Bite force quotient (BFQ) is a numerical value commonly used to represent the bite force of an animal adjusted for its body mass, while also taking factors like the allometry effects.

The BFQ is calculated as the regression of the quotient of an animal's bite force in newtons divided by its body mass in kilograms. The BFQ was first applied by Wroe et al. (2005) in a paper comparing bite forces, body masses and prey size in a range of living and extinct mammalian carnivores, later expanded on by Christiansen & Wroe (2007). Results showed that predators that take relatively large prey have large bite forces for their size, i.e., once adjusted for allometry. The authors predicted bite forces using beam theory, based on the directly proportional relationship between muscle cross-sectional area and the maximal force muscles can generate. Because body mass is proportional to volume while muscle force is proportional to area, the relationship between bite force and body mass is allometric. All else being equal, it would be expected to follow a 2/3 power rule. Consequently, small species would be expected to bite harder for their size than large species if a simple ratio of bite force to body mass is used, resulting in bias. Applying the BFQ normalizes the data allowing for fair comparison between species of different sizes in much the same way as an encephalization quotient normalizes data for brain size to body mass comparisons. It is a means for comparison, not an indicator of absolute bite force. In short, if an animal or species has a high BFQ this indicates that it bites hard for its size after controlling for allometry.

Hite et al., who include data from the widest range of living mammals of any bite force regression to date, produce from their regression the BFQ equation:

Or equivalently

where BF = Bite Force (N), and BM = Body Mass (g)

Carnivore BFQs

Animal BFQ Aardwolf 77 European badger 109 Asian black bear 44 American black bear 64 Brown bear 78 Domestic cat 67 Cheetah 119 Cougar 108 Coyote 88 Dhole 132 Dingo 125 African wild dog 138 Domestic dog 114 Singing dog 100 Arctic fox 97 Cape genet 48 Gray fox 80 Red fox 92 Gray wolf 136 Brown hyena 123 Spotted hyena 124 Jaguar 134 Jaguarundi 75 Leopard 98 Clouded leopard 137 Lion 128.1 Northern olingo 162 Sand cat 137 Sun bear 160 Least weasel 164 Spotted-tailed quoll 179 Tasmanian devil 181 Tiger 139 Thylacine 166 Table sources (unless otherwise stated):Fish That Fake Orgasms: And Other Zoological Curiosities, Matt Walker, Macmillan, 2007, pp. 98-9, (retrieved 15 August 2010 from Google Books)

Sex differences for BFQ in Canids

In a 2020 paper, the results of an estimation of the BFQ of various canid species separated by sex were published. Below there is a table with the BFQ averaged from the BFQ for each espécimen of each sex and for each species. BFQ coming from a single specimen for each sex in a given species will be marked with an asterisk.

Common name Scientific name Male BFQ Female BFQ Short-eared dog Atelocynus microtis 120.25 144.65 Senegalese wolf Canis lupaster anthus 140.66 126.24 *Golden jackal *Canis aureus *113.98 *113.25 Coyote Canis latrans 132.65 131.88 Grey wolf Canis lupus 130.59 141.06 Dingo Canis lupus dingo 133.67 127.57 New Guinea singing dog Canis lupus hallstromi 130.26 107.31 *Red wolf *Canis rufus *182.41 *124.33 Ethiopian wolf Canis simensis 144.27 158.21 Crab-eating fox Cerdocyon thous 118.24 116.41 Maned wolf Chrysocyon brachyurus 131.59 112.87 Dhole Cuon alpinus 148.80 147.85 Side-striped jackal Lupullela adusta 111.21 107.21 Black-backed jackal Lupullela mesomelas 126.95 115.11 Culpeo Lycalopex culpaeus 128.62 120.07 *Darwin's fox *Lycalopex fulvipes *154.63 *140.60 South American gray fox Lycalopex griseus 135.27 124.87 Pampas fox Lycalopex gymnocercus 127.1 116.76 Sechuran fox Lycalopex sechurae 128.84 138.14 Hoary fox Lycalopex vetulus 123.09 122.13 African wild dog Lycaon pictus 144.71 146.08 Common raccoon dog Nyctereutes procyonoides 136.49 134.94 Bat-eared fox Otocyon megalotis 107.14 126.26 Bush dog Speothos venaticus 160.28 154.63 Gray fox Urocyon cinereoargenteus 146.30 121.51 Island fox Urocyon littoralis 109.27 108.22 Bengal fox Vulpes bengalensis 128.47 139.10 Cape fox Vulpes chama 96.98 87.21 Arctic fox Vulpes lagopus 120.59 115.34 Kit fox Vulpes macrotis 109.77 110.99 Pale fox Vulpes pallida 89.47 98.21 Rüppell's fox Vulpes ruepellii 135.31 121.97 Swift fox Vulpes velox 122.57 120.38 Red fox Vulpes vulpes 116.25 118.97 Fennec fox Vulpes zerda 113 129.62

References