Adaptive behavioural syndromes due to strategic niche specialization

Abstract

Background: Behavioural syndromes, i.e. consistent individual differences in behaviours that are correlated across different functional contexts, are a challenge to evolutionary reasoning because individuals should adapt their behaviour to the requirements of each situation. Behavioural syndromes are often interpreted as a result of constraints resulting in limited plasticity and inflexible behaviour. Alternatively, they may be adaptive if correlated ecological or social challenges functionally integrate apparently independent behaviours. To test the latter hypothesis we repeatedly tested helpers in the cooperative breeder Neolamprologus pulcher for exploration and two types of helping behaviour. In case of adaptive behavioural syndromes we predicted a positive relationship between exploration and aggressive helping (territory defence) and a negative relationship between these behaviours and non-aggressive helping (territory maintenance).

Results: As expected, helpers engaging more in territory defence were consistently more explorative and engaged less in territory maintenance, the latter only when dominant breeders were present. Contrary to our prediction, there was no negative relationship between exploration and territory maintenance.

Conclusion: Our results suggest that the three behaviours we measured are part of behavioural syndromes. These may be adaptive, in that they reflect strategic specialization of helpers into one of two different life history strategies, namely (a) to stay and help in the home territory in order to inherit the breeding position or (b) to disperse early in order to breed independently.

Figure 1

Exploration behaviour (the number of pot halves visited) was positively correlated with the frequency of aggressive displays towards an intruder (r_s = 0.71, N = 12; P = 0.01). This relationship was also significant for females only (r_s = 0.86, N = 9; P = 0.003).

Figure 2

When breeders were present, the frequency of aggressive displays towards an intruder correlated negatively with the frequency of digging (r_s = -0.69, N = 12; P = 0.01). This relationship was also significant for females only (r_s = -0.66, N = 9, P = 0.05).