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영화 프리윌리(Free Willy, 1993) 의 주인공으로 나온 범고래 케이코의 자연 방사를 다룬 M. Simon 의 논문 From captivity to the wild and back: An attempt to release Keiko the killer whale 입니다.
갖힌 돌고래도 재활 훈련을 통해 자연으로 방사가 가능하며, 자연에서 살아갈 수 있음을 보여줍니다.
첨부한 영어 원문 PDF 파일을 한글로 번역할 수 있는 분을 찾습니다.
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From captivity to the wild and back: An attempt
to release Keiko the killer whale
M. SIMON
Greenland Institute of Natural Resources,
P. O. Box 570,
3900 Nuuk, Greenland
and
Department of Biological Sciences,
University of Aarhus,
C. F. Møllers Alle, Build. 1131, ´
8000 Aarhus C, Denmark
E-mail: masi@natur.gl
M. B. HANSON
NOAA Fisheries,
2725 Montlake Boulevard East,
Seattle, Washington 98112-2097, U.S.A.
L. MURREY
Moeller Design and Development,
620 S Industrial Way,
Seattle, Washington 98108, U.S.A.
J. TOUGAARD
National Environmental Research Institute,
University of Aarhus,
Frederiksborgvej 399,
P. O. Box 358, DK-4000 Roskilde, Denmark
F. UGARTE
Greenland Institute of Natural Resources,
P. O. Box 570,
3900 Nuuk, Greenland
A number of cetaceans have been released into the wild, with research or the
improved welfare of the individuals in question as the main goal. In a few cases,
releases have been monitored with methods such as telemetry or photo-identification
(Gales and Waples 1993, Veit et al. 1997, Wells et al. 1998, Reynolds et al. 2000). As
a rule, the animals released successfully into the wild had been captive for relatively
short periods of time (e.g., 2 yr, Wells et al. 1998), were held in sea pens rather than
concrete tanks, and some were released in the company of conspecifics (Veit et al.
1997, Wells et al. 1998). We describe here the last phases of a project aimed at
releasing a single killer whale that had been captured as a calf, raised in tanks and
kept isolated from conspecifics during most of his life.
12 MARINE MAMMAL SCIENCE, VOL. **, NO. **, 2009
The released killer whale, known as Keiko, was a male born into a wild group
of killer whales in Icelandic waters. He was captured in 1979 near Vestmannaeyjar,
Iceland, approximately 2 yr old, determined from tooth growth layers. After 6 yrs
with other killer whales in tanks in Iceland and Canada, he was sold to an amusement
park in Mexico. From 1985 to 1996, Keiko lived and performed in a small pool in
Mexico City, without contact with other killer whales (bottlenose dolphins were
kept periodically in the same tank). In 1996, as the first step of a program to return
Keiko to the wild, he was transported to a large concrete enclosure in Oregon. In
1998, he was moved to a bay pen in Klettsvik, a natural bay in the archipelago of
Vestmannaeyjar, Iceland, where he received training aimed at a release to the wild
(Anonymous 2000).
During the summers of 2000, 2001, and 2002, Keiko was trained to follow his
caretakers’ boat and take open ocean swims. Each summer, he spent several days
in the proximity of wild killer whales that seasonally inhabit the waters around
Vestmannaeyjar to feed on summer-spawning herring (Sigurjonsson ´ et al. 1988;
Jakobsson and Stefansson 1999; Schorr 2002; Simon ´ et al. 2005, 2006, 2007).
Biopsies of the wild killer whales were taken during 2000–2001 (Schorr 2002). DNA
analyses have shown that there are at least two genetic types of killer whales in the area
and that Keiko shared a genotype with some of the wild whales (Hoelzel 2002). In the
summer of 2002, as in previous years, Keiko was led to waters off Vestmannaeyjar,
Iceland. He experienced minimal human contact for approximately 1 mo, while
following wild killer whales. Subsequently, he spent another month swimming from
southern Iceland to Norway (Fig. 1). Keiko was taken once more under human care
Figure 1. Study area, where the location of the whale is marked during the six periods of
the release. The positions given by the satellite tag, during travel from Iceland to Norway
in period 3 are marked. The approximate core areas for mackerel in the summer of 2002 are
marked with open circles (Anonymous 2003).NOTES 3
Figure 2. Keiko after arriving in Norway with the VHF tag (on top) and SDR tag (below)
mounted to his dorsal fin. (Photo by Thorbjorg Kristjansdottir.) ¨
in Norway and a free access enclosure was constructed in Skalvikfjorden, where he ˚
remained until his death in December 2003.
