Dolphins had occasionally been released from marine parks, but few of these releases had been properly conducted and documented. They had often involved simply returning an animal to the ocean without sufficient preparation and follow-up work. More recent release projects have involved more preparation and follow-up effort, however, the best example being the "Welcome Home Project" run by Drs. Randy Wells and Ken Norris in 1988-90. They had captured 2 young male bottlenose dolphins from a much- studied population in Tampa Bay, Florida. After 2 years in captivity, the dolphins were successfully released into their native community, where they quickly reintegrated into the wild population and are still sighted today.

Nonetheless, the Atlantis project would be unique and important for several reasons relevant to the possibility of future cetacean reintroductions. Not only were we planning to release long-term captives, but also dolphins born in captivity. We hoped that by carefully planning and documenting the rehabilitation and release process, the project would provide baseline data and guidelines for future releases by determining what techniques and protocol were useful, and which aspects were unnecessary or flawed. Ultimately, we hoped to be able to suggest ways of easing the animals back into the wild, and to provide information about the chances of success, thus spelling out some of the implications of the transition, not only for long-term captives no longer required, but also for endangered species that could conceivably be bred in captivity and released into declining populations.

All dolphins were freeze-branded (on both sides of their dorsal fin) with a number 2 cm high. While dolphins are individually recognizable, it takes time and experience to notice differences reliably, e.g. darker color, a nick out of the dorsal fin, or a mark near the blowhole. The freeze brands would make the dolphins instantly recognizable by local fishermen and members of the public.

Foraging skills were tested and developed by feeding the dolphins live fish that had been caught locally, thus ensuring they would be fish species that the dolphins would encounter at sea. From the very beginning the dolphins were able to capture live prey, and their skills improved over time. Nonetheless there was a lot of variability between individuals and between trials. Among the adults the more dominant animals tended to be the most aggressive and efficient at fish capture. One male in particular was known to be highly food motivated, and he had the highest capture rate (he could even capture fish while he still had several previously caught fish in his mouth!). Although the juveniles were all able to catch fish, they did not show the same capacity as the adults. They seemed to treat the exercise as a game and would often all chase the same fish, competing more with each other than actually showing any ability to forage. It was a long time before we were sure that all of the dolphins could catch and eat live prey.

One of the more difficult changes was limiting human interaction with the dolphins so that they would spend more time interacting with each other and less focusing on events above water. At this time I began a study of the social behavior of the group. I was interested in the social relationships between individuals, how these were expressed, and whether changes would occur through the process of rehabilitation and release. The research involved endless hours of standing at the pool-side, recording details of interactions between individuals, group composition and general activity. I focused my studies on the 3 males and a colleague looked at associations among the females and juveniles. We had to be careful not to interact with the dolphins and encourage more human interaction at a time when it was supposed to be reduced. This was not easy, as the dolphins were always aware of our presence. We would often have to wait 10 to 20 minutes for them to realize that we were not there to play, pet or feed them and then settle down and go back to their own activities. The juveniles were particularly keen for attention and would spend quite a bit of time peering up at us, occasionally trying out a new activity to test our response. A favorite of their antics was to perform a behavior in unison. Although the juveniles were never formally trained, they copied the performance behaviors displayed by the adults during feeding sessions. Quite often, while we were trying to record observations of natural behavior, the juveniles would all stop, watch us for several minutes then in perfect unison embark upon a series of tail slaps or pec waves. We did our best to ignore them, and the dolphins would eventually return to playing and swimming among themselves, with just occasional bouts of observing the observers.

This part of the project gave me a fascinating glimpse into the personal lives of the dolphin group. Like any social species, the dolphins all had "friends" and, if not enemies, those with whom they rarely interacted. Each had a "best friend" with whom they spent most of their time and with whom they engaged in friendly actions like rubbing and side by side swimming. Changes occurred in these relationships, accompanied by bouts of aggression and tension in the group. The relationships we noted were similar to those reported in wild dolphins populations: adult females had strong bonds with their offspring and adult males formed bonds with each other and did not tend to interact so often with the females. Spending so much time observing the dolphins also brought home their unique "personalities", evident in the way they interact with others and with the trainers. For example, one juvenile (Nakita) enjoyed playing with rings and balls. Whenever any toys were present in the pool she was guaranteed to be in charge of them, often playing with several rings at a time. She would even approach the dominant male to take a favorite toy away from him. Of course we all had our favorites and, although the juveniles were the most amusing, I had a soft spot for Rajah, one of the adult males. He was a relatively quiet dolphin, often alone and a bit persecuted by the other males. But he was very friendly with people and would drift by the side of the pool for as long as you were willing to stroke him.

