Dolphin Captivity

by Kenneth W. LeVasseur



Keeping animals with the unique mental abilities and ecological needs of dolphins captive has lead to high mortalities, poor reproductive parameters (including high numbers of stillbirths) and aberrant behavior. The efforts of dolphin and animal protection groups to get to the root of these problems has caused the captive dolphin industry to engage in propaganda with the help of the federal government.

Wild Dolphins have comparable lifespans to aboriginal humans (30 to 45 years). The "high tech" medical practices, that have lengthened human life to 75 years, have not helped captive dolphins match the lifespans of even feral dolphins. Sixty years of effort in this area has only cut the mortality rate to 7 to 7.4 percent of the dolphins in captivity in North America, every year (Asper et al. 1990, Duffield and Wells, 1990). Half the dolphins in captivity die every seven years. Wild populations, under similar harassment stress, have a confirmed mortality rate of less than one percent per year and possibly as much as 2.59 percent per year, Wells (1990). Capture crews destroy dolphin families by capturing 2 to 4 year old baby dolphins (possibly not weaned) to replace the dolphins that died. These babies have a 53 percent chance of living the first year in captivity (DeMaster and Drevenak, 1988). The above figures come from data supplied by those institutions that hold dolphins, orcas and belugas in trust for the American people under the Marine Mammal Protection Act. Yet, the figures are from questionable data because of under-reporting by those same institutions (Ric O'Barry, Mary Mosley, personal communications).

Many of these deaths are stress related (a claim disputed by dolphin facilities). The most obvious cause of stress is due to the radical spatial constriction which occurs when dolphins are taken from the ocean and its estuaries and put into the man-made enclosures of captivity. Despite the strenuous and sincere efforts of the dolphin's care-givers, and many of them try very hard until they burn out or are injured enough to quit, they will not be able to compensate for this stress-inducing problem.

A 1990 study, presented at a captive dolphin trainers conference, is being claimed or implied to have "scientifically shown" that many parameters for reproductive performance in captive dolphins exceed wild populations. The original paper will be reviewed and its discrepancies shown to be simple propaganda by the captive dolphin industry.

Animal protection groups claim the figures on captive cetacean mortality are appalling. The consistent abuse of objective reporting methodology and misrepresentation of captive circumstances by the captive dolphin industry, constitutes a mandate for a new scientific approach to cetacean studies and cetacean captivity in general.

Captive Dolphin Industry Data and Information Regarding Mortality
and the Quality of Life of Dolphins in Captivity

The integrity of the Marine Mammal Inventory of the National Marine Fisheries Service (NMFS) has been violated, abused an distorted by the entries of dolphin holding facilities required under the Marine Mammal Protection Act. Jeff Brown, a NMF field officer at the St. Petersburg, Florida office has agreed with Ric O'Barry that the inventory is in disarray. The captive dolphin industry acts as if they have proprietary rights to the data that regulations enforcing the Marine Mammal Protectio Act require they keep. This makes their operations a de facto classified technology, not an open science. Appropriate public and scientific input (allowed and encouraged under the law), to counter captive dolphin industry propaganda, is nearly impossible under these conditions.

Support for O'Barry's and Mosley's under-reporting contention comes from page 41 of the 1975 report, Breeding Dolphins: Present Status, Suggestions for the Future. The authors are Sam H. Ridgway and Kurt Benirschke. Ridgway is the chief veterinarian for the Navy's dolphin program and in 1975 was also the chairman of the federally appointed Marine Mammal Commission's (MMC) Committee of Scientific Advisors. The MMC funded the workshop and its resulting report. The report states,

"There is a reluctance on the part of the oceanarium industry to provide data on deaths, autopsies, stillbirths, aborted fetuses, and the like because of fear that such data might be used against them by some animal protection groups. A way must be found to pool such data without reference to origin so that it can be used in a positive way. With such assurances oceanaria will be more cooperative."

The reference to a "positive" use of the information, which excludes the animal protection groups, is indicative of the serious problems facing captive cetaceans in today's oceanariums and research facilities. When comments are solicited for federal hearings to determine scientifically adequate standards and guidelines for the captivity of these totally aquatic mammals, Ridgway and Benirschke point out how information on "deaths, autopsies, stillbirths, aborted fetuses and the like" is denied animal protection groups. Yet, use of this information by animal protection groups in their comments on these standards and guidelines, would only provide actual data available (but withheld by the oceanariums -- which would be affected by the resulting standards and guidelines) to derive scientifically adequate regulations. In 1995, there is no indication that the situation has changed in the captive dolphin industry's reporting of dolphin "deaths, autopsies, stillbirths, aborted fetuses and the like".