MONITORING AND INSTRUMENTATION
Immediately before the first open ocean swim of 2002, a VHF transmitter (ATS
model 201) and a satellite-linked time-depth recorder, SDR (Wildlife Computers
SDR-T16, Redmond, WA) were attached to the dorsal fin. The VHF tag allowed us to
track Keiko in the field 24 h a day, while the SDR provided a few daily positions and
a summary of the diving behavior. The positions provided were obtained within a few
hours in the morning and thus did not provide data on Keiko’s movements during
the day. Therefore we selected the best-quality daily position (Fig. 1). The SDR-T16
tags collect dive data over 6-h time blocks and are transmitted as three different
summary histograms of dive depth, dive duration, and time at depth. During a dive,
the tag sampled depth every 10 s and logged information into one of 14 intervals
(6–26, 26–50, 50–76, 76–100, 100–126, 126–150, 150–176, 176–200, 200–250,
250–300, 300–350, 350–400, 400–450, and >450 m). The tag electronics were
over-molded in a urethane housing to fit the irregular surface of Keiko’s dorsal fin.
After 2 mo of attachment, the tags were inspected visually and there were no signs
of tag migration or damage of the tissue surrounding the tags (Fig. 2).
TIMELINE OF RELEASE EFFORT
For purposes of analysis, the study was divided into six periods, based on
Keiko’s location and contact with humans and wild killer whales (Table 1). During
periods 1 and 2, Keiko was off the archipelago of Vestmannaeyjar and adjacent waters, in southern Iceland and periodically observed from a small sailboat. In order4 MARINE MAMMAL SCIENCE, VOL. **, NO. **, 2009
Table 1. The six periods of the study.
Period Date (2002) Location Comments
1 7 July–16 July Vestmannaeyjar First period among wild whales
2 17 July–4 Aug. Vestmannaeyjar Second period among wild whales
3 5 Aug.–31 Aug. Iceland to Norway Eastward movement
4 1 Sept.–3 Sept. Skalvikfjorden Contact with people ˚
5 4 Sept.–11 Sept. Inner Skalvikfjorden Reduced activity ˚
6 12 Sept.–29 Sept. Skalvikfjorden area Behavioral control ˚
to reduce the influence of human contact, visual observations were restricted to a
few close approaches per day that allowed us to assess Keiko’s behavior and physical
condition. If Keiko approached the tracking boat, the crew went below deck or
otherwise hid from view until he lost interest. The position of the tracking boat, the
time, date, estimated direction and distances to Keiko and to the wild whales, as
well as the behavior of the wild whales, were recorded approximately every 15 min.
Period 1 and 2 are divided by Keiko swimming back to the bay pen, being fed and
receiving human care before being brought back to the wild killer whales. During
period 3, he swam from Vestmannaeyjar to Skalvikfjorden, Norway. In period 4, he ˚
interacted with people in the waters of Skalvikfjorden. During period 5, he remained ˚
in a relatively small area and in period 6, professional caretakers took Keiko for regular swims from inner Skalvikfjorden into nearby waters. Period 6 extended beyond ˚
29 September 2002, the last day included in this analysis.
Period 1
Beginning on 7 July, Keiko spent seven consecutive days in the proximity of wild
killer whales. The wild whales were divided into groups that joined, split, and moved
in loose coordination, traveling around midnight and returning to forage in specific
shallow areas during daytime (a killer whale group was defined as a cluster of animals
in close proximity to each other that appeared to be independent to other killer whale
groups in the area). Foraging was identified by the arching of a killer whale’s body
before diving, debilitated fish or fish parts at the surface and birds taking fish from
the surface (Simon et al. 2007). Keiko switched between different groups of wild
killer whales, often remaining on the periphery, at distances of 100–300 m, with his
head pointing toward the closest whales. During this period, Keiko was seen either
floating motionless (“logging”) or swimming slowly without arching his body. No
arching or other behaviors typical for cetaceans prior to dives were observed. Keiko
became separated from the wild whales after midnight on 15 July. Later that day,
at 10:10, he swam back into the bay pen in Klettsvik, where he remained until the
afternoon of 17 July. A stomach sample taken with a large tube was analyzed using
a stereomicroscope. The sample consisted of a transparent, slimy liquid without any
trace of food remains, showing that Keiko did not eat before entering the bay pen.
