Working in teams: wild professional profiles

In group living animals division of labour is sometimes based on coordinated activities of group members. In relatively rare cases individuals form groups in which the members stay together for extended periods to accomplish a certain task. Such groups are called teams or cliques (Hö lldobler and Wilson, 1990; Anderson and Franks, 2001).

For example, when working together to dig tunnels, naked mole-rats line up nose-to-tail and operate like a conveyor belt. A digger mole-rat at the front uses its teeth to break through new soil. Behind the digger, sweepers use their feet and the fine hairs between their toes to whisk the dirt backwards. At the back of the line a trailing member of the group kicks the dirt up onto the surface of the ground, creating a distinctive volcano-shaped mole hill. One of folk names of naked mole rats is “sand puppies”. There are several other creatures that join efforts of group members to survive in the running sand. Desert ants Cataglyphis pallida demonstrate the same manner of coordinated working digging tunnels like a conveyor belt.

There are several examples of hunting teams in vertebrates (for a review see: Anderson and Franks, 2001). Usually individuals coordinate efforts so that one or more individuals chase the prey, or flush it from hiding, while others head off its escape. For instance, in chimpanzees (Pan troglodytes), some group members chase and surround the prey (usually juvenile baboons) forcing it to climb a tree while at the same time other chimpanzees climb adjacent trees ready to capture the prey when it attempts to leap across to escape. In African wild dogs (Lycaon pictus) some individuals chase the prey, and can change leaders during the chase (van Lawick-Goodall, 1968; van Lawick-Goodall, Hugo and Jane, 1970).

The most organised teams in animal societies are based on discrete division of labour that may be called “professional specialisation”. Stander (1992) has shown that lion teams can be particularly organized in that an individual will tend to stick to a particular position (subtask) during the hunting on successive hunts. That is, some lions can be classed as «wingers», individuals who always tend to go around the prey and approach it from the front or from the side, while others are better classified as «centres», individuals who remain chasing directly behind the prey. Perhaps the most organized hunting teams in vertebrates occur in Galapagos and Harris’ Hawks (Faaborg et al., 1995). Hawks hunt cooperatively with several birds simultaneously swooping on their prey on such animals as wood rats, jackrabbits and other birds. However, if the prey item finds cover, some birds land and surround it, while one or two hawks will walk or fly into the vegetation to kill the prey. Once the prey is killed, all the birds feed together on the prey.

Until recently, the existence of teams within insect colonies, possibly based on individual identification, has not been known. According to Hö lldobler and Wilson (1990), ants do not appear to recognise each other as individuals. Indeed, their classificatory ability is limited to recognition of nestmates, different castes such as majors and minors, the various growth stages among immature nestmates, and possibly also kin groups within the colony. There are, however, several examples showing elements of team task distribution. In swarm-raiding army ants, large prey items are transported by the structured teams which include members of different castes (Franks 1986). In the desert ant Pheidole pallidula Ruzsky, minor workers pin down intruding ants and later major workers arrive to decapitate the intruders (Detrain and Deneubourg, 1997). Robson and Traniello (1998, 2002) found complex relations between discovering and foraging individuals in group retrieving ant species; removal of the discovering ant during the process of recruitment led to dissolution of the retrieval group.

The question of constant membership and individual recognition within group of workers in ant colonies has been so far obscure. Reznikova and Ryabko’s (1990, 1994, 2003) findings on teams in ants are connected with the discovery of the existence of complex communicative system in group retrieving ant species (see Fig. VI-13). As it was described in details in Chapter 32, such communication system is based on scouts-foragers informative contacts where each scout transfers messages to a small (5 animals in average) constant group of foragers and does not pass the information to other groups. The ants thus work as co-ordinated groups which may be called teams. Does this necessarily mean that they recognise each other as individuals? Indeed, it is possible that the animals presume on recognition of specialists’ roles rather than their personal traits.

Donald Michie (personal communication) has referred to his experience as a Rugby player (as we can see, a famous cryptographer used to play games not only with machines, see: Maynard Smith and Michie, 1964). Being a scrum half, he was always confident on his ability to spot his opposite number (that is, another scrum half) when meeting an opposing team socially before the game. To be adapted to the scrum half's specialist role, one must typically be small, resilient, agile, not necessarily a fast runner. The only other typically agile team member is the fly half, but he has also to be a fast accelerator and need not be resilient. A year later he might still recognise one of that same team's forwards, for example, but not remember the face of the scrum half.