An additional aspect of the release was an examination of the behavioral ecology of the local coastal population. Although bottlenose dolphin populations have been studied around the world, there had been no previous research around Perth. It was important to have information on the behavior, ranging patterns, and foraging strategies of local wild dolphins in order to determine whether or not the Atlantis dolphins were integrating properly. A survey project began in March 1991 and continued through June 1993, using photographic surveys to collect information on dolphin group size, structure and composition, general activity, range and association patterns.

The dolphins were moved to the sea pen in October 1991 and adapted quickly to their surroundings. All seemed eager to follow and interact with the boats. The close relationships identified at Atlantis persisted between the females and their offspring and between 2 males. The live fish trials were discontinued in the sea pen because the size of the pen and lack of clarity of the water made it impossible to determine who was catching fish. A local fishing company donated a 1 ton school of yellowtail that were released into the sea pen in the hopes that the dolphins would naturally forage from the school. Unfortunately, the dolphins by and large ignored the fish school, although they would catch and eat fish that were tossed near them. The school, however, did decrease over time, and coincidentally the local cormorant population simultaneously boomed! It is possible that the yellowtail were too small -- all were less than 6 inches in length -- to be worth the effort of chasing, considering that the dolphins were still receiving their normal daily allotment of fish. An addition to the group came in November 1992 when an adult female (Mila) gave birth to a male calf.

The final preparation involved fitting the adults with radio transmitters so that we would be able to locate the dolphins at sea. The transmitters chosen were about the size of a matchbox with a flexible antenna that would extend the length of the dorsal fin. The whole package weighed 101 g. We carefully observed the dolphins for several days to ensure there were no physical problems with the attachment site or with inhibition of normal activity. Transmitters were not attached to the juveniles as we did not want to add any stress to the young, growing animals. We also hoped that the juveniles would remain with the females a least in the early stages of the release. Dolphin group structure in the wild is fluid, meaning that group size and composition changes regularly. However, some individuals are often seen together regularly, e.g. females and their offspring, and pairs of males who form long term bonds. While we did not expect the Atlantis dolphins to remain together permanently at sea, we hoped that some of the associations noted in captivity would persist.

The very next day Rajah accompanied the boat out of the marina where he left us behind, heading out to sea. We gathered our tracking gear and set off in pursuit for a very exhilarating 3 hours. During that time Rajah was seen interacting with 2 different groups of wild dolphins. While the first was only a brief encounter, Rajah changed direction and joined the second group (consisting of 1 adult, 2 juveniles and a female and calf). Rajah remained close to the 2 juveniles, occasionally synchronously surfacing with them and engaging in friendly tactile interactions. Interestingly enough Rajah was always the first to surface after a dive, sometimes coming up for several breaths before the rest of the group, an indication that his fitness level may not have been quite up to that of wild dolphins accustomed to regularly travelling long distances.

After an hour Rajah again changed direction and left the group. Due to worsening weather conditions we had to leave him shortly afterward. We didn't see Rajah again for 10 days after this promising start, but received reports of his whereabouts and heard his radio signal twice. He traveled 75 km south where he remained in a large bay for several days before traveling 150 km north, where he was sighted at a beach. The following day (10 days after leaving the sea pen) he was found outside the Two Rocks Marina interacting with several children on the rock wall. He approached our boat so eagerly that we though he might jump aboard, and then followed us into the sea pen. Upon closer examination it was obvious that Rajah had lost a great deal of weight during his 10 days at large- 18 kg, or 10.8% of his pre-release weight. He also had several scratches on his belly and tongue, indicating that he had not been foraging properly and perhaps had been trying to eat such inappropriate prey as spiny fish or lobster. Rajah was reinstated in the sea pen in order that he regain condition.

