False killer whales (Pseudorca crassidens) are one of the least studied species of ocean dolphin, but new light has been cast on their behavior by a team of marine scientists from New Zealand. The research, published in Marine Mammal Science, reveals how a population off the coast of New Zealand has developed a relationship with bottlenose dolphins to defend themselves from predation.
The 17-year study revealed that all 61 individuals in the area were linked in a single social network, while 88% of identified individuals were re-sighted in the same area over several years.
Groups of false killer whales were also found to associate with bottlenose dolphins (Tursiops truncates). These partnerships were found to span more than 5 years and up to 650 km.
"The anti-predatory function of mixed species associations is mostly achieved through a greater chance of detecting a predator through more eyes watching out," said Jochen R. Zaeschmar, from Massey University, New Zealand. "However, it is hard to say if this is mutualistic or parasitic, that is whether the two species actually co-operate or whether one just opportunistically exploits the detection ability of the other. Lastly, as both species are highly social, sociality may also play a role."
"Given the level of site fidelity documented, a small and possibly closed false killer whale population in New Zealand waters cannot be ruled out. A reassessment of the current conservation status in New Zealand may therefore be prudent and further research warranted into the dynamics of this population," concluded Zaeschmar.
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Jochen R. Zaeschmar, Sarah L. Dwyer, Karen A. Stockin, "Rare observations of false killer whales (Pseudorca crassidens) cooperatively feeding with common bottlenose dolphins (Tursiops truncatus) in the Hauraki Gulf, New Zealand", Marine Mammal Science, onlinelibrary.wiley.com/doi/10.1111/mms.12065/abstract