Tadamichi Morisaka

Geographic variations in the whistles among three Indo-Pacific bottlenose dolphin Tursiops aduncus populations in Japan

Whistles of Indo-Pacific bottlenose dolphins from three populations in Japan were collected and analyzed quantitatively. Geographic variations in the whistles among populations were found. Significant differences in the whistles among years within each population were also found, but those differences could not explain whole differences among populations because some parameters of the whistles had more differences among populations than among years within each population. As changes with time in the whistles within each population might cause the geographic variations among populations, researchers should take the yearly change within populations into consideration when they study the geographic variation in the whistle of dolphins.

Does body contact contribute towards repairing relationships? The association between flipper-rubbing and aggressive behavior in captive bottlenose dolphins.

Bottlenose dolphins exhibit complex social affiliations that may be shaped by interactions among individuals. Affiliative body contact among dolphins may repair deteriorated relationships or reduce tension within the group following aggressive interactions. We investigated the time-series association between one type of contact behavior (flipper-rubbing) and aggression by continuous observation of three captive bottlenose dolphins. For all three dolphin pairs, the elapsed time to aggressive events was significantly greater following flipper-rubbing. In two dolphin pairs comprised of a young male and an adult female, one-zero score of inter-opponent flipper-rubbing was higher for 10 min following aggressive bouts (post-AG periods) than for the same length of control (Ctrl) periods. For all three focal pairs, one-zero score of third-party rubbing was higher for post-AG than Ctrl periods. Neither the direction of rubbing nor the identity of the partner that approached prior to rubbing showed any significant tendencies. Flipper-rubbing may contribute to restore friendly relationships between former opponents or reduce conflicts in at least juvenile-adult female associations. Our results also give preliminary suggestions of the functions of third-party flipper-rubbing among bottlenose dolphins, including tension easing by the third party, or displacement as a result of aggressive interactions.

Variability in preference for conspecific songs with syntactical complexity in female Bengalese Finches: towards an understanding of song evolution

ABSTRACT Male Bengalese Finches Lonchura striata var. domestica sing syntactically complex songs. A previous study suggested that complex songs elicit more reproductive behavior in female Bengalese Finches than do simple songs. Since the study measured passive reactions to stimulus songs, it is not clear if female birds actively choose complex songs. Here we conducted an active choice experiment using female Bengalese Finches in which selecting a particular perch resulted in the playback of a simple or a complex song. Four out of the eight birds chose complex songs, one chose the simple song, and the remaining three chose both songs randomly. These results suggest that the song preferences of female Bengalese Finches vary individually. A simple population dynamics model confirmed that such a tendency in female preference could lead to the evolution of complex songs in male Bengalese Finches.

Post-conflict affiliation as conflict management in captive bottlenose dolphins (Tursiops truncatus).

Post-conflict affiliation between former opponents or between one of the former opponents and bystanders might have the function of conflict management, which reduces the costs associated with aggressions. One of the suggested functions of post-conflict affiliation is decreased renewed aggressions directed from aggressors to victims. However, the effect of post-conflict affiliation on renewed aggressions by victims has not been investigated. We examined whether post-conflict affiliations decreased the number of renewed aggressions initiated by winners or losers in captive bottlenose dolphins. Both winners and losers initiated renewed aggressions. However, these aggressions decreased after post-conflict affiliation between former opponents, initiated by bystanders to winners, initiated by losers to bystanders, and initiated by bystanders to losers. Post-conflict affiliation between former opponents is suggested to function as reconciliation. Post–conflict affiliation initiated by losers to bystanders is suggested to function as the protection of losers. Post-conflict affiliations initiated by bystanders to one of former opponents are suggested to function as both appeasement and protection of the opponent who affiliates with bystanders.

Underwater Sounds Produced by Neonatal Bottlenose Dolphins (Tursiops truncatus): I. Acoustic Characteristics

Bottlenose dolphins (Tursiops truncatus) communicate using various acoustic signals, including whistles and pulsed sounds. Many studies have been conducted on dolphin whistle development over a long span, but little research has been done on sounds produced by neonatal dolphins just after birth. For this reason, we studied the acoustic characteristics of underwater sounds produced by two neonatal dolphins. Both whistles and burstpulses were identified as neonatal sounds at 1.5 h after birth. Whistles became longer by the hour. Whistle durations were highly correlated with respiration intervals. The neonate randomly produced various types of whistles, but no dominant whistles were documented. There were significant differences between neonates in the proportion of whistles to burst-pulses used, and also in the acoustic characteristics of their whistles. Acoustic characteristics that are unique to each individual neonate might help a mother dolphin to recognize her neonate.

