Wednesday, April 04, 2012

How hard can giant crocodiles bite?

A recent paper published in the journal PLos ONE called "Insights into the Ecology and Evolutionary Success of Crocodilians Revealed through Bite-Force and Tooth-Pressure Experimentation" presents the results of a study that was started over a decade ago measuring and comparing the bite force of different crocodilian species. I've been waiting for this to appear for years (I can almost say decades!) as I was superficially involved in the Australian work including catching wild C. johnstoni that were used. I'd also designed a very low-budget bite force meter and measured C. porosus bite force prior to this, and obtained the measure of 3,800 lbs with a 15.1 ft (4.6 m) captive saltie housed at Crocodylus Park which came in pretty close to the more accurate measurement obtained for this paper. So we've known for a while that these kinds of forces were normal for large crocodiles.

But one of the most interesting, and unexpected findings of this work was that bite force isn't dictated by jaw size and shape significantly. It plays a role, but there's no clear pattern. What does influence bite force primarily is body mass (and therefore size). That shouldn't be surprising - the bigger the croc, the harder it bites. But slender-snouted species like C. johnstoni can put the bite on as well as C. porosus can at similar sizes, which is a very cool finding. Gharials let the longirostrine side down a little, with a lower bite force relative to body mass, but they compensate for having a very specialised jaw design and also by being extremely cool.

Of course one of the reasons I've been waiting for this paper is to find out the relationship between body size (or mass in this case) and bite force with a good-sized dataset. With that information, we can start to ask some interesting speculative questions. For example, how much bite force could the world's largest crocodile generate? Let's try this with Lolong shall we? The equation used is as follows:

(Y(force, N) = 29.632x(body mass, kg)+569.35

So Lolong's mass is 1,075 kg, which means his bite force is estimated at 32423.75 Newtons, or 7289.1 lbs (about 3.3 tonnes of force!). Wow.

But what about Deinosuchus riograndensis, at an estimated 11 metres (36 feet) and therefore one of the largest crocs that has ever lived? Using figures for living crocs, his body mass is estimated at 3,450 kg, and therefore his bite force could have been a staggering 102,803 Newtons (23,102 lbs) which is 10.5 tonnes of bite pressure. Holy cow! No wonder these guys were capable of snacking on dinosaurs.