̽��ֱ�� of Cambridge - Tim Clutton-Brock

Monitoring the Meerkats of the Kalahari

jg533 — Fri, 16 Jul 2021 07:55:56 +0000

Getting close was a challenge. Cracking it was key to an incredible 30-year study of the wild meerkats of the Kalahari.

Cooperation helps mammals survive in tough environments

fpjl2 — Tue, 24 Jan 2017 11:33:11 +0000

Cooperatively breeding mammal species, such as meerkats and naked-mole rats, where non-breeding helpers assist breeding females in raising their offspring, are better able to cope with living in dry areas than related non-cooperative species, new research reveals.

A comparative study of mammals, by ̽��ֱ�� of Cambridge researchers Dieter Lukas and Tim Clutton-Brock, shows that cooperatively breeding species occur in dry areas, yet are absent in tropical climates - even though these are the places on earth with the highest biodiversity.

Researchers have found that most cooperatively breeding mammals live in areas where it might not rain for weeks. While many have long argued that climate and social behaviour are linked, the Cambridge team say these findings provide a detailed understanding of how helping behaviour is connected to the environment individuals live in.

“Rainfall often affects food availability, and cooperatively breeding mammals appear better able to cope with the uncertainties of food availability during periods of drought,” said Lukas, from Cambridge’s Department of Zoology.

In this study, published in the journal Royal Society Open Science, the researchers mapped the global occurrence of mammalian species living in different social systems to determine how averages and variation in rainfall and temperature explain species distributions.

They found that although the presence of non-breeding adults in breeding groups is not associated with contrasts in climate, non-breeders commonly play an important role in raising the offspring of breeders in species living in dry environments.

“Long-term field studies show that helpers improve offspring survival, and our findings highlight that such cooperation is particularly important under harsh conditions,” said Clutton-Brock. Previous studies of birds show that here, too, non-breeding adults often help breeders to raise their young in species living in dry unpredictable environments.

Researchers say the activities of helpers in groups of cooperative mammals may ensure that infants and juveniles born in the group (who are usually closely related to them) are adequately fed, even when resources are scare.

In turn, non-breeders may gain future benefits from helping because it increases their chance that their group will survive adverse years, giving them a chance of inheriting the breeding position.

Groups of cooperative breeders occupy territories year-round. During droughts, mortality can be high, and only the largest groups might persist. “However, females in cooperatively breeding mammals can have very high rates of reproduction as soon as conditions are suitable. Populations can rebound, and dispersers move to fill vacant territories,” said Lukas.

By contrast, he says that many other mammals that live in arid areas are migratory, moving as resources are exhausted, such as the large ungulate herds roaming across the African savannahs.

Researchers say the new study also indicates that cooperation enables cooperative breeders to occupy a wider range of habitats than non-cooperative species which are limited to more favourable habitats.

Cooperative breeders are also twice as likely as non-cooperative mammals to occupy human-modified habitats suggesting that cooperative breeding may make it possible to colonize new environments. “Cooperative breeders may also persist in areas where changes in climate make life increasingly difficult,” said Clutton-Brock.

New research suggests that cooperative breeding makes mammal species such as meerkats better suited to dry, harsh climates.

Cooperative breeders may also persist in areas where changes in climate make life increasingly difficult

Tim Clutton-Brock

graham_alton

Meerkats

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Larger brain size linked to longer life in deer

mjg209 — Wed, 14 Dec 2016 23:09:33 +0000

̽��ֱ��study, published in the Royal Society Open Science journal, shows that female red deer with larger brains live longer and have more surviving offspring than those with smaller brains. Brain size is heritable and is passed down through the generations. This is the first extensive study of individual differences in brain size in wild mammals and draws on data comparing seven generations of deer.

Across species of mammals, brain size varies widely. This is thought to be a consequence of specific differences in the benefits and costs of a larger brain. Mammals with larger brains may, for example, have greater cognitive abilities that enable them to adapt better to environmental changes or they may have longer lifespans. But there may also be disadvantages: for instance, larger brains require more energy, so individuals that possess them may show reduced fertility.

̽��ֱ��researchers, based at the ̽��ֱ�� of Cambridge's Zoology Department and Edinburgh ̽��ֱ��'s Institute of Evolutionary Biology, wanted to test if they could find more direct genetic or non-genetic evidence of the costs and benefits of large brain size by comparing the longevity and survival of individuals of the same species with different sized brains. Using the skulls of 1,314 wild red deer whose life histories and breeding success had been monitored in the course of a long-term study on the Isle of Rum, they found that females with larger endocranial volumes lived longer and produced more surviving offspring in the course of their lives.

Lead author Dr Corina Logan, a Gates Cambridge Scholar and Leverhulme Early Career Research Fellow in Cambridge's Department of Zoology, says: " ̽��ֱ��reasons for the association between brain size and longevity are not known, but other studies have suggested that larger brains are a consequence of the longer-lived species having longer developmental periods in which the brain can grow. These hypotheses were generated from cross-species correlations; however, testing such hypotheses requires investigations at the within-species level, which is what we did."