1
1
Personal communication from Gısli A. V ´ ıkingsson, Marine Research Institute, P. O. Box 1390, 121 ´
Reykjavık, Iceland, e-mail: gisli@hafro.is, 5 September 2008. ´NOTES 5
Period 2
Keiko was again led into open water on 17 July and was observed following wild
whales during the period 17 July–24 July and again during 27 July–1 August (observations were interrupted on 25 and 26 July due to bad weather). As during period 1,
Keiko followed wild killer whales that were split into three to five groups, which
moved and interacted in loose coordination inside an area with a diameter of approximately 30 km. A second stomach sample was taken on 23 July, after Keiko was led
away from a fishing boat. As with the previous sample, there was only a transparent,
slimy liquid and no food remains were observed using a stereomicroscope. During
period 2, the distance between Keiko and the wild whales progressively decreased.
By 27 July he was regularly seen closer than 30 m from the closest wild whale. A
brief physical interaction was witnessed on 30 July, when Keiko dove among foraging whales and surfaced in very close proximity to three adult males and at least
two females or immature males. There was a splash from the tail of one of the wild
whales, which was swimming ventral side up, with his head below Keiko, while he
was at the surface. The splash was accompanied by a “startle” reaction from Keiko
who swam to the tracking boat, while one of the female/juvenile whales surfaced
after him. This was the only time Keiko was seen diving among killer whales and
the only physical interaction observed. On 27 July, Keiko was seen arching his back
before diving and then later breaking the surface of the water with his rostrum, as if
ascending vertically. On 29 July, on two occasions, Keiko was seen raising his fluke
up before diving, indicating a vertical descent.
Period 3
Keiko spent the majority of period 3 offshore, swimming from Iceland to Norway.
There was no visual contact between 2 August and 29 August when he was tracked
with the satellite transmitter. As his track soon veered off the suspected migration
routes of killer whales between southern and eastern Iceland (Sigurjonsson and ´
Leatherwood 1988), Keiko might have been alone during this period although due
to the lack of visual contact we cannot be certain. On 30 August, Keiko was observed
close to Kristianssund, Norway, a few meters from shore, in very shallow water. His
physical appearance was healthy: the skin color and texture seemed normal, he did
not look emaciated, and the tissue around the tag showed no signs of tag migration
or infection. In addition, he seemed to move more actively than observed during
periods 1 and 2.
Period 4
Keiko followed a small open boat with local people that were out for a pleasure
fishing trip. He followed the boat into its home place in Skalvikfjorden and interacted ˚
with local people from 1 September to 3 September. During daylight hours, a crowd,
from land and boats, was almost constantly soliciting his attention, trying to touch
him or swim with him. In the beginning of this period, Keiko often initiated the6 MARINE MAMMAL SCIENCE, VOL. **, NO. **, 2009
interactions and swam actively from one group of people to another. At about 1900
on 3 September, Keiko was seen logging and swimming slowly toward the inner
parts of Skalvikfjorden. At the time of the observation, several small boats were ˚
following and surrounding him on four sides, with the passengers hitting the boat
hulls, trying to attract his attention. Keiko was notably less active than earlier in
this period.
Period 5
During 4 September, Keiko placed himself below and between two skiffs tied to
a floating bridge. During daylight hours, until 9 September, he remained almost
motionless close to this spot. On at least two occasions, people fed Keiko with small
amounts of fish. On the afternoon of 6 September, the local animal welfare authorities
issued a legislation prohibiting people to touch, feed, or approach Keiko closer than
50 m, whether from land or by sea. Keiko’s caretakers started feeding him again
on 8 September. In order to raise the activity level of the passive whale, caretakers
took Keiko for short swims with a boat within the waters of inner Skalvikfjorden ˚
on 9 September.
