Behavioral ecology

Behavioral ecology is the study of the ecological and  evolutionary basis for animal behavior, and the roles of behavior in enabling an animal to adapt to its environment (both intrinsic and extrinsic).

Behavioral ecology emerged from ethology after Niko Tinbergen (a seminal figure in the study of animal behavior), outlined the four causes of behavior. These four causes can be grouped into two larger classes (ultimate causes and proximate causes). The two causes that contribute to ultimate causation are phylogenetic contingencies that contribute to the development of behavior and the second is adaptive significance. Phylogenetic constraints are generally factors that might stop certain lineages developing certain behavioral or morphological traits. Hence, it is no coincidence that generally birds are able to fly and mammals cannot. The evolutionary history of these lineages have made it profitable for birds to fly and for mammalian feet to remain planted on the ground. Adaptive significance is akin to asking what a trait is good for in an evolutionary context. Therefore, the adaptive significance of flight in birds might have enabled avian ancestors to escape from predators. However, it is not sufficient to apply these explanations where they seem convenient. These have been labeled Just So Stories by some biologists after Rudyard Kipling's tales for children about the how animals came to be the way they are. To be rigorous, one must suppose a hypothesis and then test it scientifically. Hence, for avian flight, one can suppose that when birds are not at risk of being eaten, they might lose the ability to fly. This, has been observed in bird faunas on oceanic islands such as New Zealand. Historically these land masses had no mammalian predators and so had a higher proportion of flightless bird species compared with avifaunas exposed to mammalian predation.

Proximate causation is also divided into two factors which are ontogenetic factors and mechanistic factors. Ontogenetic factors are the entire sum of experience throughout the lifetime of an individual from embryo to death. Hence, factors included are learning the genetic factors giving rise to behavior in individuals. Mechanistic factors, as the name implies, are the processes of the body that give rise to behavior such as the effects of hormones on behavior and neuronal basis of behavior.

Behavioral Ecology along with other areas of evolutionary biology, has incorporated a number of techniques which have been borrowed from optimisation theory. Optimisation is a concept that stipulate strategies that offer the highest return to an animal given all the different factors and constraints facing the animal. One of the simplest ways to arrive at an optimal solution is to do a cost/benefit analysis. By considering the advantages of a behavior and the costs of a behavior, it can be seen that if the costs outweigh the benefits then a behavior will not evolve and vice versa. This is also where the concept of the trade-off becomes important. This is because it rarely pays an animal to invest maximally in any one behavior. For example, the amount of time an ectothermic animal such as a lizard spends foraging is constrained by its body temperature. The digestive efficiency of the lizard also increases with increases in body temperature. Lizards increase their body temperature by basking in the sun. However, the time spent basking decreases the amount of time available for foraging. Basking also increases the risk of being discovered by a predator. Therefore, the optimal basking time is the outcome of the time necessary to sufficient warm itself to carry out its activities such as foraging. This example shows how foraging is constrained by the need to bask (intrinsic constraint) and predation pressure (extrinsic constraint).

Ultimately, all behavior is subject to natural selection as with any other trait of an animal. Therefore animals that employ optimal behavioral strategies specific to their environment will generally leave greater numbers of offspring than their suboptimal conspecifics. Animals that leave a greater number of offspring than others of their own species are said to be fitter than their suboptimal cousins. However, over time environments change meaning that what might be good behavior today might not be the best behavior in 10,000 years time or even 10 years time. Recent glaciation and future global warming mean that one thing will certain. The behavior of animals has changed and will continue to change in response to the environment. Behavioral ecology is one the best way to study these changes. As the great geneticist Theodosius Dobzhansky famously wrote, "nothing in biology makes sense except in the light of evolution".

Another driving force in the evolution of animal behavior is the concept of evolutionary stable strategy (or ESS), a term derived from economic game theory which became prominent after John Maynard Smith's 1982 book, Evolution and the Theory of Games. However, the concept can be traced back (as with most evolutionary ideas) to W.D. Hamilton, R.A. Fisher and Charles Darwin. In short, evolutionary game theory asserts that only strategies that cannot be "invaded" by another strategy will be maintained in the population. Therefore, animal behavior can be said to be governed not only by what is optimal, but also by what other strategies are found in the population. Furthermore, the relative frequencies of each strategy can influence the fitness of the other strategies in the population (frequency dependence). It is important to consider that evolution is not only driven by the physical environment, but also the interactions between other individuals.