Do North American Monarchs Travel To Cuba? 
Orlando Luis Pardo Lazo
It was assumed
that monarchs from eastern North America
migrated only to Mexico.
North American migrant monarchs that move to Cuba
hybridize with resident populations there
and do not return to the continent.
Migration to Cuba (and possibly the Caribbean)
is likely to be a one-way movement.
An extraordinary fall migration of up to 4,000 km.
The islands of Cuba, Jamaica, and Hispaniola
undoubtedly harbor indigenous sedentary subspecies.
Differences in behavior between temperate and neotropical monarchs.
The confusing mixtures present on the islands
to distinguish native from migrant individuals.
Notice the differences in general size,
the close absence of the inner line of white spots
at the apex of the forewing:
the right fore- and hind wing of each dried specimens.
Migrants from North America
outnumbered Cuban residents in November.
There are three possible reasons:
1) they had died and/or we failed to collect them;
2) they returned to the United States,
most probably through the Florida peninsula;
3) they moved to other areas of Cuba and the Caribbean.
The extent to which Cuba may be a bridge
for migrants to the Yucatan
to other insular Caribbean areas,
now remains a question for further study.
 Dockx, Cristina, Lincoln P. Brower, Leonard I. Wassenaar, and Keith A. Hobson. Do North American Monarch Butterflies Travel to Cuba? Stable Isotope and Chemical Tracer Techniques. In: Ecological Applications, 14(4), 2004, pp. 1106–1114.