Cognitive tactics of Bengalese finch ( Lonchura striata var. domestica ) for song discrimination in a go/no-go operant task

Twelve Bengalese finches (Lonchura striata var. domestica) were trained to discriminate between a conspecific and a heterospecific song in a go/no-go operant task. Training the birds to go for the conspecifics song or to go for the heterospecific song required the same number of training sessions. Nine possible cognitive tactics could be used to solve this task, but probe tests revealed that the birds used only four. Six birds memorized only the “no-go” stimulus and responded to the rest of the stimuli (no-go memory), two birds classified songs according to the species category (open-ended categorization), one bird memorized both of the training stimuli but responded by chance to the probe stimuli (rote categorization), and two birds combined open-ended and rote categorization tactics (combined categorization). These tactics were related to the number of sessions needed to reach the species-discrimination criterion. Our results suggest that investigators should consider individual cognitive tactics and the pitfalls of go/no-go discrimination when interpreting the results of operant discrimination tasks.

A wild Indo-Pacific bottlenose dolphin adopts a socially and genetically distant neonate.

Alloparental behaviour and adoption have been reported in many mammals and birds. Such behaviours are energetically costly, and their causes and functions remain unclear. We observed the adoption behaviour of a wild Indo-Pacific bottlenose dolphin (Tursiops aduncus) near Mikura Island, Japan. A calf was seen with its mother on six observation days. Following the mother’s death, the calf was observed with a sub-adult female on all 18 observation days from May to September 2012. On three days, the calf was observed swimming with this female in the suckling position and milk was seen leaking from the female’s mammary slit. A five-year dataset revealed no significant social or kin relationships between the biological mother and allomother, indicating that kinship and social relationships did not play an important role in the observed adoption.

Sound variation and function in captive Commerson's dolphins (Cephalorhynchus commersonii).

Commersons dolphin (Cephalorhynchus commersonii), one of the smallest dolphin species, has been reported to produce only narrow-band high-frequency (NBHF) clicks and no whistles. To clarify their sound repertoire and examine the function of each type, we analysed the sounds and behaviour of captive Commersons dolphins in Toba Aquarium, Japan. All recorded sounds were NBHF clicks with peak frequency >110kHz. The recorded click-trains were categorised into four types based on the changing pattern of their Inter-click intervals (ICI): Decreasing type, with continuously decreasing ICI during the last part of the train; Increasing type, with continuously increasing ICI during the last part; Fluctuating type, with fluctuating ICI; and Burst-pulse type, with very short and constant ICI. The frequency of the Decreasing type increased when approaching an object newly introduced to the tank, suggesting that the sound is used for echolocation on approach. The Burst-pulse type suddenly increased in front of the object and was often oriented towards it, suggesting that it was used for echolocation in close proximity to the object. In contrast, the Increasing type was rarely recorded during approach, but increased when a dolphin approached another dolphin. The Increasing and Burst-pulse types also increased when dolphins began social behaviours. These results suggest that some NBHF clicks have functions other than echolocation, such as communication.

Captive bottlenose dolphins (Tursiops truncatus) spontaneously using water flow to manipulate objects.

Several terrestrial animals and delphinids manipulate objects in a tactile manner, using parts of their bodies, such as their mouths or hands. In this paper, we report that bottlenose dolphins (Tursiops truncatus) manipulate objects not by direct bodily contact, but by spontaneous water flow. Three of four dolphins at Suma Aqualife Park performed object manipulation with food. The typical sequence of object manipulation consisted of a three step procedure. First, the dolphins released the object from the sides of their mouths while assuming a head-down posture near the floor. They then manipulated the object around their mouths and caught it. Finally, they ceased to engage in their head-down posture and started to swim. When the dolphins moved the object, they used the water current in the pool or moved their head. These results showed that dolphins manipulate objects using movements that do not directly involve contact between a body part and the object. In the event the dolphins dropped the object on the floor, they lifted it by making water flow in one of three methods: opening and closing their mouths repeatedly, moving their heads lengthwise, or making circular head motions. This result suggests that bottlenose dolphins spontaneously change their environment to manipulate objects. The reason why aquatic animals like dolphins do object manipulation by changing their environment but terrestrial animals do not may be that the viscosity of the aquatic environment is much higher than it is in terrestrial environments. This is the first report thus far of any non-human mammal engaging in object manipulation using several methods to change their environment.

Spontaneous Ejaculation in a Wild Indo-Pacific Bottlenose Dolphin (Tursiops aduncus).

Spontaneous ejaculation, which is defined as the release of seminal fluids without apparent sexual stimulation, has been documented in boreoeutherian mammals. Here we report spontaneous ejaculation in a wild Indo-Pacific bottlenose dolphin (Tursiops aduncus), and present a video of this rare behavior. This is the first report of spontaneous ejaculation by an aquatic mammal, and the first video of this behavior in animals to be published in a scientific journal.