Primary Source
Erickson, G.M., Gignac, P.M., Steppan, S.J., Lappin, A.K., Vliet, K.A., Brueggen, J.D., Inouye, B.D., Kledzik, D., Webb, G.J.W. (2012). Insights into the Ecology and Evolutionary Success of Crocodilians Revealed through Bite-Force and Tooth-Pressure Experimentation. PLOS ONE, 7(3): e31781. doi:10.1371/journal.pone.0031781.
The study measured bite forces from live, wild, or captive animals across all 23 living crocodilian species using a custom-built bite transducer. Each measurement represents the maximum voluntary bite recorded for the individual.
Bite Force by Species (Selected)
16,460 N -- Highest ever measured for any living animal
13,800 N -- Africa's apex aquatic predator
13,260 N -- Sufficient to crush turtle shells
11,300 N -- South Asian species
11,070 N -- Southeast Asian species; now classified Crocodylidae
9,340 N -- Florida and Central/South American species
7,960 N -- Critically endangered; SE Asia
7,340 N -- Largest caiman, Amazon Basin
3,820 N -- Most numerous crocodilian globally
1,510 N -- Long, narrow snout designed for fish; lowest of large species
Source: Erickson et al. 2012, PLOS ONE. Values are maximum voluntary bites from measured individuals; actual bite force varies with body size. Figures rounded to nearest 10.
Context: What Does 3,700 lbf Feel Like?
A bite force of 3,700 lbf (16,460 newtons) is difficult to visualise. For reference: a 3,700 lbf force applied to a narrow point approximates the weight of a small car focused through a single square centimetre. It would fracture the femur (thigh bone) of a large human instantly. It would crush the skull of a cape buffalo. It is approximately four times the bite force of a lion (around 900 lbf) and more than four times the bite force of a hyena (860 lbf).
The American alligator's bite force of 2,980 lbf, while less than the saltwater crocodile's, is still sufficient to shatter the shell of any freshwater turtle in North America and crush the skulls and limb bones of large mammals. Erickson's team noted that per unit body size, alligators are actually highly efficient biters -- their jaw closing muscles are anatomically optimised.
The gharial's 340 lbf is at the low end of the crocodilian range, consistent with its fish-specialised jaw anatomy. The narrow jaws lack the mechanical advantage for generating large compressive forces, but the interlocking needle teeth are effective for gripping slippery fish.
Why Crocodilians Have Such Strong Bites
Crocodilian jaw muscles are unusually large relative to body size. The adductor mandibulae externus, the primary jaw-closing muscle, fills much of the temporal region of the skull in crocodilians to a degree not seen in any other reptile. This enormous muscle mass, combined with the mechanical advantage of the jaw lever system (long skull, rearward muscle attachment), generates the extreme force measurements.
The jaw-opening force, however, is weak -- a counterintuitive finding. Crocodilians have very small muscles dedicated to opening the jaw. This is why a crocodile's jaws can be held closed with a person's hands or a rubber band in controlled situations: the closing force is enormous, but the opening muscles provide almost no resistance. This asymmetry makes biological sense: in water, suction-assisted mouth opening can supplement the weak muscles.
Erickson's study also showed that bite force scales predictably with body size across all crocodilian species, allowing estimation of bite force in large extinct species. The extinct Deinosuchus (Late Cretaceous, North America) is estimated to have produced bite forces exceeding 100,000 newtons based on skull dimensions.