• Moose appear to be moving north because vegetation is growing taller in the tundra.

Alaskan moose in the U.S., northwestern moose in Canada and European moose in Eurasia are moving north to take advantage of an unlikely shrubbery salad bar: the tundra.

Over the last 160 years or so, moose have moved hundreds of kilometers north from the boreal forest to the Alaskan tundra where warmer temperatures and longer summers have resulted in increased areas of vegetation. After 1860, previously barren, treeless stretches of tundra transformed into habitat areas similar to the boreal forest because of global warming.

In Alaska in particular, shrub expansion has encouraged moose to “colonize” new areas of the tundra and maintain populations in the Arctic.

During the 19th and early 20th century, very few moose wandered the Alaskan tundra. This was initially attributed to the hunting practices of coastal peoples and miners in the region.

In a study published April 13 in the science journal PLOS ONE, however, head researcher Ken Tape and his colleagues attribute the recent rise of moose sightings in the Arctic not to human emigration (and consequent decrease in hunting) but to increased vegetation in the area.

“Northern moose distribution is thought to be limited by forage availability above the snow in late winter, so the observed increase in shrub habitat could be causing the northward moose establishment,” said the researchers in the study.

Plants have started growing taller in the tundra, increasing in average height from about 1.1 metres in 1860 to around 2 metres in 2009. For animals that only eat shrubs that poke through the snow (moose can’t dig), this height change makes all the difference.

Scientists are interested in seeing how moose expansion affects other wildlife in the region.