The Laboratory Rat: A Natural History. M. Berdoy. Oxford University. FULL & HD VERSION

[Music] as a disease carrier the wild rant has been hated and remorselessly destroyed over the centuries but its story is one of paradoxes in recent times the lab rat has been the key to many medical advances the old enemy has saved many lives [Music] generations of domestication have created an easy to keep docile subject for experimental studies could this animal ever rejoin its wild cousins to survive in the wild what ghost of a wild ancestor still lies beneath its white lab coat [Music] in the beginning was the wild rat riding on the back of human migrations this intelligent and adaptable rodent has colonized the world by following in our footsteps the brown rat is the textbook example of a commensal rodent literally one who eats at our table a competitor and a pest about a hundred years ago rat evolution and its relationship with man took a surprising turn the rat was selectively bred as a tool for science the changes selective breeding has brought go deeper than the albino features seen in the classic white lab rat it's mind has also changed and there's not just one type of lab rat but hundreds of strains many bred for a specific purpose the features that made the wild rat a pest have made the lab rat a success it breeds quickly can be housed in groups and it's easy to feed and it's modest size means that it can be kept in small facilities housed in standardized disease-free conditions the use of genetically similar laboratory animals has revolutionized biological science scientific papers on laboratory rats accumulate at the staggering rate of one per hour as a tool a model to understand mammals the rat has opened the door to many a discovery from biochemistry to psychology where it can be trained to perform complex tasks but it's all too easy to forget that rats are the sophisticated product of millions of years of evolution in a habitat far more demanding than this how many of its ancestors behaviors and drives remain locked in awaiting an outside chance to be expressed this rat may have successfully learned to associate these objects with reward but could it still find food in the wild we opened their cages and let them loose in the sort of enclosed farmyard where wild yak would thrive we followed the fate of 50 rats of two different strains wistar and Lister hooded born and raised in the laboratory but who when released in a large outdoor enclosure would have to compete like their wild cousins for shelter food and mates predictably they are immediately curious but cautious too it is after all the first time they've seen the sky but it doesn't take too long before the drive to explore which has made their wild cousins so successful it's the better of them with males venturing out first the rat from the hooded strain are more exploratory ready to venture into the unknown quicker and they take a welcome opportunity to visit the white females in the other boxes the rats then check out available shelter a sensible precaution for trade it's a good first sign that these lab rats still have some instinct for survival but equally rats have a clear desire to explore and everything is so new even climbing is new as laboratory rats are traditionally housed in a two-dimensional world and they investigate the ladder with hesitancy it didn't take them long to find water and readily took to it rats require a great deal of water and they let them stop for a drink between bites if they can some soon developed distinctive ways of drinking this rat always preferred to drink from her pores or even from a leaf perhaps it was a strategy to remain upright and vigilant [Music] it's not long before the rats are introduced to yet another new experience for which they were perhaps less well prepared a summer storm [Music] [Applause] [Music] it was a relief to see that most brats were sensible enough to sit in it undercover [Applause] it's only been a few hours but the rats have already adopted a hopping gait characteristic of wild rats and they begin to dig something that the lab rats haven't been able to do but they've not forgotten how the rats first day of freedom for 200 generations has been successful now we must leave them alone to spend their first night [Music] a new day brings new challenges they're faced with foods that they've never encountered before a buffet quite different from the homogenized pellets that they've been raised on some foods are immediately tempting others a little puzzling rats are omnivores and their willingness to test a wide range of foods has contributed to their success new foods are the key to new situations and environments but this leads to a problem not everything that looks like food is edible and some are potentially lethal rats showed typically a conflict of motivation keen to test new food stats but cautious this is the omnivores paradox a dilemma that rats share with humans wild rats have evolved a range of solutions to the omnivores paradox wood lab rats still use them feeling social is one such solution by checking what other rats do members of the colony can learn from each other please hooded rat has already discovered the rewards of blackberries very soon her breath and coat are impregnated with this new smell other rats are sensitive to this and follow this hooded pioneer this why craft learns quickly that it may be worth a try even though he has yet to discover that right Butler is our best but how can it tell that a particular food might be bad like humans rats have evolved the capacity to make a connection between the taste and smell of what they eat and how they feel later sometimes hours later the ability to learn despite this time delay was a surprise