Returning dolphins from zoological collections to the wild?

 

Returning dolphins from zoological collections to the wild?

One of the claims often made by those who oppose zoological collections, particularly facilities that house dolphins, is that these animals should simply be released back into the wild. This is a rather glib position that overlooks the serious biological, social, and practical challenges involved.

First, the vast majority of bottlenose dolphins held in zoological collections today originate from captive-breeding programmes rather than from wild capture. This creates a fundamental constraint on release, as their family groups exist within these collections rather than in natural wild populations.

As of 11 March 2025, there are 415 dolphins held in 32 facilities in the United States. Excluding killer whales, the figures for dolphin species are as follows:

Wild-caught: 55 (13%)
Captive-born: 325 (78%)
Rescued: 35 (8%)

A European snapshot can be taken from Harderwijk Marine Mammal Park, where the bottlenose dolphin inventory comprises:

Wild-caught: 3 (10%), captured in 1979, 1980, and 1989
Captive-born: 26 (90%)

Some European facilities, such as Planète Sauvage, hold dolphin populations that are entirely derived from captive-breeding programmes.

Looking specifically at resident bottlenose dolphins at SeaWorld parks in the United States, 6 animals (6%) were taken from the wild in 1972, 1978, 1982, and 1987, while 98 (94%) were obtained through captive breeding. Five animals at SeaWorld are listed as rescued and are not included in the above statistics. See the explanatory note below regarding this status and what it entails.

Activist groups often describe these animals as having been “snatched from their families”. However, dolphins born in zoological collections typically remain with their family groups. It is also important to consider the natural fusion–fission social structure of bottlenose dolphins when assessing social groupings in both wild and managed settings. An explanatory note on fusion–fission societies is provided below.

Second, even when considering the release of wild-caught animals, guidance from organisations such as the International Union for the Conservation of Nature (IUCN) is clear. Individuals should, wherever possible, be returned to their original area of capture as part of any release or rewilding effort.

And what of killer whales?

There are currently 54 killer whales held across 14 facilities worldwide:

Captured from the wild: 22 (39%)
Born in human care: 33 (58%)
Other or unspecified: 2 (3%)

The majority of these animals were therefore born in zoological collections and would not be appropriate candidates for release. The 39% that were wild-caught have also been in captivity for extended periods, which substantially alters their behaviour and survival skills. This was clearly demonstrated during the failed attempt to release Keiko, the killer whale. Despite substantial financial investment, he never integrated with wild killer whales. After being left to fend for himself, he swam to a Norwegian fjord, actively sought human contact, and begged for food. He died shortly afterwards from pneumonia.

Turning to the question of sanctuaries, only one currently exists, housing two beluga whales. This facility has faced significant difficulties during the six years the animals have been resident there. For the past two years, they have been confined to an indoor pool at a Sea Life tourist centre. The bay intended to function as the sanctuary can only be used during the summer months, and the animals must be removed for safety reasons affecting both them and their carers. At least one of the belugas became ill while in the bay, probably as a result of stress.

See: Beluga Sanctuary Blog

A sanctuary proposed for Canada remains many years away, even if it ultimately proves feasible and sufficient funding for construction and long-term operation can be secured.


Explanatory notes

Rescue and rehabilitation in the United States
In the United States, any dolphin that strands or enters rehabilitation falls under the federal authority of NOAA Fisheries, which enforces the Marine Mammal Protection Act. Decisions on whether an animal is deemed non-releasable, whether due to health concerns or because it stranded as a neonate, are made by NOAA rather than by the facilities that carry out rescue and rehabilitation.

Fusion–fission societies explained
A fusion–fission society is a form of social organisation in which group membership is fluid. Animals periodically come together into larger groups for activities such as feeding, travel, or protection, and then separate into smaller subgroups or individuals as conditions change. This flexibility allows a balance between the benefits of cooperation, such as increased safety and information sharing, and the costs of competition, including limited food resources or social conflict.

Bottlenose dolphins are a well-established example of fusion–fission dynamics. They may form large pods when hunting schools of fish or navigating predator-rich waters, but these aggregations are not permanent. Smaller subgroups, sometimes consisting of only a few individuals, frequently break off to forage independently or engage in social behaviour. Group membership is not fixed, creating a constantly shifting social landscape.

Male dolphins often form long-term alliances with one or two partners, although these alliances may temporarily merge with others during competition for mates or defence against rivals. Females tend to associate more loosely, often moving between groups depending on reproductive status or calf-rearing requirements.

CetaBase
The figures presented here are drawn from the CetaBase website, which is widely regarded as an objective and accurate source of information on cetaceans in human care.


References

IUCN/SSC (2013). Guidelines for Reintroductions and Other Conservation Translocations. Version 1.0. Gland, Switzerland: IUCN Species Survival Commission.

Carver, S., Convery, I., Hawkins, S., Hertel, S., Fallon, J., Lyons, K., Beyers, R., Locquet, A., Derham, T. and Kun, Z. (eds.) (2025). Guidelines for rewilding. Gland, Switzerland: IUCN.

Marine Animal Welfare (2025) Releasing cetaceans back to the wild. Available at: https://marineanimalwelfare.blogspot.com/p/releasing-cetaceans-back-to-wild.html (Accessed: 14 December 2025).