One can find it hard to say that ants are able to recognise each other personally. That a scout can distinguish members of its own team from members of another team is not the same thing as individual recognition. Continuing the use of the metaphor from football, one can imagine a team manager who might be able to distinguish players of his own team from those of a different team (for example by the patterns of their shirts), and this is yet not to distinguish same-team players one from another.

We have not yet distinguished reliable behavioural signs in ants indicating personal recognition like the well-knowing “eyebrow flash” in humans (see: Eibl-Eibesfeldt, 1989); neither are we able to train ants for distinguishing between pictures of different individuals like in Kendrick et al.’s (2001) experiments with sheep (see Chapter 33). Nevertheless, we can be confident on at least circumstantial evidences that group-retrieving ant species possess personalised teams as functional structures within their colonies.

The first evidence comes from ontogenetic studies. Reznikova and Novgorodova (1998) observed the ontogenetic trajectories of 80 newly hatched F. sanguinea ants in one of laboratory colonies and watched the processes of shaping of teams. There were 16 working teams in that colony which mastered mazes. From 80 individually marked naive ants, 17 entered 7 different working teams, 1 to 4 individuals in each. Only 3 became scouts, 2 of them starting as foragers joining2 different teams and 1 starting as a scout at once. The 3 new groups were composed of workers of different ages, mainly from reserve ones. The age at which the ants were capable to take part in the working groups as foragers ranged from 18 to 30 days, and the ants could become scouts at the age of 28 to 36 days. Constancy of membership was examined in two colonies of F. sanguinea and F. polyctena. In a separate experiment researchers isolated all team members from 9 scouts. 3 scouts appeared to mobilize their previous acquaintances and attract new foragers, 4 scouts were working solely, and 2 ceased to appear on the arenas. In another experiment we removed scouts from 5 F. polyctena teams. It was possible to see foragers from those groups on the arenas without their scouts. 15 times different foragers were placed on the trough with the food, but after their return to home they contacted other ants only rarely and occasionally. These results suggest that formation of teams in group retrieving ants is a complex process which is based on extensible relations and possibly include individual identification.

Another evidence of existence of teams in ants is based on division of labour within groups of aphid tenders discovered in red wood ants. It is well known that ants look after symbiotic aphids, protect them from adverse conditions, and in return, ants “milk” the aphids, whose sweet excretions are one of the main sources of carbohydrate for adult ants (Mordvilko, 1936; Bradley and Hinks, 1968). In an ant family, there is a group of ants dealing with aphids (trophobionts), which has a constant composition. Reznikova and Novgorodova (1998) were the first to describe a system of intricate division of labour (professional specialisation) in trophobionts: “shepherds” only look after aphids and milk them, “guards” only guard the aphid colony and protect them from external factors, “transit” ants transfer the food to the nest, and “scouts” search for the new colonies (see Fig. X-9). This professional specialisation increases the efficiency of trophobiosis. When ants were experimentally forced to change their roles, much food was lost. The ants belonging to the same aphid tending group, distinguish at least 2-3 shepherds from 2-3 guards within this group. Such professional specialisation was only found in the same species that exhibited the complex communication system in experiments of Reznikova and Ryabko (1994, 2003).

36. WHAT SORT OF INTELLIGENCE IS REQUIRED TO NAVIGATE SOCIAL LANDSCAPES?

The title of this chapter is borrowed from the chapter “The structure of social knowledge in monkeys” by Seyfarth and Cheney (2002) of “The Cognitive Animal”. Animals that live in groups and being connected by close social relationships can navigate social landscape relying upon their abilities to recognise associated relatives of their own as well as of their neighbours, continuously track the position, social behaviour, foraging and sexual success of other individuals, to memorise and, at least partly, predict social events. Highly social vertebrates, and first of all primates, are endowed with these abilities. There is a growing body of evidences of the association between social complexities and cognitive abilities in animals. Volumes have been written about wild social life. Here we will briefly consider several themes concatenated by experimental approaches for studying animal social problems.