January 24, 2008

Dog bites and bite force

Memo to Merritt Clifton: here's what good GSDs have really been doing for the past 100 years.

This just in: big dogs bite harder than small dogs. [In other news: this fact is completely irrelevant if you are six weeks old.]

Contrary to urban legend, canine bite force is a size thing, not a breed thing. The larger the dog, the greater the potential for damage [but see mitigating factors above and in the final blockquote, below]. If you were to ask the gentleman wearing the German shepherd on his sleeve, he'd tell you: big dogs bite harder. [Protection-sport decoys are the unsung experts on bite force.] A 100 lb SchH III Rottweiler bites a good deal harder than his 45 lb pit bull counterpart.

There is just one study that I've been able to find in PubMed regarding bite force in dogs. Here's the link. The abstract:
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. I'm betting the dog that weighed 55 kg (121 lb) was responsible for the highest bite-force measurement in the study.

So how on earth did the 2003 Handbook of Pediatric Emergency Medicine come up with the following nonsense on bite force? No footnotes or references, by the way:

Aside from treating breed identification as if it carried weight [the CDC has indicated for a decade now that it does not], the Handbook's "2000 psi in Rottweilers [...] enough to tear through sheet metal" is pulled out of thin air. Some Rotties are hard-biting dogs, but 2000 psi? For that you need an alligator.

From Animal Planet News:
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.

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.
Here's a video of a Rottie from Norway [where tail docking has been illegal since 1987, in case you were wondering]:



Strong, yes -- but the jaw strength of a 600 lb alligator? Nooo.

When Brady Barr measured the bite force of various animals for a National Geographic program, the hyena again was measured at 1000 psi pounds of force. The lion's bite measured 691, the shark 669, and a Rottweiler at 328 psi pounds of force. A pit bull was measured at 235 psi pounds of force. [Edited January 27, 2007. See "note from a scientist," below.]

Ah, but don't pit bulls have a "unique bite, hold, shake" style of attack that makes them ever so much more "potentially dangerous" than any other breed?

There are two things that come to mind when I'm subjected to this particular example of boundless, staggering ignorance:
1) Have you ever seen a protection-sport dog work a sleeve or a bite suit? For that matter, have you ever seen a puppy with a sock?
2) Which pit bull? I keep pit bulls and border collies, and at one time or another, over the years, each of my pit bulls has been bloodied by a collie bitch. In each case the pit bull did nothing in response but yip and retreat. In the worst instance my heart dog was nailed in the side so badly by one of the collies he needed sutures and a drain. The collie responsible for the damage didn't have a mark on her.

Last year my male pit bull was in such agony from injury-exacerbated arthritis of the spine [he's OK now] that he was trembling violently and screaming when handled, but when the vet touched him where the pain was worst, all he did was bump her with his closed mouth. He could easily have bitten her -- he turned towards her arm faster than anyone could have stopped him -- but with people [as opposed to possums, say] he has extraordinary bite inhibition. And my vet knows and trusts him. To quote BAD RAP, dogs are individuals -- stereotype at your peril.

Dog bites are more complex events than ignorant people would have you believe. This terrific post by Rinalia [from an open-to-everyone section of the Pit Bull Forum] explains:
How hard a dog bites depends on their bite inhibition (how hard or soft a dog bites), their past experiences and their bite threshold (how quick they are to use teeth). The severity of a bite depends on the aforementioned factors plus size of dog, size of victim, location of bite, whether the dog bites once or multiple times, etc.

Let's just say I have four 60-lb dogs. I have one dog each with the following characteristics:
Dog #1: low bite threshold & low bite inhibition = quick to bite and bites hard
Dog #2: low bite threshold & high bite inhibition = quick to bite and bites soft
Dog #3: high bite threshold & low bite inhibition = slow to bite and bites hard
Dog #4: high bite threshold & high bite inhibition = slow to bite and bites soft

And that is not to say that all dogs fit into those categories. There is a whole spectrum - dogs with moderate bite thresholds, moderate bite inhibitions. Dogs who bite once, dogs who bite multiple times. Dogs who prefer legs and arms, dogs who prefer backs or stomachs.

