Innovation in wild Barbary macaques (Macaca sylvanus)

Abstract

Innovation is the ability to solve novel problems or find novel solutions to familiar problems, and it is known to affect fitness in both human and non-human animals. In primates, innovation has been mostly studied in captivity, although differences in living conditions may affect individuals' ability to innovate. Here, we tested innovation in a wild group of Barbary macaques (Macaca sylvanus). In four different conditions, we presented the group with several identical foraging boxes containing food. To understand which individual characteristics and behavioural strategies best predicted innovation rate, we measured the identity of the individuals manipulating the boxes and retrieving the food, and their behaviour during the task. Our results showed that success in the novel task was mainly affected by the experimental contingencies and the behavioural strategies used during the task. Individuals were more successful in the 1-step conditions, if they participated in more trials, showed little latency to approach the boxes and mainly manipulated functional parts of the box. In contrast, we found no effect of inhibition, social facilitation and individual characteristics like sex, age, rank, centrality, neophobia and reaction to humans, on the individuals' ability to innovate.

Figure 1

Social network of the group of wild Barbary macaques located in Gibraltar and participating in this study. Weighted edges and nodes are proportional to the individual strength in the network (i.e. the sum of all edge weights connected to the node). Communities are shown with different colours (see Farine & Whitehead). Social network analyses (and the resulting Fig. 1) were run in R, using the vegan (version 2.5-3), asnipe (version 1.1.10) and igraph (version 1.2.1) packages (Oksanen et al.; Farine; Csardi & Nepusz).

Figure 2

Set-up of the neophobia task administered to the wild group of Barbary macaques tested in Gibraltar. The full ovals represent stones. On the left, set-up for the first and second conditions of the neophobia task. The light/yellow empty ovals represent banana slices, and the dark/blue empty circles represent blue- (in the first condition) or red-dyed (in the second condition) banana slices. On the right, set-up for the third and fourth conditions of the neophobia task. The dark/green rhombs represent local leaves, and the light/silver rhombs represent silver (in the third condition) or yellow (in the fourth condition) pieces of salt-dough.

Figure 3

Set-up of the innovation task administered to the wild group of Barbary macaques in Gibraltar, for (a) Condition 1, (b) Condition 2, (c) Condition 3 and (d) Condition 4. The light grey/yellow full oval represents food. Dark grey/green parts represent the functional parts of the boxes. Grey arrows represent the movements needed to access the food in the four conditions.

Figure 4

For each individual in the group of wild Barbary macaques tested in Gibraltar, number of trials in which the subject participated and obtained the food, in each of the four conditions.

Figure 5

For each set of models, estimates of the best models: (a) M1.8, (b) M1.5 and (c) M1.3; (d) M2.0 and (e) M2.1; and (f) M3.0 and (g) M3.2 (see Table 3 for more details).