̽��ֱ�� of Cambridge - cooperative behaviour

Speed of animal evolution enhanced by cooperative behaviour

sjr81 — Fri, 26 May 2017 15:00:16 +0000

Cooperative behaviour is a key part of animal family life: parents help offspring by supplying them with food, and siblings can also work together to acquire food. ̽��ֱ��Cambridge study, published today in Nature Ecology and Evolution, looked at the burying beetle – unusual in the insect world as the parents feed their offspring.

Larvae in small broods are well supplied with food by their parents and grow large. In the parents’ absence, larvae can also help each other to forage for food. However, in the absence of their parents, small broods of larvae are less effective at helping each other and can never grow as big.

“For our study, we played the role of natural selection. In some experimental beetle populations, we chose only the largest beetles to breed at each generation and in some we chose only the smallest beetles,” said Benjamin Jarrett from the Department of Zoology at the ̽��ֱ�� of Cambridge, who led the study.

“Crucially, we also changed the social conditions within beetle families. In some populations, we allowed parents to help their offspring, but in other populations we removed the parents, and larvae had to help each other. We found that the social conditions made a big difference to how quickly beetle body size evolves over generations.”

Beetles only evolved a larger body size when parents were present to help rear their young. In stark contrast, smaller body size only evolved when beetle parents were removed, and there were too few larvae to help each other.

̽��ֱ��experiment helps explain how different species of burying beetle might have evolved their different body sizes. In general, larger species of beetle have more diligent parents than smaller species.

Burying beetles use the dead body of a small animal, like a mouse or bird, for reproduction. ̽��ֱ��parents shave and bury the carcass, to make it into an edible nest for their larvae. ̽��ֱ��larvae can feed themselves on the carrion, but the parent beetles also regurgitate partly digested food to them. ̽��ֱ��species used in this study has quite variable levels of parental care: occasionally larvae have to fend for themselves on the carcass because they have been abandoned by their parents.

“Previous work has focused on the puzzle of how cooperative behaviour evolves, because natural selection seems to favour animals that are selfish,” said Professor Rebecca Kilner, who is senior author of this paper. “We have shown that what happens next, in evolutionary terms, is just as interesting. Once cooperation has evolved, it can change the way in which evolution then unfolds.”

̽��ֱ��researchers now hope to uses experimental evolution to understand what happens across many generations when changing the extent of parental care.

“We can remove parents from caring for their offspring in one generation, and we do this to their offspring too, and their grandoffspring, and so on,” added Jarrett. “We currently have populations of beetles that have not had parents looking after them as they grow up for 25 generations.

“What this does is change what evolution is working on. Natural selection is usually acting on the combination of parents and offspring, and now, by removing parents, we have changed the traits on which evolution acts.”

̽��ֱ��paper Cooperative interactions within the family enhance the capacity for evolutionary change in body size, published in Nature Ecology and Evolution, can be found here: http://dx.doi.org/10.1038/241559-017-0178

A study by scientists from the ̽��ֱ�� of Cambridge has revealed how cooperative behaviour between insect family members changes how rapidly body size evolves – with the speed of evolution increasing when individual animals help one another.

In some populations, we allowed parents to help their offspring, but in other populations we removed the parents.

Benjamin Jarrett

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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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Wolf species have ‘howling dialects’

fpjl2 — Mon, 08 Feb 2016 13:43:47 +0000

̽��ֱ��largest ever study of howling in the ‘canid’ family of species – which includes wolves, jackals and domestic dogs – has shown that the various species and subspecies have distinguishing repertoires of howling, or “vocal fingerprints”: different types of howls are used with varying regularity depending on the canid species.

Researchers used computer algorithms for the first time to analyse howling, distilling over 2,000 different howls into 21 howl types based on pitch and fluctuation, and then matching up patterns of howling.

They found that the frequency with which types of howls are used – from flat to highly modulated – corresponded to the species of canid, whether dog or coyote, as well as to the subspecies of wolf.

