Hearths of culture” in animal societies

As it was been already noted, we argue about cultural changes in animal societies in those cases when animals learn new living habits and pass them along to the next generation. In such a situation spread of a certain innovation results in stable conservation of a new custom that is further maintained and transmitted in a train of generations through social learning. Culture thus is displayed as the presence of geographically distinct variants of habits. Even in this limited sense, culture was long considered to be a uniquely human trait. Ethologists have investigated the problem of animal culture for decades but only in the last few years a clear picture of cultural diversity in several “elite” species begun to emerge. Insight into cultural evolution came from comparative geographic approach when researchers have thoroughly studied behavioural customs in different populations and thus revealed “hearths of culture” in animal societies.

The main methodological difficulty on the way of studying animal culture is to recognize innovations in the field. Even when the origin of a certain innovation had been observed, it is difficult to predict a living trajectory of this innovation. As it has been noted earlier in this chapter, innovations can be spread by means of relatively simple forms of social learning and even low-end innovations can lead to extensive cultural change. Remember Japanese macaque potato washing. By using the water in connection with their food, the Koshima monkeys began to exploit the sea as a resource in their environment. Sweet potato washing led to wheat washing, and then to bathing behaviour and swimming, and the utilization of sea plants and animals for food (Kawai, 1965).

At the same time, there are reasons to believe that new skills do not spread easily in animal populations. As Kummer and Goodall (1985) note, of many innovative behaviours observed, only a few will be passed on to other individuals, and seldom will they spread through the whole troop. For example, Goodall (1986) observed two instances of using stones by adolescent chimpanzees to kill dangerous insects. She supposed that usage of stones should become customary in that reference group. But this had not happen in the following thirty years, the innovation faded away.

The chimpanzee is clearly the most interesting animals from a cultural point of view. Different populations of chimpanzees seem to have their own unique behavioural repertoires, including such things as food preferences, tool use, gesture signals, and other behaviours, and these group differences often persist across generations. After collecting a great body of data in the wild (Goodall, 1964; Lawick-Goodall, 1968; McGrew, 1977; Boesch C. and Boesch H., 1983; Ghiglieri, 1984; Nishida, 1990 and others), the first intimation that chimpanzee possess “material culture” came with McGrew’s (1992) book about chimpanzee’s tool use. Since then, new observations have appeared and some researchers have argued that individual communities of chimpanzees have their own local traditions (Matsuzawa and Yamakoshi, 1996; Humle, 1999). The grand synthesis was done by a collective of primatologists published in Nature (Whiten at al,, 1999; see also a review by de Waal, 1999).

The researchers discovered the various habits of chimpanzees at seven field sites and clearly distinguished behavioural patterns. Some of them concern tool use, such as ant dipping, termite fishing, nut cracking, honey dipping, drinking water with leaves, and so on. Others concern characteristic behavioural habits such as rain-dances, hand-clasp grooming, details of courtship rituals, and so on.

For example, some populations fish for ants with short sticks, eating insects from the stick one by one. Only in one population apes developed the more efficient technique of accumulating many ants on a long rod, after which all insects are swept into the mouth with a single hand motion. Another impressive difference concerns leaf-using for drinking water. In different communities chimpanzees use “leaf sponge” crumbling leaves in their mouth, soaking them in tree hollows with their hands, and sucking the water from them. The other type is “leaf spoon” where apes use leaves like a spoon, without crumbling them up, to scoop out the water.

After compiling a first list, Whiten et al. (1999) rated behavioural patterns on a scale from customary to absent at each field site, and the ecology of each field site was taken into account. For instance, chimpanzees will not sleep in ground nests (as opposed to tree nests) at sites with high leopard or lion predation. Such ecologically explainable differences were excluded from the list leaving 39 behavioural patterns. The researchers found no evidence that habits vary more between, than within, the three existing subspecies of chimpanzees. So genetics cannot account for the observed variability.

Taking into account many results obtained in captivity, the authors suggest that mechanisms of social learning simpler than imitation could be involved in the processes of formation of new customs in chimpanzees’ populations. The most commonly suggested mechanism is stimulus enhancement, in which the attention of an observer is merely drawn to a relevant item such as a stick. Socially learned experience is combined with self practice in young and adults. Field and laboratory experiments have enabled primatologists to observe more flexible tool using behaviour than in “orthodox” communities with stable traditions. For example, in field experiments, presenting apes from Bossou group with containers filled with water and juice, Tonooka (2001) revealed a new technique of the use of leaves for drinking, that is, “leaf folding”. The chimpanzees folded leaves in a manner resembling those of the side ribs of a bellows or Japanese origami (paper folding).

