Job- swapping species
1 WHAT EXACTLY IS THIS BEHAVIOUR?
Throughout the animal kingdom, certain insects, amphibians, fish and birds practise something called ‘sex role reversal’. The male takes on the role of caring for eggs and young, while the (often) more colourful female competes for males. Though rare in birds, role reversal is found in some wading species that buck the trend. The females lay eggs and head off to find a new partner, leaving the males to tend the eggs and young.
The dotterel and red-necked phalarope (top).
2 WHICH BRITISH BIRDS DO IT?
The dotterel and red-necked phalarope. The slightly larger, subtly more colourful females arrive earlier than males on their nesting grounds. Female dotterels congregate at mating arenas high in Scottish mountains to wait for the males’ arrival. Females guard their mate from rivals, lay their eggs, then move on to find other available males, an arrangement known as sequential polyandry. Elsewhere in the world, other role-reversing birds include the spotted sandpiper and Kentish plover.
3 BUT WHAT’S IN IT FOR THESE SPECIES?
Role reversal enables a female to produce more offspring during a single nesting season. It happens in species where one sex, often the female, is less common. Because the male sires fewer young, he ensures his paternity by closely guarding his mate and copulating with her just before she lays. If a male red-necked phalarope loses a clutch of eggs to a predator, he will try to pair up with the same female again, as she is less likely to have sperm from other males.
Ed Drewitt
ubterranean forests are not a figment of S
a science-fiction writer’s imagination, but actually exist. The Hayward Gallery’s ‘Among the Trees’ exhibition (now closed, but there’s an accompanying book available) included a remarkable photograph of a 13,000-year-old tree growing beneath the red sandy soil of South Africa’s savannah. Or rather, it showed the uppermost crown, the only part of the tree in view. The appearance is of a small, ground-hugging shrub, rather than the full-sized tree it really is. Sometimes these strange trees cluster together – a veritable underground forest. Botanists have a theory that their extraordinary growth pattern, seen in several species of savannah tree, is a strategy to avoid wildfires. With the trunk and most branches below the surface, they survive the flames. Ben Hoare