̽��ֱ�� of Cambridge - meerkat

Breeder meerkats age faster, but their subordinates still die younger

fpjl2 — Fri, 31 Aug 2018 11:05:36 +0000

In many cooperative species, the dominant breeders live longest despite the wear-and-tear of leadership and reproduction.

It has even been suggested these breeders hold the secret of immunity to age-related diseases. Some social insects, such as bees, do have breeders with genetic profiles that delay ageing – but this has never been documented in our fellow mammals.

Scientists from the ̽��ֱ�� of Cambridge have now investigated the lifespans of meerkats: a highly social mammal that lives in groups of up to fifty, where a single dominant couple produce around 90% of the pups.

̽��ֱ��researchers found that the DNA of dominant breeders actually shows signs of accelerated ageing – yet they still consistently outlive the non-breeding subordinates in the group. Their study shows that dominants live an average of 4.4 years compared to subordinates 2.8 years.

This is because meerkat underlings are forced to take the often-fatal risk of leaving the safety of the group to find breeding opportunities, say scientists. Dominants rarely tolerate rival breeders, and violently eject subordinates from the group if they feel threatened.

On reaching the top of the social pecking order, however, meerkats remain ensconced within the group. ̽��ֱ��study shows an average subordinate spends more than six days each year in the wilderness, with this figure rising year-on-year. Dominant breeders are typically absent for under two hours per year.

“Dominant meerkats typically die due to internal stresses on their bodies, resulting in gradual, predictable declines until death. In humans we might describe this as ‘natural causes’,” said Dr Dominic Cram from Cambridge’s Department of Zoology, lead author of the study published today in Current Biology.

“Subordinate meerkats die due to sudden, unpredictable circumstances such as exposure to predators, killing them instantly. A meerkat’s place within the social group shapes the mortality risks it faces,” he said.

“ ̽��ֱ��secret of long life for meerkats is not to battle the inevitable declines of ageing, but to be the ruler of your community, profiting from social support and cracking down on would-be rivals.”

Cram conducted the research as part of the Kalahari Meerkat Project: a long-term study of social behavior and ecology, run for over twenty years at the ̽��ֱ�� of Cambridge by Professor Tim Clutton-Brock – a leading figure in the study of mammal societies.

̽��ֱ��project has helped train generations of zoologists through the observation of generations of meerkats, resulting in a wide range of data on the life histories of over 3000 meerkat individuals in over 100 groups.

̽��ֱ��team collected blood samples from the meerkats, and measured DNA sections called telomeres that help protect DNA from damage – much like the plastic caps on shoe-laces. As they erode over time, the chance of unravelling increases, so the length of telomeres can be used to estimate “biological age”.

While the telomeres of subordinate meerkats remained stable, dominant telomeres shrunk by a third in just 18 months – suggesting accelerated ageing caused by the toils of raising young and fending off rivals.

Yet the dominant meerkats still lived an average of 60% longer than subordinates, as the lower ranking meerkats were increasingly forced to risk more and more time outside the group as they grew older.

“Each year the subordinates spend over triple the amount of time outside the group as the previous year, reaching a peak of 35 days per year, or 10% of their time, outside the social group,” said Cram.

For subordinate males, all females in the group are their sisters or mother, so they must court females away from the group to avoid inbreeding. Subordinate females are bullied and chased away by the dominant when they become a reproductive rival.

Of all those that leave, some return – or try to – after a few days or weeks. A lucky few start their own group and become dominant breeders. Many are never seen again.

“Within a group, a sentinel always keeps look-out and sounds the alarm, allowing the meerkats to flee into burrows or bolt-holes. Each meerkat takes a turn on sentinel duty,” said Cram.

“Away from the group there is no early warning system, and meerkats are easy prey for eagles, goshawks and caracal. Letting down their guard to dig for food is too risky, so many starve for fear of being eaten.”

“Lone meerkats have even been known to be torn apart by members of a rival group. It’s a dangerous world for a solo meerkat.”

