Dolphins Interspecies Interactions
Different species of dolphins can relate in different manners. Different populations of each species have different cultures. So the way they relate can vary a lot depending of species involved and the area where interactions occur.
Dolphins social structure
Dolphins relationships are very complex. By a general and simplified explanation dolphins live in fission fusion societies. A fission fusion society is one in where individuals form different sizes groups and change from one group to others. Bottlenose dolphins form fission fusion societies with preferred companions. That means that individuals have companions that stay together with much higher than expected by probability and companions that stay together with much lower than expected by probability. They also form small groups with very stable associations that group together in higher level groups that are less stable with 1 or 2 individuals that acts as nodes witch link the 2 groups.
Some bottlenose dolphins societies segregates by age and sex. In those societies females group with other females with a similar reproductive states. Pregnant females group together, lactating females do the same. Young dolphins tend to group by age and adult males form stable long lasting alliances that fight together against other alliances. Those alliances can join together in second order alliances to fight others and that 2nd order alliances can join in 3rd order alliances creating a complex ally-enemy relations that are only paralleled by humans.
Other bottlenose dolphins societies form stable groups with very stable associations between sexes in addition to within sexes. In that societies females choose with whom male to mate. In New Zealand males perform ritualized fights in where 2 dolphins jump and headbutt each other in air.
Dolphins have very complex social structure that varies from one population to other with cultural differences even between simpatric populations of the same species. Dolphins have a huge variability in lot of behaviors and social structure between and within groups that also are transmitted culturally. Here are some examples:
Dolphins interespecies interactions
One example of inter species interaction between dolphins are interactions between bottlenose dolphins (Tursiops truncatus) and false orcas (Pseudorca crassidens).
Bottlenose dolphins and false orcas associate between each other frequently and some times they form stable relationships that maintains for more than 5 years between the same bottlenose dolphins and the same false orcas like in New Zealand.
Zaeschmar and his coworkers had found the same bottlenose dolphins associating with the same false orcas during a period of 5 years and in locations separated by 650 kilometres and doing different activity like hunting or resting or socializing. They didn´t found any mating behavior between bottlenose dolphins and false orcas in this population but bottlenose dolphins and false orcas have been reported producing fertile hybrid offspring both in captivity and in the wild.
Other mixed pods of bottlenose dolphins and false orcas have been reported all over the world but are not as well studied.
Here a mixed pods of bottlenose dolphins and false orcas hunting sardines in South Africa.
Here a mixed pods of bottlenose dolphins and false orcas in Sudan
Here a recording of communication in a mixed pods of bottlenose dolphins and false orcas in the Bremer Canyon, Western Australia
Here a mixed pods of bottlenose dolphins and false orcas in Hawaii
Here a mixed pods of bottlenose dolphins and false orcas in Azores
Here a mixed pods of bottlenose dolphins and false orcas in White Island
There are reports of a mixed group of 15 bottlenose dolphins and 25 false orcas who used sound pulses to disengage a rosseta formation of 25 to 30 female sperm whales and then killed at least one.
Bottlenose dolphins and false orcas has a similar frequency range in hearing and sound production, both uses signature whistles and probably can understand each others complex languages. That could explain why bottlenose dolphins and false orcas interact between each other more frequently than with other dolphin species.
Nevertheless, there are reports of false orcas attempting to hunt bottlenose dolphins in the gulf of Mexico and hunting spinner dolphins in eastern tropical Pacific.
Other example of dolphin interaction is spinner (Stenella longirostris)and pantropical spotted dolphins (Stenella attenuata). This species associate between each other frequently probably for protection and because they share the same preys. But their associations are not so stable and cooperative as interactions between bottlenose dolphins and false orcas. The bigger pantropical spotted dolphins sometimes to use their size to bully the smaller spinner dolphins and spinner dolphins use their greater numbers to fight back.
Similar interactions have been reported for coastal bottlenose dolphins(Tursiops truncatus) and Atlantic spotted dolphins (Stenella frontalis) in Bahamas. Where young teenagers bottlenose dolphins go to the encounter of spotted dolphins and some times use their size to bully them but Atlantic spotted dolphins use their greater numbers to fight back. Some times those young bottlenose dolphins form alliances with Atlantic spotted dolphins to fight others Atlantic spotted dolphins alliances.
Finally some bottlenose dolphins attack other dolphins for fun. In Ireland and Scotland waters some bottlenose dolphins not only kill harbour porpoises (Phocoena phocoena) but also have been reported to kill common dolphins (Delphinus delphis), striped dolphins (Stenella coeruleoalba), pilot whales (Globicephala melas) and risso dolphins (Grampus griseus). And there is a report of 3 adult male bottlenose dolphins herding a pod of pilot whales, separated a 3 meters calf from the rest of the pod an raped him in the Gibraltar straight.
There are also 2 reports of bottlenose dolphins rescuing stranded pilot whales in New Zealand.
In 1983 at Tokerau Beach, Northland, New Zealand, a pod of pilot whales ran aground during a tide. The Zealanders who lived there came out and did their best to keep the whales alive, sponging their skin and calming them, until the tide came back in. But even then the whales were having trouble orienting themselves.
Bottlenose dolphins came to the rescue. Somehow, a pod of dolphins who were nearby figured out what was happening. They swam into the shallows, putting themselves at risk, and “herded” the pilot whales out to sea, saving 76 of 80 whales. Five years earlier, a similar incident had occurred at Whangarei harbor.
So different species of dolphins interact between each other in different ways depending on their different culture.
They can form peaceful cooperative associations with different level of stability and sometimes growing up calfs of other species.
They can form sporadic or opportunistic associations and they can bully and rape smaller or weaker species or even kill them.
And sometimes they rescue dolphins from other species in distress.
But frequently they avoid each other hunting different preys in different areas.
