Smiling again

After 3 monk seal sightings in 3 days, our fourth day of research in the Gulf of Evia finally offered a bottlenose dolphin group.

The animals were found after eight hours of nonstop search, when it felt like there were no cetaceans anywhere.

A few jumps, and we were smiling again :-)

Silvia Bonizzoni

Dolphin researcher dealing with a bad knee

Following an injury and many years jumping on inflatable boats, Giovanni recently got his second run of surgery on his left knee. Thanks to such surgery he can now walk again, but more standing on choppy waters would not be a good idea. Therefore, Gio recovered an old seat from an abandoned car, built a wooden stand, and installed his "masterpiece" on the Tethys inflatable. This allows him to remain seated during surveys on wavy seas, while enjoying an appropriately high eye elevation. Gio claims the seat is comfortable and he is happy to have returned to work at sea.

Silvia Bonizzoni

Monk seal # 2

Second encounter with a monk seal in the Gulf of Evia (see previous post). This animal was observed for an hour engaging in food search in a murky bay, not far from an industrial plant. She performed dives approximately 4-6 min long followed by about 30 sec of ventilations. During those 30 sec spent at the surface we could watch the seal in all her beauty while she was elegantly swimming, staring at us from time to time (photo). While she did not seem exceedingly wary of the boat, she never came closer than 30-50 m. This is a wise behaviour, considering that monk seals in the coastal waters of Greece are still sometimes seen as vermin, and shot.

Giovanni Bearzi

Monk seal lunch

Our first day of work in the Gulf of Evia did not have dolphins to offer, but an amazing and unexpected encounter with a monk seal who was having lunch at the surface. The seal had a large octopus in his mouth and he was forcefully and repeatedly shaking it with the head out of the water, producing splashes that could be seen from far away. We speculated he intended to kill the octopus before eating it. We approached at slow speed up to about 50 m to observe this unusual behaviour, and the monk seal did not appear disturbed. He finished his lunch, gazed at us, then moved away. We managed to capture some phases of the octopus lunch, but most photos were blurry due to the distance, except for the one shown here, which even when magnified was sharp enough to capture the fierce look of this large and critically endangered marine mammal.

Giovanni Bearzi

In opposition to dolphin captivity

In this interview, Dr. Lori Marino — a neuroscientist and Senior Lecturer at Emory University — convincingly explains why dolphins do not belong in a concrete pool.

http://tinyurl.com/24aeb3z

The site also features a defense of dolphin zoos by Dr. Paul Boyle — Senior Vice President of Conservation & Education for the Association of Zoos & Aquariums.

The emergence of compassion

The following article has just been published online:

Perception of a cetacean mass stranding in Italy: the emergence of compassion

Giovanni Bearzi, Nino Pierantonio, Silvia Bonizzoni, Giuseppe Notarbartolo di Sciara, Massimo Demma. 2010.

Aquatic Conservation: Marine and Freshwater Ecosystems. DOI: 10.1002/aqc.1135


ABSTRACT

1. The view that whales are malicious monsters has been pervasive throughout history. Conversely, the idea that these animals experience suffering has emerged only recently. One way of investigating perceptual, as well as behavioural, shifts is assessing general public reactions to mortality events involving wild, rare and charismatic animals.

2. Here, the responses of 118 individuals to questions regarding the mass stranding of seven sperm whales (Physeter macrocephalus) along the Adriatic Sea coast of Italy in December 2009 are reported through interviews taken at the stranding site and in the direct proximity of the dead animals.

3. When asked why the whales were stranded, 44.1% of the respondents suggested anthropogenic causes and 21.2% non-anthropogenic. The remaining 34.7% mentioned a generic ‘disorientation’ or stated they did not know. When asked how they felt about the whales, 68.6% expressed feelings of compassion or care towards the animals. Clearly non-compassionate attitudes accounted for only 4.1% of the sample. Finally, 21.2% expressed feelings that were ambiguous in terms of being suggestive of compassionate or non-compassionate attitudes, including 11.9% amazement, 4.2% deprecation and 5.1% powerlessness.

