It seems that no matter where one travels on Earth (Remember traveling? It will be back soon, just keep wearing masks), you can’t escape mice – the rodent kind, of course. That list now includes on frozen glaciers in Alaska, where researchers looking for microbes – long assumed to be the only things that can survive in the harsh environment – have been finding the ice mysteriously covered with small, green mice moving around in formation on the surface … so many of them that the scientists received funding to study them.
Did he say green mice moving in formation? Is this Earth or Mars? Are they planning an invasion?
“What the heck is this!”
That was the initial scientific assessment of University of Idaho glaciologist Tim Bartholomaus, co-author of the new study published recently in Polar Biology. He was referring to the day in 2006 when he arrived at the Root Glacier near the former mining town of Kennicott-McCarthy, Alaska. What Bartholomaus encountered were hundreds of mouse-sized furry green egg shapes covering the ice. (Photos here.) He bravely touched one and found it was a soft, moss-covered ball of dirt. (Sorry -- not like the feature photo.) Upon finding a lack of information on what these might be, Bartholomaus called them “glacier mice” and decided to study them. The first thing he discovered is that the glacier mice are covered with different types of moss. However, the second thing is what prompted the six-year study.
"They really do look like little mammals, little mice or chipmunks or rats or something running around on the glacier, although they run in obviously very slow motion."
Study co-author and wildlife biologist Sophie Gilbert told NPR that they noticed the balls were in slightly different spots every day. Assuming the cause to be something like the wind that pushes tumbleweeds, they got down and dirty with the fuzzy dirt balls – attaching a thin loop of wire strung with identifying beads around 30 of them. That was in 2009. They measured the movements for 54 days, then left and returned in 2010, 2011 and 2012 and measured them again. The researchers found that the glacier mice were pretty indestructible. And they were surprisingly well-organized.
“We show that glacier moss balls move an average of 2.5 cm per day in herd-like fashion, initially to the south and later towards the southwest, and their movements are positively correlated with glacier ablation. Surprisingly, the dominant moss ball movement direction does not align with the prevailing wind or downslope directions, nor with the dominant direction of solar radiation. After attaining a mature size, glacier moss balls persist for many years, likely in excess of 6 years.”
Bartholomaus told NPR the movement was similar to a school of fish or a flock of birds and defied conventional explanation. They even changed directions and speeds over time. (Video here - not from this study.) The one thing for certain was that the glacier mice needed to move an inch a day so that the moss on their bellies would get sunlight. Perhaps the movement and moss growth is required to feed their gut microbes. Yes, cutting open a glacier moss exposed water bears (tardigrades) and tiny worms. This fits in with prevailing theories that the microbial ecosystem on the glaciers depends on moss – something that could suffer with climate change.
The team completed the study without going back since 2012 to see the original flock of glacier mice at Root Glacier. Batholomaus is hoping to return soon and see how many of the original group are still ‘alive’ and rolling.
They’re slow and they’re boring, but at least glacier mice don’t leave green mouse droppings everywhere.