An ostrich can’t taste a thing. Or won’t easily choke, for that matter, because of a pocket in its tongue. These are among the interesting findings that Dr Martina Crole has made while investigating the upper digestive tract of the world’s largest bird.
Dr Crole spent many a day in the field and laboratory using forceps and her fingers to manipulate and study still flexible fresh specimens. She wanted to find out exactly how it is possible for an ostrich not to choke even though it doesn’t have an epiglottis (which, in people for instance, prevents food or water from ending up in our wind pipe). It also has quite a wide glottis or opening to the wind pipe that needs to be closed during swallowing to prevent choking.
She worked out that when an ostrich’s glottis is closed and its tongue body moves backwards, the smooth tongue root becomes very folded. In the process, the pocket in the base of the tongue body also encases the rostral or front portion of the laryngeal mound with the closed glottis. For further stabilisation, the two projections at the base of the tongue (called the lingual papillae) hook over the closed laryngeal mound. Dr Crole has given this unique anatomical mechanism its own name: the linguo-laryngeal apparatus.
Over the past 200 years, a few other researchers have noticed the pocket in the tongue body of the ostrich, but so far no one could quite fathom why it was there. “They possibly didn’t realise its function because they did not use fresh specimens, but rather opted for material preserved in formalin or alcohol, which hardens the tissue and makes it rather inflexible,” says Dr Crole.
Her work led Dr Crole to discover that emu can taste. In the process, she has become the first researcher to confirm a sense of taste in any ratite species. However, she could not find any trace of taste buds in ostriches. This might help to explain why, in general, ostriches are not fussy eaters.
“I simply couldn’t find any taste buds” explains Dr Crole, who carefully dissected, removed and prepared samples for microscopy from the heads of ten ostriches and ten emus as part of her research. It will only be possible to be 100% certain that ostriches do not possess taste buds once genetic testing is done.
Dr Crole also found that both ostriches and emus have very sensitive bills with which they can touch and inspect objects. She believes an ostrich’s very well-developed sense of smell, touch and sight helps it to discriminate its food in the absence of taste. “A good sense of smell is characteristic of the ratites, with kiwis having the best smell of all,” she says. “An ostrich’s eye is larger than its brain, and therefore its vision is well developed.”
Her guess is that ostriches have no need for taste buds because of the way in which they eat. “They throw it to the back of their mouths, which doesn’t really give them an opportunity to do any tasting,” she speculates. “It could also be nature’s way of making it easier for them to eat so-called ‘bad tasting’ food.”
“These findings about ostriches and emus strengthen the case that ratite species should actually be seen as a unique group of birds that are very separate from other flying bird species,” she adds. Dr. Crole’s findings are very interesting and illuminating indeed.