Nemuro Peninsula Research Articles

Ecological factors associated with fox feces density in an Echinococcus multilocularis endemic zone in Japan.

Human alveolar echinococcosis caused by Echinococcus multilocularis is an important zoonotic disease in the northern hemisphere. The life cycle of E. multilocularis is maintained primarily in wild animals and requires an intermediate host (mainly small mammals). Human can become an intermediate host through accidental ingestion of E. multilocularis eggs. Hokkaido Prefecture is the only area of Japan in which human alveolar echinococcosis is endemic. The purposes of this study were to elucidate the land use ecological factors associated with the density of red fox feces along paved roads and the relationship between the distributions of red fox (Vulpes vulpes) populations and fox feces, which determine the level of hazard from eggs. A series of surveys was conducted in the central part of the Nemuro Peninsula of Hokkaido, excluding urban areas, over a total of 4 years in May-June in 2014 and 2016-2018 when red foxes remain with their cubs around the dens. Transects of 500 m were set up on paved roads, and feces within the transects were counted. Univariable and multivariable analyses were performed to examine ecological factors including the principal components (PCs) of five land use-type occupancy proportions within 500 m and 1 km, respectively, as explanatory fixed-effect variables. The number of feces in each transect was examined as the response variable using integrated nested Laplace approximation with negative binomial errors with a spatio-temporal autocorrelations structure to separate the effects of similarities of neighboring locations and annual variation. The multivariable models with the lowest widely applicable information criterion values were selected. The feces density was explained by the PC of the 500- m buffer (-0.27, 2.5th and 97.5th percentiles: -0.44, -0.10) characterized by mixed forests (-0.82) and scarcity of residential areas (0.29) and the proximity to the nearest livestock farm house (-0.35, 2.5th and 97.5th percentiles: -0.53, -0.17). This suggested that foxes defecate in the areas where prey is abundant, avoiding humans. Policy discussions regarding bait distribution design targeting these conditions should be initiated.

Cross-mating between the alien bumblebee Bombus terrestris and two native Japanese bumblebees, B. hypocrita sapporensis and B. cryptarum florilegus, in the Nemuro Peninsula, Japan

The rapid naturalization of Bombus terrestris across the Nemuro Peninsula has led to a decline in two closely related native Japanese species, namely Bombus hypocrita sapporensis and Bombus cryptarum florilegus, both belonging to the common subgenus Bombus. Although it is widely believed that cross-mating of native and non-native species is influenced by the common male sex pheromone in this region, no study has been conducted to substantiate this claim. Thus, we investigated the cross-activities of male sex pheromones between native and non-native bumblebees, as well as the frequencies of cross-mating, using chemical and DNA assays. Our gas chromatography–electroantennographic detector analyses and behavioral tests revealed the presence of sex pheromonal cross-activities between B. terrestris and the two Japanese bumblebees species. Furthermore, DNA analyses revealed the occurrence of cross-mating between native and non-native species in the Nemuro Peninsula. Overall, these results indicate the immediate need for conservation measures to safeguard Japanese bumblebee populations in the Nemuro Peninsula.

Origin and evolution of the Paleo‐Kuril arc inferred from detrital zircon U–Pb chronology in eastern Hokkaido, NE Asia

