![]() |
A bipedal jerboa, one of the rodent species included in a study of unpredictability in animal movements. Image credit: Talia Moore and Kim Cooper |
Bones that are separate in small jerboas are fully fused in large ones, but the bone structures that are best at dissipating the stresses of jumping are only partially fused
Foot bones that are separate in small hopping rodents are fused in their larger cousins, and a team of researchers at the University of Michigan and University of California, San Diego, wanted to know why.
It appears that once evolution set jerboa bones on the path toward fusing together, they overshot the optimum amount of fusing—the structure that best dissipated stresses from jumping and landing—to become fully bonded.
This finding could inform the design of future robotic legs capable of withstanding the higher forces associated with rapid bursts of agile locomotion.
Jerboas are desert rodents that hop erratically on two legs to avoid predators. Across the jerboa family tree, these two legs can look a lot different: there are species that weigh just three grams to those that weigh 400 grams, with heavier species sporting vastly different bones of the feet, or metatarsals. Lighter jerboas are like most other mammals, including humans: their metatarsal foot bones are separate from each other.