Rabbits and Rodents: General Articles

Importance of latrine communication in European rabbits shifts along a rural–to–urban gradient

Rabbits set up and use toilets differently according to how
urban or rural their environment is

Madlen Ziege,corresponding author David Bierbach, Svenja Bischoff, Anna-Lena Brandt, Mareike Brix, Bastian Greshake, Stefan Merker, Sandra Wenninger, Torsten Wronski, and Martin Plath

Source: BMC Ecol. 2016; 16: 29. Published online 2016 Jun 14. doi:  10.1186/s12898-016-0083-PMCID: PMC4908761

A study of rural and urban rabbits in and near Frankfurt, Germany, has found that rural rabbits have a higher proportion of latrines near their burrows, whereas suburban and urban rabbits have a higher proportion of latrines at the periphery of their territories. The study looked at rabbits in nine urban green spaces in central Frankfurt, of between 1 hectare and 4.9 hectares in size, and separated from one another by traffic. They also studied rabbits in four suburban parks at the outskirts of  Frankfurt, of between 5.5 hectares and 30.2 hectares, and rabbits in two rural locations near Frankfurt, each of 36 hectares.

Rabbits and other mammals often communicate through latrines where they excrete dry pellets smeared with secretions from anal and submandibular glands. Latrines near the burrow can pass on information about the individual rabbit to others within the social group, helping to keep the group together. Latrines at the periphery of their territory provide information to potential rabbit intruders from other social groups. Urban rabbits tend to form smaller social groups than rural rabbits, and urban rabbit territories are smaller. Rabbit population densities tend to be higher in urban areas, so there is more competition for territory. There were more paw scrapings at urban peripheral latrines. Paw scraping is a way that males mark their territory. Urban rabbits tend to be active for longer periods in the day than are rural rabbits, so have more time for marking. Urban and suburban rabbits are likely to flee at closer distances, and spend less time avoiding predators. There may be a higher density of predators, like foxes and cats, in urban areas, but predators may more food from sources other than rabbits, so risks from predators may be lower for urban rabbits. If risks from predators are greater in rural areas, this means that using peripheral latrines away from the burrow is riskier for rural rabbits than for urban rabbits.

Urban and suburban rabbits have more access to trees and shrubs than do rural rabbits, because a lot of woody vegetation has been cleared for agriculture in rural areas. As rabbits prefer shrubs and trees when they create burrows, this affects burrow formation.  Rabbits like to set up latrines in open areas, often high places, near woody vegetation, which allows them to retreat quickly if a predator appears.

Rabbits are suffering a decline in population density in rural Europe, though rabbit population densities can be high in urban and in suburban areas. This rural decline is probably caused by habitat destruction, with safe places for building burrows disappearing as agricultural production becomes intensified. Rabbits in urban areas may suffer more from intense competition with other rabbits than do rabbits in rural locations. Surburban sites have less habitat destruction than rural sites, and offer more space with fewer sealed surfaces where rabbits cannot dig than urban areas. Rabbits in suburban areas also appear to face less competition from other rabbits than do rabbits in urban areas. This finding of a rural-to-urban gradient in rabbit latrine habits indicates that suburban sites may therefore provide the best environment for rabbits.
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Empathy and pro-social behaviour in rats

Rats capable of helping each other from a sense of empathy

source: Ben-Ami Bartal I, Decety J, Mason P.

Science vol 334 no 6061 December 9 2011 pp1427–1430

An experiment to test for helping behaviour motivated by empathy in rats involved placing a free rat in a cage together with a rat trapped in a container. The free rat learnt how to liberate the trapped rat from the container after some days, and could not do this accidentally. The free rat was also allowed to choose between freeing the trapped rat, or eating chocolate from another container. The free rat usually chose to liberate the trapped companion, and more often than not, share the chocolate.  Research shows that rodents suffer distress when they perceive a fellow rodent in distress, and this is called 'emotional contagion', or 'catching' the emotion that you perceive others to be feeling. However the rats in this experiment went beyond emotional contagion, and actively helped their distressed companions. This indicates that rats are capable of empathy and pro-social behaviour, which appears to have biological roots, and can help with the survival of a group. The female rats in this experiment tended to show more empathy than the male rats, in that the females were more likely to free their trapped companion.

