graphic

Most baby mammals steer clear of dining with their elders because they simply don't have the equipment to tackle tough adult food. But when opossum mothers wean their young, the brood graduates directly from milk to competing with mum for tasty grubs and insects. But how do their tiny jaws cope? Thirty years ago, Walter Greaves developed a mathematical model that predicted the pattern and strength of a bite, so Audrone Biknevicius decided to compare the strength of an opossum's bite across the generations to see how well it fitted Greaves' theory (p. 923).

Working with Elicia Thompson and Rebecca German, the team radiographed young opossum's heads from the time they were weaned until they were five months old, using the physical measurements to see how well Greaves' model predicted the strength and pattern of the animal's bite. Theory and real life agreed well, with both showing that the opossum's bite is strongest at the back of the jaw.

They also measured the animal's bite by getting youngsters and adults to bite down on a force transducer and measuring the force generated at the front, middle and back of the marsupial's long jaws. Not surprisingly, the young opossum's bite was weaker than the adult's, but when the team compared the bite's force on a weight-by-weight basis, the juveniles did better than the adults! Of course, the youngsters compensate for their weaker jaws with sharp teeth. And the young opossums probably make sure that they don't bite off more then their baby mouths can chew!

References

Thompson, E. N., Biknevicius, A. R. and German, R. Z.(
2003
). Ontogeny of feeding function in the gray short-tailed opossum Monodelphis domestica: empirical support for the constrained model of jaw biomechanics.
J. Exp. Biol.
206
,
923
-932.