If like me you were fascinated as marine iguana hatchlings battled for their lives against multiple Galápagos racer snakes in the first episode of the BBC ‘s Planet Earth II, then read this Guardian article by the cameraman responsible: Richard Wollocombe.
Recent research published in The Condor: Ornithological Applications has shown that greater sage grouse mothers (Centrocercus urophasianus) can choose nesting habitats that better ensure the survival of their chicks after they fledge.
Evolution not only drives animals to act to benefit their own survival (direct fitness) but also that of their own offspring (indirect fitness). Maximising such lifetime reproductive success is probably what drives us to protect our own children.
But can animals actually make active decisions that benefit their reproductive success? This is the question that Dr Daniel Gibson and his colleagues set out to answer in their study of the greater sage grouse.
These birds are the largest grouse in North America, inhabiting open grassland habitats that make them particularly vulnerable to predators. The species is classified as Near Threatened by the IUCN Red List. They have a complex mating system, whereby males gather in groups (leks) to perform lively, colourful mating displays to attract females [see picture]. This means that females get to be extremely picky about who they mate with.
Dr Gibson and his team found that females are not only choosy about their sexual partners but also are picky about where they nest. They tend to choose nesting habitats with characteristics that ensure reproductive success: specifically, greater shrub cover and forb (flowering plant) diversity. By observing over 200 mothers over a period of 8 years, they found that these habitat features predicted the survival of chicks after fledging.
This means that even our feathery friends can make active choices that determine the survival of their offspring, which is pretty impressive. What isn’t so clear is whether the mothers themselves were more likely to survive – were they also acting to protect themselves as they sat helpless on their nests? Or is their behaviour purely selfless?
Whatever the answer, it is likely that many other animals are able to protect their young by making these real-time decisions – what can be termed ‘behavioural plasticity’ – something that evolution is likely to promote in order to maximise indirect fitness and pass on genes to future generations.
Knowing this will also help conservation efforts because land managers now have clues about where these birds are most likely to nest, and hence which habitats they should protect the most.