when it was discovered how do you know what has hurt you if the pain occurs several hours later yet research has shown that natural selection has shaped their brains so that these important connections are made when food is concerned this is an important part of the omnivores armory an ability that has also been found in humans and being social helps once again as rats can learn from the experience of other individuals a phenomenon called the poison partner effect if a rat smelling of a particular food staff is looking unwell other individuals will avoid that food in the future eating isn't the only problem avoiding being eaten is another danger that small creatures face the visit of an unwelcome guest sends the colony bolting into their burrows [Music] but rats don't need to see a cat to appreciate the danger they've evolved an innate aversion to cat odors it makes good sense to stay away from areas visited by such formidable predators and despite generations that have never encountered a cat these rats still show this innate aversion not all the rats witnessed this cat visit yet a whole colony stopped venturing out to take food for the rest of the day preferring instead to rely on stored foods until they judged that the danger had passed [Music] one way that mammals avoid predation is to come tonight rats are naturally nocturnal that has the week's progress the colony is becoming increasingly active after sunset and that's not the only change that we see in our rats where once they were hesitant they've become very agile and where they amble through the open spaces they now check that there is no sign of danger before moving rapidly between shelter points they've built a comfortable and complex series of boroughs and corridors the preferred spot is the straw bales the rats equivalent of luxury apartments some females are provisioning these new homes with hoarded food these laboratory rats have never lacked food but here their wild instincts dictate that they lay in provisions there may soon be more mouths to feed smell and touch are not the only senses that rats use and the colony is echoing with sounds that we can't hear rats can communicate in the ultrasonic range above the 20 kilohertz upper limit of our hearing whilst the function of these vocalizations are mostly unknown most are produced socially rats have three kinds of calls in at least two different ultrasonic frequencies this long 22 kilohertz Paul whose frequency has been lowered to make it audible can be emitted by subordinates and may express fear or even pain at other times it may be used as a warning or an alarm call it's also emitted by females prior to mating and by males after ejaculation to other types of calls operate at even higher ultrasonic frequencies in the 50 to 100 kilohertz range this play is aboard in a mating context often winged males follow females in some cases it seems to make the females more likely to be sexually receptive the Smith's complex call can be heard of in an aggressive contact and indeed there were some signs of conflict developing between our reps [Applause] lab rats have been bred to be docile but there were signs that a pecking order was emerging the larger rat is usually the winner of such aggressive interactions thereafter the subordinate will simply give way to its superior such a pecking order can be remarkably stable with individuals remaining dominant over rats they've beaten in the past long after they've outgrown them the subordinate may accept the status quo because there's more to be gained by accepting a subordinate status than risking an all-out conflict aggressive escalation amongst rats is rare resolving conflicts is part of being social and our naive rats have formed a complex and efficient colony which is now thriving they've transformed their habitat to finding important features in the environment is now made easier by the presence of brands like so many countries those raptly runs allow easy access to places of interest such as food sources boroughs or shelter they're like move to lights conveniently the width of an adult and the rats zoom through them at great speed a rat can become so familiar with its pathways that it doesn't even have to look where it's going and that's a mistake if a new obstacle has appeared in its path [Music] smells are also an important component of the Raps world they're used to identify individuals their sex dominant status and East recycling by now the rats have also probably tuned in to a clan smell a wild rat visiting the colony produces great excitement this mixture of aggression and fascination isn't only because he looks different his smell doesn't match that of the clan the wild rat is also attracted by the smells emanating from the colony one smell in particular can provide a free song of excitement like no other at least among the males that of a female on hit unless mated female rats come into estrus every 5 days or so east rest's a few hours and males are attentive to any development in areas sparsely populated in the wild males may travel over several kilometres to find females in densely populated areas where food is abundant like in farms or here females are more easily available but males have to compete and the race to find the female is on sometimes even before the Sun has set but the female doesn't make it easy moving around the colony she invites the males to chase her and encourages competition soon she has a queue following her it's only when she stops to present her rump in lordosis that the first male in the queue can mate whilst the others look on a close examination reveals that her ears are vibrating this is very sexy at least for rats [Music] [Music] after the male has copulated he licks his genital area