The myth of the dental damage

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Dental damage occurs in some cetaceans under human care, there are dolphins and orcas that can have some of their teeth wear or even broken. This situation has never been hidden, on the contrary it was identified as a veterinary concern and published in a scientific journal almost 30 years ago[1], and since then several therapies have been developed to avoid the tooth pain and mitigate the risk of infection. On the other hand, dental damage is not exclusive of cetaceans under human care, the very same lesions can be found in wild dolphins and killer whales [2] [3].  Criticism against dolphinaria is misleading, as anti-zoo groups never mention dental damage in wild cetaceans when they expose teeth wear and broken tooth of dolphins and orcas under human care.

In this case the myth is not about the dental damage itself, but about its causes. Recently it has become a common argument for some anti-zoo groups to use dental damage as the definitive prove of boredom, pain and suffering. They have even presented dental problems as deadly hazard for cetaceans under human care. Those are just unfounded speculations, as there is not a single scientific study that relates dental damage in killer whales and boredom, nor about cetacean deaths related with dental problems. On the other hand, it is highly speculative to assume that dental damage produces pain or suffering, as it has been proven with other animals [4], the pain can only be assessed with behavioural studies.  It is not possible to infer pain from a picture of a broken tooth.

Dental wear has been described as a common phenomenon in wild cetaceans [5]. There are many documented cases of dental damage in wild cetaceans for many different reasons (abrasive food, manipulation of abrasive objects, hunting prey, agression, etc.). Its occurrence is influenced by tooth anatomy, animal physiology, biomechanics and behaviour. When the frequencies of occurrence, location and intensity of dental wear in ten species of dolphins from southern Brazil was evaluated only one species presented less than 50% of teeth worn[6]. This is also the case for killer whales. The first Antarctic killer whale stranded in 1974 had 25 broken teeth [7], a killer whale stranded in South Africa in 1969 presented a severe asimetric teeth wear [8].

Jaw abscesses and dental disease are a commonly observed problem in stranded killer whales in Washington state [9] and are caused by heavy tooth wear down to the gum line resulting in exposure and infection of the pulp cavity and surrounding tissue [10] [11] [12]. The earliest scientific publications referring this dental damage in killer whales are 70 years old. The dental problems in the wild populations of killer whales are so well known by the scientists worldwide, that has been considered even in the recovery plans for Southern Resident Killer Whales [13] and also for the killer whales in Gibraltar Strait[14]. In killer whales teeth typically have extremely limited function in food processing, so how can a broken teeth compromise the welfare of an animal? If the broken tooth does not produce any pain, inflammation or infection, there will not be significant effect in the welfare of an individual.

In 2017 a scientific paper describing the dental damage in captive killer whales was published based on an exhaustive analysis of multiple pictures of several killer whales in zoo settings. There wasn’t an exhaustive analysis of the whole population of killer whales under human care, but biased to some selected individuals. And there was no data from wild killer whales for comparison, not a detailed discussion regarding the abundant scientific literature about tooth damage in stranded orcas [15].  The main goal of the paper was to infer pain and suffering from a set of pictures, but without performing any other behavioural study [16], or veterinary diagnostic. As a result, the conclusions were highly speculative and deem invalid to assess the welfare status of the killer whales.

When the anti-zoo groups speculate about the pain produced by a broken tooth they fail to consider the same (and very frequent) situation in a wild killer whale. Can you imagine how painful it must be having dental damage and infections and not being able to visit a dentist in your entire life? Well this is the situation of wild killer whales, many of them with severe tooth damage [17] [18] [19] [20](even worst that the damage you can see in any killer whale under human care), but they would never be able to get veterinary care. They have to live with these painful wounds without any relief every single day of their entire lives. If somebody is truly concerned about the welfare problems produced by dental damage, they should be focusing on the wild killer whales. Under human care the welfare of the orcas with dental damage is not compromised, as veterinarians can relief the pain and treat the lesions avoiding inflammation or even infections. Obviously, as any veterinarian can confirm, all the treatments are carried out without any pain, using local anaesthetics. The fact is that when a tooth drill has to be performed (rarely) the animals participate voluntarily; keeping the mouth open while the procedure is carried out.

