This is true for sugar gliders (Petaurus breviceps) and grey short-tailed opossums (Monodelphis domestica), say biologists from Saint Petersburg State University, Russia.
Male and female Sugar gliders eating worms (CC BY-SA 3.0)
Their study, published in the open access journal BMC Evolutionary Biology, shows that handedness in marsupials is dependent on gender.
This preference of one hand over another has developed despite the absence of a corpus callosum, the part of the brain, which in placental mammals allows one half of the brain to communicate with the other.
Many animals show a distinct preference for using one hand (paw, hoof) over another. This is often related to posture – an animal is more likely to show manual laterality if it is upright, related to the difficulty of the task, more complex tasks show a handed preference, or even with age. As an example of all three: crawling human babies show less hand preference than toddlers.
Some species also show a distinct sex effect in handedness but among non-marsupial mammals this tendency is for left-handed males and right-handed females.
In contrast, the team from Russia shows that male quadruped marsupials, such as who walk on all fours, tend to be right-handed while the females are left-handed, especially as tasks became more difficult.
“Marsupials do not have a corpus callosum – which connects the two halves of the mammalian brain together. Reversed sex related handedness is an indication of how the marsupial brain has developed different ways of the two halves of the brain communicating in the absence of the corpus callosum,” explains senior author Dr Yegor Malashichev.
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Bibliographic information: Andrey Giljov et al. 2013. Forelimb preferences in quadrupedal marsupials and there implications for laterality evolution in mammals. BMC Evolutionary Biology, 13:61; doi: 10.1186/1471-2148-13-61
