Why mole rats are more flexible than we previously thought

sjr81 — Tue, 30 Aug 2016 10:23:31 +0000

Mole rats, including the naked mole rat, live in underground colonies. ̽��ֱ��majority of rodents in the colonies are ‘workers’, with only one female (the ‘queen’) and one male responsible for breeding. All individuals cooperate by digging large underground tunnel systems to forage for food, and if a large food source is found, it is shared with the entire colony. ‘Queens’ and reproductive males remain in this role for their entire life after they have achieved this position. When a ‘queen’ dies, the strongest and largest helper is probably the prime candidate for inheriting the breeding position.

Early studies suggested that non-reproducing mole rats can be divided into non-workers, infrequent workers and frequent workers, and that most individuals stay members of distinct castes for their entire lives. Individual mole rats would focus on a particular task, such as digging, nest building or colony defence, throughout their lives.

Now, however, in a study published in Proceedings of the National Academy of Sciences, researchers from the Department of Zoology at the ̽��ֱ�� of Cambridge have shown that in Damaraland mole rats, the contributions of individuals to cooperative activities change with age and that individual differences in behaviour that appeared to be a consequence of differences in caste are, in fact, age-related changes in behaviour. Whether variation in behaviour between naked mole rats is also a consequence of similar age-related changes is not known – but this seems likely.

Dr Markus Zöttl, first author of the study, explains: “In some ants, aphids and termites, individuals are born into castes that fulfil certain roles, such as soldiers or workers. Initially, everyone thought that this was only found in social invertebrates, like ants and bees, but in the eighties, the discovery of the social behaviour of mole rats challenged this view. Social mole rats were thought to be unique among vertebrates, in that they also had castes. To understand this fully, what we needed was long-term data on many mole rats over extended periods of their lives.”

To study mole rat development in more detail, a team at Cambridge led by Professor Tim Clutton-Brock from the Department of Zoology built a laboratory in the Kalahari Desert, where Damaraland mole rats are native, and established multiple colonies of mole rats in artificial tunnel systems. Over three years, they followed the lives of several hundred individuals to document how the behaviour of individuals changes as they age. All individuals were weighed and observed regularly to document their behavioural changes.

̽��ֱ��researchers found that individual mole rats play different roles as they grow and get older. Rather than being specialists, mole rats are generalists that participate in more or fewer community duties at different stages of their lives. Instead of behaving like ants or termites, where individuals are members of a caste and specialise in doing certain activities, all mole rats are involved in a range of different activities, and their contributions to cooperative activities increases with age.

“As Damaraland mole rats do not have castes, this may mean that castes are only found in social invertebrates and have not evolved in any vertebrates,” adds Dr Zöttl. “Mole rat social organisation probably has more in common with the societies of other cooperative mammals, such as meerkats and wild dogs, than with those of social insects.”

̽��ֱ��research was funded by European Research Council.

One of the most interesting facts about mole rats – that, as with ants and termites, individuals specialise in particular tasks throughout their lives – turns out to be wrong. Instead, a new study led by the ̽��ֱ�� of Cambridge shows that individuals perform different roles at different ages and that age rather than caste membership accounts for contrasts in their behaviour.

Mole rat social organisation probably has more in common with the societies of other cooperative mammals, such as meerkats and wild dogs.

Markus Zöttl

Kyle Finn

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Tradition explains why some meerkats are late risers

bjb42 — Wed, 07 Jul 2010 00:00:00 +0000

After studying meerkats in the Kalahari for the past 10 years, Dr Alex Thornton and colleagues from the Department of Zoology found that some groups of meerkats always got up later out of their sleeping burrows than their neighbours.

These differences appear to have been maintained as local traditions, with patterns of behaviour in different groups being spread by learning from others.

Studying social traditions among animals in the wild is difficult because it is hard to prove that differences in behaviour are due to the social spread of information rather than genetics or environmental factors.

This is the first time such traditional patterns of daily activity have been observed in animals outside the laboratory, and the study is published this week in Proceedings of the Royal Society B.

According to lead author Dr Thornton: "Studies of animal traditions are essential for understanding the biological origins of human culture."

"Because most previous studies examined groups of animals separated by large distances it has been extremely difficult to work out whether behavioural differences between groups really are traditions, or whether they might be better explained by genetic differences or differences in the local ecology."

Dr Thornton's study site in the Kalahari Desert is shared by fifteen meerkat groups with overlapping territories, and group differences in getting-up time could not be explained by differences in ecological conditions.

And as male meerkats always breed outside the group that they were born into, genes get shuffled between groups, so genetic factors are unlikely to account for group differences.

"We found that new immigrants adopted the behaviour of their new groups and that differences between groups were maintained despite groups changing in size and structure as old members died and new ones were born," says Dr Thornton.

"So it seems that, like afternoon tea or an apéritif before dinner, meerkat getting-up times are local traditions passed down through the generations."

Just as afternoon tea is traditional in England but not in France, different groups of meerkats have different ways of doing things, Cambridge zoologists have found.

So it seems that, like afternoon tea or an apéritif before dinner, meerkat getting-up times are local traditions passed down through the generations.

Dr Alex Thornton

Meerkat

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̽��ֱ�� of Cambridge - Kalahari

Why mole rats are more flexible than we previously thought

Tradition explains why some meerkats are late risers