I've added a PubMed study on canine bite force, the only one of its type that I've been able to find: Measurement of bite force in dogs: a pilot study.
A force transducer was developed to measure bite force in dogs. A total of 101 readings was obtained from 22 pet dogs ranging in size from 7 to 55 kg. Bite forces ranged from 13 to 1394 Newtons with a mean for all dogs of 256 Newtons and a median of 163 Newtons. Most measurements fell within the low end of the range, with 55% of the biting episodes less than 200 Newtons and 77% less than 400 Newtons.1 newton = 0.224808943 pounds force, so 1394 newtons would be 313.38 pounds force, according to OnlineConversion.com. The dogs in the study ranged in weight from 15.4 lb to 121 lb.
From an Animal Planet news story:
Sept. 15, 2003 — Cheetahs chomp hard and even humans can bite through an ear, but one animal reigns supreme when it comes to possessing the strongest bite — the alligator.When Brady Barr measured the bite force of various animals for a National Geographic program, a hyena again was measured at 1000
American alligators, Alligator mississippiensis, have the most powerful bite force ever measured. According to a recent study published in the Journal of Zoology of London, alligators snap their strong jaws shut with a force of 2,125 pounds, or with about as much force as a mid-size sedan falling on top of someone.
"Bite force is linked to the size of an animal," explained Kent Vliet, a University of Florida zoologist who headed up the study. "Since the report was published, we measured the bite of a wild gator, even bigger than Hercules at 13 1/2 feet in length missing the end of his tail. He bit down with a force of 2,960 pounds."
To put the record measurement into perspective, hyenas, which are bone-crushing mammals, have a bite force of 1,000 pounds, slightly more than the 940 recorded for lions. Dusky sharks manage 330 pounds of force, and a common dog, the Labrador, bites with 125 pounds of force. Humans surprisingly beat out the pet dog, and measured in at 170 pounds of force.