Some cetacean species - bottlenose dolphins, common dolphins, dusky dolphins, killer whales etc. - are famous ‘fish ball’ hunters.
They gather together, circle around a school of fish, squish the fish into a ball, and then take turns swimming into the bait ball and eating the fish.
A new study suggests that sperm whales (Physeter macrocephalus) can probably do the same. Thanks to special tags attached to the animals, researchers could study movement, time and depth recorded during dives of several individuals within the same group.
‘We're speculating that the animals are herding a ball of squid’ said Professor Bruce Mate who led the study, and added: ‘Some whales appeared to guard the bottom of this bait ball, preventing the prey from sinking to unreachable depths, while other animals in the group took advantage of the centre of the ball’.
The sperm whale food-ball theory is not yet proved but researchers are working to better understand what happens when these giants feed at 1,000 m depth.
Photo: a fish ball, at http://www.sea-way.org/blog/Beneath14.JPG
For more information:
28 February 2010
25 February 2010
A few days ago, a 16-m long dead whale was spotted along the Vietnamese coast and local fishermen hauled it ashore.
In Vietnam's fishing culture whales are considered sacred and the dead animal is attracting people from throughout the region. Fishermen are burning incense in its honour and they are planning to build a temple at the burial site.
Whales are named 'ngai': the honorific title used for kings, emperors and esteemed leaders.
Photo: dead whale dragged ashore (by The Associated Press)
For more information:
Pubblicato da Silvia Bonizzoni a 06:44
24 February 2010
Il 18 febbraio Andrea Ghisotti ci ha lasciati.
Resta vivo in tutti noi il ricordo dell'amore che nutriva per il mare, del suo entusiasmo, dell'ottimismo e della forza vitale con cui ha affrontato le diverse fasi della sua vita.
Saranno sempre con noi Il suo sorriso, la sua gentilezza, le incredibili storie dei suoi incontri in mare.
Pubblicato da Giovanni Bearzi a 09:28
23 February 2010
Study bottlenose dolphins to better understand human diseases: this was the topic discussed during the session ‘Decoding the secret pathologies of dolphins: significance for human and ocean health’ held at the Annual Meeting of the American Association for the Advancement of Science in San Diego.
Diseases found in bottlenose dolphins are similar to those found in humans (including diabetes, papilloma virus and RNS-based virus disease) and dolphins diet includes much of the same seafood we consume. All this prompted some researcher to think that these animals can help us discover health effects associated to contaminated coastal water or seafood.
“Our ecological and physiological similarities make dolphins an important ‘sentinel species’ to not only warn us of health risks, but also provide insight into how our health can benefit from new medical discoveries” said Carolyn Sotka of the NOAA Oceans and Human Health Initiative and lead organizer of the session.
Researchers are now investigating whether coastal dolphin populations and human communities sharing the same seafood resources experience similar exposures.
For more information:
Pubblicato da Silvia Bonizzoni a 06:05
21 February 2010
WDCS The Whale and Dolphin Conservation Society has recently launched a new online species guide.
The guide comes in three languages (English, Deutsch and Spanish), and provides information about appearance, distribution, behaviour, classification and threats for each cetacean species. It also features 80 maps and over 400 images.
Have a look at the WDCS Species Guide.
Pubblicato da Silvia Bonizzoni a 05:36
17 February 2010
The Mediterranean monk seal (Monachus monachus), one of the world’s most endangered marine mammals, has been observed giving birth for the first time in the eastern Mediterranean.
Thanks to an automatic 24-h infrared monitoring system installed in one reproductive cave at Kimolos island, Greece, researchers from MOm (Hellenic Society for the Study and Protection of the Monk Seal) were able to document two births as well as the postpartum behaviour.
The videos highlighted two threats related to the lactation period. In one occasion, bad sea conditions deteriorated so much that one pup was repeatedly washed away from her mother. Nothing happened to the pup thanks to the mother’s care: she moved the pup to a safer part of the cave and used her body to 'brake' the incoming waves.
The second threat occurred when a person entered the cave. A mother was so frightened that, in an attempt to escape, she trampled over her newborn pup. Fortunately the pup was not injured but the mother left it alone for seven hours.
Temporary mother-pup separation due to bad weather conditions or human disturbance, is the main cause of death for young Mediterranean monk seals. Work by MOm will help design more effective conservation measures.
