Male bottlenose dolphins form bachelor groups with their relatives

When it comes to wooing the 'ladies', it turns out male bottlenose dolphins employ special tactics with their brothers or cousins to increase their odds of sexual success

Date:  March 6, 2019

Source:  Flinders University

When it comes to wooing the 'ladies', it turns out male bottle nose dolphins employ special tactics with their brothers or cousins to increase their odds of sexual success.

New research has analysed the behaviour of 12 dolphin social groups in South Australia's Coffin Bay region and shows males who team up in groups of two to five to form beneficial alliances may have more success.

The collaboration improves the bottle nose chances of finding and breeding with females in a competitive environment, ensures they stay fit, and leads to stronger family bonds over time.

Led by Dr Fernando Diaz-Aguirre at the Molecular Ecology at Flinders University, the study examined the social and genetic structure of Southern Australian dolphins dealing with population density, an unfavourable sex ratio, and their own behavioural characteristics.

"Our research shows males form tight groups likely to increase their chances at mating with limited numbers of females, and at the same time they can defend females and prevent other male groups from mating with them," says Dr Diaz-Aguirre.

"The study highlights which geographic and demographic factors directly influence how male dolphins go about increasing their success rate with females."

Male lions, chimpanzees and horses are known to form bachelor groups in the animal kingdom, but it's even more important for dolphins because females only give birth to a single calf every two to five years.

Previous research has shown other dolphin's types form similar relationships, but this study analysed why bonds are based on blood relations in the Coffin Bay region.

Continued

Endocrine disruptors found in bottlenose dolphins

Date:  September 5, 2018

Source:  American Geophysical Union

Bottlenose dolphins are being exposed to chemical compounds added to many common cleaning products, cosmetics, personal care products and plastics, according to a new study in GeoHealth, a journal of the American Geophysical Union.

The new research found evidence of exposure to these chemical compounds, called phthalates, in 71 percent of dolphins tested in Sarasota Bay, Florida during 2016 and 2017. Previous studies detected phthalate metabolites in the blubber or skin of a few individual marine mammals, but the new study is the first to document the additives in the urine of wild marine mammals.

Some phthalates have been linked to hormonal, metabolic and reproductive problems in humans, including low sperm count and abnormal development of reproductive organs. The study's authors do not know what health impacts phthalate compounds may have on dolphins, but the presence of byproducts of the chemicals in the animals' urine indicates they have remained in the body long enough to process them.

Continued

The freediving champions of the dolphin world

July 17, 2018, Frontiers

For the first time, researchers have explored the physiological adaptations that enable different populations of the same species of dolphin to vary in diving ability by almost 1000m. The research, published in two complementary studies in Frontiers in Physiology, compared the lung mechanics and metabolic rates of bottlenose dolphin populations known for their different hunting depths. Using theoretical estimates of gas management, the results support a new hypothesis that lung architecture and the management of blood flow allow the dolphins to access oxygen in the lungs while preventing uptake of nitrogen, thereby avoiding decompression sickness.

Bottlenose dolphin populations are often found close to land in shallow coastal environments, making short, shallow dives of less than 10m for their prey. However, some populations—such as the Bermudian population in this study—frequently dive to depths of up to 400m, and as deep as 1000m on occasion, spending up to 13 minutes underwater in search of food on a single breath.

"How can a single species have such extremely different life styles?" This question motivated Dr. Andreas Fahlman of the Fundación Oceanográfic in Valencia, Spain, who led both studies with his international team. "We wanted to measure what kind of differences are responsible for these huge variations. This allows us to determine how far the physiology can change within a single species and understand the threat that stressors may have on these deep diving dolphins."

Anyone who has previously scuba-dived will know about decompression sickness, commonly known as 'the bends'. This painful and potentially life-threatening condition is caused from surfacing too quickly at the end of a dive. The rapid expansion of nitrogen bubbles—which form in the bloodstream and tissues during the dive—are not given enough time to diffuse from the body naturally during the ascent.

Dolphins run the same risks when diving to great depths. The team measured the physiology of the lungs and energy consumption of several bottlenose dolphins known to make deep dives to understand how these problems are avoided.

Read more at: 

New study investigates the environmental cues dolphins use to migrate on the Atlantic coast of North America

Date: April 22, 2016

Source: De Gruyter

Seasonal migration patterns of bottlenose dolphins -- what we know for sure? With the changing of the seasons comes the urge to migrate for many animals of the world, whether they be furred, feathered, or even finned. One finned animal in particular, the common bottlenose dolphin, undertakes seasonal migrations each spring and fall, but how the dolphins know when to migrate has not always been clear. It was usually assumed that their southern migration begins when the ocean waters drop in temperature. However, until now there was little evidence to support this and it was largely unknown what factors influence the initiation of dolphin migration. A new study has discovered some of the factors that influence these seasonal migrations.