4. These results are in stark contrast with information obtained from accounts of similar events that have occurred in historical times, up until the first half of the 20th century. For centuries, responses to cetacean live strandings—typically including killing and harming of the animals—were either utilitarian or characterized by feelings including fear and a desire to ‘subjugate the beast’, with no apparent concern for their suffering and death.

5. It is concluded that attitudes towards whales—today strikingly revolving around sadness, compassion and a sense of loss—have changed dramatically over time, with a steep turnaround in the 1970/1980s. Full appreciation of the ongoing evolution in public perception can channel marine conservation efforts and assist in the design of response strategies to marine mammal strandings.

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A pdf copy can be obtained from the journal's web site:

http://onlinelibrary.wiley.com/doi/10.1002/aqc.1135/abstract

or from the first author:

giovanni.bearzi(at)gmail.com

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Photo by Silvia Bonizzoni: A sperm whale dying on the beach of Foce Varano, Italy

Vaquita – Last Chance for the Desert Porpoise

An outstanding documentary by Chris Johnson about the critically endangered vaquita in Mexico.

Strongly recommended !

http://vaquita.tv/documentary

Viewing dolphins as Taiji could show them

A very nice article featuring work by Tethys in the Amvrakikos Gulf, Greece, as well as an upcoming paper on compassionate feelings towards the sperm whales stranded in Italy in 2009:

http://search.japantimes.co.jp/cgi-bin/fe20100711rh.html

The article, written by Rowan Hooper, appeared in the Japan Times.

The Mediterranean Risso's dolphin: getting one step closer to a fascinating and neglected marine mammal

The Risso's dolphin has been studied in several locations around the world, but information on this cetacean species remains relatively scant. Risso's dolphins are not particularly shy or elusive and can be studied with relative ease in areas where continental slope waters are close to shore. In the Mediterranean Sea they are relatively widespread but not abundant and their occurrence can be unpredictable, possibly due to wide-ranging movements. This factor, together with generally low densities, has precluded sustained, focussed investigations of their ecology and behaviour.

Even within the few Mediterranean areas where Risso's dolphins are known to be consistently present, only limited information has been obtained. In large parts of the region there is nothing more than a few sightings or strandings to indicate their presence. In sum, the distribution, ecology, status and trends of this species in the Mediterranean remain somewhat mysterious. On one hand this hampers conservation, but on the other hand it offers scope for novel studies.

In the Mediterranean Sea, modern field studies of cetaceans began in the late 1980s and this has resulted in rapid advances in knowledge of several of the species known to occur regularly in the region. The Risso's dolphin, however, remains one of the least-known cetacean species in the region and has been the subject of few dedicated studies. A regional IUCN Red List workshop in March 2006 concluded that the Mediterranean subpopulation of the Risso's dolphin is ‘Data Deficient’.

A recent scientific review of the ecology and status of the Risso’s dolphin in the Mediterranean Sea, published in the renowned journal Mammalian Biology, sheds new light on a largely neglected species. This work - funded by OceanCare and WDCS The Whale and Dolphin Conservation Society - was conducted by a group of five scientists led by Giovanni Bearzi, President of the Tethys Research Institute. The second author is Randall R. Reeves, Chair of the IUCN Cetacean Specialist Group. One of the main purposes of the review is to identify knowledge gaps and areas where focussed studies should be conducted to inform conservation efforts aimed to protect Risso’s dolphins in Mediterranean waters.

Risso's dolphins occur in continental slope waters throughout the Mediterranean basin and around many of the region's offshore islands and archipelagos. No synoptic estimate of abundance is available for the Mediterranean region, but densities and overall numbers are low in comparison to some other small odontocetes. Diet consists primarily of cephalopods, with a clear preference for mesopelagic squid.

