growth and sibling competition affect telomere dynamics in the first month of life of long-lived seabird?

Telomeres are nucleotide sequences located at the ends of chromosomes that promote genome stability. Changes in telomere length (dynamics) are related to fitness or life expectancy, and telomere dynamics during the development phase are likely to be affected by growth and stress factors. Here, we examined telomere dynamics of black-tailed gull chicks (Larus crassirostris) in nests with and without siblings. We found that the initial telomere lengths of singletons at hatching were longer than those of siblings, indicating that singletons are higher-quality chicks than siblings in terms of telomere length. Other factors likely affecting individual quality (i.e., sex, laying date, laying order of eggs, and clutch size) were not related to telomere lengths. Within broods, initial telomere lengths were longer in older chicks than in younger chicks, suggesting that maternal effects, which vary with laying sequence, influence the initial lengths. Additionally, telomeres of chicks with a sibling showed more attrition between hatching and fledging than those of singleton chicks, suggesting that being raised with siblings can cause a sustained competitive environment that leads to telomere loss. High growth rates were associated with a low degree of telomere shortening observed in older siblings, perhaps because slower growth reflects higher food stress and/or higher aerobic metabolism from increased begging effort. Our results show that developmental telomere attrition was an inevitable consequence in two-chick nests in the pre- and post-hatching microenvironments due to the combination of social stress within the nest and maternal effects. The results of our study shed light on telomere dynamics in early life, which may represent an important physiological undercurrent of life-history traits