In the article, published this week and available online, Masters student Anna Taylor, from the University of Georgia (USA), and colleagues studied the common bottlenose dolphin, which migrates seasonally along the southeastern United States Atlantic coast. While this species of dolphin is widely studied, surprisingly little is known about what influences the timing of these migrations.

The scientists needed to track the comings and goings of dolphins at their study sites on the Georgia and South Carolina coasts, and they did so using photographic identification of individual dolphin fins. This technique is used with many studies of Cetaceans (whales, dolphins and porpoises), which all have dorsal fins. As the animals age, their dorsal (back) fins become worn and chipped, which allows individuals to be uniquely identified, much like fingerprints.

Continued ...

Bottlenose Dolphins and seals are being harassed in Cornwall

Some water users around Cornwall’s north coast, particularly in the St Ives Bay area, have been repeatedly harassing Bottlenose Dolphins and other marine life, such as seals, in recent weeks.

This disturbance ranges from seals being flushed from their rocks into the sea by kayakers and rock climbers, and dolphins being chased by wildlife day trip boats.

Disturbing wildlife in this way is not only illegal, but also can result in distress to the animals, make them change their natural behaviour and, in the worst case, can lead to serious injuries, amputations and even death due to propeller strike. 

Abby Crosby, Marine Conservation Officer for Cornwall Wildlife Trust says: "We are lucky enough to get 17 species of whales, dolphins and porpoises as well as basking sharks and turtles visiting the South West.

"The last thing we want to do is to drive these beautiful animals away from our coast and their feeding grounds."

Continued ....

Dolphins spotted enjoying the sun off the coast of Blackpool

Dolphin sightings are very uncommon in the Irish Sea

DOUG BOLTON

Thursday 02 July 2015

Blackpool's beachgoers weren't the only ones enjoying the heatwave - a group of bottlenose dolphins were caught on camera swimming just off the coast of the seaside resort.

The footage of the dolphins was caught on camera by sailor Simon Redfearn. The pod of dolphins swim happily just alongside the boat, while the famous Blackpool Tower and the Big One rollercoaster can be seen in the distance.

Katrin Lorenghel of the Sea Watch Foundation said the organisation had seen an increase in bottlenose dolphin sightings in North West England over the past few years, possibly because of the improved water quality following the Mersey Basin Clean Up campaign.

She said: “In the past few summers we’ve increasingly had reports of large dolphin groups, between 20 and 50 animals, in Liverpool Bay and off the North Wales coast, so it is no longer that unusual to spot a dolphin [in the waters off] Blackpool, although we don't frequently get reports of groups of this size.”

Dolphin sightings are more common in the South West of the UK, in Cornwall and Devon, and further north, in the Moray Firth in Scotland.

Read on ...

Deepwater Horizon oil spill contributed to high number of Gulf dolphin deaths

Date: May 20, 2015

Source: NOAA Headquarters

Summary: As part of an unusual mortality event investigation, a team of scientists has discovered that dead bottlenose dolphins stranded in the northern Gulf of Mexico since the start of the Deepwater Horizon oil spill have lung and adrenal lesions consistent with petroleum product exposure according to a paper published today in the peer-reviewed online journal PLOS ONE.

These findings support those of a 2011 health assessment of live dolphins in Barataria Bay, Louisiana, a heavily oiled area during the spill which showed those resident dolphins had poor health, adrenal disease, and lung disease.

The timing, location, and nature of the detected lesions support that contaminants from the Deepwater Horizon oil spill caused these lesions and contributed to the high numbers of dolphin deaths within this oil spill's footprint. Increased dolphin deaths following the oil spill are part of the northern Gulf of Mexico unusual mortality event investigation.

Continued ...

Bottlenose dolphins off US coast hit by measles-like virus

More than 1,000 migratory bottlenose dolphins have died from a measles-like virus along the US eastern seaboard in 2013 and the epidemic shows no sign of abating, a marine biologist said on Monday.

The death toll exceeds the 740 dolphins killed during the last big outbreak of the then unknown virus in 1987-88.

"It is having a significant impact and that is something we're monitoring closely," said Erin Fougeres, a marine mammal biologist for the National Oceanic and Atmospheric Administration (NOAA).

An estimated 39,206 bottlenose dolphins populated the eastern seaboard, to a depth of 25 feet, from New Jersey to Central Florida in 2010, according to the latest NOAA census.