For example, the howling repertoire of the timber wolf is heavy with low, flat howls but doesn’t feature the high, looping vocal that is the most frequently used in the range of howls deployed by critically-endangered red wolves.

Lead researcher Dr Arik Kershenbaum from the ̽��ֱ�� of Cambridge describes these distinctive howl repertoires as resembling vocal dialects, with each species having its own identifiable use of the various howl types. He says the findings could be used to track and manage wild wolf populations better, and help mitigate conflict with farmers.

̽��ֱ��origins of language development in humans are mysterious, as the vocalisations of our closest existing biological relatives such as chimpanzees are relatively simple. Kershenbaum and colleagues believe that studying the sounds of other intelligent species that use vocal communication for cooperative behaviour – such as wolves and dolphins – may provide clues to the earliest evolution of our own use of language.

“Wolves may not be close to us taxonomically, but ecologically their behaviour in a social structure is remarkably close to that of humans. That’s why we domesticated dogs – they are very similar to us,” said Kershenbaum, from Cambridge’s Department of Zoology.

“Understanding the communication of existing social species is essential to uncovering the evolutionary trajectories that led to more complex communication in the past, eventually leading to our own linguistic ability” he said.

̽��ֱ��research was conducted by a team of scientists from the UK, US, Spain and India, and is published in the journal Behavioural Processes.

̽��ֱ��researchers made use of howls recorded from both captive and wild animals, from Australia and India, to Europe and the United States, creating a database of 6,000 howls that was whittled down to 2,000 for the study. This included combing YouTube for domestic dog howls.

These were then fed into machine learning algorithms to classify the howls into discrete types. Studies on howling in the past have had to rely on subjective human comparisons by looking at soundwave patterns, but the new algorithms allowed the howl types to be compared objectively, revealing that the various species have characteristically different repertoires of howl type usage.

While the howling repertoires of most of the 13 species analysed were very distinct, some bore close similarities to each other that may influence interbreeding and, in at least one case, threaten the survival of a species.

Red wolves, hunted to the brink of extinction in the mid-20th century, were the focus of a reintroduction programme instigated by the US government, which has recently been halted due to a lack of success.

Part of the problem was red wolves breeding with coyotes, and the resultant hybridisation diluted attempts to maintain this rare wolf species. ̽��ֱ��researchers found significant overlap between the howling vocabulary of the red wolf and the coyote – with both favouring highly modulated, whining howls such as the one classed by researchers as ‘type three’.

“ ̽��ֱ��survival of red wolves in the wild is threatened by interbreeding with coyotes, and we found that the howling behaviour of the two species is very similar. This may be one reason why they are so likely to mate with each other, and perhaps we can take advantage of the subtle differences in howling behaviour we have now discovered to keep the populations apart,” said Kershenbaum.

Other conservation uses for the new findings may involve refining the use of playbacks to recreate more accurate howling behaviours that imitate territorial markings, thereby encouraging wolf packs to steer clear of farms and livestock.

However, we know very little about the meaning of different howl types and what they are actually communicating, says Kershenbaum, because – as with dolphins, that other highly vocal, smart and social species which he studies – wolves are extremely difficult to study in the wild.

“You don’t observe natural wolf behaviour in zoos, only in the wild, and you need to know where the animals are when howling before you can really begin to try and discern meanings. But, as with dolphin pods, physically following a wild wolf pack is virtually impossible,” explained Kershenbaum.

“We are currently working on research in Yellowstone National Park in the US using multiple recording devices and triangulation technology to try and pick up howl sounds and location. In this way we might be able to tell whether certain calls relate to distance communication or pack warnings, for example,” he said.

For Kershenbaum, wolves and dolphins show remarkable parallels with each other in social behaviour, intelligence and vocal communication – all comparisons that extend to humans.

“As well as being intelligent and cooperative species, wolves and dolphins have remarkably similar vocal characteristics. If you slow a dolphin whistle down about 30 times it sounds just like a wolf howl, something I often do in my lectures,” he said.