In the meantime the remainder of the dolphins had left together on 16 January with the exception of one of the juveniles (Echo) who was found alone in the marina. She was subsequently captured and reunited with the group at sea. We followed the dolphins for 9 hours that day, during which time they traveled 18 km north, milled near a reef then turned back to the south. Initially the dolphins' behavior was rather erratic and none would approach the boats. However, after several hours at sea they appeared much calmer, slowed down to a slow and steady travel pace and occasionally approached us, though not in response to the underwater signal.

The first inkling of trouble came the next day. The dolphins were located readily enough, some 45 km south where they spent most of the afternoon milling near a beach. Due to rough weather we could not stay at sea, but monitored as best we could from land. Reports were received of the dolphins interacting with people on the beach, and of the new born calf being helped into deeper water on several occasions after nearly beaching himself. One final check on the group at the end of the day revealed that a split had occurred; one of the juveniles and the two males were no longer present.

The next few weeks involved many hours of boat time and worry as the group disintegrated further and individuals proved more and more difficult to locate. Unfortunately, once the juveniles left the adults, we could not find them save for happening on them at sea or by reports from the public. Thus two of the juveniles went missing within the first week and were not re-located. One other juvenile (Echo) also left the group but was regularly sighted visiting beaches. We finally caught up with her after 8 days at sea. She was obviously losing weight and not making much effort to forage, but spending most of each day at beaches and rock jetties interacting with people. We recaptured her and returned her to the sea pen where she was reunited with Rajah. She had lost 10 kg or 8.5% of her body weight in those 8 days at sea.

After this time we were only able to locate the two adult males and Mila with her new born calf. The two males stayed together for at least 8 days (a record for the group) and traveled as far as 75 km south of Two Rocks before going their separate ways. One of the males was re-sighted when he joined up with Mila and her new born calf for three days, before moving off on his own. He has not been sighted since that time (18 days post-release).

The other male ventured south, and was found over 350 km away on his 17th day at sea. He was sighted in this area for a further two weeks, often by divers and people at beaches. Although no one on the research team actually saw him, we heard his radio signal several times and received video footage of his last two encounters which showed that his appearance was fine and indicated good health. However, he has not been seen or heard from since 16 February 1992 (one month after leaving the sea pen).

That left us with just Mila and her new born calf to worry about. They were regularly sighted 25 to 35 km south of Two Rocks after the group disintegrated and it became obvious that both were losing weight. The decision was made to feed Mila from our boat, but after four weeks at sea her calf went missing and can be presumed dead. At about the same time Mila's radio tag failed, making it very difficult for us to find her. However, she began approaching and following fishing boats, presumably begging for fish, and we were able to track her down with the help of local fishermen. When we found Mila again her condition had improved slightly, but she was still underweight and her choice of foraging methods -- following boats and accepting fish handouts -- was considered inappropriate, potentially dangerous, and evidence that she was not integrating properly into the wild. Mila was never seen interacting with wild dolphins, although on several occasions groups were nearby. We decided to recapture her and return her to the sea pen with Rajah and Echo. This was accomplished on 28 February. After 44 days at sea Mila showed a weight loss of 23 kg (15% of her pre release weight) despite receiving substantial fish handouts during the last two weeks.

After 28 February 1992, none of the Atlantis dolphins were encountered at sea again. We continued boat surveys for a further 16 months and used the radio tracking equipment for the first two months of this. Several aerial surveys were conducted covering up to 700 km in either direction of the release site-but no signals were heard. We continued to receive reports from the public and examined them as far as possible. Unfortunately many turned out to be inconclusive or inaccurate. Although public reports can be a useful aid, they are often unreliable. We only accepted as conclusive those reports corroborated by a research team member, photographs or video footage. However, in May 1992 we received some promising reports of a dolphin, sighted 981 km north of Perth, bearing a striking resemblance to one of the released adults. A similar report was received in September from a further 200 km up the coast, however, neither of these sightings could be corroborated as we would have wished.

