Data and code from: Fruit bat migration matches green wave in seasonal landscapes

Migrating grazers and carnivores respond to seasonal
changes in the environment and often match peaks in resource abundance.
However, it is unclear if and how frugivorous animals use phenological
events to time migration, especially in the tropics. The
straw-colored fruit bat (Eidolon helvum), Africa’s most gregarious fruit
bat, forms large seasonal colonies throughout much of sub-Saharan Africa.
We hypothesized that aggregations of E. helvum match the
timing of their migration with phenologies of plant growth or
precipitation. Using monthly colony counts from across much of
the species’ range, we matched peak colony size to landscape phenologies
and explored the variation among colonies matching the overall closest
phenological event. Peak colony size was closest
to the peak instantaneous rate of
green-up, and sites with closer temporal matching were associated
with higher maximum greenness, short growing season, and larger peak
colony size. Eidolon helvum seem to time their
migrations to move into highly seasonal landscapes to exploit short-lived
explosions of food and may benefit from collective sensing to time
migrations. The link between rapid changes in colony size and
phenological match may also imply potential collective sensing of the
environment. Overall decreasing bat numbers along with various
threats might cause this property of large colonies to be
lost. Remote sensing data, although, indirectly linked to
fruiting events, can potentially be used to globally describe and
predict the migration of frugivorous species in a changing world.