Period 6
During period 6, Keiko’s physical activity was systematically encouraged by his
trainers and he was taken for longer swims into Skalvikfjorden and adjacent wa- ˚
ters. During this period, Keiko’s activity increased to levels similar to the years
he spent in Klettsvik bay pen in Iceland before the release. Period 6 extended beyond 29 September 2002, the last day included in this analysis. Keiko stayed in the
free access bay pen in Skalvikfjorden. Usually he had access to the open water and ˚
he swam alone outside the bay pen, returning by himself. Keiko died in December
2003 apparently from pneumonia, approximately 26 yr old.
DIVE BEHAVIOR
Two hundred and nine dive-depth histograms were received, containing summed
information from a total of 1,264 h. Of 7,541 dives recorded, 93.4% were between 6
and 26 m deep. Of the dives deeper than 26 m, 98% occurred during periods 2 and
3. There were significantly fewer dives/h during period 5 compared to periods 1,
2, 3, and 4 (Tukey’s Studentized range test, P < 0.01). There were also fewer
dives/h during period 5 than during period 6 (Table 2), but this difference was not
significant. The largest number of dives/h deeper than 50 m was recorded on 29 July.
This coincides with the observed fluking in the surface before diving. The deepest
recorded dive of 72 m occurred on 3 August, at the end of period 2 (Table 2). During
all periods, Keiko spent more than 80% of the time in the upper 4 m of the water
column.NOTES 7
Table 2. Maximum dive depth during the six periods of the study where n is the number
of 6-h periods and the number of dives per hour during all six periods. A dive is defined as
>6 m.
Average maximum Maximum depth Average number of Range of
Period depth (SD) range (n) dives/h (SD) dives/h (n)
1 17.7 m (7.6) 12–32 m (7) 6.3 (4.4) 0–18 (36)
2 53.0 m (16.4) 32–72 m (4) 7.6 (3.0) 0.3–13.7 (37)
3 45.3 m (10.3) 36–64 m (6) 7.9 (4.2) 0–20.2 (66)
4 16.0 ma
16 m (1) 5.9 (6.1) 0–16.3 (9)
5 12.0 m (9.1) 4–28 m (6) 0.1 (0.2) 0–0.7 (18)
6 12.8 m (6.5) 0–24 m (10) 3.1 (3.6) 0–14.8 (45)
a
Only one status message was received for period 4.
One hundred and ninety-one dive duration histograms were received, which summarize 1,146 h. The dive-duration intervals are: 0–1, 1–3, 3–5, and >5 min. There
were on average significantly more dives with durations of 0–1 min during period 4
than in the other periods. The number of dives lasting 0–1 min during period 5 was
lower than in the other periods, but this difference was not significant. The average
number of dives with durations of 1–3 min was significantly lower during period 5
than in all other periods except period 6 (Tukey’s Studentized range test, P < 0.01).
There were significantly more long dives (>3 min) during periods 2 and 3 compared
to the other periods (Tukey’s Studentized range test, P < 0.01).
Two hundred and twenty-three time-at-depth histograms were received, summarizing 1,338 h. There was no significant difference in how much time Keiko spent at
6–26 m among the different periods (Nonparametric one-way ANOVA, F = 3.36,
df = 5, P > 0.05 [Barnard et al. 2001]). Keiko spent significantly more time at
26–50 m during period 2 than during all other periods, with the exception of period
3 (Tukey’s Studentized range test, P < 0.01). The diving behavior during the most
active periods were compared to the dive data presented by Schorr et al. (2001), who
deployed eight suction-cup attached time-depth recorders on wild killer whales off
Vestmannaeyjar (202 h), in summer 2000. Average number of dives per hour and
average duration of dives, for dives longer than 1 min, were compared with daytime
data from Keiko collected in periods 2 and 3. The average duration of dives was
estimated from dive duration histograms, excluding the 0–1 min bin and assuming
that the average duration of dives in each bin was the center of the bin range.