Continued

Cardigan Bay dolphins 'sent north' by noise

20 June 2013 Last updated at 07:37

Speedboats and water bikes using Cardigan Bay may be driving its famous dolphins over 100 miles north to quieter waters, experts have warned.

Bottlenose dolphins usually spend the summer months in the sea off Ceredigion before heading to north Wales and the Isle of Man for winter.

But research suggests they are spending less time in Cardigan Bay and noisy water sports could be partly to blame.

The Sea Watch Foundation has called for better protection for the mammals.

Continued and video

Dolphins attack on harbour porpoise in Moray Firth

Eight dolphins attacked a harbour porpoise

May 2013. An extraordinary attack on a harbour porpoise by a group of around eight bottlenose dolphins acting in 'tight formation' has been witnessed by a marine wildlife expert off Covesea Skerries near Lossiemouth on the south coast of the Moray Firth.

While attacks on porpoise by bottlenose dolphins are not unusual, North Grampian Regional Co-ordinator for the marine research charity Sea Watch Foundation, Alan Airey, says he has never before seen such an organised attack by a 'tight pack' of dolphins.

The attack happened while he was watching around eight bottlenose dolphins, and a mother and calf, leaping, feeding and surfing on the west side of the skerries on Friday 24 May, just as the Bank Holiday began. While the mother and calf remained feeding, slowly the behaviour of the other dolphins changed.

Tossed in the air

He says:" I also saw a porpoise quite close in heading east. Slowly the dolphins moved further west. Then at about 4.15pm, the eight dolphins started charging about shoulder to shoulder, and I realised they were attacking at least one porpoise. I saw a porpoise had been tossed in the air, with the pack all diving in after it. 

"Then I saw a porpoise swimming for its life right in front of the dolphin 'pack', the dolphins would surge forward as one as if trying to drown it by forcibly pushing it under, and then I saw another chase which resulted in a porpoise being tossed in the air again.

Continued

Several sightings of dolphins off the Isle of Man – Are Bottlenose dolphins moving north?

Plentiful herring may be luring the dolphins

May 2013. The unusual sight of a large group of bottlenose dolphins near the Isle of Man this week may be further evidence that they are shifting their summer range northwards, says the marine conservation charity Sea Watch Foundation.

The Manx Whale & Dolphin Watch not only reported around 10 bottlenose dolphins in the north eastern part of the Isle of Man on May 19, but later the same day, a large group of 50-60 bottlenose dolphins, including young calves, were seen off the eastern part of the Island.

Have you seen any Bottlenose dolphins off the Isle of Man or nearby?

Both organisations are calling for members of the public to send in photographs to photo@seawatchfoundation.org.uk of bottlenose dolphins off the Isle of Man or off the north east coast of England and the Galloway coast in the northeast Irish Sea, to see whether they can be matched with any known to frequent Cardigan Bay. Photographs need to show their fins side on which are used for ID in much the same way as fingerprints in humans!

20 Bottlenose dolphins off Abbey Head, Dumfries

Another interesting sighting - a group of 20 bottlenose sightings off Abbey Head, Dumfries and Galloway - was also reported to Sea Watch by Regional co-ordinator, Mark Pollitt, manager of the Dumfries and Galloway Environmental Recording Centre on 20 May. Photographs are again being sought to see whether these dolphins match records either from Cardigan Bay in Wales or form Scottish populations on the west and east coast.

Rissos dolphins

Daphna Feingold, Sea Watch Monitoring officer for the Cardigan Bay bottlenose dolphin Photo ID Project, says: "There were also reports of Risso's dolphins in the Isle of Man area at the same time and of the two species swimming together. Although this is not unheard of, it is quite unusual in UK coastal waters.

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Bottlenose Dolphin Leaders More Likely to Lead Relatives Than Unrelated Individuals

Mar. 13, 2013 — Traveling into uncharted territory in search of food can be a dangerous undertaking, but some bottlenose dolphins may benefit by moving through their habitat with relatives who may be more experienced or knowledgeable. It turns out that leaders in bottlenose dolphin groups in the Florida Keys are more likely to be related to the dolphins that follow them, according to research published March 13 by Jennifer Lewis and colleagues from Florida International University.

In complex habitats like the shallow waters of the Florida Keys, individuals who follow may benefit from the experience of those that lead them, but the advantages to leaders are less obvious, as they must share food resources encountered with the group. In this study, the authors assessed indirect benefits to leaders in bottlenose dolphin groups, by measuring the chances of a leader being related to their followers. They found that when two dolphins shared a leader-follower relationship, their chances of being related were much higher than seen in dolphin pairs that associated in other ways.