The three animals returned to captivity were restored to peak condition by the end of May 1992. A new home had to be found for them as we considered that they could not be successfully or humanely released. Not only did we lack sufficient resources for tracking at sea, but their difficulties in the first trial proved they were not well adjusted for life in the wild. Fortunately a local aquarium, UnderWater World, decided they would like to expand and to include the dolphins among their exhibits. A new sea pen was constructed in Hillary's Marina and the dolphins moved to this new location, where they remain. The dolphins participate in several educational shows daily and have recently been involved in a swim-with-people program. The females have each given birth to a calf and all have remained healthy in their new home. A wild dolphin regularly visits the enclosure, often spending hours swimming and drifting near the net.

Second, we found that it is crucial to ensure that natural survival skills have been honed sufficiently. Long-term practice of foraging skills in a natural location is essential. In our release, at least three dolphins had indicated in captivity that they had a capacity for pursuing and catching fish, yet failed to do so adequately in the wild. We shall never know whether the problem was with locating, recognizing or catching prey. Supplementary feeding is often used to help animals through the early stages of a release but this might not be appropriate for dolphins, as we found with Mila. Feeding her from our boat seemed to encourage her to view boats as a food resource and to approach and beg indiscriminately, a behavior which placed her at risk.

Finally, and perhaps most importantly, any release must have available sufficient technology to track animals after release in order to ensure their well being. Only with proper tracking technology is it possible to undertake even minimal health and behavior assessments and to step in if needed. In this study, funding limitations and the state of tracking technology prevented us from reliably locating the dolphins for any length of time. Technology has since improved and satellite tags (which are ideal for long term tracking) can be attached to dolphins.

My involvement in this project also changed my attitude and perception of releasing captive animals into the wild. Initially I strongly favored release, believing that to return animals to their natural habitat after years of confinement was an admirable goal as it seemed to guarantee improvement in living situation and welfare. But as the release developed and I was faced with the difficulties encountered by the dolphins and their obvious decline in welfare, my attitude changed. Was release really in the dolphins' best interests? We talk about animal welfare and animal well being and (although there are a variety of definitions), mean that animals should be dealt with humanely, that they must not be made to suffer or die unnecessarily and, that any causes of suffering must be minimized. But the entire release process is bound to be full of intense stresses and potential risk of mortality, higher than the risks incurred in captivity.

I believe that we take on responsibilities for animals brought into captivity so that, as long as they are in our care, we are responsible for maintaining their health to the best of our abilities. In the case of release this responsibility remains until the animal can demonstrate an ability to survive independent of human care. This means ensuring that projects maximize the chances of survival post release, minimize the risks and stresses encountered, and ensure through post release monitoring that the animal is truly capable of independence (even if this means introducing moderate stressors along the way to help condition the animal for its new environment).

Selected Readings

The Rehabilitation and Release of Bottlenose Dolphins from Atlantis Marine Park, Western Australia. N. Gales and K. Waples. 1993. Aquatic Mammals. Vol. 19: 49-59.

Ethical Issues in the Release of Animals From Captivity. 1997. K. Waples and C. Stagoll. Bioscience. Vol. 47: 115-121.

The Private Lives of Dolphins- Studying Behavior at Brookfield Zoo's Seven Seas Panorama. A. Samuels. 1988. Bison, Brookfield Zoo. Vol 3(1) 23-29.

Return to the Wild...An option for Managing Atlantic Bottlenose Dolphins. R. Brill. 1995. Soundings: Magazine of the International Animal Trainers Association Vol. 20(3) 5-6, 19-20.

Reintroduction into the Wild as an Option for Managing Navy Marine Mammals. R. Brill and W. A. Friedl. 1993. Technical Report 1549 for NRaD, Naval Command, Control and Ocean Surveillance Center RDT&E Division, an Diego, CA 92152-5001.

Reintroducing "Dolphins Into the Wild- Current Developments. J. Dineley. 1994. International Zoo News. Vol. 41(3) 13-16

Dolphin Chronicles C. Howard. 1995. Bantam Books, New York, NY.

Behind the Dolphin Smile. R. O'Barry. 1988. Alonquin Books, Chapel Hill, NC.

Into the Blue. V. McKenna. 1992 Harper Collins Publishers, San Francisco, CA.

The Dolphins Swim Free. 1994. M. Rogers. Kangaroo Press, Kenthurst, NSW, Australia.