Pilot whales have 'mummy's boys,' too

Jan 27, 2014

(Phys.org) —A Liverpool John Moores University scientist has revealed that sons are a bigger drain on resources than daughters for pilot whale mothers, but mums are powerless to ease the burden.

Dr Hazel Nichols from the LJMU School of Natural Sciences and Psychology led the investigation, working in collaboration with Professor Bill Amos (University of Cambridge) to reanalyse genetic and behavioural data from a previous study of over 3000 . The results were published in ScienceDirect.

Dr Nichols said that "pilot whales are a particularly interesting species to study as they show several similarities to human societies".

Previous research by Professor Amos and scientists at the Natural History Museum of the Faroe Islands revealed that pilot whales live in large social groups (known as pods) of up to several hundred individuals – similar to the number of Facebook friends that people have. Pods show extremely strong social ties and individuals rarely seem to leave their groups, often remaining in their social group for their entire lives. They also have extended periods of maternal care, as with humans.

In this latest study, Dr Nichols found that male calves grow much faster than female calves in early life, suggesting that they need greater investment from their mother in her milk.

She commented: "Producing large amounts of nutrient-rich milk is likely to be energetically costly to mothers. This might explain why pilot whale mothers are less likely to have another pregnancy after having sons, compared to mothers who have daughters."

The results build on previous work by scientists at the University of Exeter on , which found that in this species too, sons are highly dependent on their mothers, even when they are in their 30s. These 'mummy's boys' find it difficult to survive without their , being more than eight times more likely to die in the year following their mother's death.

Dr Nichols' study also found that female pilot whales seem unable to 'choose' whether to produce sons or daughters. This was investigated as part of the research due to the fact that there is evidence that some species can. This even seems to occur in humans, as previous studies have found that wealthy people were more likely to produce sons than daughters, as are heavier women.

"If Pilot whales could choose the sex of their offspring then you would expect smaller females to opt for producing daughters, but we found no evidence of this."

Explore further: Eight pilot whales found dead off Florida coast

More information: Hazel J. Nichols, Karen Fullard, William Amos. "Costly sons do not lead to adaptive sex ratio adjustment in pilot whales, Globicephala melas." Animal Behaviour, Volume 88, February 2014, Pages 203-209, ISSN 0003-3472, dx.doi.org/10.1016/j.anbehav.2013.12.015.

add to favorites email to friend print save as pdf

Related Stories

Study suggests poor mothers favor daughters

Jun 21, 2012

Poor mothers will invest more resources in daughters, who stand a greater chance of increasing their status through marriage than do sons, suggests a study in the American Journal of Physical Anthropology.

Recommended for you

Nature offers video of 10 cutest animals of 2014

17 hours ago

(Phys.org)—The journal Nature has released a video that ventures a bit from its traditional strictly-science approach to technical journalism—it's all about the cutest animal stories of the past year ( ...

Big data and the science of the Christmas tree

20 hours ago

Often called the "Cadillac of Christmas trees," the Fraser Fir has everything a good Christmas tree should have: an even triangular shape, a sweet piney fragrance, and soft needles that (mostly) stay attached ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.