Forked tongue

Forked tongue of a carpet python (Morelia spilota mcdowelli)

A forked tongue is a tongue split into two distinct tines at the tip; this is a feature common to many species of reptiles. Reptiles smell using the tip of their tongue, and a forked tongue allows them to sense from which direction a smell is coming.[citation needed] Sensing from both sides of the head and following trails based on chemical cues is called tropotaxis.[1] It is unclear whether forked-tongued reptiles can actually follow trails or if this is just a hypothesis.[2][3][4]

Forked tongues have evolved in these squamate reptiles (lizards and snakes) for various purposes. The advantage to having a forked tongue is that more surface area is available for the chemicals to contact and the potential for tropotaxis.[5] The tongue is flicked out of the mouth regularly to sample the chemical environment. This form of chemical sampling allows these animals to sense non-volatile chemicals, which cannot be detected by simply using the olfactory system.[6][7][8] This increased ability to sense chemicals has allowed for heightened abilities to identify prey, recognize kin, choose mates, locate shelters, follow trails, and more.[8]

Forked tongues have evolved multiple times in squamates. It is unclear, based on the morphological and genetic evidence, where the exact points of change are from a notched tongue to a forked tongue, but it is believed that the change has happened two to four times.[1][9] A common behavioral characteristic that has evolved in those with forked tongues is that they tend to be wide foragers.[1][10]

Hummingbirds also have tongues that split at the tip.[11] Galagos (bushbabies) have a secondary tongue, or sublingua, used for grooming, hidden under their first.[12]

  1. ^ a b c Schwenk, K. (March 1994). "Why snakes have forked tongues". Science. 263 (5153): 1573–1577. Bibcode:1994Sci...263.1573S. doi:10.1126/science.263.5153.1573. PMID 17744784. S2CID 28010522.
  2. ^ Kubie, J.L.; Halpen, M. (1979). "Chemical senses involved in garter snake prey training". Journal of Comparative and Physiological Psychology. 93 (4): 648–447. doi:10.1037/h0077606.
  3. ^ Waters, R.M. (1993). "Odorized air current trailing by garter snakes, Thamnophis sirtalis". Brain, Behavior and Evolution. 41 (3–5): 219–223. doi:10.1159/000113841. PMID 8477343.
  4. ^ Parker, M.R.; Young, B.A.; Kardong, K.V. (2008). "The forked tongue and edge detection in snakes (Crotalus oreganus): an experimental test". Journal of Comparative Psychology. 122 (1): 35–40. doi:10.1037/0735-7036.122.1.35. PMID 18298279.
  5. ^ Cooper, W.E. (April 1995). "Evolution and function of lingual shape in lizards, with emphasis on elongation, extensibility, and chemical sampling". Journal of Chemical Ecology. 21 (4): 477–505. doi:10.1007/BF02036744. PMID 24234178. S2CID 33016552.
  6. ^ Baxi, K.N.; Dorries, K.M.; Eisthen, H.L. (January 2006). "Is the vomeronasal organ system really specialized for detecting pheromones?". Trends in Neurosciences. 29 (1): 1–7. doi:10.1016/j.tins.2005.10.002. PMID 16271402. S2CID 6487660.
  7. ^ Shine, R.; Bonnet, X.; et al. (February 2004). "A novel foraging mode in snakes: browsing by the sea snake Emydocephalus annulatus (Serpentes, Hydrophiidae)". Functional Ecology. 18 (1): 16–24. doi:10.1046/j.0269-8463.2004.00803.x.
  8. ^ a b Schwenk, K. (January 1995). "Of tongues and noses, chemoreception in lizards and snakes". Trends in Ecology & Evolution. 10 (1): 7–12. doi:10.1016/S0169-5347(00)88953-3. PMID 21236937.
  9. ^ Townsend, T.M.; Larson, A.; et al. (October 2004). "Molecular phylogenetics of Squamata: the position of snakes, Amphisbaenians, and Dibamids, and the root of the squamate tree". Systematic Biology. 53 (5): 735–757. doi:10.1080/10635150490522340. PMID 15545252.
  10. ^ Cooper, W.E. (1995). "Foraging mode, prey chemical discrimination, and phylogeny in lizards". Animal Behaviour. 50 (4): 973–985. doi:10.1016/0003-3472(95)80098-0. S2CID 53189324.
  11. ^ Bill Hilton Jr (2007-06-12). "Hummingbird Internal Anatomy and Physiology". Operation RubyThroat: The Hummingbird Project. Hilton Pond Center for Piedmont Natural History. Retrieved 2008-02-13. The tongue itself splits in the floor of the mouth
  12. ^ Monkeyland. "Bushbaby - Galago moholi". Meet Our Primates. Monkeyland Primate Sanctuary. Archived from the original on 2007-10-22. Retrieved 2008-02-13. equipped with a second, pointy tongue underneath their normal one