The paper by Bearzi and colleagues reviews available information on the distribution and ecology of Risso's dolphins in the Mediterranean and identifies factors that may negatively affect them in this region. The principal known threat to populations in the Mediterranean is entanglement in pelagic drift gillnets. Other potential problems for Risso's dolphins in the Mediterranean include noise disturbance and ingestion of plastic debris.

Inclusion of Risso's dolphin habitat in networks of offshore protected areas would be one way of addressing threats to this species in the mid to long term. Indeed, various MPAs have been proposed to protect the habitat of deep-water cetacean species (including Risso's dolphin) in Spanish Mediterranean waters and there are prospects for Specially Protected Areas of Mediterranean Importance (SPAMIs) in areas beyond national jurisdiction. If effectively managed, deep-water or offshore protected areas could have long-term conservation benefits for Risso's dolphins. Pending the implementation of such area-based management strategies, any actions taken to mitigate immediate and well-known threats to cetaceans and other large marine vertebrates in the Mediterranean region, particularly entanglement in pelagic gillnets (driftnets), are bound to benefit Risso's dolphins. Considering that driftnetting is already illegal in EU waters, what is most needed is strict enforcement of that ban and its extension to the high seas and to waters under non-EU State jurisdiction.


THE REVIEW:
Bearzi G., Reeves R.R., Remonato E., Pierantonio N., Airoldi S. 2010. Risso’s dolphin Grampus griseus in the Mediterranean Sea. Mammalian Biology. DOI: 10.1016/j.mambio.2010.06.003

PHOTO:
These Risso's dolphin mother and calf photographed in the Ligurian Sea show the characteristic morphology and pigmentation of the species. Photo © Caterina Lanfredi / Tethys Research Institute.

Sealife in the Gulf of Corinth

(click on photo to enlarge)

Tuna feeding at surface on schooling fish prey, and shearwaters trying to get their share.

Gulf of Corinth, Greece, July 6th, 2010

Photo: Silvia Bonizzoni / Tethys

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For more information on the work done by Tethys in Greece, please see: Ionian Dolphin Project

Global patterns of marine turtle bycatch

An 18 yr study (1990-2008) yielded new results on marine turtle bycatch in fishing gear. The research, led by Dr. Bryan Wallace of Duke University, is based on more than 85,000 records of snared turtles. Despite this high number, reports covered less than 1% of all fishing fleets, with little or no information from small-scale fisheries around the world.

Dr. Wallace said the conservative estimation they made is in the order of millions of sea turtles killed in the past two decades. Six of the seven sea turtle types are on the IUCN Red List of Threatened Species. Especially high rates of by-catch were found in the Mediterranean and eastern Pacific.

By-catch remains a main threat for many other marine species such as sharks, cetaceans, seabirds.

Elisa Remonato

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Photo: Marine turtles drown when trapped in fishing gear (by Projeto Tamar Brazil)

Wallace B.P., Lewison R.L., McDonald S.L., McDonald R.K., Kot C.Y., Kelez S., Bjorkland R.K., Finkbeiner E.M., Helmbrecht S., Crowder L.B. 2010. Global patterns of marine turtle bycatch. Conservation Letters.
ABSTRACT -- Fisheries bycatch is a primary driver of population declines in several species of marine megafauna (e.g., elasmobranchs, mammals, seabirds, turtles). Characterizing the global bycatch seascape using data on bycatch rates across fisheries is essential for highlighting conservation priorities. We compiled a comprehensive database of reported data on marine turtle bycatch in gillnet, longline, and trawl fisheries worldwide from 1990 to 2008. The total reported global marine turtle bycatch was ∼85,000 turtles, but due to the small percentage of fishing effort observed and reported (typically <1% of total fleets), and to a global lack of bycatch information from small-scale fisheries, this likely underestimates the true total by at least two orders of magnitude. Our synthesis also highlights an apparently universal pattern across fishing gears and regions where high bycatch rates were associated with low observed effort, which emphasizes the need for strategic bycatch data collection and reporting. This study provides the first global perspective of fisheries bycatch for marine turtles and highlights region–gear combinations that warrant urgent conservation action (e.g., gillnets, longlines, and trawls in the Mediterranean Sea and eastern Pacific Ocean) and region–gear combinations in need of enhanced observation and reporting efforts (e.g., eastern Indian Ocean gillnets, West African trawls).