“ ̽��ֱ��presence of complex referential communication in species that must communicate to survive was probably a crucial step in the evolution of language. I think we can shed a lot of light on early evolution of our own use of language by studying the vocalisation of animals that are socially and behaviourally similar to us, if not necessarily taxonomically closely related.”

̽��ֱ��largest quantitative study of howling, and first to use machine learning, defines different howl types and finds that wolves use these types more or less depending on their species – resembling a howling dialect. Researchers say findings could help conservation efforts and shed light on the earliest evolution of our own use of language.

I think we can shed a lot of light on early evolution of our own use of language by studying the vocalisation of animals that are socially and behaviourally similar to us, if not necessarily taxonomically closely related

Arik Kershenbaum

Alexandre Alacchi

Photo of a white wolf of Canada, taken Gevaudan wolf park in Lozère

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Cooperative communities emerge in transparent social networks

fpjl2 — Mon, 09 Mar 2015 19:05:45 +0000

People in a society are bound together by a set of connections – a social network. Cooperation between people in the network is essential for societies to prosper, and the question of what drives the emergence and sustainability of cooperation is a fundamental one.

What we know about other people in a network informs how much we are willing to cooperate with them. By conducting a series of online experiments, researchers explored how two key areas of network knowledge effect cooperation in decision-making: what we know about the reputation and social connections of those around us.

In most social contexts, knowledge about others’ reputation – what we know about their previous actions – is limited to those we have immediate connections with: friends, neighbours and so on.

But the new study shows that if the reputation of everyone in a network is completely transparent – made common knowledge and visible to all – rather than limited to the individuals who are directly connected, the level of cooperation across the overall network almost doubles. ̽��ֱ��network also becomes denser and more clustered (so your connections tend to be connected with each other).

̽��ֱ��researchers also tested how transparency of social connections in the group influences cooperation. On its own, common knowledge of social connections had little impact on overall levels of cooperation.

However, when the researchers combined transparency of social connections with transparency of everyone’s reputation, a community of the most cooperative formed. Members of the community actively removed links from less cooperative individuals and refused their proposals to reconnect.

Researchers found that belonging to the community of cooperators is profitable. Each interaction in the cooperative community is 23% more beneficial than the equivalent interaction in the less cooperative community.

̽��ֱ��study is published today in the journal PNAS, and was conducted by Cambridge and Oxford researchers.

“We show that knowing others’ past actions is the key driver of a high contribution level. Additionally, knowing who is connected to whom matters for the distribution of contributions: it allows contributors to form their own community,” said study author Dr Edoardo Gallo, from the Faculty of Economics and Queens’ College at the ̽��ֱ�� of Cambridge.

“This finding suggests that in a world where social information is more available, people may increasingly insulate themselves in communities with other like-minded individuals. In the case we examined, belonging to the community of contributors is highly beneficial,” he said.

̽��ֱ��research sheds light on the problem of ‘public good’ provision: what motivates people to make costly actions towards a good that benefits everyone, even those who do not contribute to it. Perhaps the most defining example of ‘public good’ in the modern era is the preservation of our environment.

Gallo, along with Oxford colleague Chang Yan, devised an online experiment involving people forming connections and playing a ‘game’ of public good provision, also popularly known as the Prisoner’s Dilemma.

First, the participants in a group can freely form connections with each other which determine the network. After the network is formed, each individual decides whether to cooperate by contributing to a public good that only benefits their neighbours in the network.

Contributing benefits all the neighbours, but it is costly to the contributor. Not cooperating by not contributing, however, is costless.

̽��ֱ��best possible outcome for the group is for everyone to contribute. However, each individual has an incentive not to contribute: they can gain the benefits from others’ contributions without paying any cost themselves.

̽��ֱ��researchers recruited 364 people from crowdsourcing platform Amazon Mechanical Turk to play several rounds of a network formation game followed by a public good game. They investigated four treatments that varied the amount of knowledge subjects have about the network and previous actions of others.