For more please visit:
https://www.loroparque.com/pdf/ENG_carta_wk_n1_AF_LETTER_Anti-Captivity_Arguments_Scientifically_Debunked.pdf

[1] Graham, M. S., & Dow, P. R. (1990). Dental care for a captive killer whale, Orcinus orca. Zoo Biology, 9(4), 325–330. https://doi.org/10.1002/zoo.1430090408

[2] Ford, J. K., Ellis, G. M., Matkin, C. O., Wetklo, M. H., Barrett-Lennard, L. G., & Withler, R. E. (2011). Shark predation and tooth wear in a population of northeastern Pacific killer whales. Aquatic Biology, 11(3), 213-224

[3] Rica, C. (1996). A report of killer whales (Orcinus orca) feeding on a carcharhinid shark in Costa Rica. Marine Mammal Science, 12(4), 606-611.

[4] Fleming, M., & Burn, C. C. (2014). Behavioural assessment of dental pain in captive Malayan sun bears (Helarctos malayanus). Animal Welfare, 23(2), 131–140. https://doi.org/10.7120/09627286.23.2.131

[5] Loch, C., & Simões-Lopes, P. C. (2013). Dental wear in dolphins (Cetacea: Delphinidae) from southern Brazil. Archives of Oral Biology, 58(2), 134–141. https://doi.org/10.1016/J.ARCHORALBIO.2012.08.002

[6] Loch, C., & Simões-Lopes, P. C. (2013). Dental wear in dolphins (Cetacea: Delphinidae) from southern Brazil. Archives of Oral Biology, 58(2), 134–141. https://doi.org/10.1016/J.ARCHORALBIO.2012.08.002

[7] Castello, H. P., Tomo, A. P., & Panizza, J. S. (1974). First Antarctic record of a killer whale stranding. Sci Rep Whales Res Inst. Retrieved from https://www.icrwhale.org/pdf/SC026255-258.pdf

[8] Best, P. B., Meÿer, M. A., Thornton, M., Kotze, P. G. H., Seakamela, S. M., Hofmeyr, G. J. G., … Steinke, D. (2014). Confirmation of the occurrence of a second killer whale morphotype in South African waters. African Journal of Marine Science, 36(2), 215–224. https://doi.org/10.2989/1814232X.2014.923783

[9] Wiles, G. J. (2004). Washington State status report for the killer whale. (Orcinus orca). Washington Department Fish and Wildlife, Olympia. 106pp. 2004., (November), 106.

[10] Carl, G. C. (1946). A school of killer whales stranded at Estevan Point, Vancouver Island. Provincial Museum of Natural History and Anthropology.

[11] Tomilin, A. G. (1967). Mammals of the USSR and adjacent countries. vol. 9, Cetacea. Israel Program Sci. Transl, (1124).

[12] Caldwell, D. K., & Brown, D. H. (1964). Tooth wear as a correlate of described feeding behavior by the killer whale, with notes on a captive specimen. Bulletin of the Southern California Academy of Sciences63(3), 128-140.

[13] Marine, N., Service, F., & Office, N. R. (2008). Recovery Plan for Southern Resident Killer Whales (Orcinus orca), 1–251.

[14] Onservación, P. L. A. N. D. E. C., Orcas, D. E. L. A. S., Orca, O. R., El, E. N., Spañol, M. E. E., Adyacente, Y. A. T., … Gauffier, P. (n.d.). “p c ( o ) m e a .”

[15] Jett, J., Visser, I. N., Ventre, J., Waltz, J., & Loch, C. (2017). Tooth damage in captive orcas (Orcinus orca). Archives of Oral Biology, 84, 151–160. https://doi.org/10.1016/J.ARCHORALBIO.2017.09.031

[16] Fleming, M., & Burn, C. C. (2014). Behavioural assessment of dental pain in captive Malayan sun bears (Helarctos malayanus). Animal Welfare, 23(2), 131–140. https://doi.org/10.7120/09627286.23.2.131

[17] Wiles, G. J. (2004). Washington State status report for the killer whale. (Orcinus orca). Washington Department Fish and Wildlife, Olympia. 106pp. 2004., (November), 106.

[18] Carl, G. C. (1946). A school of killer whales stranded at Estevan Point, Vancouver Island. Provincial Museum of Natural History and Anthropology.

[19] Tomilin, A. G. (1967). Mammals of the USSR and adjacent countries. vol. 9, Cetacea. Israel Program Sci. Transl, (1124).

[20] Caldwell, D. K., & Brown, D. H. (1964). Tooth wear as a correlate of described feeding behavior by the killer whale, with notes on a captive specimen. Bulletin of the Southern California Academy of Sciences63(3), 128-140.

 

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