Toshitaka Iwamoto

Food and nutritional condition of free ranging Japanese monkeys on Koshima Islet during winter

A female with infant was chosen as material for study in an attempt to assess the nutritional condition of free ranging Japanese monkeys during winter. Her daily food composition, dry weight intake and nutritional (protein, lipid, carbohydrate, ash and calorie) intake were measured monthly (October to March). About 90% and 8% of the autumn diet consisted of fruits and invertebrate animals, respectively, while 70% of the winter diet (February) consisted of leaves of evergreen trees.Comparing the daily protein intake of this focal female with the requirement level estimated from references, only October and November represented months fulfilling this level. Also, there was a remarkable decrease in lipid intake towards winter. These results coincided well with the observed body weight loss in the female and the increasing feeding activity of her baby towards winter. It is suggested that such seasonal malnutrition of the mother might affect population parameters such as the infant mortality.

Variable stress-responsiveness in wild type and domesticated fighting fish

We combined behavioral and physiological measures to compare coping style in wild-type Betta splendens and a domesticated strain selectively bred for sports fighting. We showed previously that the fighter strain is more aggressive than the wild type during experimental conditions that most closely resemble an actual fight. We predicted that compared to the wild type, the fighter strain would show a more proactive coping style, characterized by lesser cortisol and greater sympathetic responses to non-social challenges. We introduced males to an unfamiliar environment and spatial confinement as challenges that may resemble some of those that B. splendens may encounter in its natural habitat. We developed a non-invasive stress assay that enables repeated individual measures of water-borne cortisol. We estimated sympathetic activation through opercular beat rate and recorded the duration of behavioral immobility. We found that exposure to an unfamiliar environment raised cortisol levels in the wild type but not in the fighter strain and that confinement raised cortisol levels in both. In both strains opercular beat rates were significantly reduced during the latter stages of confinement compared to during the early stages. The fighter strain, but not the wild type, adopted a behavioral strategy of immobility from the very beginning of confinement.

Differences in aggression between wild-type and domesticated fighting fish are context dependent

We investigated differences in aggression between wild-type Betta splendens, Betta smaragdina, two domesticated strains of B. splendens selectively bred for cockfight-like contests and appearance, and Betta sp. mahachai, an unclassified Betta variety. We tested the fish for aggression once they reached sexual maturity as well as during adulthood. We used a combined mirror and video playback test and a mutual-viewing test to measure close-range gill extension and biting attempts as principal measures of aggression. As predicted, the short-finned domesticated strains were significantly more aggressive than wild-type B. splendens. However, the difference in aggression manifested itself only in the mutual-viewing test, which is the test that most closely resembled an actual fight. Betta splendens and the closely related B. smaragdina did not differ in aggression across the experimental contexts; however, B. sp. mahachai responded more aggressively to the combined mirror/video test than B. splendens. Four of the five groups of fighting fish tested responded significantly more aggressively to video images of an aggressive conspecific male than to blank screen controls, suggesting that video playback can be a useful tool for measuring aggression in fighting fish. Our results are relevant for improving our understanding of key aspects of territorial aggression in teleost fish as well as for developing the most reliable ways of measuring them.

Anti-predator behavior of gelada baboons

The anti-predator behavior of gelada baboons has been observed to consist of simple flight (i.e. they flee to cliffs after becoming alarmed by potential predators). However, active antipredator behavior was observed in a recently found gelada population in Arsi, Ethiopia. This population showed frequent active counter-attacks and severe mobbing at predators. Males fought domestic dogs on the plain and exhibited a systematic mobbing behavior towards a leopard on the cliff face to chase it off. These active anti-predator behaviors are the first confirmed reports on gelada baboons and may provide a useful insight for the understanding of the process of evolutionary adaptation to highland habitats by gelada baboons, as well as for the origin of this small southern population.

A Case of Infanticide in a Recently Found Gelada Population in Arsi, Ethiopia

There have been no reports of infanticide in wild gelada baboons and it has been argued that infanticide is not necessary in geladas, since the birth interval of female gelada can be shortened after takeover of a unit by a new leader male without infanticide. However, we observed an instance of infanticide in a newly-found wild gelada population in the Arsi Region of Ethiopia.After a leader male of the unit was severely wounded by a leopard attack, he was quite weakened. The second male of the unit, a young adult male, became the leader of the unit three weeks later, but the former leader continued to stay in the unit as a second male. After a week, two other adult males joined the unit which, therefore, came to include four adult males. The infanticide took place nine days later. The perpetrator was one of the immigrant males and he showed great interest in the mother of the unweaned victim infant. Although the perpetrator copulated with her after the infanticide, the usurper was found to own all three adult females after two weeks following the infanticide; i.e. the perpetrator could not own any female. The wounded former leader showed conspicuous protective behavior towards the victims mother and the dead infant.One possible explanation for the occurrence of infanticide in this population of geladas is as follows. Gelada males in this area may be able to join units more easily to form multi-male units but then have shorter tenure in the units. Facing the unstable condition of units, they may sometimes engage in infanticide to increase their breeding opportunities, even before becoming a leader.

Local distribution of two species ofApodemus in Kyushu

Local distributions of two species ofApodemus, A. argenteus andA. speciosus, were studied by the correct estimation of peak density of mice and the detailed description of the habitat. Multiple regression analysis is applied to these distributional data setting with four variables as altitude, forest type, relative cover of shrub layer and age of forest. The local densities of both species and the percentage abundance ofA. argenteus can be completely predicted by use of the regression coefficients. The density ofA. speciosus correlates with the altitude of habitats, and that ofA. argenteus does with the age of forest. The mean relative cover of shrub layer influences the dominancy ofA. argenteus when both species occur sympatrically.