Keiko made fewer dives >1 min than did the wild killer whales from Vestmannaeyjar. However, there was no significant difference between Keiko and the wild
whales in the duration of these dives (Table 3). When looking at the different depth
intervals of dives longer than 1 min, Keiko dove more often than the wild whales to
depths of 6–26 m, but less often than the wild whales to depths >26 m (Table 3).
Schorr et al. (2001) noted that the wild killer whales off Vestmannaeyjar spent an
average of 76% of their time in the top 10 m of the water column. In comparison,
Keiko spent more than 80% of the time in the upper 4 m.8 MARINE MAMMAL SCIENCE, VOL. **, NO. **, 2009
Table 3. Number of dives per hour and dive duration, for dives longer than 1 min, of wild
killer whales (n = 202 h). The data on Keiko’s dive behavior include periods 2 and 3, minus
time block 2100–0300. Average number of dives per hour for the four depth intervals for
wild killer whales (n = 5.5 h, Schorr et al. 2001) and Keiko (n = 468 h from periods 2 and
3).
Wild whales (SD)
Day Night Keiko (SD)
Average dives/h 9.2 (2.16) 9.6 (3.70) 5.41 (2.88)
Average duration (min) 2.4 (0.7) 1.8 (0.37) 2.84 (0.97)
6–26 m 1.6 7.6
26–50 m 1.8 0.8
50–76 m 3.6 0.1
76–100 m 0.36 0.0
KEIKO’S BEHAVIOR AMONG WILD WHALES
During the initial efforts to release Keiko into the wild in 2000 and 2001, he and
the wild killer whales seldom approached and often moved away from one another. In
contrast, Keiko followed the wild killer whales shortly after first being led to them
in 2002 and the wild whales seemed to tolerate his presence. The distance between
Keiko and the wild whales diminished gradually, and one physical interaction was
observed close to the end of period 2. The fact that Keiko was observed to follow
some of the same individuals for several weeks during 2002, and that some of
these same individuals were present during 2000 and 2001 (photographic data,
unpublished), suggest that a mutual acclimatization may have facilitated a growing
familiarity between Keiko and these particular wild killer whales. This process
seemed to be ongoing at the time of the last visual observation off Vestmannaeyjar in
2002. However, keeping in mind that limited visual contact did not allow drawing
definitive conclusions, the fact that Keiko was usually seen either on the periphery
of the wild whale groups, or logging at various distances from them, suggests that
he was not socially integrated with the wild whales at the time of the last visual
observation.
DID KEIKO FEED?
Prior to summer 2002, Keiko’s diving performance was modest, with maximum
recorded dive depths shallower than 35 m.
2
During summer 2002, the diving profile
evolved from relatively short and shallow dives during period 1, to deeper and longer
dives in periods 2 and 3. The increased diving activity recorded during period 2
corresponds well with observations of Keiko performing behaviors characteristic
of deep dives, such as arching the body and lifting the flukes before diving. This
2
Personal communication from Jeff Foster, Marine Research Consultants LLC, 2420 Nellita Road
NW, Seabeck, WA 98380, U.S.A., e-mail: jefffoster13@yahoo.com, June 2001.NOTES 9
evolution caused Keiko’s most active diving profile to resemble the profiles observed
for wild Icelandic killer whales. Because he made shallower and less frequent dives
than wild killer whales, and due to the failure to observe him consistently diving
among feeding wild whales, it seems unlikely that Keiko actively participated in
the wild whales’ cooperative hunts. However, the increase in depth and duration of
Keiko’s dives during period 2 suggests that he nevertheless may have been able to
obtain food while among the feeding wild whales. Observations of stunned herring
at the surface, as well as underwater recordings, indicate that Icelandic killer whales
immobilize herring by hitting the fish schools with the underside of their flukes,
as Norwegian killer whales do (Simon et al. 2005). Underwater observations of
Norwegian killer whales feeding showed that a considerable number of immobilized
herring were not taken by the killer whales that debilitated them, but by other killer
whales, fish, or sea birds (Simila and Ugarte 1993). A similar situation seems to take ¨
place when Icelandic killer whales hunt herring (Simon et al. 2005). Though Keiko
was not seen feeding on live herring, it is possible that he could have fed on already
stunned fish without diving as deep or as often as the wild killer whales. However, it
is unlikely that he consumed any significant amount of food shortly before 15 July
and 23 July, when samples of his stomach contents were obtained. During period