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Brain tweak makes wimps mighty

Brain connections affect social status in mice

source: New Scientist vol 212 no 2833, October 8 2011 p16

Connections in the medial prefrontal cortex (MPFC) of the brains of mice affect their social status. Hailan Hu, from Shanghai's Chinese Institute of Neuroscience, tested mouse pairs for dominance. After infection with a virus carrying a gene that strengthens electrical signals in the MPFC, mice that were subordinate became dominant. Mice that were dominant became subordinate after implantation of a gene that reduced the electrical signals. Stronger connections may help mice to control aggression, anger and emotion.
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Rat reflections give pause for thought

Rats may have a sense of self

source: Jessica Hamzelou
New Scientist vol 212 no 2833, October 8 2011 p14

Rats and monkeys have a similar structural network in their brains as that used by humans for introspection. There are some ten networks active when humans are resting, and one is called the default mode network or DMN. It is only active when humans allow their minds to wander, and it is suppressed during the performance of external tasks. The network relates to consciousness, though may be be responsible for being conscious. It may help to consolidate memories through self-reflection. Connectivity between the DMN and memory areas can be boosted through tasks involving memory retrieval. Both monkeys and rats may possess a sense of self, though it is likely to differ from that of humans.
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Breeding for aggression

Russian team breeds rats for aggression and tameness

source: Roger Highfield
New Scientist vol 211 no 2825, August 13 2011 p25

A Russian team has bred rats for aggression. The work was begun by Dmitry Belyaev in 1972. He divided rats into two groups, one bred for aggression, and the second for tameness. After Belyaev's death in 1985, Lyndmila Trut continued his work at Novosibirsk's Institute of Cytology and Genetics. Svante Paabo from Germany's Max Planck Institute for Evolutionary Anthropology, Leipzig, has studied the genetics of these rats, and believes that a minimum of half a dozen genes relate to tameness.
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For better sperm, try polygamy, it works for mice

Male fertility of mice may be improved by competition

source: Wendy Zukerman
New Scientist vol 209 no 2797, January 29 2011 p9

Male fertility of mice may be improved by competition. House mice are able to be both polygamous and monogamous. Leigh Simmons, a researcher from Western Australia University, Crawley, created polygamous and monogamous strains of mice. He then mated 16 females with both polygamous and monogamous males. The polygamous males were fathers of 76% of the resulting offspring when mated first, and 58% when mated after the monogamous males. Polygamous males produced greater quantities of sperm, which also had improved motility.
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Rats fall victim to peer pressure

Social learning and conformity in brown rats

New Scientist vol 198 no 2655, 
May 10 2008 p18

Humans and chimps are known to have a strong urge to conform, and this is also true of brown rats. Bennet Galif and Elaine Whiskin, from McMaster University, Hamilton, Ontario, have discovered that rats which initially did not like food tasting of cinnamon will eat it if they meet rats that have eaten cinnamon-flavoured food. The rats were fed food tasting of cinnamon, then injected with a chemical that produced nausea. After that, the rats chose food tasting of cocoa. However, after meeting rats that had eaten cinnamon-flavoured food, and so smelled of cinnamon, the rats went back to eating cinnamon-flavoured food. The researchers say that this raises the question of why animals conform, despite knowledge from their own experience.
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Beware, the rats are listening

Rats can distinguish between human languages

source: New Scientist vol 185 no 2482
January 15 2005 p18

A team led by Juan Toro from Barcelona University, Spain, has discovered that rats can distinguish between Japanese and Dutch. One group of rats was rewarded for pressing a lever when they heard Japanese from a speech synthesizer, while another was rewarded for pressing the lever when they heard Dutch. The rats rewarded for responding to Japanese did not press the lever when they heard Dutch, and vice versa. They were unable to distinguish between the two languages when sentences were said backwards. This research was reported in the Journal of Experimental Psychology: Applied Behaviour Processes, vol 31 p95.
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In from the cold

Interesting facts about gerbils

source: Justine Hankins
Guardian Weekend June 21 2003 p107

Gerbils are burrowing rodents that are found in the wild in central Asia, some parts of China, the Middle East and North Africa. There are some 90 species of gerbil, though most pet gerbils are Mongolian gerbils. They were sent to the UK and US during the 1950s and were used as laboratory animals, and were then adopted as pets. The National Gerbil Society was set up in 1970. Gerbils do not bite, and stay awake in the daytime. They do not smell much, since they don't urinate a lot, being desert animals. These characteristics mean that they make good pets. They can, however, breed fast.