Despite rapidly ageing, dominant animals live longer because their underlings are driven out of the group – becoming easy targets for predators. ̽��ֱ��secret of a long meerkat life is to be “ruler of your community… cracking down on would-be rivals,” say scientists.

A meerkat’s place within the social group shapes the mortality risks it faces.

Dominic Cram

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Female meerkats compete to outgrow their sisters

Anonymous — Thu, 26 May 2016 08:40:26 +0000

Meerkats live in groups of up to 50 individuals, yet a single dominant pair will almost completely monopolise reproduction, while subordinates help to raise offspring through feeding and babysitting. Since only a small minority of individuals ever get to be dominants, competition for the breeding role is intense in both sexes and females are unusually aggressive to each other.

Within groups, subordinate females are ranked in a hierarchy based on age and weight, forming a “reproductive queue”. When dominant females die, they are usually replaced by their oldest and heaviest daughter, though younger sisters sometimes outgrow their older sisters and can replace them in breeding queues.

̽��ֱ�� of Cambridge scientists working on wild Kalahari meerkats identified pairs of sisters and artificially increased the growth of the younger member of each pair by feeding them three times a day with hard-boiled egg.

̽��ֱ��scientists weighed them and their (unfed) older sisters daily for three months. ̽��ֱ��results, published today in the journal Nature, show that the increased growth of younger females stimulated their older sisters to increase their daily food intake and weight gain in an attempt to outgrow their rivals.

Tellingly, the extent to which the older sister increased her weight was greater when her younger sister’s weight gain was relatively large than when it was slight.

These results suggest that subordinate meerkats are continually keeping tabs on those nearest them in the breeding queue, and make concerted efforts to ensure they are not overtaken in size and social status by younger and heavier upstarts.

But competitive growth does not stop there. If a female meerkat gets to be a dominant breeder, her period in the role (and her total breeding success) is longer if she is substantially heavier than the heaviest subordinate in her group.

During the three months after acquiring their new status, dominant females gain further weight to reduce the risk of being usurped. Regular weighing sessions of newly established dominants showed that that, even if they were already adult, they increased in weight during the first three months after acquiring the dominant position – and that the magnitude of their weight increase was greater if the heaviest subordinate of the same sex in their group was close to them in weight.

This is the first evidence for competitive growth in mammals. ̽��ֱ��study’s authors suggest that other social mammals such as domestic animals, primates and even humans might also adjust their growth rates to those of competitors, though these responses may be particularly well developed in meerkats as a result of the unusual intensity of competition for breeding positions.

“Size really does matter and it is important to stay on top,” said senior author Professor Tim Clutton-Brock, who published the first major overview of research on mammalian social evolution this month in the book Mammal Societies (Wiley).

“Our findings suggest that subordinates may track changes in the growth and size of potential competitors through frequent interactions, and changes in growth rate may also be associated with olfactory cues that rivals can pick up,” Clutton-Brock said.

“Meerkats are intensely social and all group members engage in bouts of wrestling, chasing and play fighting, though juveniles and adolescents play more than adults. Since they live together in such close proximity and interact many times each day, it is unsurprising that individual meerkats are able to monitor each other’s strength, weight and growth.”

Male meerkats leave the group of their birth around the age of sexual maturity and attempt to displace males in other groups, and here, too, the heaviest male often becomes dominant. ̽��ֱ��researchers found a similar strategy of competitive weight-gain in subordinate males.

̽��ֱ��data was collected over the course of twenty years and encompassed more than forty meerkat groups, as part of the long-term study of wild meerkats in the Southern Kalaharu at the Kuruman River Reserve, South Africa, which Clutton-Brock began in 1993. In the course of the study, the team have followed the careers of several thousand individually-recognisable meerkats – some of which starred in the award winning docu-soap Meerkat Manor, filmed by Oxford Scientific Films.