When the reputation (previous actions) of everyone in the network was rendered transparent, the overall levels of cooperation were almost twice as high as when only the previous actions of immediate connections were known.

When the social connections for the entire network were also revealed to all, the cooperators formed their own community, leaving those with a history of being uncooperative out in the cold.

Gallo points out that whether the community formation – the insulating and ostracizing – that occurred in the transparent network is a desirable outcome depends on the nature of the behaviour that leads to the separation.

“In the experiment, the ‘good’ cooperators ostracize the ‘bad’ defectors, but one can argue the defectors brought it on themselves with their actions. If the same pattern occurred because of another more neutral behaviour, like an accent when speaking a language, then the ostracization might be undesirable for society,” Gallo said.

An online experiment reveals that the overall level of cooperation in a group almost doubles when the previous actions of all its members are rendered transparent. When all social connections within the group are also made transparent, the most cooperative band together to form their own community – ostracizing the less cooperative.

This finding suggests that in a world where social information is more available, people may increasingly insulate themselves in communities with other like-minded individuals

Edoardo Gallo

Marina del Castell

Cooperation

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Male Eurasian jays know that their female partners’ desires can differ from their own

jfp40 — Wed, 26 Mar 2014 10:52:41 +0000

Knowing what another person wants is not a trivial issue, particularly when the other’s desires are different from our own. ̽��ֱ��ability to disengage from our own desire to cater to someone else’s wishes is thought to be a unique feature of human cognition.

New research challenges this assumption. Despite wanting something different to eat, male Eurasian jays can disengage from their own current desire in order to feed the female what she wants even when her desires are different to his. ̽��ֱ��study, which was funded by the BBSRC, is published today in the Royal Society journal Biology Letters.

“We found that males could respond to the female’s desire even when their own desire was conflicting. That said, the males were also partially biased by what they wanted – a bias similar to one commonly found in human children and adults,” said Dr Ljerka Ostojić, who led the ̽��ֱ�� of Cambridge study.

For the study, nine male-female pairs of Eurasian jays (a member of the Corvid family) from two colonies were tested during the breeding season – the only time when jays share food. To manipulate what food the males and the females desired, the researchers used a phenomenon termed ‘specific satiety’ – after eating a particular food item to satiety, jays prefer to eat a novel food item that they are not currently sated on.

Once a day the females and males were placed in adjacent compartments with a mesh window in between. ̽��ֱ��male was then pre-fed either wax moth larvae or mealworm beetle larvae – both favourite treats for jays - until he did not want more. At the same time, the female’s desire was manipulated by giving her the same food as the male (meaning that their desires were matching), a different food from the male (meaning that their desires were conflicting), or her usual diet (meaning that the female’s desire was neutral towards the two types of larvae).

During the pre-feeding, the male had visual access to the female and saw her eat. At the end of pre-feeding, all food was removed. ̽��ֱ��males were then given 20 choices between a single wax moth larva and a mealworm beetle larva which they could either eat, cache (hide for later) or give to the female.

Not surprisingly, when the male and female birds’ preferences were the same, the male fed the female the food desired by both. However, when the female’s desire differed from the male’s, then he took his partner’s wishes into account, often feeding her the food that she desired. This ability to ascribe to another individual an internal life like one’s own and at the same time understand that the other’s internal, psychological states might differ from one’s own is called state-attribution.

Professor Nicky Clayton, whose Comparative Cognition lab at Cambridge ̽��ֱ��’s Department of Psychology conducted the study, said: “As humans, we ‘put ourselves into someone else’s shoes’ in order to respond to what the other person wants. Although we are biased by our own current desires, we can inhibit these to put the wants and desires of another before our own. ̽��ֱ��current findings show that the jays can also do this. So what this research suggests is that a common mechanism might underlie ‘desire-state attribution’ in humans and jays.”

New research shows that male jays are able to disengage from their own current desires to feed their female partner food that she wants.

We found that males could respond to the female’s desire even when their own desire was conflicting.

Dr Ljerka Ostojić

Male Eurasian jay

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