Tag Archives: rodent

Rodents race around cage in NASA microgravity experiment

Humanity dreams of one-day becoming an interstellar species. But before that happens many challenges need to be addressed. Studies have shown that long-stretches of exposure to space can have important consequences for the health of astronauts. For instance, astronauts stationed aboard the International Space Station (ISS) have reported muscle and bone loss, poorer vision, DNA and brain structure alteration, and other effects. In order to better understand how space affects basic biology, NASA has performed over a dozen experiments with mice on the ISS since 2014. The most recent findings suggest that rodents are well accustomed to life in microgravity — and have even learned to do some nifty tricks.

Rodent astronauts

A small group of mice spent 37 days in microgravity — which is equivalent to a long-duration mission (18 months) given a rodent’s lifespan — inside NASA’s Rodent Hardware System, which is basically a high-tech cage. The rodent space habitat was specially designed to accommodate mice in groups, in order to reduce stress and better record the motions of the animals. Unlike previous space habitats, NASA’s most recent version also included grates on its wall which the rodents could grab onto.

NASA scientists focused on observing the behavior of the rodents, looking for anything peculiar. When compared to mice that stayed on Earth, the space mice were remarkably similar. The mice behaved as they normally would: feeding, grooming their fur, huddling together, and interacting with their peers. By the end of the study, space mice weighed about the same as their Earth counterparts and their fur was in excellent condition, both signs of good health.

NASA’s Rodent Habitat module with both access doors open.
Credits: NASA/Dominic Hart.

The rodents aboard the ISS quickly adapted to their environment, anchoring themselves to the habitat walls with their hindlimbs or tails and stretching out their bodies. The same pose is commonly employed by mice on Earth, which stand up on their back legs to explore their surroundings.

“Behavior is a remarkable representation of the biology of the whole organism,” said April Ronca, a researcher at NASA’s Ames Research Center and lead author of the study published in the journal Scientific Reports. “It informs us about overall health and brain function.”

Space mice also exhibited some remarkable, never-before-seen behavior. The experiments included both younger and older mice, and it seems like the younger mice would sometimes run laps around the cage, an activity which NASA scientists have called “race-tracking”.

Researchers aren’t sure what spurred this behavior, although some reasons may be for physical exercise, as a response to stress, or for stimulation of the body’s balance system which is thrown off by microgravity. Future experiments in space involving mice will now have to take into consideration the increased blood flow due to the extra activity.

Far from feeling threatened or stressed, these mice seem to be enjoying living in space.

“Our approach yields a useful analog for better understanding human responses to spaceflight, providing the opportunity to assess how physical movement influences responses to microgravity,” the researchers concluded in their paper.

Mixed cat-and-dog teams are the best defense against rodent pests

Cats and dogs working side by side may be the best rodent control method at our disposal according to an international team of researchers. The question now is, how do we reconcile these age-old rivals for the task at hand?

Image credits Rihaij / Pixabay.

Working as part of an international research team, Robert McCleery, associate professor of wildlife ecology and conservation at the University of Florida’s Institute of Food and Agricultural Sciences, found that a combined team of cats and dogs reduced rodent foraging in and around households or storage buildings. They also detail that neither species working by itself will help deter the pests.

Paw and claw

Pest rodents have caught on pretty early that agriculture means ample food. Even better for them, there’s a species who will do the heavy lifting of growing, harvesting, and storing all that food in one place for them to nibble on — that’s us. So they’ve become a staple of human settlements since times immemorial.

Naturally, this didn’t sit well with us humans. We brought our pet animals to bear upon the pests, starting the most literal game of ‘cat-and-mouse’ in history. That this idiom today stands for a very contrived, lengthy process with little chances of success should tell you how well it’s been going for us.

Hint: he didn’t bake his own bread.
Image credits Alice Rosen / Flickr.

So what can we do to finally stack the deck in the cat’s favor? Bring in dogs, one team of scientists says. Working in tandem, these two species of pets can significantly reduce pest rodents’ activity in and around human households or farms, they say.

Led by Themb’alilahlwa Mahlaba at the University of Swaziland, the team conducted an experiment in four agricultural villages in Swaziland. Although the research is limited geographically, McCleery said the findings apply globally. The worked on 40 households in the villages, dividing them into groups of ten. One group had only dogs, another only cats, one group of homes was guarded by both species, and a control group with neither. They studied rodent pests living in these households.

McCleery said that the team considered a species a pest if it “lives in your house or eats your crops and is usually not native to the area where it is found.” Their data shows that individual species of working animals aren’t very effective at deterring pests, but using both dogs and cats provides good results.

“This might reduce food damage and potential for disease transmission,” McCleery said.

“Farmers might want to consider cats and dogs as a way to discourage rodent pests in areas where they store their crops.”

