The mating strategies of whales and dolphins are sometimes complex and can vary widely between species dependening on evolution, social structures, and the environment around them.
Danny Groves from Whale and Dolphin Conservation explains what we know.
How do whales and dolphins attract a mate?
For some species of whale and dolphin mating occurs in warmer months or locations because this offers newborns the chance to thrive in more favourable conditions.
Food availability is also key. Recent advancements in technologies (such as drones) have improved opportunities to study and observe behaviours of marine mammals in coastal and offshore habitats.
When it comes to attracting the attention of a mate, behaviours can be spectacular, acrobatic, elaborate, and noisy. Male dolphins, for example, may leap from the water or create bubbles, to attract females.
In some whale species, males may compete for female attention through displays of size, strength and agility, including breaching and tail slapping.
Courtship can involve complex social interactions. In species like bottlenose dolphins, males often form alliances where they take part in cooperative displays to increase their chances of mating.
They may even seek to protecting a female from rival males. Mating behaviours may be conceptive and non-conceptive, including sexual interactions between individuals of the same sex and with juveniles, which may be part of social bonding, dominance and social learning.
Some baleen whales, such as humpbacks, like to croon, using elaborate songs during the mating season, which may advertise their fitness, establish dominance over other males and attract females. Male Amazonian river dolphins may carry sticks as part of display competition.
How do dolphins and whales mate?
When it comes to physicality of mating, rituals can depend on body size. Dolphins mate relatively quickly often in seconds, sometimes repeatedly. The male aligns himself with the female and uses his penis, which is retractable, to mate. But when you are the size of a great whale, with genitalia to match, mating is a longer process.
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Right whales mate with multiple partners within the breeding season, during frequent physical contact - possibly to promote sperm competition among males, and this could explain the large testis to body size ratio.
How long are gestation periods?
Once pregnant, gestation periods vary between species. For orcas this can mean up to 18 months, whereas it ranges from 10 months in harbour porpoises, to 14 or 15 months for sperm whales. Gestation times are approximately 10 to 12 months for baleen whales.
How are calves born?
It is often forgotten that whales and dolphins (like us) need to come to the surface to breath. Calves are typically born tail-first to prevent drowning and mothers will immediately begin caring for their young, providing nourishment and protection in their early months.
Orcas live in a matriarchal structure, where females often stay with their mothers for life. Some dolphin species adopt a polygynous approach to reproduction, with dominant males mate with multiple females.
The phenomenon of having a long post-reproductive life is known to exist in only five species, humans, pilot whales, belugas, narwhals and orca, and female orcas past child-bearing age, go on to become group leaders, helping to boost the survival of their kin through knowledge transfer.
Can whales and dolphins cross breed?
Hybrisation (breeding together of individuals from two different species) has been documented in several types of whales and dolphins in the wild.
Species that share similar traits (including behaviour, vocalisation frequency and body size) are most likely to hybridise, for example blue whales and fin whales, Risso’s dolphins and bottlenose dolphins and recently a hybrid common dolphin and striped dolphin was observed off Cornwall.
Studying mating and social behaviours of whales and dolphins can be very challenging. But what we have uncovered is fascinating
There is much we still don’t know about whales and dolphins but their mating behaviours can tell us a lot about their social structures and biological needs. This all helps us to understand these intelligent creatures more and further enhances the importance of protecting them and their habitats from manmade threats, to ensure their survival.
