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)
16,414 N -- Highest ever measured for any living animal (531 kg individual)
9,452 N -- Highest of the alligatorids; crushes turtle shells
7,295 N -- South Asian species
6,450 N -- Long-snouted Southeast Asian species
4,577 N -- Critically endangered; SE Asia
4,355 N -- Florida and Central/South American species
4,310 N -- Largest caiman, Amazon Basin
3,172 N -- Tested individuals were small (~86 kg); large wild adults scale far higher
2,006 N -- Long, narrow fish-catching snout; low compressive force
1,303 N -- Most numerous crocodilian globally; small-bodied
Source: Erickson et al. 2012, PLOS ONE, Table 1 (maximum recorded bite force per species). Newton figures are as tabulated; pound-force values are rounded conversions.
Read this before comparing species
Erickson's central finding was that bite force scales tightly with body size. Each figure above is the strongest bite recorded from the largest individual of that species the team managed to test, not a fixed property of the species. The ranking therefore tracks the size of the animals sampled as much as the animal itself.
The clearest example is the Nile crocodile. The two Nile crocodiles in the study averaged about 86 kg, so their measured bite (3,172 N) sits low on the list. A 750 kg wild adult Nile, the size this species actually reaches, would by Erickson's own body-mass regression bite in the same league as a large saltwater crocodile. The saltwater crocodile tops the table partly because the team tested a 531 kg giant. Do not read this list as "weakest to strongest species".
Context: What Does 3,700 lbf Feel Like?
A bite force of 16,414 newtons (about 3,700 lbf) is difficult to visualise. For reference: applied to a narrow point it 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. Erickson's team noted it eclipses the strongest bite recorded in any land mammal, 4,500 N (about 1,010 lbf) in the spotted hyena.
The largest American alligator in the study bit at 9,452 newtons (2,125 lbf), the strongest of any alligator or caiman measured, and enough to shatter the shell of any freshwater turtle in North America and crush the limb bones of large mammals. Erickson's team noted that per unit body size, alligators are highly efficient biters -- their jaw closing muscles are anatomically optimised.
The gharial's 2,006 newtons (450 lbf) is low for its length, 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.