At the outset, It would seem like Dog #1 is the most dangerous - he'll bite you at the drop of a hat and he'll bite you hard...but maybe he only bites once. But let's say Dog #3, when he is FINALLY provoked into biting, likes to bite multiple times and aims for the neck.

Add to that dog size, victim size, location of bite, warning behaviors, etc. ad nauseam, you can quickly see that there is no logic in making a statement like "Pit bulls cause more damage than other breeds." Such a generalized statement is both inaccurate and ignores the myriad factors that cause a dog to bite.

Breed is perhaps the LEAST important factor.
What a pity this is all over the heads of certain idiots in Ontario and Denver -- the dog-killing idiots that make Michael Vick look like an amateur. These legislators could have saved far more children and adults from harm by addressing swimming pool safety or handing out bicycle helmets, but with the pitchfork-waving mentality common to all bigots they decided instead to confiscate good dogs from law abiding citizens, to confiscate family pets and kill them, based on nothing more than a broad skull or a brindle coat.


"[Laws] banning breeds will not make you safer, and the illusion that they will do so is dangerous to humans and unfair to dogs." [Dr. Karen Overall]

*Note from a scientist:
"A newton equals 0.2248 pound force, which is the force a one pound weight would exert on whatever it is resting on on Earth. Thus 12 newtons = 2.7 pound weight equivalent, and 9452 newtons is equivalent to 2125 pounds of pressure exertion on an object. A newton does not distinguish the area of the force it is exerting on, ie 12 newtons or 2.7 pounds if it was pushing against a square inch, then it would be 2.7 pounds per square inch, but if it was an exertion on 12 square inches, then it woud be 2.7 pounds per square foot. It was interesting to see in the article that human and lab dog have about the same bite force, and wolves only have about 2.5 times more bite force than humans."
See the comment from Caveat in response to this post, which includes the following:
"I corresponded with Canada's version of Beck/Clifton, Stanley Coren, when I found him making the '2000 psi' statement in a little book I'd bought about 'dangerous dogs'. He switches it between 'rottweilers' and 'pit bulls' depending on the day of the week.

He could not support it, had no idea where he'd heard it, hemmed and hawed and ducked and weaved but didn't have a reference for it.

Trouble is, people like Coren or Beck, who the media think are experts, or journals such as the Pediatric one, merrily repeat these things and they put another put another nail into the coffin, not only of certain breeds, but of dog ownership as a whole."
Caveat's 2006 bite force article can be found here, and includes the "Note from a scientist" I 've quoted above.

8 comments:

Mac`s Gang said...

[quote]Last year my male pit bull was in such agony from injury-exacerbated arthritis of the spine[/quote]

I can relate to this,my male "Pit Bull" unfortunately had cancer in his spine,but yet when handled he just leaned into people for comfort.
I would have bitten.

Unfortunately the Press and most of the public are going to seize upon
the following words

Pit Bull Terrier
47%
Sheet metal
Rottweiler
2000 psi

They are looking for sound bites,pictures(Beware of dog signs),anything that fits their agenda now.

But I`m off to read all the great info you have provided so I will be able to defend my next Pit Bull in court.

Thanks for all the research.
Appreciate it.

Caveat said...

Good post, this can't be said often enough. I'm on the run this morning but will read it in detail later.

I put something up on this in 2006, thought you might be interested:

http://caveat.blogware.com/blog/_archives/2006/7/23/2152355.html

It gets read quite often to this day. Not great writing but I hope it gets the point across to people.

There is a big problem with journals such as the Pediatric one you mention making unsupportable statements about bite pressure.

Bite pressure, the 'psi' measurement, is not the same as bite force, which is measured in Newtons and is not area-specific. At my post is a link to how to convert Newtons to psi.

In the Lindner study you cited (the only study of its kind and a pilot at that) the highest bite force was for a Rottweiler with a lot of training. It measured at 1394 N, which is around 330 pound-force which is - wait for it - about .202 psi. Yes, .202 psi.