GUD news

The team first placed plastic lunchboxes filled with sand and peanuts in the houses for seven consecutive days so the rodents would get used to this source of food. Then, they installed ‘control tiles’ — basically white square tiles sooted black — alongside the lunchboxes for 5 consecutive days and nights in July (the cool dry season) and 5 in October (the hot dry season).

As rodents passed over the tiles, their little paws would leave a white track. Each tile’s surface was broken down into squares, and the percentage of squares with tracks gave an estimate of rodent activity in each house.

The bait was refreshed before the control tiles were installed, and then each day during the experiment.

“A total of 86 rodents of two species were captured within buildings and out-houses around homesteads in the study area. The majority (73) of specimens were Rattus rattus, with the remainder (13) being Mastomys natalensis,” the paper reads.

The team also observed the rat’s Giving Up Density (GUD), which showed how often the animals gave up forage in homesteads with both cats and dogs — basically, the intensity of the ‘fear factor’ the guardians instilled. In boxplot below, you can see how much ‘ratctivity’ the houses have seen in July (left) and October (right).

I’ve put the basic gist of the graph in the caption, but here’s a more in-depth guide to reading boxplots.

Boxplots show the upper limit (topmost line), median value (strong line) and lowermost limit (lower line) of rodent activity. 
Image credits Themb’alilahlwa A. M. Mahlaba (2017) PLOS One.

And here’s the GUD.

Image credits Themb’alilahlwa A. M. Mahlaba (2017) PLOS One.

The results show that rodents displayed significantly more fear and reduced foraging activity in homesteads guarded by both cats and dogs. Taken alone, either species had less success deterring rodents, with cats having a slight edge across the board.

“The results of this study are particularly interesting to me as they will make a big contribution to the efforts at managing rodents in and around homesteads,” Mahlaba said.

“Showing that dogs have a role in rodent management has overturned my long held ideas on this subject. Now all we need to do is to find out why and how the combination of cats and dogs drastically reduces rodent activity in and around homesteads.”

The full paper Domestic cats and dogs create a landscape of fear for pest rodents around rural homesteads” have been published in the journal PLOS One.

The American pika is being killed off by climate change

The American pika, “one of the cutest animals” in the country, is feeling the heat as a hotter, drier summers threaten its habitat.

I brought you a gift! Don’t kill us please.
Image credits NPS Climate Change / Flickr.

Whole populations of the tiny rabbit-like mammal known as the American pika are vanishing from the animal’s historic range in the mountainous areas of the western USA. The main culprit seems to be loss of habitat powered by climate change, according to findings by the US Geological Survey. After observing the animal from 2012 to 2025, the Survey found that the pika’s range is shrinking in southern Utah, north-east California, and in most of Nevada, parts of Utah, Oregon, Idaho and California — almost the entire Great Basin.

The study provides more conclusive evidence to the effect of global warming on the tiny mammal, building on earlier research which found that climate change was at least partly contributing to the animal’s decline. It did not measure how many total American pika still exist, but studied several areas where it has historically roamed eating grass, weeds and wildflowers. While the pika overall seems to be struggling, the study found that it’s thriving in a few places — most notably the Columbia River Gorge in Oregon and Grand Teton National Park in Wyoming.

But don’t rest easy just yet. The American pika (all species of pika are extremely cute) has completely disappeared from the Zion National Park in Utah, despite sightings as recently as 2011. In the nearby Cedar Breaks National Monument, the animal was nowhere to be seen on three-quarters of their historical range according to Erik Beever, a research ecologist with the USGS and lead author of the study. In north-eastern California, the pika was only found in 11 of the 29 sites of confirmed habitat. In the Great Basin, which stretches from Utah’s Wasatch mountains in the east to the Sierra Nevada and Cascade mountains in the west, the population is down about 44% compared to historical records.

“The longer we go along, the evidence continues to suggest that climate is the single strongest factor,” said Beever.

Essentially, the pika are dying of exposure in their own burrows, and it’s all because of us.

The pika are tailored to live in a very specific conditions, and are very sensitive to changes in temperature and humidity. The animals make their home on mountain slopes, known as talus, where they search for open spaces in the ground to burrow. But the talus fields are becoming a much hotter, drier place in summer and a very harsh place in winter, with less snowfall to insulate the critter from cold.

The historical range of the American Pika. The animal resides in cool, moist microhabitats on high peaks or watercourses. Distribution data from IUCN Red List.
Image credits Wikimedia user Chermundy.

The study is the latest argument in the long-running efforts of wildlife advocacy groups, which have been trying to get the pika on the endangered species list for a few years now. In 2010, the US Fish and Wildlife Service rejected one such request, citing that not all populations are declining. The latest petition was made this April by a high school student in New York state. This situation isn’t singular — ZME Science reported the other day that the average waiting time for a species to make the Endangered Species list is 12 years, or six times more than the designated timeline. 