AbstractThe Nemuro and Saroma Groups and Yusenkyo Formation occur in eastern Hokkaido and are considered to be forearc or intra‐arc basin sediments of the Paleo‐Kuril arc (PKA) deposited during the Late Cretaceous to middle Eocene. To further clarify the origin of the PKA, we examined the U–Pb ages of detrital zircons within these sandstones and acidic tuff beds; based on our results, we drew the following conclusions. (1) The PKA originated from an oceanic island arc on the oceanic Izanagi Plate around 85 Ma, to which the Nikoro Group greenstone complex was accreted between 81–80 Ma; the Lowest Unit of the Saroma Group covered the surface of the Nikoro accretional greenstone complex. (2) The PKA then first collided with NE Asia around the beginning of the deposition of the Hamanaka Formation (~70 Ma) and transitioned to a continental arc adjacent to NE Asia. This collision generated giant slump beds during deposition of the Akkeshi Formation. During deposition of the Kiritappu Formation, the entire Nemuro Peninsula was uplifted, supplying large volumes of clastic sediments. (3) Although we do not have data directly bearing on why the North American Plate was established in the edge of NE Asia, we speculate that it separated from the Eurasian continent around ~70 Ma when NE Asia first collided with the PKA. Subsequently, the PKA has behaved as part of the North American Plate. The Paleo‐Japan arc (or East Sikhote–Alin arc) and the PKA became joined via the Hidaka Belt. Around 40 Ma, during the deposition of coarse conglomerate beds of the Urahoro Group, the PKA was uplifted and bent clockwise due to a second collision with NE Asia. (4) The modern Kuril arc was established around 36 Ma (late Eocene–early Oligocene), and the Kuril backarc basin opened into the present tectonic setting in the late Oligocene–early Miocene.

Low mitochondrial DNA variation in the endangered bumble bee Bombus cryptarum florilegus

The distribution of the bumble bee Bombus cryptarum florilegus is very local: Nemuro Peninsula and Notsuke Peninsula in Japan and the southern part of Chishima (Kuril) Islands. It is listed as a near-threatened species in the Japan Red List. In this study, we sequenced 687 bp of the mitochondrial COI gene of Japanese B. c. florilegus to obtain information about its genetic structure. We found three base substitutions between samples from Nemuro Peninsula and those from Notsuke Peninsula, whereas sequences within each peninsula were identical. The results indicate that the population of Nemuro Peninsula and that of Notsuke Peninsula are fragmented, and both populations have lost genetic diversity. In addition, the sequence of Notsuke Peninsula is identical to that from Etorofu Island (Chishima (Kuril) Islands), suggesting that the population of Notsuke Peninsula is maintained by individuals immigrating from Chishima (Kuril) Islands. Previous studies suggested that a potential cause of B. c. florilegus decline is the expansion of feral populations of the alien commercial pollinator Bombus terrestris. To conserve B. c. florilegus, and to preserve the natural ecosystem, it is better to use native species as agricultural pollinators.

Satellite-Tracking of the Spring Migration and Habitat Use of the Brent GooseBranta berniclain Japan

Abstract Japan hosts more than 40% population of Brent Goose Branta bernicla wintering in East Asia. We used satellite-tracking technology to monitor the seasonal movements and habitat usage of Brent Goose wintering in northern Japan. We marked five geese on the Oya sandy beach, Miyagi Prefecture, northeast Honshu, on 21 January 2014. The geese utilized areas along the seacoast, especially concentrating at a small bay, close to the capture site. Most of the geese offshore were found at fishery rafts. No geese were found more than 2 km offshore or more than 6 km from the capture site along the seacoast. In early April, the geese left the southern Sanriku coast and moved up to eastern Hokkaido, crossing the sea directly or via the coastal areas of Iwate and Aomori Prefectures. The geese predominantly remained in the vicinity of the Veslovskiy Peninsula, Kunashiri (Kunashir) Island, while some were distributed along the northern coast of the Nemuro Peninsula. We identified eastern Hokkaido and Kunashiri Isla...