̽��ֱ��meerkats were habituated to humans and individually recognisable due to dye marks. Most individuals were trained to climb onto electronic scales for their weigh-ins, which occurred at dawn, midday and dusk, on ten days of every month throughout their lives. This is the first time it has been feasible to weigh large numbers of wild mammals on a daily basis.

Weighing meerkats. Image credit: Tim Clutton-Brock

Latest research shows subordinate meerkat siblings grow competitively, boosting their chance of becoming a dominant breeder when a vacancy opens up by making sure that younger siblings don’t outgrow them.

Size really does matter and it is important to stay on top

Tim Clutton-Brock

Russell Venn

Sub-adult meerkats playing.

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‘Extreme sleepover #13’ – the wet-nursing meerkats of the Kalahari

jfp40 — Wed, 04 Jun 2014 13:15:50 +0000

I never thought I would be quizzing people over a radio about the sandiness of nipples. Then again, I never foresaw that for many months my days would start with a bump, lurching over sand dunes in a Land Rover, heading off to find meerkats, to whom those nipples belong. Life in the Kalahari is inherently full of surprises.

My PhD research with Professor Tim Clutton-Brock has brought me here, to the far northern reaches of South Africa, where I study the phenomenon of allolactation – essentially, wet-nursing. In each of the 16 groups of meerkats scattered across our large reserve, only one dominant female will breed. ̽��ֱ��other females in the group will help her to raise her young, sometimes even lactating for them. This year though, those females are not being forthcoming, and their nipples, which will have wet, sandy rings around them if they are allolactating, remain dismally dry.

̽��ֱ��radio crackles as the network of volunteers spread out in separate cars and on foot to begin the task of monitoring different meerkat groups. I’m dropped off, and suddenly am in a state of solitude that I’ve come to find blissful. At the top of Sandy Hill, a large dune and one of our main landmarks, I leave grey flat scrub behind me and come to my favourite part of the reserve. Here the grass is a dry platinum, and dunes tumble gently into wide valleys. Tall trees, now erupting into a lush green after the first rains, are dotted evenly like a wild orchard. I love best the southward vista, where the dunes drop so suddenly to the flats that it looks like the edge of the world.

It is the edge of the world for my favourite group of meerkats, the Sequoia group. I find their burrow just in time – the first to rise, just as the sun is coming up, is Bruce. He’s the dominant male of the group, a well-built and handsome meerkat easily recognisable from his striking left shoulder and left thigh dye marks, our means of identifying each individual. Bruce is a local hero for his audaciously bold guarding of his group – he can often be seen high up in some tree, watching the horizon with a fierce expression. ̽��ֱ��dominant female, Ru, is a big, good-natured girl, and her cohort are characterful and a pleasure to wander in the dunes with.

After weighing each individual and conducting a roll-call, I follow the females I’m interested in – the dominant female and the potential allolactators – and collect detailed data on their every move, as well as staying aware of what’s going on with the whole group. Summer in the Kalahari is a time to watch your step too. I walked past the same bush dozens of times in Sequoia territory last week before we heard the telltale deflating-football sound of a deadly poisonous puff adder coiled menacingly at its base. It raised a lazy head at a young male venturing too close, who thankfully alerted the group, and me, to its presence.

Watching my step is also important for happier reasons – to avoid the plucky little pups who dart around the adult females that I’m following in the hope of getting fed a juicy grub. ̽��ֱ��pups at Sequoia are obsessed with shoes, and play-forage around my heels as I record observations on their mother. If I sit down, there’s soon an investigation of my hems, laces and pockets. ̽��ֱ��pups are still the size of my palm, though getting heavier by the day.

There is a time somewhere between 11 o’clock and midday when the Kalahari turns from a balmy, soft-edged paradise to a hell that crackles underfoot and becomes alien and angry, with a sudden fierce heat. Time to head home, and sleep off our early morning.

