The myth of the early deaths

One of the most widespread falsehoods from the anti-zoo groups is the high mortality of cetaceans under human care, or the myth of the early deaths. The main argument of these organizations is that handling, restraint, confinement, transport, isolation or crowding and an artificial diet lead to stress in captive cetaceans and, ultimately, a reduction in their life expectancy. And that is exactly what could be expected, if the terrible situation of suffering and deprivation described by the anti-zoo groups would be true, dolphins and orcas should have a much higher mortality rate. But, is this the case? If we analyze the scientific literature this is clearly not the case.

It has been recently published that dolphins under human care at least live as much as their wild counterparts, and can live more [1]. This research provides the most comprehensive assessment of life expectancy and survival rates for bottlenose dolphins, based on data from U.S. zoological facilities between 1974 and 2012. The mean life expectancy for bottlenose dolphins under human care based on this data is 28 years. This result is comparable to the life expectancy for bottlenose dolphins in European facilities [2] or even to Chinese aquariums [3], which indicates that under the best husbandry dolphins can live more than their wild counterparts. In some particular cases, like the United States Navy Marine Mammal Program, the mean life expectancy was even higher, reaching 30 years [4]. When mean life expectancy for wild bottlenose dolphins is calculated is typically half of the mean life expectancy for bottlenose dolphins under human care in recent years [1] [5]. Despite the lack of data and difficulties to measure the survivorship in wild dolphins results in non-statistical significance, it is clear that dolphins under human care live longer. Another relevant difference about dolphins under human care is that the mortality of calves during the first year is lower that the estimates for wild dolphins [6].

When analyzing killer whales, the situation is similar, the most recent scientific research proves that killer whales under human care live, at least as long as their wild counterparts [7]. The mean life expectancy for wild killer whales ranged from 29.0 years (Southern Residents) to 42.3 (Northern Residents), while the captive killer whales have a mean life expectancy of 41.6 years 7. These results debunk other myth: the idea that zoos do not spread correct longevity figures for dolphins and killer whales [8]. And also questions the post-reproductive theories in female killer whales [9].

If we look at maximum life expectancies (MLE), the dolphins under human care have a MLE of 50 years, while in the wild the maximum life expectancy for a dolphin varies from 31 to 36 years. The oldest dolphin under human care ever was Nellie, a female who died at Marineland Dolphin Adventure when she was 61. When the ages of wild orcas off the coast of Washington State are analyzed (over 350 individuals) it can be seen that less than 1% of the specimens exceed 60 years. Despite there have been killer whales under human care for less than 50 years (professionally managed) some individuals like Lolita or Corky are already in their 50s.

In the light of this scientific knowledge, which proves that life expectancy of cetaceans is similar or even greater under human care, it is clear that the speculations of suffering and deprivation spreaded by the anti-zoo groups during decades are not sustained by the facts.

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[1] Jaakkola, K., & Willis, K. (2019). How long do dolphins live ? Survival rates and life expectancies for bottlenose dolphins in zoological facilities vs . wild populations. Marine Mammal Science, 36(3), 248–261.

[2] Hartmann, M. G. (2000). The European studbook of bottlenose dolphins (Tursiops truncatus): 1998 survey results. Aquatic Mammals, 26(2), 95-100.

[3] Zhang, P., Sun, N., Yao, Z., & Zhang, X. (2012). Historical and current records of aquarium cetaceans in China. Zoo Biology, 31(3), 336–349.

[4] Venn-Watson, S. K., Jensen, E. D., & Ridgway, S. H. (2011). Evaluation of population health among bottlenose dolphins (Tursiops truncatus) at the United States Navy Marine Mammal Program. Journal of the American Veterinary Medical Association, 238(3), 356-360.

[5] Stolen, M. K., & Barlow, J. (2003). A model life table for bottlenose dolphins (Tursiops truncatus) from the Indian River Lagoon system, Florida, USA. Marine mammal science, 19(4), 630-649.

[6] Sweeney, J. C., Stone, R., Campbell, M., McBain, J., Leger, J. S., Xitco, M., … & Ridgway, S. (2010). Comparative Survivability of Tursiops Neonates from Three US Institutions for the Decades 1990-1999 and 2000-2009. Aquatic Mammals, 36(3).

[7] Robeck, T. R., Willis, K., Scarpuzzi, M. R., & O’Brien, J. K. (2015). Comparisons of Life-History Parameters between Free-Ranging and Captive Killer Whale (Orcinus orca) Populations for Application Toward Species Management. Journal of Mammalogy, 96(5), 1055–1070.

[8] Robeck, T. R., Willis, K., Scarpuzzi, M. R., & O’Brien, J. K. (2016). Survivorship pattern inaccuracies and inappropriate anthropomorphism in scholarly pursuits of killer whale (Orcinus orca) life history: A response to Franks et al. (2016). Journal of Mammalogy, 97(3), 899–905.

[9] Foster, E. a., Franks, D. W., Mazzi, S., Darden, S. K., Balcomb, K. C., Ford, J. K. B., & Croft, D. P. (2012). Adaptive Prolonged Postreproductive Life Span in Killer Whales. Science, 337(6100), 1313–1313.


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