Starting in 1976, a year after the publishing of the Ridgway and Benirschke report, the captive dolphin industry did indeed begin a process of reporting "deaths, autopsies, stillbirths, aborted fetuses and the like". These elective submissions have been published in the International Zoo Yearbook (IZY) during the years of 1978 (Cornell & Asper), 1982 (Cornell et. al.), 1988 (Asper et. al.), and 1990 (Asper et. al.). But, the conflict between the lack of complete regulatory compliance by dolphin holding facilities (required under the MMPA for use in the Marine Mammal Inventory - a "shambles" and available for all to investigate), and the nature of collecting data for the reports in the IZY (available only to those sympathetic to captivity for dolphins), has created a dense cloud of scientific doubt over the "objectivity" of the IZY information and the captive dolphin industry's statements about dolphins in captivity.

Mortality Rates vs. Survivorship

The are two survivorship / mortality rate studies that have been done for captive dolphins from information supplied in the Marine Mammal Inventory. They are the DeMaster and Drevenak,

"Survivorship Patterns in Three Species of Captive cetaceans.", 1988; and the Karen L. Steuer unpublished manuscript A Comparative Institutional Survey of Factors Influencing Mortality of Cetaceans in U.S. Zoos and Aquaria. The DeMaster and Drevenak study was funded by the Marine Mammal Commission and the Steuer study was funded by the Animal Protection Institute of America, the International Wildlife Coalition and the Humane Society of the United States. The DeMaster and Drevenak study covered the 10 years between 1975 and 1985, and the Steuer study covered the 12 years between 1975 and 1987. DeMaster and Drevenak reported that of the 864 dolphins studied there were 319 deaths over the 10 year period - almost 37% died. But, the mortality statistic was incidental to the approach used in the DeMaster and Drevenak study and calculated only for this analysis. Steuer showed that of 431 dolphins studied, 191 deaths occurred over the 12 year period - 44% died. Both studies employed statistical analyses that, although they can be used to study any species survivability, are usually used in the study of much smaller animals with higher metabolisms and correspondingly shorter life spans. The more detailed Steuer study was a response of sorts to the DeMaster and Drevenak study. As such she used the same statistical analysis along with other analytical strategies. The lower sample of data in Steuer's data is due to her use of 34 institutions covering the 12 years, and DeMaster and Drevenak using data from 57 institutions covering the ten years. There were almost 32 deaths per year spread among the 57 dolphin holding facilities in Demaster and Drevenak report. Steuer's study reported almost 16 deaths per year spread among the 34 facilities. Both mortality rates were identical when calculated on an annual basis (3.69% of the population per year). These studies were required to make selective use of the data supplied in the Marine Mammal Inventory because of the inadequate reporting mentioned earlier.

Table 1. presents information taken or derived from DeMaster and Drevenak's study and Steuer's study in comparison with information taken or derived from a Wells and Scott (1990) study with wild dolphins in Sarasota Bay. The study by Wells and Scott (1990) showed only 6 confirmed deaths out of a possible census of 116 of these feral dolphins spread over 8 years. If one adds dolphins that disappeared from the study area (losses), that Wells and Scott state are possibly due to unconfirmed death, mistaken identification or simply leaving the area (as some males in the study area were documented to do); the total of 24 dolphins is still only an average of three dolphins "lost" per year - much smaller than the average of 32 or 16 confirmed dolphin deaths per year seen in captivity.

Table 1.
Reported Information
Study YearW 19901988C 1990
Years of Study81012
# of institutions15732
Total Dolphins116864431
Total Mortalities6319191
Total Losses24319191
Crude Mortality %5.17%36.92%44.32%
Crude Losses %20.69%36.92%44.32%
% Mortality/Year0.65%3.69%3.69%
% Losses/Year2.59%3.69%3.69%

The W 1990 column represents information taken or derived from Wells and Scott 1990. The 1988 column represents information taken or derived from DeMaster and Drevenak 1988. The C 1990 column represents information taken or derived from Steuer 1990

As mentioned earlier, the mortalities percentage of the total population per year in both tables is the same for both DeMaster and Drevenak's study and Steuer's study, (3.69%). Duffield and Wells, 1990, list a mean of .074 for the mortality rate in their paper. This translates to 7.4 percent of the population in mortalities per year. Asper et al., 1990, quote "approximately" 7 percent for their crude annual mortality rate. The Duffield and Wells, 1990, and Asper et al., 1990, annual mortality percentages come from voluntary submissions to researchers sympathetic with the captive dolphin industry and are double the annual mortality percentages derived from Marine Mammal Inventory information regulated by NMFS (DeMaster and Drevenak, 1988; and Steuer, 1990). Both annual mortality percentages are far excessive of Wells and Scott's annual confirmed mortality percentages (.65 of 1 percent) and annual loss percentages (2.59 percent).