Efficacy of anthelmintic baiting of foxes against Echinococcus multilocularis in northern Japan

Field application of anthelmintic baits against Echinococcus multilocularis in red foxes (Vulpes vulpes) was conducted on Nemuro Peninsula at the eastern edge of Hokkaido, Japan. The total study area was 412km2, of which 135km2 were used for bait distribution. Commercial baits containing 50mg praziquantel were distributed by car along roads outside towns and villages in a density of 15/km2. Additional baits were distributed around fox breeding dens. Baiting was done from November 1999 to January 2006 at an average frequency of 4.3 distribution rounds per years (in total 27 rounds). Prevalence in foxes collected in the baiting and non-baiting areas were determined by necropsy. Base prevalence (before baiting) was 49.4% (CI95%: 43.7–55.0) in the baiting area and 70.5% (CI95%: 60.2–79.2) in the non-baiting area. During the first and second half of the baiting period, the prevalence in the baited area changed to 26.2% (CI95%: 14.4–42.3) and later to 15.8% (CI95%: 7.9–28.4), but remained at a high level in the neighboring non-baited area with 60.4% (CI95%: 45.3–73.9) and 65.0% (CI95%: 40.9–83.7). Our data show, that significant prevalence reduction (but not elimination) of E. multilocularis in foxes can be achieved by this method under epidemiological conditions, which are fundamentally different from those in Europe where most previous studies have been done.

Spatiotemporal variations in the statistical parameters of the shear wave splitting from local events beneath Eastern Hokkaido

Statistical analysis is carried out of the distribution of the fast Swave $$(\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\frown}$}}{\phi } )$$ , polarization azimuths, time delays between the split shear waves $$(\delta \overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\frown}$}}{t} )$$ and the dominant frequencies of P waves $$(\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\frown}$}}{f} _P )$$ from weak seismic events that hit Eastern Hokkaido during the period of 1998–2003, which also includes strong events with M > 6 and the strong Tokachi-oki earthquake (M8.0) of September 26, 2003. The analysis revealed oscillatory pattern of variations in wave parameters along Eastern Hokkaido. In the rigid crustal blocks beneath the Tokachi and Kushiro Plains, stability is observed in the fast azimuth orientation and unstable behavior of $$\delta \overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\frown}$}}{t}$$ and $$\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\frown}$}}{f} _P$$ in the interval of periods 0.5–2.5 years. In the weakened zones beneath the Hidaka Range and the Nemuro Peninsula, periodical alternation of $$\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\frown}$}}{\phi }$$ along orthogonal directions is revealed. It is found that the parameters of the waves coming from the seismic events originating in different depth intervals experience anomalous changes before strong earthquakes. These anomalies reflect depth changes in the type of deformation of the medium. Active deformation is observed beneath the Hidaka Range. Dynamic changes in beneath the stations on either side of the range (ERM, MYR), their antiphase pattern, and the discrepancies in the behavior of the parameters from the events that originate in different depths indicate that these regions act as active buffers in the redistribution of stresses in the Kuril-Japan arc-arc junction zone. The onset of instability that develops before the Tokachi-oki earthquake is marked by gradual shortening of the period of oscillations in $$\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\frown}$}}{\phi }$$ and transition to the north and east azimuths as well as by the decreasing of $$\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\frown}$}}{f} _P$$ from the intermediate-depth events starting from middle 2002, and for deep events, starting from 2000. The acceleration of the process begins in the middle of 2003 and is recognized by a noticeable increase in and a decrease in $$\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\frown}$}}{f} _P$$ beneath almost all stations.

Magmatic Fractionation by Compositional Convection in a Sheet-like Magma Body: Constraints from the Nosappumisaki Intrusion, Northern Japan