Orca: maybe more than one species

In recent years differences in foraging techniques, prey preferences, behaviour and minor physical features within different killer whale populations drove researchers to question the existence of only a single species. A new study provided genetic evidence supporting the idea that there may be several kinds of Orca.

Researchers mapped the genome of 139 tissue samples from different areas and they found clear differences. Three types of killer whales may be different species. Several other types may also represent separate species or subspecies, but additional analyses are required.

Should species diversity be confirmed by future studies, we hope the animals will be given common names less stupid than 'killer whale'.

Silvia Bonizzoni

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Photo: a killer whale spy hopping, by www.russianorca.com

For more information:
http://www.sciencedaily.com/releases/2010/04/100422121704.htm

Morin P.A., Archer F.I., Foote A.D., Vilstrup J., Allen E.E., Wade P., Durban J., Parsons K., Pitman R., Li L., Bouffard P., Abel Nielsen S.C., Rasmussen M., Willerslev E., Gilbert M.T.P., Harkins T. 2010. Complete mitochondrial genome phylogeographic analysis of killer whales (Orcinus orca) indicates multiple species. Genome Res DOI: 10.1101/gr.102954.109

Abstract -- Killer whales (Orcinus orca) currently comprise a single, cosmopolitan species with a diverse diet. However, studies over the last 30 years have revealed populations of sympatric "ecotypes" with discrete prey preferences, morphology and behaviors. Although these ecotypes avoid social interactions and are not known to interbreed, genetic studies to date have found extremely low levels of diversity in the mitochondrial control region, and few clear phylogeographic patterns worldwide. This low level of diversity is likely due to low mitochondrial mutation rates that are common to cetaceans. Using killer whales as a case study, we have developed a method to readily sequence, assemble, and analyze complete mitochondrial genomes from large numbers of samples to more accurately assess phylogeography and estimate divergence times. This represents an important tool for wildlife management, not only for killer whales but for many marine taxa. We used high-throughput sequencing to survey whole mitochondrial genome variation of 139 samples from the North Pacific, North Atlantic and southern oceans. Phylogenetic analysis indicated that each of the known ecotypes represents a strongly supported clade with divergence times ranging from approximately 150,000 to 700,000 years ago. We recommend that three named ecotypes be elevated to full species, and that the remaining types be recognized as subspecies pending additional data. Establishing appropriate taxonomic designations will greatly aid in understanding the ecological impacts and conservation needs of these important marine predators. We predict that phylogeographic mitogenomics will become an important tool for improved statistical phylogeography and more precise estimates of divergence times.

Dolphins not to be blamed

A new paper by Tethys authors has recently been published in Aquatic Conservation: Marine and Freshwater Ecosystems

Biomass removal by dolphins and fisheries in a Mediterranean Sea coastal area: do dolphins have an ecological impact on fisheries?

The study evaluates the biomass removed by of dolphins and the fishing fleet on a coastal ecosystem in the Ionian Sea. They found that the total biomass consumed annually by local dolphin populations – 15 short-beaked common dolphins and 42 common bottlenose dolphins – was 15.5 and 89.8 tonnes, respectively. The total biomass removed by the local fishing fleet (307 fishing boats) was 3469.2 tonnes, i.e. about 33 times greater than that removed by dolphins.

In other words, dolphins remove 2.9% of the total biomass and fisheries 97.1%.

The message is clear: dolphins in Mediterranean coastal waters are too often blamed for competing with fisheries and deemed responsible for reduced catches, but reality can be different when measured.

SB

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Figure (click to enlarge): Total biomass removed by dolphins and fisheries, as calculated by Bearzi et al. 2010; dolphins remove 2.9% of the total biomass, fisheries 97.1%.

