Ever try playing softball after a barbecue? Doesn’t work so well, does it? Now imagine trying the long jump–just the thought makes me a little queasy. But animals in the wild have to do this all the time. Does it affect their performance? Lizards and other animals are known to have their running abilities diminished by carrying a large load, such as a meal or eggs, but no one previously has looked at the effect of increased weight on jumping.
Until now. In a recent paper, Kuo et al. increased the weight of green anoles 30% by wrapping a weighted cloth around their midsection and then induced them to jump (pdf of the paper here). As a control, they wrapped light paper around the lizard in the same manner. As you might expect, the encumbered anoles were less proficient leapers; jump distance declined 18% and takeoff speed 10%. However, their accuracy, as judged by ability to land on a target, was not affected.
The next question, of course, is whether this diminution is relevant in nature. Lizards will sometimes eat very large prey, so the scenario is real. Are post-prandial anoles in jeopardy? Years ago, Duncan Irschick (in whose lab this work was conducted) and I published a study in which we showed that on narrow surfaces, several anole species suffered decreased sprinting ability, but jump distance was not affected. We predicted that, as a result, anoles would rely more on jumping for escape on narrow surfaces as opposed to their manner of fleeing on broad surfaces; field trials confirmed this prediction. Kuo et al. report that although jump distance is diminished when carrying more weight, the effect appears to less than the decrease in sprint speed. Thus, it may be that an anole’s best bet when it’s tummy is full is to lie low until the meal is digested, but if forced to flee, they may opt to jump rather than run. Sounds like a cool project to me!
One more thing: nice videos of trials from this and other experiments can be seen on the Irschick Lab Youtube Channel.