How long do dolphins live? Survival rates and life expectancies for bottlenose dolphins in zoological facilities vs. wild populations

Abstract

Survival rates and life expectancies are commonly agreed upon indicators of well‐being for animals in zoological facilities, but even the most recent survival statistics for bottlenose dolphins (Tursiops truncatus) in marine mammal parks and aquariums use data that are now more than 25 yr old. The current study provides a comprehensive assessment of life expectancy and survival rates for bottlenose dolphins in U.S. zoological facilities from 1974 to 2012, utilizing three different analyses (annual survival rate, age‐at‐death, and Kaplan‐Meier), examining historical trends, and comparing to comparable data from wild populations. Both survival rate and life expectancy for dolphins in zoological facilities increased significantly over the past few decades, with a modern ASR of 0.972, and mean and median life expectancies calculated via Kaplan‐Meier of 28.2 and 29.2 yr, respectively. Survival rates and life expectancies for dolphins in U.S. zoological facilities today are at least as high as those for the wild dolphin populations for which there are comparable data.

Bias and Misrepresentation of Science Undermines Productive Discourse on Animal Welfare Policy: A Case Study

“…First, Marino et al selectively apply validity criteria to calculations in different studies. That is, they correctly note that the equation used for converting Annual Survival Rate (ASR) to median life expectancy in Robeck et al [ 41 ] assumes a constant survival rate for all animals in the calculation, which is violated by both historical and age-related changes in mortality [ 38 , 105 ]. However, this exact same assumption is also required for the calculation of ASR in the studies that analyzed survival data prior to 1992 [ 38 , 39 ], which they accept without question.…”

“…However, this exact same assumption is also required for the calculation of ASR in the studies that analyzed survival data prior to 1992 [ 38 , 39 ], which they accept without question. It is unclear to what extent this violation affects the results of these calculations [ 105 ]; however, one must apply the criterion consistently. Since the same assumption is violated in both sets of studies, either both results must be accepted or both must be rejected.…”

Physiological Parameters Monitored on Bottlenose Dolphin Neonates (Tursiops truncatus, Montagu 1821) over the First 30 Days of Life

“…The 2013 Report on T. truncatus of the European Association of Zoo and Aquaria Ex situ Program (EAZA EEP) [ 11 ] and the more recent long-term EEP management plan for the species [ 12 ], showed how the neonatal mortality of dolphins under human care in Europe has steadily decreased decade by decade in the last 40 years, from 77%, reaching a historical minimum of 33% (26/80) for the period 2011–2015. Jakkola et al in 2019 [ 16 ] show that in United States, dolphin survival rates have increased significantly. Median life expectancy has more than tripled over the last few decades.…”

“…Life expectancy is at least as high as in the wild populations. Nevertheless, the comparison with the survivability of young calves in the wild is not available, as neonatal mortality events are usually unreported or remain unnoticed [ 8 , 17 , 18 ], rendering the levels difficult to determine with certainty [ 16 , 19 , 20 ].…”

“…OLT opened in 2004, and had several calves born by 2008, which all died within the first nine days of life due to bacterial infections. Considering the history of these facilities and the lack of handling experience, and highlighting that neonatal mortalities occur during the first month of life, prompt intervention after birth was considered essential [ 3 , 5 , 9 , 10 , 13 , 16 , 21 ]. In 2010 a combined protocol was created by veterinarians and biologists to schedule all the procedures and observations to occur prior to, during and after birth, in order to intervene with the calf in due time.…”