There was an attempt by Israeli security agents at Tel Aviv airport to train gerbils to detect suspicious characters, since they can easily smell sweaty people. The gerbils used for this work, however, were unable to detect the intent of sweaty people. Some of the sweaty people simply had heavy luggage, and were not planning hijacks.
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Mouse sperm jump aboard the love train

Wood mouse sperm join together to reach eggs faster

source: Nicola Jones
New Scientist July 13 2002 p17

Male wood mouse sperm join together to reach eggs faster, according to University of Sheffield biologist, Harry Moore. Thousands of sperm use hooks to link together, like a long express train. This may give the sperm a better chance of getting to an egg than sperm from another mouse. The chains may have between 50 and 2,000 sperm, and their speed can be as much as 50% faster than one sperm travelling alone. Marsupials also have sperm that cooperate, in their case by swimming alongside each other. Guinea pigs' sperm joins in clumps, though it's not clear how this helps the sperm. The clearest case of sperm showing altruism, however, is shown in wood mice.
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Rodents to rat on criminals

Sniffer rats being trained at Baltimore University

source: Jon Copley
New Scientist June 15 2002 p13

Baltimore University reseearchers, led by James Otto, have trained rats to track simulated coacine and explosive smells, eben when distractions are present such as almond extract and engine oil smells. The rats stand up on their back legs when they locate the substance they have been trained to find. The rat wears a harness that records the find with its time and location.

Using rats has a number of advantages over sniffer dogs. They can be trained en masse, Otto has found, with computers controlling rewards after measuring performance. Rats can also enter emaller spaces than dogs, and are less dependent on particular handlers.
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Say hello to the roborat

Ethical debate on usage of brain implants to influence rats’ behaviour

source; Duncan Graham-Rowe
New Scientist May 4 2002
starts p6, 2 pages long

Sanjiv Talwar and his research team from the State University of New York have developed ‘roborats’ with brain implants that can make the rats jump and turn in different directions. This research has triggered a debate on the ethical issues involved. Talwar argues that the rats are not forced to perform specific actions. The technique relies on stimulating the rats’ reward centres in the medial forebrain bundle. Other implants were placed in the somatosensory cortical area, where stimulation comes from right and left whiskers. The rats also had radio receivers plugged into their skulls. They were rewarded when they performed actions in response to stimulation of a whisker. Talwar argues that the rats had control of their movements, despite the pressure from their wanting to be rewarded. He sees the rats as having potential for search and rescue operations, seeking survivors in rubble.

Critics, such as Gary Francione, disagree. Francione, from Rutgers University School of Law, argues that the rats suffer discomfort, and operate under the control of another. Another critic, Gill Langley, notes that the Federal Animal Welfare Act provides no protection for birds or rodents used in experiments in the US.
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Rabbits blamed as E coli infects 10 children

Wild rabbits thought to have infected children with e coli in Norfolk, England

source:James Meikle
The Guardian, Nov 9 2001

Wild rabbits are thought to have infected two adults and 10 children under ten-years-old with a type of E coli infection, an outbreak which could lead to changes in regulations. The outbreak occurred at Thrigby Hall wildlife park in Norfolk, England, from July to September 2001. Hospital treatment was needed by four of the victims, one of whom suffered renal failure. New fencing has been put up at the park, and rabbits have been killed. Vets believe that the rabbits transported the infection from cattle dung at a farm near the park.

Large-scale killing of wild rabbits is not seen as practical due to their large numbers, and there could also be protests. It is also difficult to erect rabbit-proof fencing using wood or wire, and brick walls with foundations are more effective. There is safety guidance for wildlife parks, children’s farms, and those setting up outdoor events, for example on handwashing facilities and dung removal.
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MI5 hatched plot to train gerbils as mole catchers

Usage of gerbils to catch terrorists at airports considered in 1970s

source: Michael Smith
Daily Telegraph June 30 2001 p3

Britain’s MI5 agency studied a plan in the 1970s to use gerbils at airports, to detect incoming terrorists and spies, according to MI5 director general, Sir Stephen Lander. Gerbils can sense adrenalin changes, which affect the smell of sweat, and they were used for this purpose at Tel Aviv airport in Israel. The gerbils were put alongside security checks, and trained using Pavlovian methods, to press a lever to obtain food, if they sense raised adrenalin. The gerbils were unable to tell whether adrenalin rates were high because passengers were fearful of air travel, or whether they were terrorists, however, and the Israelis abandoned the idea, as did MI5. Research was carried out during the 1970s for the Mounted Police in Canada on the feasibility of using gerbils to detect terrorists.
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Well ratted

