Using discrete video cameras, scientists have been able to study the long-term natural behaviour of beavers "at home" in their lodges.
The tiny, waterproof cameras, inserted into beaver dens, show that beavers lead very different private lives when at home than when outside.
At home, the animals are surprisingly co-operative and scientists have even recorded baby beavers growing up.

Kits exhibited multiple sleep wake cycles lasting only a few hours, much like a human infant waking up every few hours during the night Professor Cy Mott

"Much of what we know about beavers and their use of dens is limited to questions like 'what times of day do they go in and out of the den'", says Cy Mott, a biologist at Kentucky Wesleyan College, in Owensboro, US.
"Simply because, until recently, we haven't had the technology to follow their behaviour within the den without potentially disturbing natural behaviour."
So Professor Mott and colleagues, Craig Bloomquist and Clayton Nielsen of Southern Illinois University in Carbondale, US, decided to study American beavers (Castor canadensis) denning on the Mississippi flood plain in south-western Illinois.
Beavers in this region declined drastically in the 19th and 20th Centuries, but have since recovered due to a ban on hunting them for their pelts.
The researchers used special "probe" cameras that do not disturb the beavers to record the animals' behaviour in 23 colonies over the course of more than a year.

Beavers make sophisticated homes, either in dens burrowed into river banks, or more complex lodges.
Lodges are essentially dens built from wooden branches that are surrounded by water, the level of which beavers help maintain by also building wooden dams.
Video taken of beavers within 17 lodges and six bank dens revealed some surprising behaviours.
Living in their elaborate shelters, beavers were thought to be cut off from the outside environment.
But the video study shows that they exhibit regular patterns of behaviour, leaving to feed at roughly the same time every day, for example.
"This suggests that they may not be as cut off from the external environment as we think they are," says Professor Mott.

BEAVER BEHAVIOUR FACTS American beavers are the third largest rodent in the world, after the capybara of South America and the Eurasian beaver An 850m-long beaver dam was discovered in Canada this year Watch video clips of American beavers

Male and female beavers appear to take equal responsibility for raising their babies, known as kits, perhaps because the young are so "high maintenance".
In the privacy of their own home, beavers also spend 95% of their time feeding, sleeping, and grooming.
"It supports the assumption that the relative security of the den is a place where they can exhibit behaviours that would be potentially dangerous outside of dens," says Professor Mott.
Baby sleep
Another surprise relates to the private lives of baby beavers, and their sleeping patterns.
Baby beavers, and adults, follow a similar sleep schedule to humans, the researchers report in the journal Mammalian Biology.
Adults beavers tended to sleep at a similar time, though not all the adults fall asleep at once, perhaps to ensure the babies are looked after.
"Kits, on the other hand, exhibited multiple sleep wake cycles throughout the day and night, with each interval lasting only a few hours, much like a human infant waking up every few hours during the night," says Prof Mott.
Finally, "given that beavers are in incredibly close confines within dens, we fully expected to document aggressive behaviours," he explains.
Most social animals that live in close-knit groups tend to use aggression to establish a "pecking order" between individuals.
But "one of the most interesting things we didn't find was aggression within beaver colonies," Prof Mott told the BBC.

SOURCES Visit Mammalian Biology to learn more about the private lives of beavers

The researchers know of only two previous studies that attempt to explain what happens within a den, despite the fact that beavers spent considerable portions of their lives in these structures.
In one study, scientists cut away one side of a lodge to view the beavers directly via a glass panel, which likely disturbed the animals' natural behaviour.
The other study consisted of a researcher "listening in" while outside the lodge, in an attempt to describe what was happening inside.
"To our knowledge, our study is the first to use long-term video data to follow behaviour for months at a time, over successive years, and even during the period from birth of beaver kits until they disperse to find territories of their own," says Professor Mott.

By Mark Kinver Science and environment reporter, BBC News

Researchers reached their conclusion by modelling how white-nose syndrome (WNS) is passed from bat to bat.
Writing in Conservation Biology, they add that a cull would not work because the source of the fungal pathogen is believed to occur in the environment.
Earlier studies have warned that WNS could wipe out bat populations in the north-east of the US within 20 years.
Carrying out a cull of bats in areas where the disease is known to be present is one of the options available in an attempt to contain the spread of the killer fungus.
"Given the dispersal aspect of the problem and the complexity of hibernating bat ecology, it was a case that these things together certainly meant that culling would not work in the case of bats."
WNS, described by some as the worst wildlife health crisis in the US in living memory, is named after a white fungus that appears on the muzzle and/or wings of infected animals.
However, bats with WNS do not always have the characteristic visual symptoms, but may display abnormal behaviour around their hibernacula (caves and mines where bats hibernate during winter months).
These behaviours include flying outside during the day (when their insect prey is not available) in sub-zero temperatures, or clustering near the entrance to the hibernaculum.
Professor Hallam explained that there was a high degree of bat-to-bat interaction, which has been identified as the main way the disease is transmitted, during the course of a year.
In autumn, the mating season brings together large numbers of males and females.
This occurs shortly before colonies enter hibernacula, some of which are large enough to house in the region of half-a-million bats.
In the spring, females head to a maternity roost to have their young. Again, this brings bats into contact with members of different colonies.
Since WNS was first recorded in February 2006 in a commercial cave in New York, it has spread to at least 14 states. Cases have also been recorded in a number of Canadian provinces.
Researchers say the fungus associated with the disease, Geomyces destructans, thrives in the dark, damp conditions - such as caves and mines.