Until recently chimpanzees were considered the only species among great apes that possess elements of “material culture”. Nowadays researchers consider chimpanzees displaying the highest level of manufacturability but not a single species sharing with human the membership in the club of animals with culture. Besides Africa's gorillas and chimpanzees great apes include orangutans, the fabled red apes of the forests of Indonesia. Orangutans Pongo pygmaeus are less social than other primates, living a rather solitary life in the wild. They are slow in movement, not leaping vigorously from limb to limb like chimps or crashing through underbrush like the gorilla (Galdikas and Briggs N. 1999). Thirty years of field observations of the shy Southeast Asian orangutan allow the international group of researchers to conclude that these apes definitely have the ability to adopt and pass along learned behaviours (Fox et al., 1999; van Schaik et al., 2003; Wich et al., 2004).

Studying six populations of orangutans in Borneo and Sumatra, Indonesia, researchers identified 24 examples of behaviours that have been defined as cultural variants. Many of the culturally transmitted behaviours involve tool use such as using sticks to dig seeds out of fruit, to poke into tree holes to obtain insects, or to scratch; using leaves as napkins or as gloves to protect against spiny fruit. Twelve other behaviours, such as making a pillow with twigs, were seen only rarely or were practiced by only a single individual. The practices common in one group and absent in another are of great interest to researchers because variations on these behaviours found among the different populations seem to be cultural. For example, in a Sumatran swamp, one particular group of orangutans like a fruit that was protected by needle-like spines, and to get to the edible seeds inside, the apes used a tool. With a sharp stick, they pried open the fruit to extract the seeds. Only a single group of the six observed has discovered how to use sticks to extract insects from tree holes or to wedge out seeds from fruits. Such tool use is common among chimpanzees, but the Sumatran orangutan band puts a unique twist to the practice - they grip the stick with their teeth instead of their hands. On the far side of the river another group of orangutans have plenty of sticks available, but they do not use them on fruit; most ignore the fruit, others smash it to get the seeds. The stick trick seemed to be an invention created by one group that was passed along. This is what researchers call “a cultural boundary".

A group in Sumatra has learned to use leaves as gloves when handling spiny fruits. The dainty use of a napkin has been discovered by one band. Apes in a Borneo band routinely wipe their faces with leaves and parents teach the social skill to their young. A second Sumatran band has learned the unique skill of getting a drink by dipping a leafy branch into a water-filled tree hole and then licking the moisture from the leaves.

Comparative data on tool use geography in northern Sumatra have shown that ecological and genetic factors are involved as necessary preconditions, but that the geographic variation in orangutans is cultural, as in chimpanzees. Thus, the incidence of skilled behaviours such as tool use in a social unit must be explained with reference to the ontogenetic process of skill acquisition: invention, diffusion (importing skills invented elsewhere) and social transmission.

Recent data obtained by Krü tzen et al. (2005) allow adding marine mammals to the catalog of culturally transmitted forms of tool use in nonhuman populations. In Shark Bay, Western Australia, wild bottlenose dolphins (Tursiops sp.) apparently use marine sponges as foraging tools. Sponge carrying came to the attention of scientists 20 years ago when a boater reported seeing a dolphin in Shark Bay with a " tumor" on its beak. The tumor turned out to be a sponge, and in 1997 researchers proposed sponge carrying as the first known example of tool use in dolphins (Smolker et al., 1997). Dolphins have devised a way to break marine sponges off the seafloor and wear them over their snouts when foraging. Researchers believe that dolphins use sponges as a kind of glove to protect their sensitive rostrums when they probe for prey in the substrate. Unlike in apes, tool use in this population is almost exclusively limited to a single matriline that is part of a large albeit open social network of frequently interacting individuals. To discover whether tool-use is a genetic trait, or one transmitted culturally, Krü tzen and colleagues analysed DNA from 13 of 15 spongers, only one of which was male, and 172 non-spongers. They found that most spongers were maternally related - sharing the same mitochondrial DNA, which is only transmitted through the female line. A comparison of their nuclear DNA showed that the spongers were closely related, suggesting that spongers are descendants of a recent “Sponging Eve”. However, the pattern of sponging among the dolphins could not be explained by a “gene for sponging” - the trait’s pattern of inheritance just did not fit. The researchers conclude that the behaviour is culturally transmitted, presumably by mothers teaching the skills to their sons and daughters, although they have not actually observed this feat in action.

Tool-use is the most amazing but not a single population-specific behavioural trait enabling cetacean biologists to claim that marine mammals possess culture (Whitehead, 1998; Deecke et al., 2000) or at least traditions. Mann and Sargeant (2001) have listed many population-specific patterns concerning foraging strategies, styles of diving and other behavioural traits many of them have been clearly demonstrated as transmitted by means of social learning.