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Cavorting dolphins might look like they're just having fun, but dolphin watchers are being warned not to misread the signals.
Dolphins' seemingly playful behaviour in summer is mainly focused on basic needs such as getting a feed, taking care of the baby and looking good for potential partners.
Dr Rochelle Constantine, an Auckland University dolphin expert, says summer is particularly demanding for dolphins with young calves to rear and which need to stock up on food to build up blubber for cold winter seas.
It is also their mating season, which prompts some of the showy behaviour captured by readers in dozens of photos sent to the Herald's Holiday Picture competition.
"It is not for human entertainment but part of mating rituals or feeding patterns," Dr Constantine said.
Dr Constantine, who spent years studying dolphin behaviour in relation to tourism in the Bay of Islands, says many people do not seem to know that dolphins are protected by laws.
For instance, no more than three boats at a time are allowed to be within 300m of dolphins, and boaties are advised to stop or travel slowly among them.
* Kelly James, the Auckland woman crushed by a dolphin in a freak Boxing Day boating accident, is recovering "remarkably well" although she is likely to remain in hospital for a few more weeks.
A spokeswoman for the James family said the 27-year-old's injuries were no longer life-threatening although there was still concern about her chest and pelvic injuries.
