Dr Nobby Yamaguchi
Current Research Activities and Areas of Interest:
Area of interest (1): Behavioural ecology of terrestrial mammalian carnivore on the basis of species evolutionary history
Research activities: Although behavioural ecology is considered as an evolutionary science, the fact that most studies are based on observations at present may be often overlooked. For example, a particular type of benefit of behaviour-A may be observed in a species living in environment-A, but not in environment-B. If so highlighting the observed type of benefit concerning the evolution of the behaviour-A may be misleading if the species evolutionary centre has been in the environment-B. It may be especially so concerning medium-large sized terrestrial mammalian carnivores, which are naturally highly mobile and used to have large contiguous geographical ranges, and yet are now often confined to isolated small populations with their ranges having been substantially reduced. Furthermore, the ongoing anthropogenic isolation and confinement may create extra factors (eg, disappearance of a large scale population replacement) to be carefully considered when observations are interpreted in the context of evolutionary biology. On the other hand, their relatively large body size makes tracing fossil records feasible for some species, amongst which charismatic species are recorded well in many human cultures too making it possible to follow their range contractions during the historic time. I try to interpret behavioural ecological observations based on the extant populations in the context of species evolutionary histories.
Area of interest (2): Evolutionary approach to the conservation of terrestrial mammalian carnivores
Research activities: Conservation sciences, as well as conservation practices, have been heavily influenced by rarity (eg. extinction risk) and distinction (eg. distinguishable populations), and evolutionary history of species may have attracted disproportionally little attention. To assess the current status of a species, we need an objective yardstick against which it can be compared. Such yardstick would not be given either by rarity-based approach (eg. extant total population size) or by distinction-based one (eg. whether or not a population is currently recognised distinct). It may be especially so in medium-large sized terrestrial mammalian carnivores, which naturally occur in low densities, and anthropogenic isolation of (and confinement of remaining individuals to) small populations, may result in many mutually distinct small populations. It may be appropriate to define such yardstick as the possible natural state of the species, which in turn may be defined as the state in the late Pleistocene – Holocene period before anthropogenic effects become conspicuously recognisable. Such state would not be reconstructed without understanding the evolutionary history of the species. I try to develop an idea of evolutionary approach to conservation on the assumption that conservation is to push the species current status back towards its natural state.
Area of interest (3): Mammalian reproductive tactics with special references to their reproductive physiology
Research activities: The behavioural ecology and sociobiology require an understanding of individual tactics that maximise survival and reproductive success, which are, in turn, determined by the availability of important resources: food and shelter for both sexes, and receptive females for males. In spite of this theoretically accepted importance of females being receptive, detailed evaluation of the receptivity of females, which may change throughout the year and animal’s life, often appear to be unsatisfactory in many studies based on field work. This may be partly due to the lack of detailed information concerning reproductive physiology and endocrinology of many species. I try to highlight the importance of understanding laboratory-based reproductive physiology for field-based behavioural ecological and sociobiological studies.