The mechanism of fractionation in a sheet-like magma body was investigated based on observations from the Nosappumisaki intrusion, northern Japan. This is one of a number of late Cretaceous shoshonite sills in the Nemuro peninsula and has a compound structure comprising a bottom cumulate zone containing � 50 vol. % cumulus crystals and a overlying middle zone free of such cumulus crystals. These zones are sandwiched between porphyritic rocks of upper and lower chilled and marginal zones. It is inferred that massive crystal settling or flotation from a magma initially laden with � 20 vol. % of crystals (primocrysts) in a sheet-like magma body formed a cumulus pile and an overlying crystal-free melt layer. After the formation of the compound structure with partial freezing of the upper and lower marginal zones, the internal part of the intrusion slowly solidified. During this period the melt in the central part of the intrusive sheet underwent fractional crystallization. This is shown by patterns of vertical variation in the composition of the interstitial melt. The overall patterns are inverted (mirrorimage) S-shaped and S-shaped for incompatible and compatible elements, respectively. The incompatible element abundances show maxima near the bottom of the middle zone, which corresponds to the final solidification horizon. They show minima in the cumulate zone, which suggests discharge of an evolved melt from the crystal pile. Fractionation is inferred to have taken place via compositional convection without settling of crystals grown after the intrusion event or collapse of the upper boundary layer.The melt in the central melt layer descended into the permeable crystal pile counterbalancing discharge of buoyant evolved melt formed by crystallization of the pore melt in the crystal pile.This conclusion is based on the following observations. (1) There is no accumulation of crystals grown after the intrusion of the magma above the cumulate zone. (2) Leucocratic pipe-like structures, which represent relict pathways for the evolved melt, are developed in the cumulate zone.These structures increase in diameter, decrease in number density, and increase in abundance of incompatible elements with height. (3) Cumulus augite in the cumulate zone has Ca-rich and Al-poor dissolved rims. The extent of dissolution increases with stratigraphic height, suggesting downwelling of an H2O-rich melt from the overlying melt layer. (4) There is no evidence for extensive compaction accompanying pore melt crystallization in the main part of the cumulate zone. (5) The initial melt composition estimated from the groundmass of the chilled margin rocks and the average composition of the material interstitial to the primocrysts for the whole sill are statistically identical. A mass-balance model for compositional convection was constructed to quantify the melt transportation processes. Model parameters were optimized by fitting the observed vertical variation of the interstitial melt compositions. The optimized results suggest that the evolved melts discharged from the crystal pile and rose through the central melt layer as plumes with minor mingling with the surrounding melt. The initially formed compound structure is a highly preferential environment for compositional convection.

Time variations in parameters of split S waves from weak local earthquakes beneath eastern Hokkaido

Parameters of seismic waves from clusters of local weak earthquakes that occurred at the upper boundary of the seismofocal zone in depth intervals of 40–60 and 70–90 km along eastern Hokkaido are investigated for the period 1998–2003, including the strong (M = 8.0) Tokachi-Oki earthquake of September 26, 2003. Analysis of data indicates that the distribution of anisotropic properties along Hokkaido is inhomogeneous and parameters of split waves (the azimuth of the fast S wave and the time delay between split S waves) are sensitive to variations in the stress-strain state of the medium. Unstable behavior of split wave parameters and increased values of the ratio VP/VS for clusters of events in the areas of the Hidaka Mountains and Nemuro Peninsula imply that the medium is in a mechanically weakened state (in the regime of intense dilatant deformation). On the contrary, the regions beneath the Tokachi and Kushiro plains are more rigid and are characterized by lower VP/VS values and comparatively stable behavior of wave parameters. Anomalous parameters of split waves from events of clusters in areas of different stations correlate with each other and are related to occurrence times of large earthquakes around Hokkaido, which may point to a redistribution of stresses and strains and fluid migration in the subduction zone.

根室半島・納沙布岬におけるサケ定置網によるアザラシ類の 2002–2003年混獲数調査

根室半島・納沙布岬におけるサケ定置網によるアザラシ類の 2002–2003年混獲数調査

Diploid male production in a rare and locally distributed bumblebee, Bombus florilegus (Hymenoptera, Apidae)

