Plasticity in behavioural timing

Serge Daan

University of Groningen, The Netherlands

The question of behavioural resilience and plasticity in the face of global climate change deals with the extents of rigid genomic programming versus adaptive flexibility. Behavioural variation often has a genetic component, but we rarely know the degree of phenotypic plasticity. I focus on timing of behaviour, where underlying molecular genetic mechanisms are better understood than in most behaviours.

In ‘annual timing’, optimal solutions change as the food supply in warmer springs is advanced. Annual breeding is under photoperiodic control in countless species. A mismatch between the photoperiodically programmed breeding cycle and the shifted food cycle has been claimed as one of the serious threats from climate change to, for example, migratory birds. I will discuss the flexibility of annual timing with respect to the extent of this threat. A broad scatter of individual optimal solutions allows birds to tune their timing to varying environments.

‘Daily timing’ bears no obvious relation to climate change, as the earth will not turn faster on its axis as its surface heats up. Here, too, there is substantial phenotypic flexibility in the expression of circadian rhythmicity. I will illustrate this with data from small rodents.

Both on the annual and daily time scales, animals are equipped with sophisticated and precise timing systems, which allow a great deal of phenotypic flexibility. Global climate change may pose threats to animals by destroying their food supplies and habitats, but their behavioural resilience is a strong weapon helping to fight these threats.