Photo: a monk seal mother with her male newborn (from Karamanlidis et al. 2010)
Karamanlidis A.A., Paravas V., Trillmich F., Dendrinos P. 2010. First observations of parturition and postpartum behavior in the Mediterranean monk seal (Monachus monachus) in the Eastern Mediterranean. Aquatic Mammals 36(1):27-32.
For more information:
Pubblicato da Silvia Bonizzoni a 09:39
16 February 2010
Fisheries can affect seabird movements and behaviour. This
is the result of a recent study conducted in the Balearic islands, south of Spain.
Researchers analysed and modelled satellite tracking data of 10 foraging trips of breeding Balearic shearwaters (Puffinus mauretanicus) and 26 trips of breeding Cory’s shearwaters (Calonectris diomedea). By relating the birds movements with trawling activities, an interesting link was found.
When trawlers were active, the birds tended to concentrate in certain high-resource density area where the fishing boats were operating. When trawlers were inactive - during weekends, holidays or trawling moratorium days - the birds engaged in more widely spread and long flights.
Birds were probably attracted to the fish discarded by trawlers, as this represents an easy meal which does not require spending too much time and energy. Availability of discards may improve the breeding performance of Mediterranean seabirds but it may also decrease their fidelity to certain areas.
It’s unclear whether this may be good or bad for the birds in the long run, but it’s obvious how human activities are continuously impacting on nature.
trawler and pelagic seabirds http://www.twooceanssportfishing.com/pelagic-birding
For more information:
Bartumeus F., Giuggioli L., Louzao M., Bretagnolle V., Oro D., Levin S.A. 2010. Fishery discards impact on seabird movement patterns at regional scales. Current Biology 20:215–222.
Summary - Human fishing activities are negatively altering marine ecosystems in many ways, but scavenging animals such as seabirds are taking advantage of such activities by exploiting fishery discards. Despite the well-known impact of fisheries on seabird population dynamics, little is known about how discard availability affects seabird movement patterns. Using scenarios with and without trawling activity, we present evidence that fisheries modify the natural way in which two Mediterranean seabirds explore the seascape to look for resources during the breeding season. Based on satellite tracking data and a mathematical framework to quantify anomalous diffusion phenomena, we show how the interplay between traveling distances and pause periods contributes to the spatial spreading of the seabirds at regional scales (i.e., 10–250 km). When trawlers operate, seabirds show exponentially distributed traveling distances and a strong site fidelity to certain foraging areas, the whole foraging process being subdiffusive. In the absence of trawling activity, the site fidelity increases, but the whole movement pattern appears dominated by rare but very large traveling distances, making foraging a superdiffusive process. Our results demonstrate human involvement on landscape-level behavioral ecology and provide a new ecosystemic approach in the study of fishery-seabird interactions.
Pubblicato da Silvia Bonizzoni a 06:22
12 February 2010
10 February 2010
Why conservation is a slow process?
A (small) part of the problem could be that it takes longer for conservation biologists to submit scientific papers than it does for other experts. This, at least, is the result of a recent study published in Conservation Biology.
After data collection, the average conservation biologist waits nearly two years to submit a paper. For a taxonomist it takes about 20 months, 17 for a behavioural scientist, and only 6 for an evolutionary biologist.
One of the challenges is therefore trying to submit a bit earlier, hoping this will encourage a ‘greener’ management.
Indeed, journal Editors also may play a role in delaying publication of conservation-oriented work.
Photo by Nciri Khaled at http://photo.net
For more information:
O’Donnell R., Supp S., Cobbold S. 2010. Hindrance of conservation biology by delays in the submission of manuscripts. Conservation Biology. DOI: 10.1111/j.1523-1739.2009.01424.x
Abstract - Timely dissemination of scientific findings depends not only on rapid publication of submitted manuscripts, a topic which has received much discussion, but also on rapid submission of research after the research is completed. We measured submission delay (time from the last date of data collection to the submission of a manuscript) for every paper from 14 journals in 2007 and compared these submission delays among four fields of biology (conservation, taxonomy, behavior, and evolution). Manuscripts published in leading journals in the field of conservation biology have the longest delays in publication of accepted manuscripts and the longest intervals between completion of research and submission of the manuscript. Delay in manuscript submission accounts for more than half of the total time from last date of data collection to publication. Across fields, the number of authors was significantly negatively correlated with submission delay, but conservation journals had the second highest number of authors and the greatest submission delay, so submission of conservation manuscripts was not hindered by a shortage of collaboration relative to other fields. Rejection rates were greater in conservation journals than in behavior and evolution, but rejection times were faster; thus, there were no obvious net differences among fields in the time papers spent waiting to be rejected. Publication delay has been reduced significantly in the last 7 years, but was still greater in conservation journals than in any of the other three fields we studied. Thus, the urgent field of conservation biology is hindered in both preparation and publication of manuscripts.
