Orange patches help lizards attract mates
Female dragon lizards in Australia develop orange patches on their underbellies when they are fertile; the patches disappear only after they lay their eggs. A new study finds that the intensity of the color and the size of the patches help males in their search for mates.
The researchers – Devi Stuart-Fox and Jennifer Goode of the University of Melbourne in Australia – collected lizards from their arid homes under the salt crust of Lake Eyre and then used paint to manipulate the amount of orange on females in various stages of fertility. Then they observed how males responded.
Regardless of a female’s reproductive state, the males preferred those with orange patches, particularly small, bright patches, according to the study, which appears in the journal Frontiers in Ecology and Evolution. They were least interested in pale lizards.
Bright orange might be an indication of peak fertility, Stuart-Fox said, while a large patch might mean that a female is pregnant and uninterested in mating.
But males do not completely avoid pregnant females. “The females can store sperm, and so he could still father another set of eggs,” Stuart-Fox said.
Pregnant females work hard to fend off aggressive males, flattening their bodies and gaping to signal rejection. As a last resort, they flip onto their backs, a position that does not allow for mating and displays their orange patches.
Sparrows welcome wimpy neighbors
Male chipping sparrows seem to have a curious motto: Love thy neighbor, as long as he is a weakling. If an intruding bird enters another male’s territory, a neighboring male might intervene, according to a study in Biology Letters, but only if the victim is weaker.
One way to measure an individual male’s level of aggression is to listen to his trill, said Sarah Goodwin, a doctoral student at the University of Massachusetts, Amherst, who led the study. A fast trill signals that a bird is more aggressive; a slower one indicates a meeker bird. Goodwin and her adviser, Jeffrey Podos, found that neighbors came to the aid of only those birds with trills slower than theirs.
– New York Times