SIBLINGS SET THE SOCIAL SCENE

Abstract

Brush-turkeys probably won't win the `most doting parent' prize. Abandoning their newly laid eggs to develop in enormous compost heap incubators, the parents return to the Australian bush ready to resume their solitary existence. So brush-turkey chicks must be resourceful from the start,scratching around without a mother's example to guide them; `brush-turkey chicks are probably the most precocial chicks there are' explains Ann Göth. But it wasn't clear whether these abandoned hatchlings had the same social skills as other precocial chicks, which imprint on their mothers. Göth wondered whether brush-turkey chicks could imprint on other brush-turkey chicks instead. Working with Christopher Evans, she decided to test whether newly hatched brush-turkey chicks could recognise each other, and what attracts a hatchling to another chick shortly after it emerges from its decomposing incubator (p. 2199).But getting hold of brush-turkey eggs was far from straightforward. Göth had to brave leeches as she manually excavated the bird's enormous leaf litter incubators and transferred the eggs to soil incubators in the lab at Macquarie University. Having got some eggs, Göth also knew she had to keep the newly hatched chick's contented and unaware of their unnatural surroundings when they hatched, which meant constructing large net aviaries in an area of native forest on the University's campus.Having ensured that the chicks' Macquarie home was as natural as possible,Göth had one final test to do before putting newly hatched chicks through their social paces. The chick robots, which she and Evans had built, looked fine to human eyes, but would the real chicks fall for their doubles?Tentatively she tested five newly hatched youngsters' reactions to the pecking impostors, and was delighted when all of the chicks began acting socially,copying the robot's pecking action. Happy that the chicks were none the wiser about the chick-doubles, Göth was ready to test their preferences.Suspecting that the chicks would be most attracted to pecking actions,Göth allowed the newly hatched youngsters to choose between either a pecking robot or a robot involved in some other activity. But no matter which choice the chicks were offered, they always seemed to prefer spending time with the pecking robot chick, even trying to steal the food that the automated model appeared to dine on. The chicks were very sociable, despite their parents antisocial reputation.Göth wondered whether any other aspects of a brush-turkey chick's appearance attracted the youngsters and found that UV wavelengths reflected from brush-turkey's legs and beak were essential if the chick was to mimic its pecking actions. The team suspect that the chick's spectral properties could form part of a secret signal visible only to the UV sensitive chicks, but invisible to mammalian predators and airborne hunters.So even though they don't have a mother to imprint on, newly hatched brush-turkey chicks seem to have well developed social responses, despite the lack of parental guidance.