Published Papers - KOGA Tsunenori

SEXUAL DIFFERENCES IN FORAGING BEHAVIOR OF SIKA-DEER, CERVUS-NIPPON

T KOGA, Y ONO

JOURNAL OF MAMMALOGY ( AMER SOC MAMMALOGISTS )  75 ( 1 ) 129 - 135   1994.02

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We compared the foraging behavior of five age-sex classes of sika deer (Cervus nippon nippon) in grasslands in Nozaki Island, Japan. Seasonal changes in feeding time and food plants were greater for males than for females. For males, feeding time decreased and time allocated to social activities increased with age in the breeding season. In spring, when antlers of deer began to regrow, adult males spent more time feeding on plants with high ash contents than did younger males and females. In winter, males spent more time feeding on plants with high protein content than did females. The trend was much different from that reported in many previous investigations, perhaps because of abundant food in our study area, which was at a low latitude.

MATING-BEHAVIOR OF THE SAND BUBBLER CRAB SCOPIMERA-GLOBOSA

Y HENMI, T KOGA, M MURAI

JOURNAL OF CRUSTACEAN BIOLOGY ( CRUSTACEAN SOC )  13 ( 4 ) 736 - 744   1993.11

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The mating behavior of the sand bubbler crab Scopimera globosa was studied in an intertidal area of Fukuoka, Japan, from 1988-1991. This species mates both on the surface and underground, as do some fiddler crabs. In surface copulations, wandering males mate sequentially with resident females beside burrows of females. In underground copulations, resident males chase and capture wandering females, carry them to their burrows and push them below. Males then enter their burrows and plug them within minutes. Pairs presumably copulate in these burrows. Unlike the fiddler crabs, however, most females that stayed in burrows of males did not have mature ovaries and wandered again within a few days. Consequently, only 30% of the females that stayed in burrows of males spawned in those burrows. After the spawning, males abandoned their burrows, while females remained in them during incubation. Thus, forced copulation characterizes the mating system of this species, though there is room for female choice. Mating success was much lower in underground than in surface copulation. However, males that succeed in forcing females into their burrows may gain a reproductive advantage, because the sperm of the last male to mate with a female prior to egg extrusion is used to fertilize most of the eggs.

SPERM COMPETITION AND THE ASSURANCE OF UNDERGROUND COPULATION IN THE SAND-BUBBLER CRAB SCOPIMERA-GLOBOSA (BRACHYURA, OCYPODIDAE)

T KOGA, Y HENMI, M MURAI

JOURNAL OF CRUSTACEAN BIOLOGY ( CRUSTACEAN SOC )  13 ( 1 ) 134 - 137   1993.02

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Studies of sperm competition are necessary for understanding mating systems in species where two or more males copulate with a single female. We studied fertilization ratios of successive male mates in the sand-bubbler crab Scopimera globosa (de Haan) (family Ocypodidae). Males copulate on the surface or pair underground. The male pairing underground is the last to inseminate the female before she extrudes eggs, as is the case in most ocypodid crabs. In serial mating experiments using irradiated and normal males, the last male to mate fertilized over 90% of the eggs. Females forced to mate in the burrows of irradiated males extruded infertile eggs, indicating that sperm transfer occurred in the burrow.

TERRITORIAL BEHAVIOR OF BOTH SEXES IN THE WATER STRIDER METROCORIS-HISTRIO (HEMIPTERA, GERRIDAE) DURING THE MATING SEASON

T KOGA, K HAYASHI

JOURNAL OF INSECT BEHAVIOR ( PLENUM PUBL CORP )  6 ( 1 ) 65 - 77   1993.01

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Territorial behavior of overwintered individuals of Metrocoris histrio was observed in an upstream area. Adults of both sexes held territories, but male territories were larger than those of females. Severe competition occurred among males for territories which give them access to receptive females. The effects of male body length and midleg length on establishment of territories were not significant. The effect of female midleg length on activity of females entering preferred foraging sites was equally not significant. Instead, territorial behavior increased with male age and males stayed longer at prime sites. Females of intermediate age were likely to occupy prime sites. Females had longer territory residence time than males. The sexes were dimorphic with respect to midleg length, and dimorphism in M. histrio may be related to a difference in life history, in that sexual selection may be relaxed due to asynchronous adult emergence patterns.