whilst the female moves on followed by the rest of the board although it is the female who ultimately decides when to mate there's a fine line between solicitation and harassment even then the other males interfere very little with the mating male and don't fight with each other reduced biting may be a feature of generations of laboratory breeding but it's also found in wild rats because the female is constantly on the move males engaged in fighting would rapidly lose her and therefore lose the opportunity to mate this may also only why subordinates are inclined to accept their social ranking in colony without too much fuss then they might have a chance to mate in such an indiscriminate scramble for pole position why do such multi-male multi-female mating patterns exist it's clear why males benefit from mating with several females since it will increase the number of their offspring but why should females since females are limited by the number of pups that they can produce this isn't only a feature of harassment as females when given the choice actively choose to mate with several males whilst it's still a bit of a mystery there are several possibilities for example females may ensure their eggs are fertilized by reducing the chance of mating with an infertile male it may also be a way of inducing competition between males and ensuring that only the best sperm or the fittest males most able to keep up with her win the scramble competition three weeks later 10 pups are born litter size in lab rats is generally more than their wild cousins but like them the litter can be fathered by different males females make attentive mothers as virtually no care is provided by the males pups are born blind and hairless and will be dependent on their mother for several weeks they are at the mercy of predators and that includes other members of the colony infanticide though not frequent is widespread amongst mammals many instances of infanticide our attempts to limit competition in some rodents females may kill the pups of other females but the real danger other males who profiting from the females brief absence may kill some or all of the pups this infanticidal mail is probably not the father of this litter as males are less likely to attack the litter of females with whom they've made it however cruel it may see it makes biological sense of course as these pups will never compete with his offspring perhaps it's because of this biological equivalent of a protection racket that females accept indeed solicit mating with several males in the mating frenzy the male's can't be sure that at least some of the pups are not theirs the ruse appears to work as this was the only incident that we observed during the filming three weeks later and the first new arrivals in the enclosure demonstrate how well the colony is doing the appearance of the pups is testimony to the mixed matings in the colony within three weeks the pups are able to feed by themselves but first they have to decide what to eat to some extent they already have some idea they will have learned what to expect from the taste of their mother's milk as well as from the smells emanating from other individuals in the colony the burrows are now acting as information centers as the rats carry with them a wide panoply of smells from the outside world and following along after their mother is useful too [Music] [Music] by now the rats have learned to exploit food in the more remote places and climb on small branches with great agility well most of the time [Music] the rat diet has also become far more varied than the food pellets that were their staple in captivity an apple a snail a stray egg even a dead bird all were devoured by the colony but this diversity poses a problem since foods vary in their nutrient content how do the rats know how to select a balanced diet they're helped by another ability evolved by their omnivorous wild ancestors in addition to having learned whether some foods are better than others rats possess like humans some specific appetites allowing them to compensate for specific deficiencies in some proteins or salt the colony did differ markedly from wild rats in at least one aspect though despite their increased caution they remain less fearful of novel objects than their wild counterparts a feature called neophobia it's been said that paranoia in wild rats is a sign of a good grasp of reality but lab rats have become less suspicious you wouldn't catch a wild it so easily [Music] six months have passed the colony is now thriving and the borough complex has been extended fermentation in the straw triggered by the ammonia from the rats urine is even keeping them warm as the colony now watches the approaching winter nights from the close comfort of a centrally heated accommodation it's clear that our laboratory rats initially naive and hesitant when released soon gelled into a structured and complex society it didn't take them long when given the opportunity to resolve successfully many challenges in ways similar to their wild cousins clearly many wild instincts remain understanding how much of the wild rat remains hidden is relevant when housing them it's also relevant when designing experiments even the most causal of scientists exclusively interested in mechanisms are in a sense studying the product of evolution and we may have taken the rat out of the wild but clearly we haven't taken the wild out of the rat [Music]

Channel: ratlife.org

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Keywords: Ratlife, Rat, rattus norvegicus, berdoy, ratlife.org, animal welfare, oxford university, rspca, rats, manuel berdoy, NC3R, NC3Rs, dr berdoy

Id: giu5WjUt2GA

Length: 27min 27sec (1647 seconds)

Published: Sun Jun 11 2017