Different
plants have different strategies for dispersing their seeds far and wide. Without
that, they are vulnerable to being stuck in a backwater and overcome by other
plants. One tried and tested technique is to produce a tasty fleshy fruit with
an indigestible seed, which, in the fullness of time, will be neatly deposited
some distance from the parent plant. Big fruits with big seeds need big
beasties to munch away and be saving the rainforest one nut at a time.
Back
in the Pleistocene, this was the job of very big beasties, but what is
happening now that they aren’t around? Trees like the Black Palm have continued to produce large very
hard nuts so how do these continue to spread? Jansen et al lay the blame
squarely at the paws of the agouti with a little bit of help from the spiny rat
with squirrels and land crabs being dilettante about it too, occasionally
(1,2).
The
program meant supplying some 16 agoutis with their own VHF radio so they could
be in constant contact at all times. Video cameras were set up at their seed
caches (50+). But the big idea was to dry and radio tag 590 nuts. The comings
and goings were monitored in great detail – one could be forgiven for comparing
to London coming up to the Olympics.
Exciting
results followed. The first hiding place for 90% of the nuts was within 50
meters of its initial location, but then a great deal of dishonest agouti
behavior surfaced with multiple agoutis stealing nuts and hiding them somewhere
else. In the end, about 10% of the nuts made it 200 meter or more away.
In
the course of a year, some were eaten others suffered the ignominy of being
de-tagged. These tended to be ones that had been moved a lot and were often a
good way away from their starting point when contact was lost. In the end 1 in
7 of the nuts survived until the next year and 1 in 3 nuts made it out to more
than 100 meters from its starting place.
These
stats are easily good enough to ensure dispersal so the agouties are saving the
rainforest one nut at a time by handling stolen nuts.
- http://www.bbc.co.uk/news/science-environment-18856362
- http://www.pnas.org/content/early/2012/07/10/1205184109.full.pdf
