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How to Tell If a Hamster Is Truly Happy

Is your hamster happy? A new tool to assess moods in the furry little rodents can tell if they are optimistic or depressed.

Hamsters can experience happiness, optimism, sadness and depression much the way that we do, suggests a new study that describes a method for determining the feelings of these cute and cuddly popular pets.

While the tests are best left to scientists, the end results are clear: hamsters love extra comforts, such as comfy hammocks, ample bedding material, ledges, chew toys and snacks. Without these and other perks, the furry rodents show signs of depression, indicates the study, which is published in the new issue of Royal Society Open Science.

Wild Animals Enjoy Exercise Wheels Too: Photos

Authors Emily Bethell and Nicola Koyama of Liverpool John Moores University explain that "cognitive measures may detect shifts in emotion not apparent from behavioral observation or traditional behavioral tests of emotion alone."

In other words, a person could spend all day watching a hamster, and not really know what it is feeling. This is not to say that the rodents don't experience many emotions. Instead, we do not easily detect their social cues. It's not as though a hamster can look up, flash a smile and say, "I feel great today!"

To get around this problem, scientists have developed a "go/no-go" task to measure levels of optimism that, in turn, are linked to feeling of happiness or sadness in humans and other animals.

In this case, the researchers trained 30 captive-born male Syrian hamsters to approach a drink station at one location to obtain a reward (i.e., to go toward sugar water) and to refrain from approaching a drink at another location to avoid an aversive liquid ("no go"). The scientists then created ambiguous situations in which it was unclear to the hamster if the drinker offered a reward or the bad-tasting liquid.

Video: Dogs Have Feelings Too

The scientists included a number of controls and additional behavioral tests to overcome possible limitations, such as odors released by the drinks.

Before the tests, some of the hamsters were raised with multiple comforts, such as soft extra bedding, while the others just received basic care. Hamsters given the added "enrichments" repeatedly exhibited more optimism in their decision-making throughout the study.

Bethell and Koyama wrote that "the addition of extra cage enrichment leads to a more ‘optimistic' judgment bias in the hamsters. Removal of the additional enrichment items (back to standard enrichment condition which hamsters were used to) resulted in a negative shift."

Similar studies have involved rats, mice, cats, dogs, dairy calves, sheep, chickens, honeybees, rhesus macaques, marmosets, starlings, pigs, horses and goats.

Human Hamster Wheel Turns Up Productivity

The researchers explained, "So far, studies have revealed that manipulations presumed to create a negative state (such as disrupted housing conditions or dehorning in calves) lead to reduced responses (more ‘no-go's) to the ambiguous probes. This negative shift in judgment bias is presumed to arise from a negative shift in underlying emotion state."

They continued, "Positive manipulations (e.g. addition of environmental enrichment) generally lead to increased responses (more ‘go's) at one or more of the ambiguous probes. This is presumed to arise from positive shifts in judgment bias and underlying emotion state."

It is known that happy people make more optimistic decisions, while depressed individuals tend to make more negative assumptions, so studies on humans support the new research's overall findings.

You might say that it's common sense that a pampered person or pet will be happier than those without such comforts, but, as mentioned earlier, proving this for animals whose visual and audible communications we don't understand is difficult.

The researchers hope that their work will "lead to improved welfare assessment across species."

A hamster eating a piece of carrot in its owner's hand.

Animals, such as pet hamsters, really do enjoy exercise wheels, suggests a new study that found most small wild creatures voluntarily use the wheels when they encounter them. The study, published in the latest issue of Proceedings of the Royal Society B, is the first to look at wheel running in the wild. "Locomotion can be inherently rewarding for animals," Johanna Meijer, a professor in the Department of Molecular Cell Biology at Leiden University Medical Center, told Discovery News. She co-authored the study with colleague Yuri Robbers.

Rodents Fear Men (Women, Not So Much)

Exercise wheels are ubiquitous for small captive animals. Larger animals may use them too, as this cat shows, if the wheel is big enough and the animal is not afraid of the device. Some animal activists have questioned the behavior, concerned that it is a product of being cooped up in a cage. The new study, though, found otherwise. "Our results indicate that running wheel activity is not necessarily an aberrant behavior initiated as a consequence of captivity and perhaps stress, but rather an elective behavior that can be observed in a natural environment," Meijer said.

Cats Don't Actually Ignore Us

Among the animals proving Meijer and Robbers' pro exercise wheel stance was this wild mouse. For the study, the researchers anchored an exercise wheel in both a "spacious green urban area and a dune area not accessible to the public." They then set up a video camera with night vision and a motion detector. A food tray was placed nearby, just to attract wild beasties to the spot. Wild mice went for the food, and the wheel too. "Mice run in the wheel; they never just walk," Meijer said. "They are frequently observed leaving the wheel, and immediately going back in, suggesting it is a voluntary act." She added, "Sometimes two mice run in the wheel at the same time."

Pets Go Clean, Wild Animals Find Safety in Filth

Surprisingly, the second most common visitors to the wheel placed in the wild were slugs. "They can slide along for hours," Meijer said. Slugs aren't exactly high on the food chain, so no one has ever studied whether or not they play. Meijer, however, said they could be exhibiting play behavior, although she thinks that slugs and other organisms "have an intrinsic motivation to be active." Perhaps, like a couch potato person getting the sensation of activity while watching television, the slug has the sensation of exciting activity as it slides and the wheel creates additional movement.

Snails might be cleverer than we think. "Snails in the wheel cheated," Meijer said. "They activated the wheel without running. They climbed up vertically until center of mass was moved above the central axis of the wheel, making it turn."

Frogs don't walk or run, and yet wild frogs seemed to enjoy the exercise wheel too. "Frogs sit in the wheel and jump, making the wheel move back and forth, then jumping again," Meijer said.

PHOTOS: Superhero Frogs, Giant Fish

In the future, larger exercise wheels might become more commonplace for larger pets, such as dogs. It is likely that younger pets will be more likely to use the equipment. Throughout the study, the researchers noticed that juveniles of all species used the wheel more often than adults did. This was true for mice, rats, shrews, frogs, snails and slugs. "Shrews occasionally enter the wheel, run for a moment, and then leave again," Meijer said. "Rats enter the wheel, but do not use it for very long at all, possibly because the wheel is a bit small for them."

Dogs Remember Our B.O. When We're Away

Playgrounds are starting to include more equipment modeled after exercise wheels. Even adults often can't resist hopping on for a spin. Our usage of the equipment isn't clear. Do we have an urge to hop on because we want to exercise, because we enjoy playtime, because we inherently enjoy unexpected movement, all of the above, or for some other unknown reasons? The researchers hope to better understand animals' attraction to exercise equipment. As it stands, there is just one animal that seems not to gravitate to exercise wheels: birds. But even they might get their kicks in another, creative way. Meijer said that one bird seemed to like jumping up and down on top of the wheel, making it move.