01 January 2008

Humpback whale echolocation, Pelorus jack, Dolphin News (Episode 5)

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In this week’s episode, we will  review breaking Dolphin News from around the world, focus our Science Spotlight on humpback whale echolocation, and in our Kids’ Science Quickie,  we’ll discuss Pelorus Jack.

 

DolphinPod News

 

Sonar ban canary island, Risso dolphin rescue in Maui, Tasmania dolphin stranding rescue

Cambodia launches plan to save the endangered Irrawaddy dolphin. The Mekong River in Cambodia is home to approximately 100 Irrawaddy river dolphins – a critically endangered river dolphin species. The largest threat to this species is fishing, which leads to either accidental entanglements, or depleted food resources for the dolphin. In an effort to reduce human impact, the Cambodia government is launching a program to encourage tourists to the area to view the dolphins.  The program will help decrease use of the river for food by promoting alterative food sources for local villagers, as well as boost the local economy by developing local dolphin-watching tourism. 

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A man in Scotland has been fined for harassing dolphins while jet skiing. Believed to be the first successful prosecution of its kind, the jet skier was fined 500 Pounds for recklessly harassing a group of dolphins near Moray Firth in June of 2006.  Moray Firth in Scotland is home to a resident population of approximately 130 bottlenose dolphins. Dave MacKinnon, a wildlife crime officer for Grampian Police, told the BBC that “this incident will send a strong message to people who use the marine environment for their work and leisure. What we ask is that people using such crafts do so in a responsible manner for their safety and that of others including protected wildlife.”

 

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The New Zealand government has delayed a decision on protective measures for the endangered Maui’s and Hector’s dolphins. The government is reviewing a threat management plan calling for set-netting and trawling to be prohibited within two nautical miles of the Te Wae Wae Bay shore in order to protect Hector’s and Maui’s dolphins from possible entanglement. WWF-New Zealand released a statement saying “We are deeply concerned that the Government is delaying protecting our dolphins.  The decision means that more dolphins will die in fishing nets this summer.” New Zealand Fisheries Minister Jim Anderton and Conservation Minister Steve Chadwick announced that because of the huge number of submissions on the proposed plan, a decision would not be made until March of 2008.


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Science Spotlight


Do humpback whales echolocate?

There are many things that differentiate odontocetes or ‘toothed whales’ from mysticetes or ‘baleen whales. ’ The most obvious difference of course being that odontocetes have teeth and mysticetes have baleen. Coming in at a close second, however, is the fact that odontocetes echolocate while mysticetes do not. But, hold the boat folks:  this fact may not be a fact after all.  Just last year a team of scientists published an article in the Royal Society journal Biology Letters describing the first-ever recordings of something they termed “Megapclicks”: strange click sounds produced by humpback whales. The name Megapclick is derived from the scientific genus of the humpback whale Megaptera – combined with the word click.

In order to understand why this is an important discovery, let’s have a quick review of what echolocation clicks are all about .  Here is what dolphin echolocation sounds like. *play clip*

The dolphin makes a click sound that it sends out in the water. When the click hits an object, it creates an echo, which then travels back toward the dolphin. By listening to the click echoes, the dolphin can then produce a kind of “mental” image of the object. Typically, a dolphin will wait to produce a click until it receives the echo from previous clicks. This means that as the dolphin moves closer to the object, it starts producing clicks more rapidly. You can hear in this audio clip how the clicks seem to speed up – in this case, the dolphin is approaching our camera. *play clip*

Okay, with that information fresh in your mind, have a listen to this clip. *play megapclicks*

This is an audio recording made from a humpback whale, and upon first listen, it sounds an awful lot like the bottlenose dolphin echolocation recording. In order to make this recording, scientists from the Hawaii Institute of Marine Biology, Woods Hole Oceanographic Institution, University of New Hampshire, and NOAA’s National Marine Sanctuary Program placed recording tags on humpback whales . The tags, known as DTAGS, are attached by suction cup to the whale’s back. The tags record the whale’s position and movements, as well as the whale’s vocalizations. The clicks recorded by the tag had two important properties: 1) they were only recorded at night, and 2) they were recorded during feeding episodes. These two observations certainly suggest that these might in fact be echolocation clicks: that is, clicks used by the whale in order to locate and track prey.

