March 22, 2012 — When does a lemur reach across the gap between branches and when does it leap? The answer may be related to the flexibility of its spine, says Duke graduate student Michael Granatosky.
The theory is that leaping from branch to branch uses more energy than reaching across, so a lemur will try to bridge the gap until it is no longer able to do so. However, different types of spines are better at different activities. For instance, blue-eyed black lemurs have flexible, mobile spines that are better for leaping. Lorises have relatively rigid spines that work like cranes and these lemurs are expected to be able to bridge longer gaps.
To test this, Michael and the two member team that is the Research Department are clustered in the research room at the Lemur Center, peering intently at a lone blue-eyed black lemur running back and forth across a couple of wooden poles that are separated at the center by a short gap. The set-up is meant to emulate a terminal branch environment, and Tarantino the lemur is enticed to cross from “branch” to “branch” by means of a raisin dropped into a metal bowl. He seems to enjoy this activity – after a while he doesn’t bother to wait for the “plink” of a raisin into the bowl before turning and racing back across the “branches”.
The gap-end of one of the poles is attached to a super-sensitive scale that measures the movement of the lemur in 3D as it bridges the gap between the poles. It looks like Tarantino is moving non-stop from one end of the pole to the other across the gap but Michael shows us a graph on the computer screen that tells us that Tarantino has braked as he notices the gap, moved from side to side, and accelerated as he crosses to the other side. At the same time, two video cameras are recording Tarantino’s movements for later analysis in slow motion. He has white dots of non-toxic paint strategically located on his limbs so that a 3D picture can be built up of the way he moves.
As the trials progress, the gap will be widened, until the point where the lemur no longer bridges the gap but has to leap instead. Eventually, flexible, wobbly ends will be attached at the gap, more like real branches and other lemur species will be tested, including three species of Loris, and fat-tailed dwarf lemurs.