Arrest of woman for inebriation with a guinea pig

source: Guardian, Society March 27 2002 p12

A woman from Devon, England, has been arrested on a charge of being intoxicated while she had control of a guinea pig. She spent the night in police cells.
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Squeals of delight

Guinea pigs and other Latin American rodents

source: David Alderton
Guardian, Weekend March 16 2002 p69

There are 1,500 species of rodent world wide, and only some dozen rodents have become popular as pets. Many of these pets originate from the Andean region of Latin America. They include guinea pigs.

Guinea pigs’ ancestors were domesticated in Peru several centuries prior to Europeans arriving there. They were initially kept to be eaten, not as pets. The earliest mention of guinea pigs by Europeans was in 1554. Sailors then started to bring guinea pigs to Europe during the 16th century. It’s not known how they got their name, though it may have come from Dutch Guiana, now called Surinam, where they were first found by the Europeans who brought them back. The ‘guinea’ in their names may derive from their having cost one guinea, or there could be a link with Guinea in Africa. They do look and squeal like pigs. They are also called cavies, and their scientific name is ‘Cavia’.

Guinea pigs can be found in all sorts of colours, with both smooth and rosetted coats. There are also long-haired guinea pigs that need a lot of grooming, called Peruvians.

Other Latin American rodents include chinchillas, which have very dense coast to help them survive cold weather in the Andes. These dense coats mean that they don’t get fleas easily. Wild chinchillas almost became extinct at the start of the 20th century, and are still endangered.

Degus are also rodents from the Andes. They were used for medical research during the 1950s. They look like large gerbils, and have faces like squirrels, They are also active and gnaw a lot, like chinchillas, so need metal-framed enclosures.
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The effect of environmental enrichment on the behaviour of caged rabbits (Oryctolagus cuniculus)

Rabbits show less stress in an enriched environment

source: L.T. Hansen and H. Berthelsen
Applied Animal Behaviour Science (68) 2000
starts p 163, 16 pages long

A study of caged rabbits has found that they can benefit from an enriched environment. Traditional cages tend to restrict social behaviour and foraging, and rabbits may not have enough room to move, which could affect their skeletons. Traditional cages are often not high enough for rabbits, which need to be able to sit upright and not have their ears touching the cage top.

There were 47 male and 49 female rabbits used in this study, all French Lop crosses with New Zealand Whites. They had previously lived alone in conventional cages. Half the rabbits were put in enriched cages, which were 80 cm high at the back, compared to 40 cm for conventional cages, and which also had a wooden box at the back. Daylight from windows supplemented artificial light, turned on from 7am to 4 pm. Videos were recorded of some of the rabbits, and the rabbits were also observed during the daytime by a researcher. The rabbits were also observed in a large area (‘open field test’) as well as in their cages.

There were some sex differences, for example, females spent longer gnawing, and males spent longer grooming. Females in the enriched system were also more likely to use the nest box.

Rabbits in the enriched system were less restless than rabbits in conventional cages. Restlessness, or not finishing activities, is seen as a symptom of stress. Rabbits from enriched cages were also less timid when being caught following the open-field test, and this was especially true for female rabbits. Females were also more likely to gnaw bars in the conventional cages. Females do appear less able to cope with a barren environment compared with an enriched environment. A disturbance often caused rabbits in enriched cages to jump onto the nest box, where they seem to have a better lookout position. Few rabbits went inside the nest box to shelter or for rest, and those that did were mainly females. Female rabbits in the wild tend to spend more time in burrows than do male wild rabbits. There was little difference between rabbits from enriched and conventional cages in terms of space covered in the open field test, though the rabbits from enriched cages may have moved out of boldness, and those from conventional cages may have moved due to fear.

Rabbits in both systems spent longer grooming than do wild rabbits. This may be a displacement activity arising from disturbance, or linked to understimulation, or to social deprivation. Both wild and caged rabbits tend to spend much of the time inactive.

