The Bottlenose Dolphin

Tursiops truncatus


Diana Reiss and Lori Marino. 2001. Mirror self-recognition in the bottlenose dolphin: A case of cognitive convergence. Proceedings of the National Academy of Sciences.


Mirror self-recognition (MSR) is an exceedingly rare capacity in the animal kingdom. To date, only humans and great apes have shown convincing evidence of MSR. In this study we present the first conclusive evidence for self-recognition outside of the primate domain in a species phylogenetically distant and neuroanatomically different from primates, the bottlenose dolphin. Two dolphins was exposed to reflective surfaces under conditions of control, sham-mark and marking of the body. Analysis included measures of frequency, duration, and latencies of behaviors under different experimental conditions. Behaviors were categorized as either mark-directed or not. Results demonstrate that both subjects are capable of using a mirror to investigate parts of their own body. These results indicate that bottlenose dolphins possess the capacity for self-recognition. These findings provide a striking example of evolutionary convergence in cognitive capacity.

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Samuels, A.* and T. Gifford. 1997. A quantitative assessment of dominance relations among bottlenose dolphins. Marine Mammal Science 13(1): 70-99.

* Conservation Biology, Chicago Zoological Society, Brookfield, IL 60513, USA; Biology, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA


Agonistic behavior of bottlenose dolphins was studied at Brookfield Zoo for nearly 4.5 yr, and dominance relationships were determined using a quantitative technique adapted from primate behavioral research. Dominance relations among dolphins were incluenced by the gender of participants. Male dolphins were clearly and consistently dominant to females, and intersexual agonism occurred at moderate reates with seasonal peaks in spring and fall. Dominance relationships among female dolphins were age-ordered and stable, even though agonism among females did occur at uniformly low rates. In contrast, the two males had a changeable dominance relationship in which periods of stability and low-level agonism were interspersed with episodes of intense competition. Zoo-based research revealed patterns of behavior that conformed to current knowledge about bottlenose dophin social structure. Moreover, reserach in a zoo setting facilitated development of a quantitative technique that can be used to assess cetacean dominance relationships in field research.

Felix, F. 1997. Organization and social structure of the coastal bottlenose dolphin _Tursiops truncatus_ in the Gulf de Guayaquil, Ecuador. _Aquatic Mammals_ 23(1): 1-16.

Fundacion Ecuatoriana para el Estudio de Mamiferos Marinos (FEMM), PO Box 09-01-11905 Guayaquil, Ecuador


A study on the coastal bottlenose dolphin was carried out between February 1990 and October 1992 in the inner estuary of the Gulf of Guayaquil, Ecuador (3 S, 80 W). In 143 boat surveys, a total of 4021-4351 dolphins in 241 groups were recorded. 441 different dolphins were identified by natural marks of which 1557 resightings were obtained. Based on resightings, it was established that this population of dolphins is organized in communities of around 115 animals (S.D.=37). Three resident and two non-resident communities were recorded in the study area. Resident communities occurred along 20-40 km of coast in overlapping home ranges. There were interactions between groups of different communities in 13.3% of the observations. Association patterns among individuals of different age and sex classes were analyzed. Females mainly associated with other females and formed bands. Every band showed preferences to use different sites of the community home range. Subadults associated to a particular adult female band. In contrast, adult males did not show preference to associate with any band. Several males occurred in high-stable pairs and competed for females in what seems to be a hierarchically structured society, with one pair of dominant males controlling the access to females in the community. These findings suggest a marked polygynous mating behavior in this tropical population that contrasts to what was observed in other temperate and subtropical populations.

Harzen, S. and B.J. Brunnick. 1997. Skin disordes in bottlenose dolphins (_Tursiops truncatus_), resident in the Sado estuary, Portugal. _Aquatic Mammals_ 23(1): 59-68.

Blue Dolphin Research and Consulting, P.O. Box 9243, Jupiter, FL 33458, USA


Throughout two periods, in 1986/87 and 1992/93, a systematic study was conducted of a group of bottlenose dolphins inhabiting the Sado estuary. At the end of the second study period, 85% of the long term residents showed signs of skin disorders. Forty percent of these animals show signs of the skin disorder for 6 or more years. Skin samples were not collected or analysed to date, therefore, it has been impossible to determine the cause of the skin disorders. Comparison with observations in other areas suggest that habitat degradation may play an important role when dolphins become sick and/or entire communities decline and eventually disappear. The appearance of skin disorders may indicate depressed or overworked immune systems that would normally counteract the disease. Such immune system deficiencies may be caused by stress, habitat degradation or contamination with pollutants.

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