Dolphins are a highly social species. Tursiops truncatus has become one of the most widely used dolphin species in oceanariums because its coastal nature made it relatively easy to catch. It has also proved to respond very well to training, and therefore makes an effective ‘show animal’. Thus, a wealth of information exists on the behaviour of bottlenose dolphins in captivity. However, studies on their behaviour in the wild are more less abundant. The many limitations of conducting research underwater –particularly time, depth and speed restraints- have made it difficult to make definitive conclusions about certain aspects of dolphin social systems. For example, knowledge about kin selection and the relatedness dolphins within pods is limited.

On the following pages you will find a compilation of research and theories concerning the social spacing, mating systems, parent-offspring care, and social relationships of Tursiops truncatus in the wild. The information focuses mainly on coastal bottlenose dolphins since these are easier to study than offshore populations of the same species.

Shape:
Short, well-defined snout. Its body is aerodynamically designed to travel at high speeds through the water. Tail flukes are horizontal, unlike fish (always vertical). Flukes are a powerful propulsion tool.

Photo courtesy of Andy

Physiological adaptations for the water:
Bottlenose dolphins are mammals; therefore they breather air. Air is through a blowhole located on top of their head, which opens when a dolphin breeches the surface of the water. They have several physiological adaptations for living in the water. Dolphins have a thick layer of blubber, to conserve body heat and to serve as an energy store. Their eyes are protected from the harshness of saltwater by greasy tears. The external ears have been virtually lost while the inner ear has developed to discern the directionality of sounds underwater, and to detect sounds over long distances. Finally, dolphins have developed a complex system of echolocation whereby they can determine the distance, size and shape of an object when sounds emitted from their rostrum bounce off the object and return to the rostrum.

• Temperate to coastal waters
  
• Dolphins divided into coastal and offshore communities
  
• Follow prey distribution in a home range
  
• Seagrasses are important nursery habitats
  
• Migration occurs in some populations, while others are fairly sedentary

Prey

• Squid, octopi, shrimp, eels, crabs, but primarily schooling fish
  
• Eat 6-7kg/day
  
• Seagrasses are an important feeding habitat (protection and practice for juveniles)
  
• Locate prey via echolocation and passive listening (very vocal prey)

• Solitary or cooperative
  
• Strategies: Herding, bubble-bursts, leaping

• Sharks, humans
  
• Shark scars are common, suggesting that many shark attacks are unsuccessful
  
• Juveniles most vulnerable
  
• Dolphins actively chase and attack potential predators

• Groups (1+ individuals). Consist of Mother and offspring or males. Likely kin relations.
  
• Herds (15+ individuals). All female or all male.
  
• Schools/pods (Large, temporary). Very fluid mixing of herds, therefore little genetic relatedness.
  
• Breeding schools form containing males and females.

• Dominance interactions
  
• Cooperative hunting
  
• Male-female consortships
  
• Allomaternal care

• Promiscuous
  
• Breeding schools contain females in oestrus or ready to mate
  
• Aggressive herding of females by males
  
• Temporary consortships form (under 1 hour, to 14 days)
  
• Playful, non-reproductive sexual behaviour reinforces important social bonds

• No male care
  
• Calves highly dependent for upto 4 years
  
• Allomaternal care or babysitting occurs
  
• Babysitting gives inexperienced females training for motherhood

• Kin selection likely
  
• Reciprocal altruism possible in interspecific situations.