3, while traveling to Norway, Keiko moved on average 71.8 km/d, calculated from
straight-line connections between satellite locations. The mean swimming speed of
undisturbed resident killer whales in British Columbia was 5.19 km/h, SD 2.52 km/h
(Kruse 1991). Assuming Keiko moved with an average speed of 5 km/h, which
allows for low energy consumption (Yazdi et al. 1999), he would have been capable
of traveling this distance of 71.8 km/d in 14.4 h, resulting in a surplus of nearly
10 h/d. This can be interpreted in two ways: either he did not swim in a straight
line between satellite positions, or he spent time engaged in other activities such as
resting or foraging. The relatively high diving activity during period 3 indicates that
Keiko performed behaviors other than resting or horizontal traveling during this long
trip, including the possibility that he was foraging. Of the potential prey species that
Keiko was likely to encounter, blue whiting and squid are found at depths deeper than
200 m during daylight, outside his observed diving range. However, these potential
prey items ascend to the surface at night and it is therefore possible that they were
intermittently available. Mackerel seem a likely prey candidate during period 3, since
Keiko spent approximately 10 d in an area with a high concentration of this species,
which can be found within the upper 20 m of the water column throughout the
day and night (Fig. 1, Anonymous 2003). The fact that no difference was detected
in the diving behavior between the times Keiko spent inside and outside of the
mackerel grounds may suggest that he did not take advantage of this prey. However,
as the mackerel are available in the top of the water column during the day, Keiko
might have captured this fish without significantly changing his diving behavior.
It is possible that Keiko did not feed at all during the time he was independent of
human care. Newly captured killer whales are able to live without food for several
weeks before eating dead fish (Hoyt 1998). However, this seems unlikely given the
healthy appearance and behavior of Keiko when he was first observed in Norway, as10 MARINE MAMMAL SCIENCE, VOL. **, NO. **, 2009
well as the fact that a veterinarian, based on girth measurements, blood samples and
photographs, concluded that the whale had fed (Cornell 2002).
HUMAN IMPACT ON KEIKO’S BEHAVIOR
Before July 2002, Keiko had no contact with the tracking boat and, as a rule, had
very little contact with her crew. During periods 1 and 2, the tracking boat spent
18 d at sea tracking Keiko. Keiko approached the tracking boat on 16 occasions,
with durations ranging from 2 min to <2 h. During these approaches, Keiko would
either swim close to the boat or log with his head almost touching the hull. On two
occasions, repeated loud vocalizations attributed to Keiko were heard below deck.
During periods 1 and 2, Keiko approached the caretakers’ boat on the two occasions
when this boat was out of the harbor. The first time was on 8 July, when Keiko had
been on his own for one day, during which the caretakers’ boat had been drifting with
the engine off. When the caretakers’ boat switched on the engine for the first time,
Keiko, who was 2 nmi away, homed straight for it and remained in its proximity for
57 h. Keiko approached the caretakers’ boat a second time, during a crew change on
22 July, and remained in its proximity until 23 July.
Despite the fact that the crew of both the tracking boat and the caretakers’ boat
reacted the same way to Keiko’s approaches (i.e., by going below deck and ignoring
him), Keiko remained for much longer periods of time by the caretakers’ boat,
suggesting that he was more strongly attached to it (or to its crew) than to the
tracking boat. When Keiko arrived in Norway in period 4, he actively sought out
human company, swimming to boats and people. To begin with he was very active,
though staying near the surface only diving for 0–1 min at a time. After a few days
Keiko became inactive staying near a small boat (period 5), possibly to avoid the large
and steadily increasing crowd of people, now seeking his attention. The frequency of
dives and the number of dives lasting more than 1 min were significantly less during
period 5 than during the rest of the study, and all other parameters showed the
lowest levels of activity during this period. The lack of activity was also evident from
visual observations, and possible explanations, not necessarily mutually exclusive,
include: stress triggered by the extremely high rate of interactions with people
during period 4, physical exhaustion or an infection. A moderately high white cell
count from a blood sample taken during period 5 supports the suspected infection.
