Page 69 - BBC Wildlife Volume 36 #06

LEMON SHARKS

MAGICAL MANGROVES

Not only do mangrove forests ofer a safe nursery
to lemon shark pups and many other fish, they also
provide a host of essential ecological functions.

MANGROVES HELP the fight MANGROVES IMPROVE coastal
1 against climate change by burying 4water quality, by absorbing excess
masses of carbon deep in the soil. nutrients and pollutants – including
One study found that mangroves are even the heavy metals that are
more efective at capturing carbon byproducts of mining, such as iron,
than forests on land. manganese and nickel.

FOR LOCAL COMMUNITIES, MANGROVES PROVIDE habitat for
2mangroves can be a sustainable 5everything from tigers to saltwater
source of timber, charcoal and food, crocodiles and proboscis monkeys.
such as oysters and honey. Some of these species live virtually
nowhere else, including birds such
THE DEEP, TANGLED roots and as the mangrove hummingbird and
3stout trunks of mangroves protect mangrove pitta.
coastlines from erosion by waves and
storms, the scale and frequency of
which are likely to increase due to
climate change.

Above: the warm down a creek and out to nearby sand flats where they or more sharks swimming together; sometimes following
sea water and hunt fish and small crabs. Their skin is yellow-tinted each other, sometimes swimming in parallel and
abundant plant
life of mangroves from certain angles, which gives lemon sharks their sometimes circling, head to tail. And some of the
make them name and provides camouflage against the sandy seabed. sharks stayed in the same gangs throughout the whole
extremely rich Usually, though, these areas are relatively safe at low tide two years of the study.
habitats, although because the water is too shallow for large predators. But Young sharks also make friends under controlled
they’re under as soon as the tide rises again, the young sharks retreat laboratory conditions. Given the choice, these captive
threat from
climate change back into the mangrove forest. sharks prefer to spend time with other sharks they’ve
and development met previously rather than total strangers. These social
often associated STUDIES AT THE SHARKLAB networks probably form because they help sharks to
with tourism. The lemon sharks’ preference for warm inshore waters, learn from each other how to find food and avoid
coupled with the fact that they can thrive in aquaria, predators. It may also make life more peaceful and
is what makes the species ideal for study. Since 1990, reduce the chances of fights breaking out.
scientists at the Bimini Biological Field Station in the There is even some evidence that lemon sharks can
Bahamas, colloquially known as the Bimini Sharklab, learn simple tricks from one another. Captive sharks in
have been studying the species in considerable detail. tanks have been seen to observe and copy the actions of
Hundreds of students have made the pilgrimage to the other sharks that had previously been trained to access
facility that lies approximately 95km off the coast food rewards in a certain way. This is the sort of complex
of Miami to help out. And incredible discoveries have behaviour you might expect from primates, dogs or
been made as a result – including that lemon sharks crows, but not sharks.
hang out in gangs. Do lemon sharks learn to recognise other individuals
For two years, on and off, members of the research and know who is who? For now, we’re not sure. It
team took it in turns to climb to the top of three could be that they simply learn to tell the difference
tall towers in a mangrove inlet, armed with a pair between familiar and unfamiliar animals. Studies of
of binoculars, to peer down into the water at free- these youthful gangs are adding to the growing body of
swimming sharks that had been tagged with coloured evidence that not all sharks are alike – in fact, it seems
markers. Often, the scientists saw the same two, three as if they have individual personalities. Within a gang,
June 2018 BBC Wildlife 69