Just like dolphins, sharks can be trained to roll over to be cuddled by humans. In experiments carried out in the United States, several species of shark allowed themselves to be picked up from the water and cuddled by their trainers.

The U.S. trainers used coloured boards and sounds to train their sharks to respond to commands. No one had attempted to train sharks in this way before and the results are truly ground breaking. Shark keepers now hope that the new technique will give sharks a higher quality of life in captivity. When sharks ned to be moved, the normal practise is to chase them around, but a trained shark could instead be thought to just gently swim to a certain spot.

“The US team has shown that many varieties of sharks can quickly learn to respond to a combination of audible and visual signals”, says Carey Duckhouse of UK’s Sea Life Centres.

Keepers at the UK’s Sea Life Centres are planning to use the methods developed in the U.S. to train sharks kept in British facilities. Colour boards and sounds will be used to show each shark when it is his or her turn to receive food. If everything goes according to plan, the fastest learners in the shark tanks will grasp the idea within three months.

When a shark have learned to associate particular colours and sounds with food, the signals will make it approach its keeper who will be holding a “target stick” against which the shark will rub its nose in hope of getting a tasty treat.

”Some species, such as zebra sharks, will even roll over to have their tummies scratched or allow themselves to be lifted from the water without any kind of struggle,” says Dickhouse.

Amber, a porpoise living at the Harderwijk dolphin centre in the Netherlands, has given birth to a calf this spring, making her the second porpoise ever to give birth in captivity.

Visitors are now gathering to come and see the calf, which has been given the name Kwin.

Picture is GNU

“Mum Amber and her baby, Kwin, are doing fine,” the centre said in a statement on Thursday.

The sex of the calf has not yet been determined and will continue remain unknown for several weeks. Another conundrum concerns the paternity of the calf. According to the dolphin centre, two male porpoises were swimming with Amber at the time of conception and any of them may be Kwin’s father.

The very first porpoise ever to give birth in captivity lives in Denmark where it had a calf in 2007 and the Harderwijk dolphin centre is now enlisting the aid of Danish porpoise keepers to make sure that baby Kwin is properly cared for.

“As we don’t know much about newborn porpoises, a team of Danish minders has come to help us,” the centre says in its statement.

The porpoise is a small ocean-dwelling mammal related to whales and dolphins. There are six recognized species of porpoise and their common ancestor is believed to have diverged from the dolphins roughly 15 million years ago. Porpoises are not as large as dolphins and have stouter bodies with small, rounded heads. Compared to dolphins, wild porpoises bear young more quickly and some species give birth to a calf as often as once a year. However, porpoises do not adapt to life in captivity as well as dolphins do and successful reproduction in zoos is therefore extremely rare.

Last week, a leaping 9-foot dolphin accidently ended up in an 18-foot boat in the Intracoastal Waterway near New Smyrna Beach, Florida. As the panicked animal tried to escape from the vessel, it repeatedly hit the two boaters, 64-year-old Norman Howard and his wife Barbara, with its powerful tailfin.

“It was slapping me pretty hard,” Howard said. “Yeah, it was throwing some good punches. Mike Tyson couldn’t hit harder than that.“

The U.S. Coast Guard arrived to the scene after receiving calls from witnesses of the weird accident, and promptly rushed the couple to Bert Fish Medical Center. Howard says he was smacked in the face and ribs, while his wife received lacerations to her face.

The dolphin could be rolled back into the Intracoastal Waterway after the accident.

Many dolphin species are agile jumpers and the Bottlenose dolphin (Tursiops truncatus) is for instance known to leap up to 10 feet (3 metres) or more. The maximal height of a leap depends on the individual animal and the surrounding water, since the dolphin uses its flukes to projectile itself into the air. In shallow waters, dolphins cannot jump very high.

As we release more and more carbon dioxide from fossil fuel into the atmosphere, the world’s oceans become more and more acidic. Exactly how this will affect marine life remains unknown, but a paper published this week by marine chemists Keith Hester and his co-authors at the Monterey Bay Aquarium Research Institute is now shedding some light on how a change in acidity affects sound waves under water.

Beluga Whale

So, why is the speed of sound underwater of any interest to Monterey Bay Aquarium researchers? As sounds travel faster, the amount of background noise in the sea will increase and this could affect the behaviour of marine mammals. Many marine mammals, such as whales, dolphins, and porpoises, relay on sounds for communication and food location.

According to conservative projections by the Intergovernmental Panel on Climate Change (IPCC), the chemistry of seawater could change by 0.3 pH units by 2050. According to Hester and his colleges, such a change in acidity would allow sounds to travel up to 70 percent farther underwater in some areas, especially in the Atlantic Ocean. The paper also states that sound may already be travelling 10 percent farther in the oceans than it did a few centuries ago.

According to Hester et al, a change by 0.3 pH units by 2050 will have the greatest effect on sounds below about 3,000 cycles per second. This range includes most of the low frequency sounds that marine mammals are known to use, but it also includes a lot of sounds produced by human activity, such as boating, shipping, and certain military activities. As if acidification of the ocean wasn’t enough, the amount of underwater sound produced by human activities has increased dramatically over the last 50 years. So, even if acidification would make it possible for sound produced by marine mammals to travel farther than ever before, it might also cause these sounds to be effectively drenched by a cacophony of human generated low frequency noise. In such a noisy sea, a marine mammal’s ability to locate prey animals and a suitable mate and could be severely impinged on.

The paper will be published in the October 1, 2008 issue of Geophysical Research Letters.

According to Christian Agrillo, an experimental psychologist at the University of Padua in Italy, the North American mosquito fish can count up to four. This rudimentary mathematical ability makes it possible for the North American mosquito fish to count how many other fish that are nearby – but only up to four. Similar counting abilities have already been observed in dolphins, but until now researchers only new that fish could tell big shoals from small ones, not that they were able to actually count.

In earlier research, Agrillo and his colleagues found that a female specimen of the North American mosquito fish will swim to the largest nearby shoal to protect herself from a harassing male. In order to do so, she must of course be able to somehow tell the difference between a larger shoal and a smaller one.

To establish exactly how advanced the counting ability of the North American mosquito fish was, Agrillo et al continued their research by testing if a lone specimen would prefer to join a shoal consisting of 2, 3 or 4 other fish. The study showed that female fish could tell the difference between two shoals even when the shoal size differed by only one specimen. Females would significantly more often prefer to join a shoal consisting of four others rather than three, and would also favour shoals comprised of three fish rather than of two.

When a new series of experiments were conducted using even larger shoals, researchers found that the female North American mosquito fish were unable to directly count over four. If two shoals differed in size by a ratio of 2:1 she would go for the larger one, but if the difference was smaller she seemed to conclude that they were “both big”. She would for instance not favour a shoal consisting of 12 fish over a shoal of 8, but could clearly tell a shoal of 16 from a shoal of 8. The female North American mosquito fish therefore seems to have the ability to estimate larger numbers, but not very exactly.

The results of the study can be found on BBC’s site Loveearth.com