Lewis adds, "These results are particularly interesting because bottlenose dolphins do not stay in the same groups all the time. In fact, they change over periods of hours or days. That specific pairings within these groups (according to their roles of leader and follower) does occur, suggests that these associations are not random and that individual choices are made about leaders."

http://www.sciencedaily.com/releases/2013/03/130313182146.htm

Dolphin disgrace – 101 taken into captivity and 27 killed

Huge pod of Bottlenose dolphins virtually destroyed

December 2012. Every year, between September and March, local fishermen drive pods of dolphins and whales into a small cove in south-east Japan. Many are killed for food, many are taken into captivity to be trained to perform in shows, and just a very few are released, usually those too old or young to be included in the above.

At the beginning of December 2012, a huge pod of some 200 Bottlenose dolphins was driven into the cove and penned in by nets. After 6 days in captivity in the cove, 101 dolphins had taken into captivity, 25 killed for human consumption and at least 2 babies had died.

The dolphins that are taken into captivity are taken to a local captive facility, where they are usually trained before being sold all around the world.

Latest update - Apparently the boats have left harbour again, to drive another pod of dolphins into the cove.

For more updates, and the full story, go to the Cove Guardians website or the Sea Shepherd Facebook page

http://www.wildlifeextra.com/go/news/dolphin-taiji.html

Bottlenose dolphins: Large pod sighted in Manx waters

A pod of more than 100 bottlenose dolphins has been spotted off the coast of the Isle of Man, according to the Manx Whale and Dolphin Watch.

The group has received numerous sightings of the dolphins from both the east and west coasts of the island.

Tom Felce, of the group, said: "They are a magnificent sight."

Common bottlenose dolphins are widespread, except in polar waters. They are extremely sociable and sometimes hunt their prey in teams.

The dolphins normally visit Manx waters between October and March to feed on herring, mackerel and whiting.

Mr Felce added: "The group sizes tend to be relatively ginormous. So if they are here you can't miss them.

'Extraordinary creatures'

"They are very, very active and create a huge amount of white water. They leap all over the place. So sightings will be magnificent.

Continued:  http://www.bbc.co.uk/news/world-europe-isle-of-man-20295708

Flipper on a mission: Ukraine resuming dolphin combat training

A Soviet program of dolphin military training is reportedly being revived in Ukraine. The unit's tactical objective will be search operations and patrolling the waters near the Russian and Ukrainian Naval base in Sevastopol.

In the Soviet Union, dolphin training started in 1965, while a special naval dolphinarium was initiated in 1973 in Sevastopol, the homeport of the USSR's Black Sea fleet.

Bottlenose dolphins (Tursiops truncates), who naturally inhabit the Black Sea, were chosen as future subversives, set to infiltrate enemy lines, mine warships and counteract military swimmers. For that purpose dolphins were properly armed with knives and underwater pistols fixed on their heads and specially designed baldric for mine carriage.

Later, the center also obtained dolphins of other species, reportedly from the White Sea of the Arctic Ocean and from the Pacific of Russia’s Far East. According to some sources in the Soviet Union, there were specialists training seals, sea lions and even orcas for the same tasks.

Continued:  http://rt.com/news/sevastopol-combat-dolphins-revived-350/

Divided dolphin societies merge 'for first time'

A unique social division among a population of bottlenose dolphins in Australia's Moreton Bay has ended, according to a new study.

The dolphins lived as two distinct groups that rarely interacted, one of which foraged on trawler bycatch.

But scientists think that a ban on fishing boats from key areas has brought the two groups together.

They believe these socially flexible mammals have united to hunt for new food sources together.

The findings are published in the journal Animal Behaviour.

The Moreton Bay dolphins were thought to be the only recorded example of a single population that consisted of groups that were not associating with each other in a split dubbed "the parting of the pods".

But since the study that discovered the rift, trawlers have been banned from designated areas of the bay leading to a 50% reduction in the fishing effort.

Continued:  http://www.bbc.co.uk/nature/18985101

BP Oil Spill May Have Contributed to Dolphin Deaths, Study Finds

The 2010 BP oil spill contributed to an unusually high death rate for dolphins in the Gulf of Mexico, a new study suggests.

Between January and April 2011, 186 dead bottlenose dolphins washed ashore between Louisiana and western Florida. Most alarmingly, nearly half of these casualties were calves, which is more than double the usual proportion of young to old dolphins found dead. Scientists now blame both natural factors and human catastrophe for the unusual die-off.