The European bumblebee B. terrestris was recently introduced in Japan for agricultural purposes and has now become naturalized. The naturalization of this exotic species may have great detrimental effects on closely related native Japanese bumblebees. The Japanese bumblebee Bombus florilegus is a rare and locally distributed species found in the Nemuro Peninsula of Hokkaido, Japan. In order to assess its population genetics, we estimated the genetic structure of B. florilegus in 16 breeding colonies (queen, workers, and males) and 20 foraging queens by analyzing microsatellite DNA markers. Of the 36 queens analyzed by genotyping and dissection, 32 had been inseminated by a male. The remaining 4 had not been inseminated at all. Of the 4 nonmated queens, one was triploid. Diploid males were found in 4 breeding colonies. Based on the microsatellite data, it appears that B. florilegus has low reproductive success. Since matched mating and nonmating within local populations are high, the extinction risk is correspondingly higher. Our results suggest that conservation of the Japanese B. florilegus is required in order to protect it from both habitat destruction and the naturalization of alien species.

Vegetation on and around Periglacial Hummocks in the Nemuro Peninsula, Northern Japan

Hummocky microforms (non-sorted patterned ground) occur extensively under seasonal frost environments, including Japanese high latitude and altitude regions. This paper focuses on vegetation contrasts between hummock apexes and interhummock depressions, and on its contribution to hummock formation in a representative hummock field in Japan. Vegetation cover in the study area serves to classify the hummocks into three types: covered with mire herbs, pasture weeds and forest-related species. The first type has a remarkable contrast in vegetation, characterized by entirely vegetated (sedged) apexes and bared inter-hummock depressions. Such uneven vegetation is likely to generate and/or develop these sedged hummocks associated with differential frost penetration (cryoturbation). The last two types lack sedges, but permit weed invasion on their inter-hummock depressions as well as hummock apexes. The last type, covered with a bamboo grass, is considered to be relict forms which indicate changes in hydrological environments induced by deepening groundwater.

Morphology and Environmental Factors of Periglacial Hummocks in the Nemuro Peninsula, Northern Japan

Morphology of hummocky patterned ground (hummocks) reflects various physiographic factors such as frost conditions, surface gradient and hydrological environments. Hummocks in a seasonally frozen mire in the Nemuro peninsula include two types in terms of the presence of live sedgy-tussock. Sedged forms (Type Y) concentrate in a waterlogged condition, while sedge-free forms (Type T) are densely or sparsely distributed in a shallow (including waterlogged) or deep groundwater condition, respectively. Morphometric analyses indicate the contrast between high and horizontally circular Type Y hummocks, and wide and vertically half-circular (flatter) Type T hummocks. The distribution and geometry imply that the waterlogged condition promotes hummock development by differential frost penetration (cryoturbation) in combination with deep seasonal frost and sedge-controlled uneven vegetation. The hummock development produces a thermal contrast between the apex and the depression, which enhances differential frost heave. Assisted by flat terrain, these processes produce closely-spaced high hummocks, up to 52cm in height. These results demonstrate that relatively large hummocks intensively occur even in a climatically marginal region for periglacial hummocks (mean annual air temperature=6°C), where flat and waterlogged mire environments with deep seasonal frost enhance periglacial processes.

Soil properties of miniature cryogenic mounds in the Nemuro peninsula, eastern Hokkaido, Japan

Soil properties of miniature cryogenic mounds in the Nemuro peninsula, eastern Hokkaido, Japan

External and internal morphology of hummocky microforms in the Nemuro peninsula, eastern Hokkaido, Japan

External and internal morphology of hummocky microforms in the Nemuro peninsula, eastern Hokkaido, Japan

Mechanism of Crystal Redistribution in a Sheet-like Magma Body: Constraints from the Nosappumisaki and Other Shoshonite Intrusions in the Nemuro Peninsula, Northern Japan

