 The
California real estate market isn’t
just tough on humans. Male California fiddler crabs need to have
the right home or they may not be able to attract a female. A UCSD
study found that females of this species may be the world’s
pickiest when
it comes to selecting a mate.
Catherine deRivera, Ph.D. ’99, a lecturer at UCSD, discovered
that females of the species Uca crenulata may check out 100 or
more male fiddler crabs and their burrows before finally deciding
on a mate. “As far as I know,” says deRivera, “no
other species has been observed sampling nearly as many candidates
as the California fiddler crab.”
Male fiddler crabs attract partners
by standing in front of their burrows and waving their enlarged
claws at prospective females
passing by, much
as humans motion “come here” with their arms and hands.
Interested females initially eye the males, who select their burrows
based upon their body size and, if they’re interested, partially
or fully enter
a burrow to size it up.
When a female has found a mate and burrow to her liking, the couple
will plug up the opening of the burrow and mate. The male surfaces
the next day, eats, maintains his burrows and, according to deRivera, “waves
to other females.” Meanwhile the female remains in the burrow
without feeding, for the full 10 to 16 days of incubation. When
the eggs hatch, tiny crab larvae are released and quickly flushed
from the
estuary by high night tides.
DeRivera says previous studies of
mate selection in other animals, such as birds and the natterjack
toad, found that females of most
species typically investigated only
a handful of potential mates before making a final selection. But
she discovered in her study that female California fiddler crabs
are much pickier, checking out male suitors and their bachelor
pads an average of 23 times before making their choice. One
particularly discriminating crab visited 106 male burrows, fully
entering 15 of them, during her one hour and six minute search.
Why are female fiddler crabs so picky? In her experiments deRivera
found that survival of the offspring appears to be strongly linked
to the size of the male and, more importantly, his corresponding
abode.
“The size of the male’s burrow affects the development time
of his larvae,” she says.
“A burrow of just the right size allows larvae to hatch at the safest
time, the peak outward nighttime flow of the biweekly tidal cycle.”
So size does matter.
— Kim McDonald
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