"Unfortunately, it was a 'perfect storm' that led to the dolphin deaths," study researcher Graham Worthy, a biologist at the University of Central Florida, said in a statement. "The oil spill and cold water of 2010 had already put significant stress on their food resources. … It appears the high volumes of cold freshwater coming from snowmelt water that pushed through Mobile Bay and Mississippi Sound in 2011 was the final blow." 

Continued:  http://www.livescience.com/21730-dolphin-deaths-bp-oil-spill.html

Bottlenose dolphins: 'Gangs' run society, scientists say

Male bottlenose dolphins organise gang-like alliances - guarding females against other groups and occasionally "changing sides".

A team studying dolphins in Shark Bay, western Australia, say the animals roam hundreds of square kilometres, often encountering other dolphin groups.

The researchers observed the dolphins there over a five-year period, recording their movements.

They report their findings in the Royal Society journal Proceedings B.

Dr Richard Connor, a researcher from the US who took part in this study, first began his studies of the Shark Bay dolphins in the early 1980s.

This latest study reveals that these highly intelligent marine mammals live in an "open society". Rather than males guarding a specific territory, groups have what Dr Connor described as a "mosaic of overlapping ranges".

The fact that the dolphins travel in their troops and frequently encounter strangers reveals a great deal about their intelligence, because when one group meets another, the animals have to decide how to respond.

Shark Bay dolphins deal with this by organising themselves into three different types of alliances.

The first is pairs or trios that work together to capture and herd fertile females. "These consortships can last over a month," Dr Connor explained.

In a "second-order alliance", the animals form "teams" of between four and 14 males which mount attacks on other groups to take their females, or to defend against attacks.

In a third level, the dolphins have "friendly relations" between these larger teams; they join forces to form larger dolphin armies, working together to defend their females against other large, aggressive groups.

Read on:  http://www.blogger.com/blogger.g?blogID=4348728589329576621#editor/target=post;postID=1153991544644509296

Some Gulf Dolphins Severely Ill After Gulf Oil Spill

ScienceDaily (Mar. 26, 2012) — Bottlenose dolphins in Barataria Bay, Louisiana, are showing signs of severe ill health, according to NOAA marine mammal biologists and their local, state, federal and other research partners.

Barataria Bay, located in the northern Gulf of Mexico, received heavy and prolonged exposure to oil during the Deepwater Horizon oil spill.

Based on comprehensive physicals of 32 live dolphins from Barataria Bay in the summer of 2011, preliminary results show that many of the dolphins in the study are underweight, anemic, have low blood sugar and/or some symptoms of liver and lung disease. Nearly half also have abnormally low levels of the hormones that help with stress response, metabolism and immune function.

Researchers fear that some of the study dolphins are in such poor health that they will not survive. One of these dolphins, which was last observed and studied in late 2011, was found dead in January 2012.

Read more:  http://www.sciencedaily.com/releases/2012/03/120326133633.htm

Successful breeding for New Zealand's Doubtful Sound dolphins

Bottlenose dolphins in Doubtful Sound

December 2011. Doubtful Sound's resident pod of bottlenose dolphins have had the best two breeding seasons for some time.

Over the last two summers, the dolphins have had the most surviving calves for more than a decade. This gives the Department of Conservation (DOC), Otago University researchers, and the local tourism industry optimism about their future.

DOC's marine mammal ranger Kath Blakemore said alarm has been raised about the rapid rate of decline this well-researched population has been undergoing in recent years. Calf survival rates have been low since around 2002. This is more critical as research shows that this small group of dolphins lives separately from others, living almost exclusively within Doubtful Sound.


16 calves born - 11 survived
Sixteen calves have been born over the last two summers and 11 of these have survived so far. Otago University researcher, Shaun Henderson said that in 20 years of the University's research there has only been one other year with more calves born. If most of these calves survive it will be a significant boost to the population.


"While we don't know the reason for this increased rate of births, everyone involved is hoping this trend continues," Mr Henderson said.


Dolphin watching rules
Since 2009, DOC has been working with boat operators to implement a set of rules for vessel use in Doubtful Sound to minimise any potential impacts from the dolphins interacting with boats. In addition, a research programme has begun to explore some of the other potential causes of the decline, such as genetics, habitat modification, broad-scale climate changes and diet.

The commitment from the Doubtful Sound tourism industry to work alongside DOC and others to help these dolphins has been encouraging. All boat operators, private or commercial, must be familiar with the protection guidelines before heading into Doubtful Sound. These are readily available from the DOC website or your local DOC office. The guidelines aim to reduce the amount of time dolphins spend interacting with boats so they can spend more time doing what dolphins should naturally do.

http://www.wildlifeextra.com/go/news/doubtful-dolphins.html