Do Monarch Butterflies Shiver?
Observations of Shivering Behavior
Contributed by Dr. Bill Calvert
is most common when the temperatures are low. But it's possible to even
see a monarch shivering during the peak warmth of the day. When butterflies
are down on the ground to drink water they would be cooled by the cold
water and need to shiver to raise their body temperature for movement.
Shivering butterflies look like you might imagine from
your own experiences in cold weather. The butterflies shiver their wings
rapidly in an attempt to warm the muscles inside.
At What Temperatures Can Monarchs Fly?
You'll often hear people say the butterflies are trying
to get warm enough to fly. But it may be that shivering helps them get
warm enough even to crawl off the ground when they are too cold to fly.
and crawling at 49 degrees F, but not able to fly. How much warmer
must it get before it can fly?
can crawl at temperatures as low as 5 degrees C (41 degrees F).
- The monarch's
flight threshold is about 13 degrees C (55F). (Flight threshold
means that this temperature, 13C, is the lowest temperature at which
they can fly somewhat.)
- In order
to fly WELL, with lots of control, they need to attain
thoracic temperatures in the upper 20s or even 30s--pretty close to
the temperatures that warm blooded mammals run.
- They can
manage to get themselves airborne and glide--and occasionally flap with
some control--at temperatures much lower than that, but they cannot
fly well at temperatures in the teens.
Keep in mind
that the temperature can sometimes drop to zero C or even a few degrees
below zero in the sanctuaries. Monarchs are paralyzed by temperatures
Do Monarchs Stay on the Ground?
I wondered how long a butterfly might be at risk on the ground--whether
minutes, hours, half days, a full week. How long would it take one to
reach necessary temperatures and move upward?
My impression from observations is that the sunflecks move around the
forest each day and probably cover virtually all locations. ("Sunflecks"
are small circumscribed areas where solar radiation is entering gaps in
the canopy and striking the ground.) So if it is sunny the day after a
butterfly is grounded, a sunfleck will find its position sometime during
the next day, and warm the butterfly enough to move out of its predicament.
is a period of cloudy weather it's a different story, and the risk period
could be much longer. If buried by snow, monarchs might stay on the ground
under the snow for more than a week. But they are not at much risk buried
under the snow, except perhaps by being stepped on.
in 1999 Snowstorm
Snow doesn't always kill monarchs. They can remain alive for days
trapped or buried in snow.
Science Education Standards
- The behavior
of individual organisms is influenced by internal cues (such as hunger)
and by external cues (such as a change in the environment).
- An organism's
behavior patterns are related to the nature of that organism's environment.
- All organisms
must be able to obtain and use resources, grow, reproduce, and maintain
stable internal conditions in a constantly changing external environment.
of an organism's internal environment involves sensing the internal
environment and changing physiological activities to keep conditions
within range required to survive.