Rabbits do appear to benefit from an enriched environment, and this is especially true for female rabbits.
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Jurassic pipsqueak

Ancestor of modern mammals discovered

Source: Jeff Hecht
New Scientist June 2 2001 p18

A skull 13mm long from a shrew-like mammal, discovered in Yunnan province, China, is estimated to be 195 million years old, when dinosaurs were still alive. Zhexi Luo, from Carnegie Museum of Natural History, Pittsburgh, calculates that this mammal, called the Hadrocodium, weighed two grams. The skull is smaller than any discovered so far from this period, and differs from the skulls of contemporary mammal relatives in having a relatively large brain case, as is found in modern mammals. Modern mammals also have a middle ear made from bones that are part of the jaw in reptiles, and this new skull appears to have had a middle ear similar to that of modern mammals, unlike other mammal relatives living at that time. Harvard University’s Alfred Crompton, a palaeontologist, believes that the change in bone structure occurred as mammal ancestors’ skulls became smaller. This may have helped mammals develop sharp hearing. Mammals living during the age of dinosaurs probably had to be nocturnal to survive.
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The mouse that sniffed and roared

Male mice become bolder after smelling receptive females

Source: New Scientist December 8 2001 p27

University of Western Ontario researchers have discovered that male mice become bolder after smelling receptive female mice. The males exhibited less aversion to the scent of cats when the mice had smelt female mice for a minute. These mice also had higher testosterone levels and lower stress hormone levels. These effects disappeared after the males had been exposed to female scents for an hour or more. This research is described in ‘Hormones and Behavior’, vol 40, p497.
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It's a sex thing

Nitric oxide affects aggression in male and female mice in different ways

source: Alison Motluk
New Scientist September 25 1999 p16

Aggression in female mice is affected by nitric oxide in a different way from aggression in male mice. Male mice lacking a gene producing nitric oxide become aggressive, according to Stephen Gammie and team from John Hopkins University, Baltimore, US. The team found that female mice, which are usually only aggressive in defense of their pups, were less aggressive when they lacked nitric oxide. Normal female mice with young pups attack strange males approaching them, whereas females lacking nitric oxide do little to intervene. Female mice appear to need nitric oxide in order to be aggressive, and neurotransmitters appear to have different impacts on males and females. This finding may apply to other mammals, including humans.
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Mice and men

Mice lacking oestrogen do not show aggression

source: New Scientist December 2 2000 p23

Male mice lacking an enzyme which turns male hormones into oestrogen do not exhibit aggression when their territory is encroached on by other mice, Japanese researchers report. This changed if the mice had oestrogen supplements just after they were born, though they were not aggressive if there was a delay until seven days after birth before they had oestrogen supplements. The research was carried out at Japan's Kochi Medical School, and is to be reported in 'Journal of Endocrinology'.
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You scratch my back, honey, then maybe...

Female woodmice may seek grooming in exchange for sex

source: New Scientist December 4 1999 p23

Researchers from University of Oxford, England, have found that male woodmice tend to occupy themselves grooming females for longer than females groom males (Ethology, vol 105, p982). The researchers, David Macdonald and Pavel Stopka, believe that females seek grooming in exchange for sex. Males may only be able to offer grooming as a resource, due to the promiscuity of wood mice.
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Family way

Nurturing instincts of mice linked to genes from fathers

source: Philip Cohen
New Scientist April 17 1999 p17

Mice with defective Peg3 genes have been found to gather straying pups more slowly than average, and build nests more slowly. The gene also affects neuronal development, which in turn affects reactions to oxytocin, a hormone that induces maternal behaviour and lactation. The Peg3 gene is an imprinted gene, only one copy of which is found to be active in mice, which usually have two copies of genes, one from each parent. The research was carried out by University of Cambridge researchers, Eric Keverne and Azim Surani, who have previously discovered that a different, and unrelated gene, Mest, which mice inherit from their fathers, affects maternal behaviour.
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The Mozart effect

Rats perform tasks better when listening to Mozart

source: Gary Kliewer
New Scientist November 6 1999
starts p34, 4 pages long

Listening to Mozart appears to help both humans and rats peform tasks better. Rats can solve maze problems faster when they are raised with Mozart's music. 30 rats heard Sonata in D for 12 hours a day for more than eight weeks. Frances Rauscher, University of Wisconsin, Oshkosh, psychologist, found that these rats made 37% fewer mistakes in maze tests, and performed 27% faster than other rats raised with silence or white noise. She is carrying out a new study using a control group of rats with toys to play with, as well as rich social interaction, in case the original controls performed badly due to their deprived environment. There is evidence that Mozart may also help humans with conditions such as Alzheimer's and epilepsy.
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