Butterfly Migration in 2016
From end of September to November, every year, from time immemorial, Nym-
phalidae butterflies like Dark Blue Tiger, Blue Tiger, Common Crow and Double-
branded Crow along with a few other species will undertake their migration journey
to Western Ghats from plains and Eastern Ghats of Tamil Nadu.
Butterflies undertake migration mainly to escape from harsh climate for their living
and lack of sufficient food and environment for their survival. The Monarch Butter-
fly migration happening in America is a well-known and closely followed event.
In India, especially in South India, the Danainae butterfly mentioned above under-
take their journey every year, fairly regularly and in large numbers of tens of thou-
sands. The data available with Tamil nadu Butterfly Society (which has been track-
ing these since 2012) indicates that this migration to Western Ghats just before the
commencement of North East Monsoon happened between September last week
and October middle.
The return to the plains and Eastern Ghats by these species happens during April-
May, before the commencement of South West Monsoon in the hills.
In the current year under observation, the butterfly
migration from plains to Western Ghats has not hap-
pened till end of December. The migration is almost
nil except a very few places reporting smaller num-
bers, not much to be called as a regular high number
migration that was being witnessed every year.
Even in 2015, a reduction in number of species mi-
grating to hills from plains is seen. In fact, it was
Euploea species (The Crows) which were dominating
on the migration and the Tirumala species (The Blue
Tigers) almost gave a miss.
This reduction in migration last year and delayed
migration so far is a worrying factor.
While these may be just an aberrant occurrence on
large time scale over many years, we have to watch
carefully in coming years to see its real impact. The
delay in current year migration may be due to one of
the worst monsoon that the state of Tamil Nadu had
from the North East monsoon especially between
Sep and Nov.
However, on the long run, if the migration numbers
come down, then they have to be taken as a meas-
ure of eco-system, as they are known to be the indi-
cators of healthy eco-system and environment.
The butterfly season, especially in Western Ghats on
the Tamil Nadu side is from October to December,
and many a species are seen during these months
than in any other months and in good numbers.
However, as the rains giving a miss this season, even
those species were not seen in good numbers so far.
Hopefully Nymphalidae species resume the migra-
tion in coming the year !
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