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Displays of complex instinctive behaviour






Arguing about drifts toward instinctive behaviour as a part of learning process, we should discuss a question about what is “instinct” itself. The concept of instinct is one of the oldest in behavioural sciences and therefore this concept has fuzziest boundaries. Early authors wrote about “imperial instinct” in “queens” in social insects. As it has been described in Chapter 1, one of the first articles in this field was Ray’s scientific text on the study of “instinctive behaviour” in birds published in 1676. Darwin helped to prepare the ground for the study of the interplay of instinct and early learning, soon to be taken up by Spalding (1873), and later by founders of ethology, Lorenz and Tinbergen.

Although the term “instinct”, through the years, had many meanings, students of behaviour agree with a general concept that those behavioural patterns are considered to be “instinctive” that are relatively constant throughout a species and are not acquired through previous experience or learning. Probably this idea is too simplistic, and the real picture of intimate relationships between innate and learned behaviours is much more complex. For our consideration it is important to note that sophisticated behaviour in many species can be based mainly on inherited patterns.

There are many examples of species-specific behaviours in nature. If we recall just one kind of activity, such as “dances”, we then can list courtship dances in fishes (such as “zigzag” dance in sticklebacks), birds and even insects (such as mating “dances with balloons” in several fly species). Informative “Dance language” in honey bees is much more flexible than courtship dances but basic figures of bees’ dances are inherited. Recently the use of “tactile dances” for ritualised interspecies communication has been described by Grutter (2004): in cleaning interaction between fish species, cleaners evolved specific behavioural strategy to avoid conflict or being eaten. Cleaners tactically stimulate clients while swimming in an oscillating dancing manner. This “tactile dancing” enables cleaning fishes to avoid conflicts with potentially dangerous clients.

Let us consider several examples of highly specific behaviour in animals based on innate stereotypes.

The first example concerns bowerbirds, a family of birds in which males attract mates by collecting brightly coloured objects which they display to females in 'avenues' or on 'maypoles'. From Darwin’s time forward, bowerbirds have been considered an example of a bird with a human-like aesthetic sense. What is may be more important, these birds provide an outstanding model system for testing hypotheses about the evolution and functional significance of complex behavioural display. These hypotheses have been tested in long term experimental works of Borgia and colleagues with all 19 species of bowerbirds living in Australia and New Guinea (Borgia and Presgraves, 1998; Patricelli et al., 2002). An interesting relationship has been revealed between the colourfulness of a male's plumage, the visual properties of the objects they collect, and the complexity of the structures they build to house these objects. Some species of male bower bird are relatively drab, but they make up for this by building elaborate structures decorated by brightly coloured objects. In other words, they fill a gap in their attractiveness with sophisticated behaviour. The latter aspect is of most interest here. Polygynous species of bowerbirds build stick bowers on the ground associated with a decorated display; females provide parental care at nests built in trees. Multifaceted male displays involve the decorated display court and the bower that act as a stage for energetic vocal and dancing male display that is observed by the female from inside the bower. Courtship and mating occur in the bower. Bower quality, numbers of preferred decorations, vocal and dancing elements all contribute to male mating success. Male reproduction is skewed; one male may mate with 25 different females at his bower in one season. Males of different species choose colours of decorations in response to different light regimes. In Amblyornis bowerbirds, males in species using foggy ridge tops use predominantly black decorations while closely related species displaying on more sunlit slopes use a variety of decorations with a wide array of bright colours.

F. Cuvier (1825) considered animals somnambulists in the power of instincts. So the second Australian “somnambular” bird that is probably fainting under a weight of its behavioural stereotypes is a so-called moundbird. The matter concerns species of various large-footed, ground-dwelling birds of the family Megapodiidae, found in Australia and South Pacific islands. Their astonishing nesting habits were described in early literature (Wallace 1860; Banfield, 1908; Fleay, 1937). The three Australian megapode species- Australian brush-turkey, Orange-footed megapode and Maleefowl - build mounds of leaf litter and other organic materials in which microbial decomposition produces an incubation temperature of around 340. Direct solar radiation may also contribute significantly. These birds have to overcome a hardship “ab ovo”. Megapode hatchlings are the most independent of all avian species. The large egg enables the hatching of a very advanced chick. One report of a chick unearthed from a mound states that it immediately flew about 10 meters. But what is even more amazing is that the chicks hatch deep in the soil, digging its way up to the surface, all by itself, and then live without any parental care. A very complex behavioural scenario is unwinding independently in each member of species. Especially hard lot falls on males. First, a male build a mound. A typical mound is 2-3 metres tall, up to 15 metres in diameter and can weigh over 50 tonnes, maintained by a pair throughout the year (Fig. VII -2 and VII-3).

