Motion sensors like
those used in smart phones are helping to reveal how sharks spend each
moment in the wild, say Mote Marine Laboratory scientists who were the
first to use such sensors to classify mating and other behaviors in wild
sharks.
During their study,
which was recently published in the science journal Endangered
Species Research, Mote scientists monitored mating in wild nurse
sharks by attaching accelerometers to them. Accelerometers are the
motion-sensitive computer chips used in smart phones, iPods and the
Nintendo Wii. Attached to sharks, accelerometers can detect each flick
of a shark's tail or tilt of its body and give scientists insight into
what sharks are doing and when.
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Also called
"acceleration data loggers," these accelerometer tags are slightly
larger than AA batteries and are designed to fall off the shark's dorsal
fin after a few days so scientists can recover the tags and the data
they store. Photo credit: Mote Marine Laboratory.
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For years, Mote
scientists have studied where sharks travel using sound-emitting tags
that are detected by underwater receivers, or hydrophones, as well as
satellite-linked tags that track sharks' locations continuously.
But these types of
tags can't reveal what sharks do once they arrive at their favorite
places. Like teenagers hanging out at burger joints, sharks also stop
traveling to feed, rest, find a mate and more - behaviors that are
especially hard to monitor in wild aquatic animals like sharks and other
fish that don't even surface to breathe.
"Accelerometer tags
are unique in that they record the actual physical movements of the
animal's body," said the study's lead author, Dr. Nick Whitney, a
post-doctoral scientist in Mote's Center for Shark Research. "So that
gives us a much better idea of what the animal is doing - not just where
it's going."
Whitney and
colleagues fitted four female nurse sharks in the Dry Tortugas with
accelerometers in June 2008. These islands off the Florida Keys were
chosen as the study site because Mote scientists had already shown that
it was a breeding ground for the species. The Dry Tortugas also have
shallow areas with clear water and the researchers would be able to see
what the sharks were doing as the accelerometers recorded the sharks'
movements.
Mote's accelerometer
tags successfully showed when nurse sharks were swimming and resting.
They also picked up on mating behaviors - thrashing, barrel rolls,
headstands and all. "There doesn't seem to be much mating going on at
night, which is really surprising, because sharks are thought to be more
active at night," Whitney said. The sharks also mated in deeper water
than scientists had ever observed for sharks in this area.
Whitney hopes that
accelerometers can eventually be used to study mating behaviors in other
species that are harder to observe: bull sharks, hammerheads, sandbar
sharks and more. Finding where sharks mate is critical for protecting
their breeding grounds, he says.
Mote scientists have
a history of groundbreaking research on shark breeding. The first
detailed studies of sharks mating in the wild were conducted by Mote
scientist Wes Pratt and Mote adjunct Dr. Jeffrey Carrier of Albion
College, whose research on nurse sharks and other species since the
1990s has documented their complex mating behaviors and helped reveal
important breeding areas in the Dry Tortugas. Carrier and Pratt, who is
now a scientist-in-residence at Mote, are co-authors of the current
study along with Mote volunteer Theo Pratt.
Mote scientists plan
to refine their accelerometer studies with sharks in the lab, and hope
to eventually track these fine-scale behaviors in wild sharks for weeks
at a time.
Media: Photos, B-roll of shark
tagging and a video interview with Whitney are available for dubbing at
Mote. Please contact Hayley at 941-374-0081 or hrutger@mote.org.
Founded in 1955,
Mote Marine Laboratory is an independent nonprofit marine research
organization. We are dedicated to advancing the science of the sea
through the study of marine and estuarine ecosystems, through our public
Aquarium and through an education division that provides unique
programs for all ages. Throughout 2010, we're celebrating Mote's 55th
Anniversary with special events highlighting our groundbreaking ocean
research and outreach. Learn more at www.mote.org/55.
