Cat tongue biomechanics and feline grooming mechanics are revealing how species from house cats to lions manage body temperature and coat care, according to a study by Alexis Noel and David Hu at Georgia Tech published in 2018 in PNAS. Researchers discovered that the backward-pointing spines on feline tongues, known as filiform papillae, are hollow rather than solid cones, functioning as precision wicks that deliver saliva deep into the undercoat.
Micro-CT Scans Reveal Hollow Papillae Structure
For decades, anatomists relied on a 1982 paper published in Acta Anatomica by Boshel, Wilborn, and Singh that characterized cat tongue papillae as solid cones. That long-standing assumption shifted when Noel and Hu ran papillae from six cat species through a micro-CT scanner. The scans revealed that each papilla features two cavities: a base anchored into soft tissue and a U-shaped scoop at the tip.
When the authors touched the tips with food dye, fluid climbed into the scoop in under a tenth of a second, matching Washburn’s law for wicking into a half-pipe. According to the study, fluid stays securely inside the cavity once wicked, even when the papilla is inverted. A domestic cat carries roughly 290 large papillae in the active region of the tongue, holding a total volume of about 4 microliters—roughly one-tenth of a single eyedropper drop.
Did you know? While a flat cat tongue surface only soaks fur to a depth of 0.54 millimeters—leaving the undercoat dry—the hollow papillae are long enough to push through and deposit saliva directly at the roots of the hair strands.
Papilla Length Across Six Felid Species
Physical measurements across a thirty-fold range in body weight show that papilla height barely changes as cats get bigger. According to the Georgia Tech research team, the fitted relationship between papilla height and body mass remains nearly flat across six species, including the domestic cat, bobcat, cougar, snow leopard, tiger, and lion.
The mean height sits at 2.3 millimeters, give or take 0.2. Lion papillae measured the longest in the set at 2.7 millimeters—only about a third longer than a house cat’s spines. Scaled geometrically by body mass, a lion should possess spines three times longer. Instead, a lion’s tongue is vastly larger than a tabby’s, but its individual hooks are remarkably close in size, spread across a much broader surface area.
Grooming and Thermal Regulation in Felines
Because cats possess sweat glands exclusively on their paws, researchers have long suspected that grooming plays a major thermal role. Thermal imaging recorded in the PNAS study documented temperature differences of up to 17 degrees Celsius between wetted skin and topcoat following a single lick.
Based on their mathematical models, saliva delivered by papillae can supply about 1.3 watts of cooling. This accounts for under a quarter of the roughly 5.7 watts that a 2.2-kilogram cat must shed, with conduction, convection, and radiation managing the rest. This figure represents an upper bound from a theoretical model rather than a direct measurement of an active animal in high heat, as it assumes every papilla refills completely inside the mouth after every lick.
Feeding Mechanics: Meat Stripping vs. Gripping
Zoo institutions frequently credit tongue spines with distinct culinary duties. Zoo Atlanta’s carnivore team describes the papillae as aiding in the removal of hair from flesh and flesh from bone. Meanwhile, Denver Zoo’s African lion fact sheet lists the backward-curving spines as tools for scraping meat from bone and for grooming, omitting any claim about separating hides.
The 2018 PNAS study, however, measured grooming mechanics rather than feeding behavior. In a separate review titled The tongue as a gripper published in the Journal of Experimental Biology, the authors note that rigid papillae measuring above one millimeter serve grip and tissue penetration. While cat tongues hook into raw meat to hold it, the authors point out that how those hooks tear flesh without tearing out of the tongue itself remains unstudied in detail.
Ultimately, lions cut their food using carnassial teeth—meaning a biological rasp works behind a set of blades rather than replacing them.
Comparative Morphology Across the Cat Family
Descriptive mapping of feline tongues continues to expand through species-specific research. Sadeghinezhad and colleagues published a morphological study of the Persian leopard tongue in Anatomia, Histologia, Embryologia, while Freire and colleagues detailed the papillary architecture of the ocelot tongue in the same publication.
While these morphological papers map form across the cat family in high detail, very few measure actual mechanical force. The popular understanding of how feline tongues operate relies on anatomy, captive-animal observations, and inference from shape, as researchers have yet to instrument a lion’s tongue while working a carcass.
Frequently Asked Questions
What material are lion tongue spines made of?
The spines on a lion’s tongue are made of keratin, which is the exact same material found in claws and human fingernails.
Why do cat licks feel like sandpaper?
Cat licks feel abrasive because of backward-pointing hollow spines called filiform papillae, which act like a wood rasp against skin and fur.
Do lions have much larger tongue spines than house cats?
No. Despite a massive difference in body size, lion papillae average 2.7 millimeters long, which is only about a third longer than the spines found on a domestic house cat.
How much cooling does cat saliva provide during grooming?
Thermal models suggest saliva delivery can supply about 1.3 watts of cooling, which covers under a quarter of the thermal load a small cat must shed.
Explore More: Want to stay updated on the latest developments in biomechanics and wildlife research? Subscribe to our newsletter or explore our archives for more deep-dives into animal anatomy.