Dr Logan adds: "We found that some of the cross-species predictions about brain size held for female red deer, and that none of the predictions were supported in male red deer. This indicates that each sex likely experiences its own set of trade-offs with regard to brain size.”

̽��ֱ��study also showed that females' relative endocranial volume is smaller than that of males, despite evidence of selection for larger brains in females.

"We think this is likely due to sex differences in the costs and benefits related to larger brains," adds Dr Logan. "We don’t know what kinds of trade-offs each sex might encounter, but we assume there must be variables that constrain brain size that are sex specific, which is why we see selection in females, but not males."

Professor Tim Clutton-Brock, who set up the Rum Red Deer study with Fiona Guinness in 1972 and initiated the work on brain size, points out that the reason that this kind of study has not been conducted before is that it requires long term records of a large number of individuals across multiple generations and data of this kind are still rare in wild animals.

Reference
C.J. Logan, R. Stanley, A.M. Thompson, T.H. Clutton-Brock. Endocranial volume is heritable and is associated with longevity and fitness in a wild mammal. Royal Society Open Science; 14 Dec 2016; 10.1098/rsos.160622

̽��ֱ��size of a female animals' brain may determine whether they live longer and have more healthy offspring, according to new research led by the ̽��ֱ�� of Cambridge.

We found that some of the cross-species predictions about brain size held for female red deer, and that none of the predictions were supported in male red deer. This indicates that each sex likely experiences its own set of trade-offs with regard to brain size.

Corina Logan

Alex Thompson

Deer skulls

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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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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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Monogamy evolved as a mating strategy

gm349 — Mon, 29 Jul 2013 19:00:02 +0000

Social monogamy, where one breeding female and one breeding male are closely associated with each other over several breeding seasons, appears to have evolved as a mating strategy, new research reveals. It was previously suspected that social monogamy resulted from a need for extra parental care by the father.

̽��ֱ��comparative study, by ̽��ֱ�� of Cambridge researchers Dieter Lukas and Tim Clutton-Brock, shows that the ancestral system for all mammalian groups is of females living in separate ranges with males defending overlapping territories, and that monogamy evolved where males were unable to monopolise and defend multiple females. ̽��ֱ��research is published in the journal Science.

For the study, the researchers classified all 2500 mammalian species for which information exists as either solitary, socially monogamous or group-living (several breeding females share a common range and either eat or sleep together). They showed that nine per cent of mammals are socially monogamous, including a few rodents, a number of primates, and some carnivores, like jackals, wolves, and meerkats.

Previously, it had been suggested that monogamy evolved as a result of selection for paternal support in raising offspring (for example, if the female alone could not provide enough food or adequately defend the young). This study shows that paternal care usually evolved after monogamy was already present.

This advance in understanding was, says Lukas of Cambridge's Department of Zoology, due to the volume of information they collected and the availability of genetic information that allowed the researchers to determine the sequence in which different traits evolved.

"Up until now, there have been different ideas about how social monogamy in mammals evolved," says Lukas. "With this study we were able to test all these different hypotheses at once. Paternal care evolves after monogamy is present, and seems to be a consequence rather than a cause of the evolution of monogamy. It appears to occur in about half of all socially monogamous species, and once it does evolve, it provides a clear benefit to the female."

They found convincing support for the hypothesis that monogamy arose as a mating strategy where males could not defend access to more than one female. Monogamy is associated with low density of females, low levels of home-range overlap, and indirectly, with their diets. ̽��ֱ��study showed that monogamy evolves in species that rely on high quality but patchily distributed food sources, such as meat and fruit. In contrast, in herbivores, which rely on more abundant resources, social monogamy is rare.

"Where females are widely dispersed," says Clutton-Brock, "the best strategy for a male is to stick with one female, defend her, and make sure that he sires all her offspring. In short, a male's best strategy is to be monogamous."

̽��ֱ��analysis did not include humans, and the researchers are sceptical that these results tell us much about the evolution of human breeding systems.

Clutton-Brock adds: "It is debatable whether humans should be classified as monogamous. Because all the African apes are polygamous and group living, it is likely that the common ancestor of hominids was also polygamous. One possibility is that the shift to monogamy in humans may be the result in the change of dietary patterns that reduce female density, and another is that slow development of juveniles required extended care by both sexes. However, reliance by humans on cultural adaptations means that it is difficult to extrapolate from ecological relationships in other animals."

For more information about this story, please contact: Genevieve Maul, Office of Communications, ̽��ֱ�� of Cambridge. Email: Genevieve.Maul@admin.cam.ac.uk; Tel: 01223 765542.

New research indicates that social monogamy evolved as a result of competition for females.

Where females are widely dispersed, the best strategy for a male is to stick with one female, defend her, and make sure that he sires all her offspring. In short, a male's best strategy is to be monogamous.