Before a female lays an egg, the male digs a tunnel within a mound leading to an egg chamber. It takes not less than an hour and after that the female walks out of the bushes and inspects the temperature in the chamber. If the female is not satisfied, she returns to the bush and the male has to dig another tunnel. He makes up to four before the female lays an egg. She lays several eggs, once in three-five days because each egg weights about 10% of her body. The female covers each egg by soil and walks away, and now the male takes up its duty. He defends a mound vigorously from snakes and other predators, and, what is the hardest duty, he attends to the mound adding and removing litter to regulate the internal heat while the eggs hatch (Frith, 1956 a). Early naturalists noted melancholic and solemn style of movements of Megapode males which lack the nice vivacity which is so typical for many birds. Even in midday sun when other creatures conceal themselves being languid with the heat, Megapode males continue to dig in soil, gloomy and lonely.

Megapodes can serve a good example of intricate combination of morphological adaptations (such as notably large eggs, very advanced and equipped chick, specific palatine thermo-sensors that allows birds to control the temperature), strong behavioural stereotypes and essential elements of flexible behaviour. It is a question of great importance, how many degrees of freedom brush-turkey has.
Let us compare brush-turkey’s reaction on attempts to disturb its work with correspondent behaviour of another fanatic digger, Digger Wasp, Ammophyla, with whom we have already met in Chapters 12 and 17. Let the Digger Wasp dig her hole, bring several carpenters as the food for future larvae, and lay eggs. Now she is making sand-up bridging. If we disturb her and take all contents out of the hole in the view of the owner, the Wasp will quickly return and close the hole up as if nothing was wrong.

The brush-turkey male responds quite differently. When researchers took his nest material away, or packed it in different ways, or add some, he responded on-the-fly determining the change on temperature by its thermo-sensor and working nearly to the point of exhaustion in order to keep the temperature inside the mound of about 340. In special series of experiments, investigators built electrical heaters into the mound and frequently switched them on and off thus keeping the male alarmed. The bird responded to these diversions in very effective way and soon celebrated victory (Frith, 1956 b). So this bird appears not to be a whole “somnambulist”.

Does this mean that the brush-turkey behaves in flexible and creative manner whereas the behaviour of a “low” insect is governed by a “blind instinct”? Again, the picture is not so simple. As we have seen in Chapter 12, the Digger Wasp displays wonders of intelligence when remembers where each of her several holes is situated and how many carpenters should be killed and placed into each of them. Being disturbed at other stages of her behavioural circle than closing holes, she responds adequately and effectively. When researchers took from one to three prey items out of her holes, the Wasp refilled each whole adequately (Tinbergen, 1951).

It seems that species have different spaces for flexibility at different stages of their general and particular behavioural cycles. It is an essential part of complexity of life that in some species nearly all behaviours include deeply intertwined innate and flexible components whereas in others these components can be distinguished with relative ease. In order to make this picture clearer, some specific features of instinctive behaviour will be later analysed later in this chapter.

Returning to a special case of Megapode, one comparison can be of help. One can say that flexibility of their constructive behaviour is at about the same (relatively high) level as in beavers building their dams and lodges. Both species erect their imposing constructions under the guidance of inherited predisposition. F. Cuvier (1825) first raised two young beavers in deprivation from adults and thus revealed that their engineering talents are highly predisposed. At the same time, both species flexibly adjust their efforts to requirements of their environment. There is much evidence concerning flexibility of dam constructing in beavers (Wright et al., 2002). As far as Megapodes are concerned, one of early observers of scrub fowls’ behaviour described mounds that were constructed by birds living in a particularly rugged part of Dunk Island. They were made from boulders, and inclination towards each other provided safe protection from rain. The author afforded this as illustration of “purposive conscious action” (Banfield, 1908).

One can say that both species demonstrate sophisticated combination of behaviours; some of them are based on innate stereotypes whereas others amaze observers with flexibility and rationality. We will return to some, may be unexpected, aspects of behaviour of the same organisms further in this part.

 


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