I corresponded with Canada's version of Beck/Clifton, Stanley Coren, when I found him making the '2000 psi' statement in a little book I'd bought about 'dangerous dogs'. He switches it between 'rottweilers' and 'pit bulls' depending on the day of the week.

He could not support it, had no idea where he'd heard it, hemmed and hawed and ducked and weaved but didn't have a reference for it.

Trouble is, people like Coren or Beck, who the media think are experts, or journals such as the Pediatric one, merrily repeat these things and they put another coffin into not only certain breeds, but dog ownership as a whole.

I might contact the journal, ask them to query the authors about the source of the measurement because I've looked 15 ways to Sunday and I can't find it. Either can the people who casually repeat it. Go figure.

Luisa said...

Thanks so much for this comment -- I'm editing the post to add Alan's "note from a scientist" as well as your remarks on the Beck/Clifton/Coren phenomenon. A phenomenon that deserves a post of its own, really.

Caveat said...

Oops - I meant 'put another nail into the coffin of...'

I need a holiday.

Thanks for the link, Luisa! I'll return the favour later on this morning - your article is great and keeps the heat on these charlatans!

Incidentally, I believe another important factor in bite-force is length of muzzle.

The longer the muzzle, the more force in the bite.

A dachshund like my old guy has a grip like a moustrap. My Griffs, with their monkey faces, have adequate force for chewing or eating but a very weak jaw by comparison with the old guy.

I haven't seen this anywhere, not that I've searched too hard, but it seems reasonable.

Luisa said...

"favour"? Por favor ;~)

Interesting thoughts on muzzle length. Have you seen these two links?

Anonymous said...

"The 1992 Guinness Book of Records records the achievement of a bite strength of 975 lbf (4337 N) for two seconds."

Although this is obviously a freak case. It would suggest that humans have the capability to exert more force in a bite than most dogs. This is actually a result of humans having a much smaller jaw than most dogs.

"What distinguishes the masseter is not anything special about the muscle itself, but its advantage in working against a much shorter lever arm than other muscles."

A long muzzle is a disadvantage when applying force to a bite. A dog with a shorter solid jaw should "theoretically" be able to bite a lot harder.

To use an analogy consider the difference between a pair of long bladed hedge trimmers and a lopper designed to cut through branches. Due to the additional leverage offered by the loppers you will be able to apply much more force with the same effort, this theory applies to jaws as well.

Incidentally I would be interested to know how they measured the force of a bite. Logic would dictate that a bite would be far more powerful when it originates from the back of the mouth. Animals with long jaws like an Alligator should have a huge variance in the force their mouths can exert from the front teeth to the back.

One more thought... How do we know that these animals are biting with their full force? You can't talk to an animal and inform it that it has to apply 100% effort to its bite. I am sure that the man who managed the 975lb bite was very motivated, and had probably developed some kind of weird bite training regime; the same cannot be said of our animal friends!!!

Anonymous said...

test of bite force in national geographic: tosa-inu(81kg of weight): 556livres = 251kg ; american bulldog: 305livres = 138kg ; belge shepherd(malinois): 195livres = 88kg ; holland shepherd: 105kg . / The maximum of bite force of big dogs(mastiffs) and of big wolves , is around of 200kg at 300kg of pressure maximum !

Anonymous said...

The maximum of bite force(force de morsure / machoire) officiel of a man human , is of around 120kg ( test bite force of monkeys: orang-outan: 385livres = 174kg(estimation maximum of bite force of orang-outans: + of 200kg of pressure !) ; rhesus macaque: 500newtons = 50kg ! / Différents tests of bite force(force de morsure / machoire): Komodo dragon: 74kg ; turtle snapp(tortue-alligator): 455kg ; devil tasmanian: 395livres = 178kg ; rat: 50newtons = 5kg ; macaw parrot(perroquet ara):167livres = 75kg ; 2 big crocodiles: 2500livres and 5000livres( 1133kg et 2265kg ) ; 2 pit-bulls: around 107kg et around 127kg ; 2 rottweilers: 149kg et around 161kg ; humans(mens): 58kg , 77kg , 89kg et 120kg(records) !