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Bearzi G., Agazzi S., Gonzalvo J., Bonizzoni S., Costa M., Petroselli A. 2010. Biomass removal by dolphins and fisheries in a Mediterranean Sea coastal area: do dolphins have an ecological impact on fisheries? Aquatic Conservation. DOI: 10.1002/aqc.1123

ABSTRACT

1) Dolphins are often claimed to compete with fisheries, including through removal of substantial biomass. To calculate the biomass removed by fisheries and the degree of resource overlap with dolphins in a coastal area of Greece, estimates of dolphin abundance based on photographic capture–recapture were combined with an assessment of fishing effort and catch.

2) The estimated total biomass consumed annually by local dolphin populations – 15 short-beaked common dolphins and 42 common bottlenose dolphins – was 15.5 and 89.8 tonnes, respectively. The total biomass removed by the local fishing fleet (307 fishing boats) was 3469.2 tonnes, i.e. about 33 times greater than that removed by dolphins.

3) Dolphins removed 2.9% of the total biomass, fisheries 97.1%. Nine purse seiners (representing only 3% of the active fishing fleet) were responsible for 31.9% of biomass removal. Similarity of biomass composition between dolphins and fisheries was expressed by a Pianka index of 0.46 for common dolphins and 0.66 for bottlenose dolphins.

4) Overlap differed according to fishing gear. Common dolphin overlap was higher with purse seiners (0.82), and lower with beach seiners (0.31), bottom trawlers (0.11) and trammel boats (0.06). There was virtually no overlap with longliners (0.02). Bottlenose dolphin overlap was higher with trammel boats (0.89) and bottom trawlers (0.75), and lower with longliners (0.38), purse seiners (0.24) and beach seiners (0.18). There was minimal overlap (0.12) between the two dolphin species.

5) This study suggests that ecological interactions between dolphins and fisheries in this coastal area have minor effects on fisheries. Conversely, prey depletion resulting from overfishing can negatively affect dolphins. Fisheries management measures consistent with national and EU legislation are proposed to ensure sustainability and to protect marine biodiversity.

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A post by Carolyn Kraft

First gray whale in the Mediterranean Sea

A few days ago an adult gray whale (Eschrichtius robustus) has been spotted off Israel. Researchers from IMMRAC (Israel Marine Mammal Research and Assistance Center) photo-identified the animal and recorded behavioural data. They followed her for about two hours from Herzliya Marina (close to Tel Aviv) to Jaffa, where she was last spotted heading south.

Robert Brownell, a famous cetacean expert, said this is "The most amazing sighting in the history of whales". The sighting is indeed intriguing: first observation in Mediterranean waters and, because the animal must have come from the Atlantic Ocean where the species is believed to have been extinct for about 300 years, first time in Atlantic waters after so many years.

The grey whale might have travelled from the Pacific Ocean, the only area where the species is found, to the North Atlantic. Experts are now discussing which could be the most reasonable route: through the Panama Channel, the Northwest Passage or around Cape Horn?

Silvia Bonizzoni

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Photo: the flukes of the gray whale, by Aviad Schenin / IMMRAC

For more information:
http://www.petethomasoutdoors.com/2010/05/gray-whale-sighting-off-israel-a-truly-remarkable-event-.html
http://news.bbc.co.uk/earth/hi/earth_news/newsid_8672000/8672970.stm

An unforgettable 'Dalmatian' experience

This morning, after following a group of bottlenose dolphins for about an hour and a half we encountered a large group of Dalmatian pelicans Pelecanus crispus. In total, we estimated 24 individuals. Slowly approaching them with our research boat they allowed us to observe them from just a few meters away.

Dalmatian pelicans are large and elegant waterbirds which wingspan can easily reach about 3 m. In the past they were widely distributed throughout Europe and Asia. During the last century, however, their population dropped drastically and occurrence in Europe is now limited. The species is classified as Vulnerable in the IUCN Red List.