Although the captivity data come from much larger populations, the loss rate (which includes some mortalities), is less that 21 percent of the total population. This smaller percent is also spread over 8 years rather than 10 or 12 years as in the captive studies. To make the data comparable by the number of years of the study, Table 2. extrapolates the data of Table 1. to 10 and 12 years.

Table 2.
Extrapolated Data10 Years12 Years
Study YearW 19901988C 1990W 19901988C 1990
Years of Study101010121212
# of institutions1573215732
Total Dolphins116864431116864431
Total Mortalities83191599383191
Total Losses3031915936383191
Crude Mortality %6.90%36.92%36.89%7.76%44.33%44.32%
Crude Losses %25.86%36.92%36.89%31.03%44.33%44.32%
% Mortality/Year0.69%3.69%3.69%0.65%3.69%3.69%
% Losses/Year2.59%3.69%3.69%2.59%3.69%3.69%

The extrapolations of Table 2 show that when the annual loss percent is stretched to ten years it shows a 26 percent "mortality" equivalent compared with 37 percent for captivity. When extrapolated to 12 years, the percentage becomes 31 percent compared to 44 percent, but these percentages are losses not mortalities. In the captivity studies, the survivorship analysis capitalizes on the fact that most animals survive to the next day with high levels of probability, even though small differences in percentages may mean enormous risks encounters by one animal population verses another and the resulting higher death rates. Also, the figures are less direct and do not have the emotional impact of simple mortality figures. For example, DeMaster and Drevenak report average survivorship probabilities of 93% but 37% of the dolphins died during the study period. The Wells and Scott study reports an annual survivorship rate of 96% while 21% of the dolphins were "lost" during the time of the study, a difference of 16 percentage points in total mortality but only 3 percentage points of survivability.

If we were to create an emotional reaction rating system for data of this type we would see a ratio of more than 5 to 1 between the two approaches to representing results. If we extrapolate the Sarasota mortality data up to 10 years instead of the 8 years of the study, we get 26% compared to 37%, a difference of 11 percentage points compared with 3 percentage points for the survivorship data, a ratio of almost 4 to 1. It should be remembered, though, that the population of Sarasota dolphins "lost" these members through death, mis-identification or leaving the study area. The Sarasota percentages of 21%, 26% or 31% can be expected to be much higher than actual mortality. The captivity data are actual mortality.

In the first paragraph of the Discussion section, Steuer states,

". . . While the annual survivorship rate for all three sample classes of bottlenose dolphins is 91%, the fact that 191 of 431 dolphins - or 44 percent of the sample - were dead by the end of the study period may indicate that a different method of analysis is warranted."

The Steuer study goes on to show how science can serve the plight of dolphins held captive in aquaria and research facilities by providing objective information for those who can use it to help dolphins. There are glaring differences between the approaches to the data in the Steuer study and the DeMaster and Drevenak report; along with the fact mentioned earlier that the Steuer study goes into much more detail and names those institutions covered in the data. The overall impression from reading the two reports is that Steuer is attempting to document what can be seen as a serious plight of dolphins held in captivity, while the DeMaster and Drevenak report seeks to protect the institutions holding dolphins. The method employed by DeMaster and Drevenak appears to have been chosen to minimize the impact of scientific research on the opinions of the public so that "science" can proceed.

That this approach to the data also had questionable accuracy, DeMaster and Drevenak conceded in the report that machine limitations created the need to interject, ". . . a normal approximation to estimate the upper limit for the number of deaths when the observed number of deaths was greater than five."

It is demonstrated almost daily that the general public is concerned about these high mortality rates for dolphins in captivity. Most people are appalled when they learn the statistics. Science and the technology of human / cetacean interactions can proceed without causing the high mortality rates seen in cetacean captivity. Science identifies the need for change and is the source of solutions for the predicament. Only those interest groups that do not wish to embrace scientific progress risk being "sacrificed" through market pressures and possibly Congressional action.

An Example of Propaganda Parading as Science Regarding
Successes at Dolphin Holding Facilities

In 1990, The International Marine Animal Trainers Association (IMATA) was thought to have published in the proceedings of their Chicago conference a study by Deborah Duffield and Randy Wells titled "Bottlenose Dolphins: Comparison of Census Data from Dolphins in Captivity with a Wild Population". Unfortunately, IMATA did not actually publish such a proceedings until 1993. The paper did make it into their newsletter "Soundings" though, but in 1991. This paper was very difficult to find in the early 1990s but was quoted widely by the industry. There is no Duffield and Wells, 1990, that deals with captivity. On another subject, yes, but not captivity.

This paper is consistently represented such as, "In fact, a 1990 study done by Duffield and Wells indicates that all parameters measuring reproductive performance of dolphins in parks and aquariums exceed those of the wild population." Please notice that there is never a complete source citation. The paper is always presented as if it was a scientific study containing the above parameters as scientific "fact" in a way that the reader is unlikely to investigate for accuracy. In fact the paper is best represented as propaganda for the captive dolphin industry.