A preliminary ruling is due this September, but the new study won’t be taken into account because the agency’s staff only takes into consideration information submitted with the petition, said Serena Baker, a USFWS spokeswoman. Hopefully, the ruling will be in favor of the pika. But, should the USFWS turn it down, the study should help future petitions to have the animal declared endangered, as the study confirms that climate change is putting the animal at real risk, says endangered species director at the Center for Biological Diversity in Arizona Noah Greenwald. Without such a ruling, future generations of mountain enthusiasts may not have the chance to see these lovable critters on their hikes, he adds.

“It’s gotta be one of the cutest animals in North America. It’s like a cross between a bunny rabbit and prairie dog,” Greenwald said. “Part of what makes our world interesting is the diversity of animals and plants that you can see when you go to different species.”

President Barack Obama is a big supporter of the issue. During his Yosemite National Park speech in June this year, he talked about the damage climate change is inflicting on the country’s national parks. He said the pika was being forced further up-slope at Yosemite to escape the heat.

“It’s not that they’ve just moved, they are gone all together,” Beever said.


Scientists learn to decode prairie dog language – discover they’ve been talking about us

After studying prairie dogs for 25 years, one researcher believes he figured out what prairie dogs are communicating about. He believes that the animals are not only very efficient communicators, but they also have an eye for details.

Prairie dogs communicate not only through vocalizations, but also through physical interactions, like kissing. Photo by Brocken Inaglory.

Gunnison’s prairie dog (Cynomys gunnisoni) is one of five species of the prairie dog. Their name is a bit misleading, since the animals are actually part of the squirrel family of rodents. Their communication system is one of the most complex in the natural world, involving vocalizations as well as several types of physical cues, such as cuddling and kissing. Con Slobodchikoff, a Northern Arizona University biology professor, has been researching the behavior of prairie dogs for 20 years. He’s probably the world’s leading experts on prairie dogs and he states that they “have one of the most advanced forms of natural language known to science.”

What Slobodchikoff found is that prairie dogs give out short chirps and these chirps actually identify each individual species they spot. They’ve basically developed a different alarm by which they call not only who is coming, but how they look like.

They also have a specific call for humans, which they characterize based on size, shape, and clothing color.

“For example, a human alarm call not only contains information about the intruder being a human, but also contains information about the size, shape (thin or fat), and color of clothes the human is wearing,” says Dr. Slobodchikoff.

“When we do an experiment where the same person walks out into a prairie dog colony wearing different colored t-shirts at different times, the prairie dogs will have alarm calls that contain the same description of the person’s size and shape, but will vary in their description of the color.”

There is still much to learn about animal communication, but what Slobodchikoff is doing is truly pioneering and groundbreaking. It makes me wonder if prairie dogs are unique in the way they communicate or rather if other animals are doing it as well, but we just haven’t figured it out yet.

Rats have a double view of the world

Rodents are able to move their eyes in different directions, thus always keeping an eye on the the airspace above them, researchers from Max Planck Institute have shown.

rat eye

Using miniaturised high-speed cameras and high-speed behavioural tracking, they found that rats can move their eyes in different directions, both in the horizontal and in the vertical plane; the eyes move individually depending on how the animal is running around and moving its head.

Like most mammals, rats have their eyes on the side of the head, giving them a wide view which is very useful in detecting predators. However, generally speaking, three-dimensional vision requires an overlap of the visual fields of the two eyes; so the visual system needs to fulfill two needs, which are pretty conflicting: on the one hand they need maximum wideness field, and on the other hand, they also need detailed binocular vision.

The research conducted by the Max Planck Institute for Biological Cybernetics has, for the first time, characterized the eye movement of freely moving rats – and their findings came as a total surprise.

“Humans move their eyes in a very stereotypical way for both counteracting head movements and searching around. Both our eyes move together and always follow the same object. In rats, on the other hand, the eyes generally move in opposite directions,” explains Jason Kerr from the Max Planck Institute for Biological Cybernetics.

In their series of behavioral experiments, they also found that the movement of the eyes come as a response to the movement of the head.

“When the head points downward, the eyes move back, away from the tip of the nose. When the rat lifts its head, the eyes look forward: cross-eyed, so to speak. If the animal puts its head on one side, the eye on the lower side moves up and the other eye moves down.” says Jason Kerr.

For us humans, the situation lies quite differently. The direction in which the eyes look must be precisely aligned, otherwise the object isn’t fixated and it all becomes blurry. Any slight deviation, of under a degree, will cause double vision. In rats, the opposing eye movements between left and right eye mean that the line of vision varies by as much as 40 degrees in the horizontal plane and up to 60 degrees in the vertical plane.

Although the observed eye movements prevent the fusion of the two visual fields, the scientists postulate that permanent visibility in the direction of potential airborne attackers dramatically increases the animals’ chances of survival.


Peer reviewed article