Professor Tim Clutton-Brock

Peter Brotherton

̽��ֱ��socially monogamous dik-dik, a small antelope that lives in Africa.

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Whos the boss? Why female meerkats come out on top

tdk25 — Fri, 22 Dec 2006 00:00:00 +0000

A new study by the Kalahari Meerkat project of the ̽��ֱ�� of Cambridge shows that female meerkats fight more than their male counterparts for dominance.

In most animals, females invest more in raising offspring, with the result that males compete intensely to gain access to fertile females.

However, meerkats provide an exception to this rule. In meerkat colonies a single Alpha female mates with a single dominant male while the rest of the group cares for their pups. Unusually, meerkat females compete more intensely than males, even though they contribute far more than males to parental duties.

To better understand the causes of this aggression, behavioural ecologist Professor Tim Clutton-Brock of the ̽��ֱ�� of Cambridge, and his colleagues spent 13 years tracking meerkats in the Kalahari Desert. ̽��ֱ��researchers monitored 33 dominant females and 53 dominant males.

They identified the animals by markings on their fur, but data collection was aided by the fact that the meerkats became so tame that they could train them to walk on electronic scales to monitor their growth as well.

̽��ֱ��study revealed that, compared with dominant males, dominant female meerkats produced twice as many pups during their time in the dominant position. Dominant females also remained dominant for nearly twice as long as dominant males.

This means that fewer females are likely to become dominant, so that each dominant position is worth more, hence the need to fight for it.

This may explain why dominant female meerkats possess traits which help them control other females. They are more than 10% heavier than subordinates, have three times as much testosterone, and are more frequently aggressive than subordinates or dominant males.

̽��ֱ��study will provide a better explanation for why, like males, females in many species also evolve traits that allow them to compete with members of the same sex.

A new study by the Kalahari Meerkat project of the ̽��ֱ�� of Cambridge shows that female meerkats fight more than their male counterparts for dominance.

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Wild meerkats school their young

tdk25 — Fri, 14 Jul 2006 00:00:00 +0000

Older meerkats teach younger meerkats how to handle prey.

̽��ֱ�� of Cambridge scientists have discovered that older meerkats teach pups how to obtain food by incrementally introducing dead, injured and then live prey. Although learning per se wouldn't be surprising, whether wild mammals teach their young was still debated. ̽��ֱ��findings were published in this week's edition of the journal Science.

Meerkats live in groups of three to 40 individuals in the arid regions of southern Africa. Each group includes a dominant male and female who produce over 80% of the pups. However, helpers (meerkats older than 90 days) and parents of both sexes aid in rearing the young.

Pups (meerkats younger than 90 days of age) are initially incapable of finding their own prey and therefore rely on provisions from other members of the group by responding to their begging calls for food. Meerkats typically feed on a range of unwieldy and often dangerous prey (including scorpions).

̽��ֱ��Cambridge researchers discovered that in order for the helpers to teach the pups how to handle food without putting them in harm's way, the older meerkats would kill or disable the prey before providing it to the pups. In the case of the scorpions, they often removed the sting. ̽��ֱ��helpers would then modify the frequency with which they killed or disabled the prey according to the pups' age, recognised by their call, gradually introducing pups to live prey as they became older.

Alex Thornton, Department of Zoology, ̽��ֱ�� of Cambridge, stated, "A greater understanding of the evolution of teaching is essential if we are to further our knowledge of human cultural evolution and for us to examine the relations between culture in our own species and cultural behaviour in other animals."

Like any good teacher, the helpers would also monitor the pup after they had provided it with food. If the pup was reluctant to handle the prey, the older meerkat would nudge the item towards them to encourage it. Additionally, if the prey wondered off the helper would retrieve the item and return it to the pup, sometimes further disabling it before returning it to the young meerkat.

̽��ֱ��researchers, Alex Thornton and Katherine McAuliffe, Department of Zoology, ̽��ֱ�� of Cambridge, are part of the Kalahari Meerkat Project, located at the Kuruman River Reserve, South Africa. ̽��ֱ��project is a decade-old initiative by Professor Tim Clutton-Brock FRS in collaboration with the ̽��ֱ�� of Pretoria. A study earlier this year by Dr Andrew Young and Professor Clutton-Brock reported that dominant female meerkats kill and eat their rival's young.

Older meerkats teach younger meerkats how to handle prey.

A greater understanding of the evolution of teaching is essential if we are to further our knowledge of human cultural evolution and for us to examine the relations between culture in our own species and cultural behaviour in other animals.

arsheffield from flickr

Meercats

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̽��ֱ�� of Cambridge - Tim Clutton-Brock

Monitoring the Meerkats of the Kalahari

Cooperation helps mammals survive in tough environments

Larger brain size linked to longer life in deer

Why mole rats are more flexible than we previously thought

Female meerkats compete to outgrow their sisters

Monogamy evolved as a mating strategy

Whos the boss? Why female meerkats come out on top

Wild meerkats school their young

Whos the boss? Why female meerkats come out on top