Pubblicato da Silvia Bonizzoni a 09:19
09 February 2010
Remarkable and curious underwater photos of beluga whales (Delphinapterus leucas) as ‘stars’, have been taken in the northern Russia White Sea.
Capturing these images was not so simple. Before each dive the photographers had to create holes in the three-foot-deep ice using a hand saw, to have access to a cold, cold sea.
While divers were enjoying the company of beluga whale, someone else had to stay above the ice — and wait in the wind at temperatures of up to -30°C (!) — to make sure the ice hole didn’t freeze over and trap the underwater group. BRRR!
To see the photos:
Photo: a beluga's close approach, by Franco Banfi
For more information:
Pubblicato da Silvia Bonizzoni a 07:31
07 February 2010
A scientist who is deeply preoccupied with the solution of a problem will find not so much that he allocates special times to thinking about it but rather than reflection upon the problem is the equilibrium state or the zero point on the dial to which his mind tend automatically to return when it is not occupied by anything else.
-- P.B. Medawar in Advice to a Young Scientist (1979)
Pubblicato da Giovanni Bearzi a 16:52
06 February 2010
The bottlenose dolphin is one of the most adaptive cetaceans. Numerous studies of its behaviour highlighted various and different feeding strategies to have a food-full belly.
Thes dolphins are able to surface-feed, patrol fish-farms looking for wild fishes around the cages, take advantage of various fishing gear, ‘crater-feed’, ‘beach-feed’, use sponges to ferret prey from the sea floor, and prepare their meal by removing the ink and the calcareous bone from cuttlefish.
The ultimate hunting trick is ‘mud-ring feeding’.
By beating the tail down hard and swimming in tight circles, they create a wall of mud around shoaling fish. Inside of these rings, scared fishes try to escape by jumping out of the water but... they end directly into a dolphin's mouth!
This strategy has been caught by video and showed in the first episode (Challenges of Life) of the new BBC series Life.
Pubblicato da Silvia Bonizzoni a 06:13
04 February 2010
Some think Antarctic minke whales (Balaenoptera bonaerensis) are more numerous than usual, that they compete for food with larger whales and they are preventing them from recover after decimation by industrial whaling. Therefore, culling of minke whales was proposed as a valid management solution to allow blue, sei, fin and humpback whales to increase in numbers.
A recent study published on Molecular Ecology confuted this theory. Based on analyses done on samples of minke whale meat purchased at Japanese markets, researchers proved that numbers B. bonaerensis have not increased unnaturally in the wake of industrial whaling. No way. Their numbers are close to historical ones.
Image: Four main species of baleen whale hunted in the Southern Ocean in the early 1900s (from Ruegg et al. 2010)
For more information:
Ruegg K., Anderson E., Baker C., Vant M., Jackson J., Palumbi S. 2010. Are Antarctic minke whales unusually abundant because of 20th century whaling? Molecular Ecology 19(2):281-291.
Abstract - Severe declines in megafauna worldwide illuminate the role of top predators in ecosystem structure. In the Antarctic, the Krill Surplus Hypothesis posits that the killing of more than 2 million large whales led to competitive release for smaller krill-eating species like the Antarctic minke whale. If true, the current size of the Antarctic minke whale population may be unusually high as an indirect result of whaling. Here, we estimate the long-term population size of the Antarctic minke whale prior to whaling by sequencing 11 nuclear genetic markers from 52 modern samples purchased in Japanese meat markets. We use coalescent simulations to explore the potential influence of population substructure and find that even though our samples are drawn from a limited geographic area, our estimate reflects ocean-wide genetic diversity. Using Bayesian estimates of the mutation rate and coalescent-based analyses of genetic diversity across loci, we calculate the long-term population size of the Antarctic minke whale to be 670 000 individuals (95% confidence interval: 374 000–1 150 000). Our estimate of long-term abundance is similar to, or greater than, contemporary abundance estimates, suggesting that managing Antarctic ecosystems under the assumption that Antarctic minke whales are unusually abundant is not warranted.
Pubblicato da Silvia Bonizzoni a 09:47