There are other clues suggesting that these clicks might be echolocation. Firstly, the click trains (or series of clicks) usually ended in a rapid series of clicks called a buzz. This pattern, called a terminal buzz, has been observed in echolocating odontocete species and usually coincides with the final phase of prey capture. These terminal buzzes were also accompanied by a sharp roll – that is, the animal turned quickly on its side – another behavior associated with prey capture.

To watch a video 3-D model reconstruction of a humpback during one if its feeding dives using Megapclicks, visit the dolphin pod website for links.

Video of Megapclicks from NOAA 

As intriguing and convincing as this all sounds, the scientists involved are very cautious about stating that humpbacks are indeed echolocating. It may be that these click sounds are simply a way for the humpback to herd or startle fish. In order for this to truly be called ‘echolocation’, we would need to know if the humpbacks are actually even able to hear these clicks themselves, let alone if they are able to use the echoes to gain object or environmental information.

At the recent Society for Marine Mammalogy biennial conference in Cape Town , scientists working on Megapclicks presented their findings. After the presentation, someone in the audience asked if the scientists had considered the idea that these click sounds might in fact be a form of communication, or more precisely, part of the humpback’s song repertoire. Humpbacks are famous for producing elaborate songs , and, according to this expert, these Megapclicks apparently resemble one of the song elements.

This discovery highlights the fact that scientists still know so very little about the behavior of whales and dolphins. Only a few decades ago, we did not even know that dolphins had a sense of echolocation; although today, we understand it to be a fundamental aspect of their behavior, biology, physiology and evolution. Whatever Megapclicks are – whether echolocation or a simple vocalization – they will be keeping scientists busy for years to come.

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Kids' Science Quickie

Pelorus Jack

Pelorus Jack was a Risso’s dolphin who was famous for helping guide ships through a dangerous stretch of water in New Zealand known as French Pass. The legend of Pelorus Jack states that, back in the late 1800’s, Jack would appear whenever a ship approached the straight, and would help guide the ship through the treacherous rocks and currents into Pelorus harbor. Legend tells that a drunken passenger on a steamboat called Penguin once shot Jack with a rifle. After that, Jack would never appear to help guide the Penguin into harbor, although he still helped other ships. Ironically, the Penguin was wrecked years later while trying to navigate French Pass without Jack’s help. No ship ever wrecked in the pass when Jack was there to guide them. Jack was spotted regularly for over 25 years before disappearing in 1912 – presumably having died of old age. What do you think about the legend of Pelorus Jack – is his story science fact or science fiction? Do you really think he helped guide ships into the harbor? To learn more about the legend of Pelorus Jack and to conduct your own investigation, visit the dolphin pod website for links.

The Legend of Pelorus Jack

Pelorus Jack on Wikipedia

Pelorus Jack Encyclopedia of New Zealand entry 

 

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Dolphin Quiz

How do Risso's dolphins get white scratches?

Last show’s winner was Izzy who correctly stated that a “wholphin” is a hybrid cross between a false killer whale and a bottlenose dolphin. Now, for this week’s quiz: where do the white scratches seen on the skin of Risso’s dolphins come from? Think you know the answer? Surf on over to thedolphnipod.com and click on Dolphin Quiz – leave your answer in the comments section. Winners will randomly be chosen from the correct answers, and will be announced on next week’s show. 

Risso's Dolphin

Image from David Hofman's website 

 


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Wrap-up:

That’s it for this week’s edition of The Dolphin Pod – thanks for tuning in. If you would like more information about the stories from this week’s episode, check out thedolphinpod.com. If you’ve got questions or comments about this week’s podcast episode, please contact us through the website. Why not consider signing up for the Dolphin Communication Project’s online community? You’ get access to a forum where you can discuss the The Dolphin Pod with other listeners. The DCP website offers a chance to adopt one of our dolphins from the Bahamas, as well as learn more about volunteer, internship and ecotour opportunities.

Don’t forget to join us next week for more dolphin science news and info. And remember, the dolphin pod is only a click away.

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