Processes of crystal separation in a magma heavily laden with crystals without phase change are investigated from observations on frozen magma systems: Nosappumisaki and other shoshonite intrusions in the Nemuro peninsula, Japan, for which the origin of the crystals and the initial conditions are well constrained. The Nosappumisaki intrusion is 120 m in thickness and extends for more than 1·5 km. It exhibits a wide range of lithological variation, principally as a result of crystal redistribution after intrusion. Crystals in each lithology can be clearly divided into two kinds according to their composition and texture: those present before the intrusion of the magma (‘phenocrysts’) and those that crystallized in situ after intrusion. From the vertical change in mode and size of ‘phenocrysts’, it is shown that (1) augite ‘phenocrysts’ were rapidly deposited, with little overgrowth after intrusion, by significant coagulation or clustering on a time-scale of more than a few years, and (2) plagioclase ‘phenocrysts’, definitely denser than the melt but concentrated in the upper level, floated by counter flow of massive deposition of augite ‘phenocrysts’. These results indicate that in a magma heavily laden with crystals of a few millimeters in size (>20 vol. %), crystal–crystal and crystal–melt interaction play an important role in the separation of crystals from the host melt.

Source depth dependence of micro-tsunamis recorded with ocean-bottom pressure gauges: the January 28, 2000 Mw 6.8 earthquake off Nemuro Peninsula, Japan

Micro-tsunami waves with a maximum amplitude of 4–6 mm were detected with the ocean-bottom pressure gauges on a cabled deep seafloor observatory south of Hokkaido, Japan, following the January 28, 2000 earthquake ( M w 6.8) in the southern Kuril subduction zone. We model the observed micro-tsunami and estimate the focal depth and other source parameters such as fault length and amount of slip using grid searching with the least-squares method. The source depth and stress drop for the January 2000 earthquake are estimated to be 50 km and 7 MPa, respectively, with possible ranges of 45–55 km and 4–13 MPa. Focal depth of typical inter-plate earthquakes in this region ranges from 10 to 20 km and stress drop of inter-plate earthquakes generally is around 3 MPa. The source depth and stress drop estimates suggest that the earthquake was an intra-slab event in the subducting Pacific plate, rather than an inter-plate event. In addition, for a prescribed fault width of 30 km, the fault length is estimated to be 15 km, with possible ranges of 10–20 km, which is the same as the previously determined aftershock distribution. The corresponding estimate for seismic moment is 2.7×10 19 Nm with possible ranges of 2.3×10 19–3.2×10 19 Nm. Standard tide gauges along the nearby coast did not record any tsunami signal. High-precision ocean-bottom pressure measurements offshore thus make it possible to determine fault parameters of moderate-sized earthquakes in subduction zones using open-ocean tsunami waveforms.

Precursory seismicity changes associated with the Nemuro Peninsula earthquake, January 28, 2000

We investigated the characteristics of the precursory seismicity changes associated with the M=6.8 Nemuro Peninsula earthquake, January 28, 2000 by applying the RTL (Region–Time–Length) algorithm to the earthquake catalogue of the Japan Meteorological Agency (JMA). The RTL parameters at the epicentre indicated that a seismic quiescence started in 1995 and reached its minimum during October 1996. An activation stage with a duration of about eight months followed. Our detailed investigations indicated that the RTL anomaly around 1996 was not an artificial effect due to the changes of the model parameters, the upgrade of the JMA seismic network or the process of aftershock elimination. The spatial distribution of quiescence in 1996 revealed a significant anomaly in a broad region around the epicentre of the Nemuro Peninsula earthquake. Following the quiescence stage, an activation zone, which was on the order of the rupture length of this earthquake, was obtained around the epicentre during October 1996–July 1997. The consistency of the rupture region and the anomalous activation zone that appeared after the seismic quiescence stage may provide useful information for determining the future risk zones. This study may strengthen the understanding of the seismogenic process of strong earthquakes.

Vegetation history in Nemuro Peninsula since the Late Pleistocene.

Vegetation history in Nemuro Peninsula since the Late Pleistocene.

北海道東部根室半島・歯舞湿原と落石岬湿原における 晩氷期以降の植生変遷史

北海道東部根室半島・歯舞湿原と落石岬湿原における 晩氷期以降の植生変遷史