When asking what is typically mammalian in behavior, we must first consider which adaptations and preconditions of a mammal normally shape its life and body. Mammals are warmblooded, or endothermic, and their system of body temperature regulation through metabolism requires more energy than what is needed by ectotherms. Foraging is also an important aspect of behavior, and has to be considered as a decisive factor in shaping social systems. Also, mammals in general (and female mammals specifically) invest a lot more in terms of time, effort, energy, nutrition, and risk, into their offspring than most other vertebrates do. Again, this shapes social systems, in particular mating and rearing, but also puts severe demands on foraging strategies. Another characteristic is the highly developed brain, specifically in those areas that are necessary for behavioral plasticity and variability, such as the highly evolved forebrain and its hemispheres. This in turn allows the mammal to adapt to a diversity of ecological conditions, and also to form complex and individualized societies. In connection with the intensive and often long periods of infant care, not only by the parents but also other members of the group, this can lead, again, to highly variable and adaptable solutions to ecological as well as social problems and situations. In this chapter, we will cover two of those areas in which mammals are special: learning and behavioral plasticity, and social systems (which include mating and rearing as well as foraging and anti-predator systems). Each of these fields is currently the focus of scientific attention in many places, and by many different approaches. In order to fully understand any biological phenomenon, Tinbergen in 1963 proposed to answer four questions, and only after getting satisfactory answers to all four can we presume that we have "explained" this phenomenon. They are:

• Where did it come from in evolution?

• What selective advantage does an individual get from having this particular trait (the so-called ultimate reasons)?

• How does it work (physiology, so-called causal mechanisms)?

• How does it develop in an individual's life (so-called ontogeny)?

We shall use these four questions to structure our discussion of mammalian behavior. In order to answer these ques tions, a combination of different scientific approaches is necessary. Thus, we will draw data from long-term field studies as well as from laboratory and zoo research, from experimental trials as well as from purely observational approaches, and will also need support from other biological disciplines such as endocrinology and molecular genetics. Behavior in itself is at the interface of genetics and ecology, and its understanding is central also to questions of animal welfare, conservation biology, zoo management, and our relationship with pets and companion animals.

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