The worlds smallest primate is not an intimidating animal. It has outsizeeyes, nibbles on fruit and insects, and would fit in your breast pocket. Yet at least one species has a super-strong grip, which might help humansunderstandhow our own hands evolved.
Amongmany species of mouse lemur, thelargestnot that thats much of a distinctionis Microcebus murinus, the gray mouse lemur. Like all other lemurs,M. murinuslives wild only in Madagascar. But a captive population lives at the French research institutionUMR7179 CNRS/MNHN, where graduate student Pauline Thomas and her colleagues decided to measurethe strength of the petiteanimals arms.
Having a strong grip is crucial for an animal like a lemur that lives in the trees. Some lemurs are acrobats thatswing and leap between http://www.health.gov.au/ branches; other species, like mouse lemurs,do more subdued clinging. But all of them would be in trouble if they lost a handhold in a high branch. And since the earliest primatesour ancestors as well as the lemursare thought to have lived in trees too,their need to hang on tight may have influenced what our hands look like today.
The researchers studied 62 captive gray mouse lemurs, both males and females. They measured pull strength, or how http://canmiceclimbwalls.healthfitnessjourney.com wellthe animals can hang on to something. As has been done with other species, the researchers studied this by simply letting the lemurs latch on somewhereand then gently pulling them free.
In this case, the lemurs grippeda little iron bar. The bar was mounted to a force plate, which measuredhow much force the lemurs were exerting. Then a researcher tugged the animals horizontally away from the bar. The experiment was repeated multiple times with each animal to make sure thetiny athletes performed consistently.
Comparing the results to the lemurs body measurements, the researchers found that heavier individuals couldpull more strongly. Longer forearm bones also made for stronger lemurs. As the animals got older, their gripsweakened. And females with more young were stronger, probably because their bodies had beenin better condition to begin with. On average, the mouse lemurs could pull over 10 times their own body weight.
This was an impressive performance, compared to some other http://www.bhg.com/health-family/ animals whose pull strength scientists havetested. Mice can pull less than a quarter of their body weight, and rats can pull just 7 percent.
Gripping tree branches and grasping bugs to eatarent the only tasksthat require a mouse lemurs hand strength. Mouse lemurs are promiscuous, and during mating the males have to cling to the slightly larger females. Scientists dont know yet how the gray mouse lemurs grip strength compares to other primates, though. The diminutivelemursmight only be average.
But if senior author Anthony Herrel had to guess, he thinks mouse lemurs are likelyextraordinary.
Mouse lemurs liveon especially narrow branches, Herrel explains. To walk on narrow branches you need to be able to grip really well, as otherwise you will topple sideways. To get some data, Herrel hopes to compare M. murinusto other lemur species with different lifestyles.
Herrel says the earliest primates may have been adaptedfor hanging on to narrow branches, just like the mouse lemur does. So further researchmight provide hintsabout how all primate hands evolved, as well as whether mouse lemurs are really strength champions. Our data suggest that, at least, they are quite strong, hesays.
http://www.youtube.com/watch?v=co-Eyh6v-rM
Image: courtesy of Pauline Thomas.
Thomas, P., Pouydebat, E., Brazidec, M., Aujard, F., & Herrel, A. (2015). Determinants of pull strength in captive grey mouse lemurs Journal of Zoology DOI: 10.1111/jzo.12292
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