There are many facts in the original paper and the authors do not compromise their scientific credentials by having the work presented at an industry conference and the paper published in the conference's trade newsletter. If the paper is seen and presented as a pep-talk for a trade association so that the trade practitioners keep trying to improve their standards of care for captive dolphins, then the manipulation of data to create a "best case scenario" could possibly be excused. It is only in the reading of the original 1990 Duffield and Wells paper and the originals of the cited studies of the paper that one can see the more accurate assessment. In a very relative sense, the statement quoted above is marginally supported by the charts and tables of the paper, although certainly not by actuality. At each stage of preparation for the charts and tables, the reality of the data is quantified or qualified to such an extent that the data represented in the tables are obviously skewed to the benefit of the captive dolphin industry's propaganda.

There are at least five areas of the study that distort the data.
  • 1. Duffield and Wells make selective use of study cut-off points when they ascertain age distribution. They use Well and Scott (1990) data ending in 1987 (1980-1987) for age distribution of the wild population and 1990 data (1983-1990) from Asper et al. (1990), for the captive age distribution. They simply add three years to age distributions of the captive population without specifically mentioning it or making an effort to balance the data.
  • 2. Duffield and Wells make selective use of study cut-off points when they ascertain "maximum" longevity. They use Wells and Scott (1990) data ending in 1987 (1980-1987) but add supplementary data from the year 1988 for "maximum" longevity of the wild population and 1990 data (1983-1990) from Asper et al. (1990), for the "maximum" longevity of the captive population. They add two years, this time, to age of the captive population without specifically mentioning it or making an effort to balance the data.
  • 3. Duffield and Wells again make selective use of study periods in calculating reproductive parameters. Crude birth fecundity rate, recruitment rate and mortality rate all use the 1980-1987 Wells and Scott (1990) Sarasota data. But for the captivity data they only use data from 1976-1988 even though data from 1989 and 1990 was available. Duffield and Wells acknowledge that 1988 was a record year for births in the Sarasota population and that 1989 and 1990 were above average years, but do not include the data because it followed the "cut-off" point. Adding data from 1988 that also followed "cut-off", did not stop them from including it in the longevity data of Table 4. They even added earlier data from 1976-1979 to the longevity data set and could have added it to this data set. Such a strategy would have yielded a common study period of 1976-1990.

One indication of why this strategy was not used is the low number of births in captivity in 1990. The Asper et al. (1990) paper says in Table 2., and cited for Table 2. of the Duffield and Wells paper, that between 1983-1990 there were 122 births for bottlenose dolphins with an average of 19 births per year, including still births. To find out how many were born in 1990 in captivity, there is the "Captives (all)" data in Duffield and Wells Table 3. (Average Age) that does not include births or deaths of the year because they are "not a complete annual interval". These births would be in the last year of the study, 1990 since the table used the 1990 Asper et al. census data. The Asper et al. (1990) census data says that there were 328 bottlenose dolphins "on display" in 1990.

The difference between Duffield and Wells data and Asper et al. data is 12 births and deaths of the year 1990. Therefore there could be no more than 12 births in 1990 and maybe less if any dolphins died. Compared to the 19 births averaged for 1983-1990, 12 or less births for 1990 would have slanted the reproductive parameters downward significantly if the data was included. There is no way to determine the number of births in 1989 from the papers, but if they were 19 or higher, they would most likely have been included in the data.

  • 4. Duffield and Wells (1990) modify original data published in Wells and Scott (1990) by not using the same weighted averages for the calculated means and a binomial variance for the standard deviations in Table 5 (Duffield and Wellst 1990). They tell you that a difference is there but do not explain the need for the alteration.
  • 5. The mortality rate information is also altered by adding the young of the year to the Duffield and Wells population data when they were eliminated from the Wells and Scott (1990) data. This resulted in a significantly higher mortality rate for the Sarasota dolphins in the Duffield and Wells paper.

Scientifically, these manipulations compromise the enthusiastic conclusion of the paper that the captive dolphin industry's maintenance and breeding program for bottlenose dolphins has been a success story. There is no doubt that there have been improvements over the last sixty years dolphins have been held captive by the industry, but no one should regard propaganda as scientific fact.

Dolphin and animal protection groups want to get to the bottom of the scientific issues surrounding captive dolphin mortalities, reproductive problems and quality of life. The problem is that the "science" practiced by the captive dolphin industry does not allow information they control to be used by scientists that do not agree with the captive dolphin industry's philosophy. The information available to the public is sanitized to skirt the issues raised and pursued by dolphin and animal protection groups.

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