Biology Reference
In-Depth Information
mouth. In other populations, however, the chimps use a small stick to collect a few ants
at a time and then they transfer them directly to the mouth with the stick (Whiten
et al
.,
1999). While these differences may well reflect cultural differences transmitted by
social learning, it is difficult from observational studies alone to exclude the possibility
that the differences might reflect genetic differences between populations, or differences
in ecological conditions, such as resources available (Laland & Janik, 2006).
The best evidence for traditions in the wild maintained by social learning comes from
translocation experiments with fish. Helfman and Schultz (1984) found that French
grunts
Haemulon flavolineatum
had traditional daytime schooling sites on coral reefs and
then also used traditional migration routes at dusk and dawn, to and from feeding grounds
on nearby grass beds. These schooling sites and migration routes persisted for longer than
the lives of individual fish. To test whether new recruits to the school learnt the local
resting and migration routes from others, some fish were transplanted to other sites. These
individuals quickly adopted the movement patterns of the residents at the new sites. By
contrast, when residents were removed, newcomers used new sites or routes. Therefore,
the local tradition broke down once the opportunity for social learning was removed.
In a similar experiment, Warner (1988) showed that mating sites of blueheaded
wrasse
Thalassoma bifasciatum
on reefs could be maintained by socially transmitted
traditions, rather than through individuals choosing the best sites based on resource
quality. Mating sites remained in daily use for twelve years (four generations), yet when
entire local populations were removed and replaced by new individuals, new sites were
adopted and then maintained.
In future studies it would be interesting to examine the circumstances in which
individuals benefit by following the social traditions of their group rather than investing
in costly individual exploration, which might erode traditions or lead to new ones. In
some cases, traditions persist even when they are maladaptive. In laboratory experiments
with guppies
Poecilia reticulata
, Laland and Williams (1998) found that naïve fish would
follow others that had been trained to adopt an energetically costly circuitous route to a
feeder rather than select a less costly short route. Furthermore, once fish had been
trained to follow the long route, they were slower to learn the quicker route than control
fish. Therefore, socially-learned information can sometimes inhibit learning of the
optimal behaviour pattern.
Local traditions
in chimpanzees
and fish
Teaching
In cases where individual learning or inadvertent social learning is very costly, or
where opportunities for these are lacking, knowledgeable individuals may actively
'teach' others. Three criteria have been suggested for regarding an individual as a
'teacher': (a) it modifies its behaviour in presence of a naïve observer, (b) it incurs an
initial cost from doing so and (c) the naïve observer acquires skills or knowledge more
rapidly as a result (Caro & Hauser, 1992). Evidence for all three criteria in non-human
animals is scarce.
Nigel Franks and Tom Richardson (Franks & Richardson, 2006; Richardson
et al
.,
2007) have shown that teaching, as defined above, does not require a large brain. When
an ant,
Temnothorax albipennis
, finds food it leads another, naïve individual from the nest to
the food source by 'tandem running' (Fig. 3.13). The leader runs ahead, with the follower
maintaining frequent contact by tapping the leader's legs and abdomen with its antennae.
Three criteria
for teaching