Sociological and demographic characteristics of a recently found arsi gelada population in ethiopia

A new population of gelada baboons isolated from other known gelada populations living on the opposite side of the Rift Valley was found in 1989 in the Arsi region of Ethiopia (Mori &Belay, 1990). Subsequent observations were conducted on the new gelada population in three study periods of 16 to 55 days over three consecutive years, 1994–1996. When we compare this population with other well studied northern populations, densities were lower, band size was smaller and the ratio of juveniles to adult females was lower. Based onOhsawa andDunbars (1984) criteria these results suggest that this population exploits the harshest environment among known gelada populations. This may be due to the severe effect of the dry season at low altitude in the study site. Band size was small in the study site. Association rates of units were low, and each unit behaved more independently than those of northern populations. Age-sex composition of units changed drastically between consecutive study periods, indicating unstable unit structure. Moreover, there seems to be a tendency in this population whereby several adult males easily invade and are incorporated into a unit but the unit is expected to thereafter divide. The phenomenon can be explained by two factors: (1) Each unit fed rather independently in this area, where units fed intensively on both plateau and the slope of the cliff; and (2) Males may be incorporated in a unit for defense against leopards. As the units were vary small in size and unstable as compared with the Semien gelada units, the traditional concept of a stable gelada unit formed by blood related females, does not seem to fit this population.

Extra-unit paternity of hamadryas baboons (Papio hamadryas) in Saudi Arabia

Sex-biased dispersal and female choice for non-related mates are mechanisms of inbreeding avoidance in animals. In species with limited dispersal of both sexes, the latter mechanism is of greater importance. We investigated a wild population of hamadryas baboons (Papio hamadryas) living in Saudi Arabia and surviving on human garbage. Paternity relationships between adult males and juveniles of three social units were analyzed using 12 loci of tetra-repeat microsatellite DNA. Of 16 juveniles and infants (0-3 years old), 13 were not sired by the leader male of each unit. This extra-unit paternity suggests the possibility that females conducted extra-unit copulations (EUCs) leading to extra-unit fertilizations (EUFs). We discuss this and other possible explanations for the apparent extra-unit paternity, as well as the plausibility of EUFs as a function of inbreeding avoidance in the hamadryas baboon. This is the first molecular study to investigate kin relationships within wild units of hamadryas baboons.

A study on the social structure and dispersal patterns of hamadryas baboons living in a commensal group at Taif, Saudi Arabia.

Three levels of hamadryas social structure—the one male unit (OMU), the band, and the troop—have been observed at all sites studied, but a fourth—the clan—has been observed at only one site, Erer-Gota, Ethiopia, during a longitudinal check of the dispersion of identified individuals. The clan is important since it appears to provide the basis for male philopatry, although comparative data is needed from other sites to confirm this. We studied a huge commensal group of hamadryas baboons (over 600 animals) in Saudi Arabia. We put ear tags on baboons between 1998 and 2004 and analyzed social structure, relying on the interactions of these tagged animals by focusing especially on their dispersal patterns from OMUs. OMU membership tended to be looser than that of the Ethiopian hamadryas. Females tended to shift between OMUs on an individual basis in our study group, whereas the collapse of an OMU was a major occasion of adult female transfer in Ethiopia. We found neither stable bands (a “band” in our study group was defined as a regional assemblage of OMUs) nor clans that lasted for several years. Some OMUs moved and transferred into neighboring areas over both the short and long term. Further, some post-adolescent males appeared to move out of the study area. The ratio of adult females in an OMU in our study group was larger than for any other documented study site, and this may be the reason for enhanced female transfer between OMUs. A large proportion of the adolescent females showed no clear membership to OMUs, and no “initial units” (commonly observed in Ethiopia) were discernible. The ease with which young males acquired adult females at the study site must have disrupted the formation of a clan, a “male-bonded society.”

Pollination partners of Mucuna macrocarpa (Fabaceae) at the northern limit of its range

Mucuna macrocarpa is a plant found in tropical and subtropical regions that requires an “explosive opening.” Explosive opening is the process that exposes the stamen and pistil from the opening of the carina. This process is needed for cross pollination; however, the plant cannot open itself and opening by an animal is needed. The most common opener of Mucuna flowers is several nectar-eating bats (e.g., Syconycteris), but the flying fox, Pteropus dasymallus, is the only opener of M. macrocarpa on the subtropical island of Okinawajima. Here, we present the explosive openers and possible pollinators in the northernmost and temperate Kamae region, Kyushu, Japan, where nectar-eating bats are absent. The Japanese macaque, Macaca fuscata, and the Japanese marten, Martes melampus, were the explosive openers observed during our survey in Kamae. Martens opened flowers using their snout in a manner similar to that of the flying fox, whereas macaques opened flowers using their hands. This is the first time that an animal has been observed opening these flowers with its hands rather than snout. In total, 97% (n = 283) of explosively opened flowers were opened by macaques, and the macaque largely contributed to the overall flower opening. Because many pollen grains become attached to the explosive openers, they are considered to be primary pollinators. Furthermore, two bee species, Apis cerana japonica and Bombus ardens ardens, also visited opened flowers and collected pollen, and they were possibly secondary pollinators.