Abstract
At Enoshima Aquarium, small cetaceans have been kept since 1957, and at present there are 14 individuals of 4 species (10 bottlenose dolphins Tursiops truncatus, 2 Pacific white-sided dolphins Lagenorhynchus obliquidens, 1 Risso's dolphin Grampus griseus, and 1 false killer whale Pseudorca crassidens) including seven captive-born bottlenose dolphins. In Japan, the number of captive-born dolphins is more than the number of wild-caught dolphins in two aquariums including Enoshima Aquarium. Since 1990, small cetaceans, even pregnant dolphins, have been trained to accept blood samples, rectal temperature and ultrasound diagnosing by husbandry behavior. In 1992, we first observed a decrease in rectal temperatures pre-partum in bottlenose dolphins, and subsequently most parturitions were predicted by a drop in rectal temperature.1 We also observed several physiological changes during pregnancy with blood data.2,3 Currently, we perform ultrasound diagnosing to investigate fetal growth and to predict a parturition day by measurement of bioparietal diameter of the fetus.4 Our previous breeding pool was divided by a net, but a new facility constructed in 2004 does not use a net. From 1994 to 2013, there were 21 live births (Table 1), 1 stillborn and 5 abortions (including a pair of twins). Among them, 12 infants survived more than a year. The numbers of total live births in Enoshima Aquarium is less than one-tenth of the three US institutions. Although it is very hard to compare them both, the survivability of Tursiops neonates (77.7% of live births) in 2004–2013 for Enoshima Aquarium was in between the amount achieved by the three US institutions: 1990–1999 (71.8%) and 2000–2009 (86.3%).5 The present study aims not only to compare and contrast our results, but also to realize our shortcomings while sharing our advantages. As for the reproduction of bottlenose dolphins, one of our next steps is to achieve the survival of all infants for at least one year.
Table 1. Neonate survivability: Enoshima Aquarium vs. three US institutions
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Enoshima Aquarium
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Three US institutions*1
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1994–2003
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2004–2013
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1990–1999
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2000–2009
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Total live births
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12
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9
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110
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139
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Live birth living < 30 d
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4 (33.3)*2
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2 (22.2)
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24 (21.8)
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13 (9.4)
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Lost Day 0 to 1
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1 (8.3)
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0 (0.0)
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6 (5.5)
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7 (5.0)
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Lost Day 2 to 7
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1 (8.3)
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1*3(11.1)
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8 (7.3)
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1 (0.07)
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Lost Day 8 to 30
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2 (16.7)
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1 (11.1)
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10 (9.09)
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5 (3.4)
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Live birth living > 30 d
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8 (66.7)
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7 (77.8)
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86 (78.2)
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126 (90.6)
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Live birth lost > 30 d to 1 year
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3 (25.0)
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0 (0.0)
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7 (6.4)
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6 (4.3)
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Total live living 1 year or longer
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5 (41.7)
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7 (77.8)
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79 (71.8)
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120 (86.3)
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*1Sweeney et al. 2010 (Reference 5)
*2(%)
*3This infant was born in a different aquarium.
Acknowledgements
The authors wish to thank Mr. K. Hori and the staff of Enoshima Aquarium for their support and dedicated care of the animals.
Literature Cited
1. Terasawa F, Yokoyama Y, Kitamura M. Rectal temperatures before and after parturition in bottlenose dolphins. Zoo Biol. 1999;18:153–156.
2. Terasawa F, Kitamura M. Hyperlipemia of captive bottlenose dolphins during pregnancy. J Vet Med Sci. 2005;67:341–344.
3. Terasawa F, Arai T, Tokura T, Ohshita I. Fibrinogen concentrations in captive bottlenose dolphins during pregnancy. J Vet Med Sci. 2008;70:1277–1279.
4. Terasawa F, Koie H, Chino H, Hori Y. Current status of ultrasound diagnosing for pregnant bottlenose dolphins (Tursiops truncates) in Enoshima aquarium. In: Proceedings from the IMATA 41th Annual Conference, Las Vegas NV; 2013: 67.
5. Sweeney JC, Stone R, Campbell M, McBain J, St. Leger J, Xitco M, Jensen E, Ridgway S. Comparative survivability of Tursiops neonates from three U.S. institutions for the decades 1990–1999 and 2000–2009. Aquat Mamm. 2010;36(3):248–261.