February 4, 2019 by Zoe Gentes, Ecological Society
of America
Although it has been ranked as the cutest creature in US National
Parks, the American pika is tough, at home in loose alpine rocks in windswept
mountain regions. Related to rabbits and hares, pikas live in cold, wet
climates and high terrain, spending winters in snowy homes living off of stored
grasses and other forage they have gathered, only venturing out for more when
weather permits.
Unfortunately for these adorable little mammals, they have a
fairly severe sensitivity to overheating—they die if they are exposed to
temperatures above 77°F for longer than six hours. Due to their lethal
threshold for heat stress, pikas are indicators of how changing environmental
conditions can affect mountain-dwelling species.
It might appear that the danger for pikas lies mostly with
increasing temperatures and summer heat extremes. In some cases, however,
decreased snowpack and lower air moisture may threaten pikas more.
Vapor-pressure deficit (VPD) can be likened to air's
aridity—higher VPD is drier. VPD governs the growth of many plants that pikas
depend on for food, and controls cloud formation and snow. If VPD becomes
higher, it will inhibit the growth of plants that pikas depend on for food, and
will shrink snow packs which they use for insulation against extreme temperature.
The snowpack also stores water until springtime, when it provides water for
forage plants that pikas eat.
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