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This introductory chapter explains the theme of this book, which is about the treeshrews of Borneo. It provides a brief overview of thought on treeshrew taxonomy and phylogeny and the search for their true, but often mistaken, identity. The chapter explains that before 1900, treeshrews were generally thought to be in the order Insectivora and related to the true shrews, but by the first decade of the twentieth century comparative anatomists separated them from that order and proposed a closer relationship to other groups. It suggests that treeshrews are the most closely related living models of the very earliest primate ancestors of the late Cretaceous period, and that their lifestyles can provide a window onto our earliest antecedents, and perhaps a view of why evolution may have taken the direction it did.

This chapter reviews selected aspects of the anatomy and physiology of treeshrews that are especially pertinent to their ecology. It suggests that the teeth and digestive tracts of treeshrews are similar to those of many other insectivorous mammals, and that they possess a number of both primitive and more derived features. The chapter describes the sensory skills of treeshrews and argues that their body size may have tight ecological constraints. It also reflects on treeshrews' social behavior.

This chapter describes field-study research on the habitats of treeshrews in Malaysia. About 20 percent of the mammal species of Borneo are endemic to it, including seven of its ten species of treeshrews. All of these treeshrews dwell in the tropical rainforests, and the large geographic extent and elevational variation of Borneo may have provided a field for speciation and persistence for this family poorly represented elsewhere. The chapter describes the fruiting phenology, the history of disturbance, and the biogeographic history of treeshrew habitats in Malaysia.

This chapter describes the behavior of treeshrews in their habitat. It explains the paths down which treeshrews travel in the forest outline where they seek and find food, and that their physical distribution thus describes ecological features with a potential to define the roles of species in the environment. The chapter explores treeshrews' substrate use, as well as their vertical use of the forest, foraging levels, and habitat ranges.

This chapter examines the diet and foraging behavior of treeshrews in Malaysia, explaining that the diet of treeshrews was from earliest reports correctly known to consist of fruit and insects. It describes the nature of fruit- and insect-eating by treeshrews, along with the behavioral characteristics of foraging for each food type, and analyzes the possible relation between diet and morphology. The chapter evaluates the possible competitive interactions that might occur for different food types, both among treeshrew species and among treeshrews and other vertebrates in their community.

This chapter examines the nesting behavior and maternal-care system in treeshrews. It explains that treeshrews' nest site and the nest itself are primary defenses against exposure and predation, and suggests that the absentee maternal-care system of treeshrews is linked to their nesting behavior as young are placed in one nest and their mother uses another. The chapter describes the nesting sites, the use of sleeping sites, and the nest-building strategies of treeshrews.

This chapter describes the daily activity patterns of treeshrews based on the recorded activities of radio-tagged individuals. It describes the length of active and resting period of treeshrews and suggests that rain is the main climatic event which influences animal activity. The findings reveal that the least-active species spent a mean of 8.7 hours each day in motion, while the most active averaged 11.44 hours in motion. The result also indicates that treeshrews spent little time with others, and that most of their activity seemed to be concerned with foraging or feeding.

This chapter investigates the treeshrews' use of space. The analysis of daily activities of treeshrews indicates that the home ranges of treeshrews are often highly irregular in outline, with odd hollows and protuberances. The chapter explains that the mean home-range sizes for treeshrews ranged from 1.5 to 10.5 hectares, and suggests that the size of their home ranges is partly determined by their rate of metabolism. It also describes the speed and daily distance travelled by treeshrews, and their patterns of travel and destinations.

This chapter examines the social organization of treeshrews. It describes their social relationships from the deployment of their home ranges, and the relative movements of radio-tagged and trapped individuals. The chapter explores territory formation and evaluates the ecological aspects of territoriality. It reveals that treeshrews are territorial within sexes, with males either monogamous or perhaps overlapping a second female.

This chapter examines the life history of treeshrews. It describes the absentee system of parental care in treeshrews, their birth seasonality, and the reproductive output of individual females. The chapter investigates the growth rates of young treeshrews, the age at first reproduction, the seasonal patterns of adult weight, and the persistence or survivorship of individuals. It reveals that treeshrews' explosive reproductive potential from continual breeding, rapid growth, and early sexual maturity seen in laboratory treeshrews is not realized in the wild, where discontinuous breeding, slow growth, and late maturation are more typical.

This chapter examines the predation and alarm behaviors in treeshrews. It explains that the chief antipredator strategy of treeshrews is to avoid being noticed, and they accomplish this by inconspicuous movements and by keeping undercover. Each treeshrew species can be identified by its distinctive alarm calls, and most alarm calling is accompanied by an upward flick of the tail to vertical.

This chapter sums up the key findings of this study on the treeshrews of Borneo. It explains that the small number of living tupaiid species and the fossil record suggests that the treeshrews' characteristics never provided much potential for evolutionary diversification, but that they can be considered an evolutionary success because they have been able to hold their own amid more populous orders. The chapter argues that the while the absentee maternal-nursing system works, it provides little flexibility in litter size or maternal behavior, and would not seem likely to offer much potential for evolving into other strategies needed for treeshrews to succeed in very cold climates or in places where survival of young was much lower.