3
Alternatively, the white cell count could have been due to dehydration caused by
lack of food. At the end of period 5 and during period 6, when professional caretakers
took charge of Keiko, his diving parameters began to approach levels similar to those
measured at the start of the study.
EVALUATI ON AND CONCLUSIONS
A release program can be considered a success when the released animal is able
to feed, maintain health and stress levels comparable to his wild conspecifics, show
3
Personal communication from Colin Baird, Noble Caledonia Limited, 2 Chester Close, Belgravia,
London SW1X 7BE, U.K., e-mail: colinbaird@hotmail.com, September 2002.NOTES 11
normal predator avoidance behavior, and ultimately reproduce (unless unable for
other reasons, such as reproductive senescence). Under these criteria, Keiko’s release
to the wild was not successful, since though physically unrestricted and free to leave,
he kept returning to his caretakers for food and company.
Two bottlenose dolphins were released in Florida in 1990 and resighted continuously until at least 1996 (Wells et al. 1998). Based on this successful release, Wells
et al. (1998) listed several recommendations, some of which can be summarized
as follows: (1) release more than one animal together in a social functional unit;
(2) released animals should be young of age; (3) release short-term captive animals;
(4) keep animals in acclimatizing pen before release; (5) release in native waters;
(6) locate sources of live prey for readaptation; (7) study ranging and social association patterns in host community before, during, and after release; and (8) study
behavior of released animals before, during, and after release. Keiko’s release effort
fulfilled to some extent recommendations 4–8, but failed to fulfill recommendations
1, 2, and 3; Keiko was not part of a killer whale social unit, he was not young, and
he had been in captivity for the majority of his life.
Wellset al.’s (1998) recommendations were made for bottlenose dolphins, generally
living in fission-fusion societies (Wells 1991), and additional factors may need to be
taken into account when considering release of captive killer whales. The best-studied
killer whale populations form strongly bonded matriarchal family groups throughout
life (e.g., Bigg et al. 1990, Baird and Dill 1996), that forage cooperatively (Simila¨
and Ugarte 1993). Even the males keep strong bonds with their close relatives,
communicating with a group-specific repertoire of calls and whistles (Ford 1991,
Strager 1995, Ford and Ellis 1999, Riesch et al. 2006). Thus the survival of a released
captive killer whale might depend on an adoption to a wild group of killer whales.
The successful reintroduction of a North Pacific northern resident killer whale A73
(called Springer) in 2002, demonstrates that killer whales can re-bond after at least a
relatively short period of separation, even if their mother is no longer present (Francis
and Hewlett 2007). Springer was a suitable candidate for release: she was a juvenile,
had been under human care for only 1 mo, and was released into her well-researched
maternal group, at the time when they feed on abundant salmon runs. Springer was
captured with the aim of releasing her into her native group, after it was established
that she was lost and unable to survive on her own.
Keiko lived in a very small tank in an amusement park in Mexico City when he
performed in the 1993 family film Free Willy. Thereafter, there was a strong public
pressure to release Keiko to the wild, preferably to his “family” group in Iceland.
Keiko was not chosen for release based on his suitability. In retrospect, Keiko was
indeed a poor candidate for release, due to the early age of his capture, long history
of captivity, prolonged lack of contact with conspecifics, and strong bonds with
humans.
The release of Keiko demonstrated that release of long-term captive animals is
especially challenging and while we as humans might find it appealing to free a
long-term captive animal, the survival and well being of the animal may be severely
impacted in doing so.
Through the last decades, several captive dolphins have been released to the wild.
The fate of the majority of these animals is unknown, and most of those monitored12 MARINE MAMMAL SCIENCE, VOL. **, NO. **, 2009
ended up being recaptured and under human care (review in Gales and Waples 1993).
Because there is a high risk of not succeeding, Gales and Waples (1993) concluded
that it is absolutely necessary to monitor released animals with any technology
available, in order to help the animals if they are in distress. Due to the effective
VHF and satellite tracking of Keiko after release, his caretakers were able to reestablish contact with him when he showed signs of distress. In agreement with
Gales and Waples (1993), this report shows that a combination of VHF and satellite
tracking and a contingency plan for return to human care are necessary if the goals
of a release project include the long-term well-being of the animal
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