I’m back out again mid-afternoon though, this time looking for Pandora, a group at the far edge of the land we cover. I find them using signals from a tiny radio collar that the pregnant dominant female, Toblerone, wears around her neck. But something odd is going on this evening and I find I’m getting a strong signal for Toblerone below ground, at the group’s burrow. Luckily most of the rest of the gang, including a lovable adult male called Cecil – an incorrigible lothario with neighbouring groups – are foraging fairly nearby.

It’s cooling now, but it’s been a long, hot afternoon, and when we return to the burrow at dusk, they are all eager to jump on my scales and be weighed, and then receive the gulps of water we reward them with.

After a few moments, I discover the reason for Toblerone’s absence is just as I expected – she emerges, sleek and placid, with the suckle marks on her belly of some strong and healthy pups, born this afternoon. And even better news for me, the oldest subordinate female also appears, and by the sandy rings around her nipples, it looks like she has also started lactating – the first allolactator of my study. Like I said, the Kalahari is full of surprises – the tiny bundles of life produced in this dry, hot world are the best of them all.

Kirsty MacLeod

Kirsty MacLeod is a PhD student with Professor Tim Clutton-Brock In the Department of Zoology.

Reporting back from her time spent in the Kalahari Desert, PhD student Kirsty MacLeod describes the fascinating life of a gang of meerkats that includes an audacious boy called Bruce and a good-natured girl called Ru.

Bruce is a local hero for his audaciously bold guarding of his group – he can often be seen high up in some tree, watching the horizon with a fierce expression.

Kirsty MacLeod

Kirsty MacLeod and meerkats

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Research suggests meerkat predator-scanning behaviour is altruistic

ljm67 — Fri, 15 Feb 2013 10:16:50 +0000

In order to spot potential predators, adult meerkats often climb to a higher vantage point or stand on their hind legs. If a predator is detected, they use several different alarm calls to warn the rest of the group. New Cambridge research shows that they are more likely to exhibit this behaviour when there are young pups present, suggesting that the predator-scanning behaviour is for the benefit of the group rather than the individual.

Meerkats are a cooperatively breeding species, with a dominant breeding pair and up to 40 ‘helpers’ of both sexes who do not normally breed but instead assist with a number of cooperative activities such as babysitting and feeding of offspring.

However, scientists have questioned whether sentinel behaviour, when helper meerkats climb to a high point to scan for predators, and other vigilance behaviour, such as standing on their hind legs, is done for their own preservation (with the group’s increased safety being an indirect consequence) or if the primary goal is altruistic, with the main purpose being the protection of the group.

Peter Santema, a PhD student at the ̽��ֱ�� of Cambridge’s Department of Zoology, said: “You see similar behaviour in a range of mammal and bird species, and we know from previous work that other group members are less likely to be attacked by predators when someone is on guard. Biologists have been debating, however, whether the protection that other group members enjoy is just a side-effect or one of the reasons why individuals perform these guarding behaviours.”

For the research, which was funded by the BBSRC, scientists observed non-breeding helpers in the period just before the dominant female’s pups had joined the group on foraging trips. They repeated the observations immediately after the pups joined the group. When they compared the results, they found that after the pups had joined the group on foraging trips, helpers showed a sudden increase in their vigilance behaviour.

Santema added: “These results are exciting, as they show us that individuals are not just on the look-out for their own safety, but that the protection of other group members is another motivation for these behaviours. Our results thus suggest that vigilance and sentinel behaviour in meerkats represent forms of cooperation.”

̽��ֱ��Cambridge research was published today in the journal Animal Behaviour.

Meerkats are more likely to scan for predators from high vantage points or guard on their hind legs when young pups are present in the group.

These results are exciting, as they show us that individuals are not just on the look-out for their own safety, but that the protection of other group members is another motivation for these behaviours

Peter Santema, a PhD student at the ̽��ֱ�� of Cambridge’s Department of Zoology

Research suggests meerkat predator-scanning behaviour is altruistic

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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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