The islets in the lagoons Tsoukalio and Logarou in the northern Amvrakikos Gulf is one of the few European sites where they are regularly nesting.

Today we enjoyed the largest congregation of these magnificent animals registered since we started working in the Gulf, i.e. since 2001. Watching their majestic wings spreading right in front of us for takeoff left us all wide-eyed and speechless. Unforgettable!

Joan Gonzalvo

What does 'overfishing' mean?

In case 'overfishing' was still an obscure concept, a recent study makes it clearer.

The study is focused on the dramatic fish stock decline (cod, haddock, ling, halibut etc.) occurred in British Isles waters across 118 years, 1889-2007.

Researchers analysed landings per unit power and found that the availability of bottom-living fish for the fleet fell by 94%.

Modern high-tech fishing fleets of today require 17 times more effort to catch the same amount of fish as compared with the late 1800s.

According to Callum Roberts, one of the authors of this study, "This research shows that the state of UK bottom fisheries, and by implication European fisheries since the fishing grounds are shared, is far worse than we had thought."

With these findings, researchers underlined the need for urgent action to eliminate overexploitation of European fisheries and rebuild fish stocks to much higher levels of abundance than those that exist today.

SB

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Figure: Landings of bottom-living fish per unit of fishing power of large British trawlers from England, Wales and Scotland. Closed circles show landings per unit of fishing power into England and Wales, open circles show those into Scotland (from Thurstan et al. 2010).

The article:
Thurstan R.H., Brockington S., Roberts C.M. 2010. The effects of 118 years of industrial fishing on UK bottom trawl fisheries. Nature Communications 1, Article #:15 - doi:10.1038/ncomms1013
Abstract -- In 2009, the European Commission estimated that 88% of monitored marine fish stocks were overfished, on the basis of data that go back 20 to 40 years and depending on the species investigated. However, commercial sea fishing goes back centuries, calling into question the validity of management conclusions drawn from recent data. We compiled statistics of annual demersal fish landings from bottom trawl catches landing in England and Wales dating back to 1889, using previously neglected UK Government data. We then corrected the figures for increases in fishing power over time and a recent shift in the proportion of fish landed abroad to estimate the change in landings per unit of fishing power (LPUP), a measure of the commercial productivity of fisheries. LPUP reduced by 94%—17-fold—over the past 118 years. This implies an extraordinary decline in the availability of bottom-living fish and a profound reorganization of seabed ecosystems since the nineteenth century industrialization of fishing.

For more information:
http://news.bbc.co.uk/2/hi/science_and_environment/10096649.stm
http://www.independent.co.uk/news/science/fall-in-fish-stocks-far-worse-than-feared-study-shows-1962541.html

Overfishing in a coastal ecosystem in Greece

A collaboration between Tethys researchers and the University of British Columbia Fisheries Centre in Vancouver has recently resulted in a new paper: “Effects of local fisheries and ocean productivity on the northeastern Ionian Sea ecosystem”.

The study considers the time span 1964-2008 and 22 functional groups including dolphins, tuna, swordfish, monk seals, sea turtles as well as plankton, crustaceans and detritus.

Application of Ecopath with Ecosim highlighted a decline of top predators since the late 1970s. Decline of commercial fish resources, caused by overfishing, provoked a cascade-up effect through the ecosystem and had important negative consequences on species such as the short-beaked common dolphin - that almost vanished in this part of Greece.

The study was published in Ecological Modelling.

SB

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Piroddi C., Bearzi G., Christensen V. 2010. Effects of local fisheries and ocean productivity on the northeastern Ionian Sea ecosystem. Ecol. Model. doi:10.1016/j.ecolmodel.2010.03.002

Abstract -- To better understand the effects of fisheries and ocean productivity on the northeastern Ionian Sea we constructed an Ecopath with Ecosim model with 22 functional groups. Data on biomass, production/biomass, consumption/biomass, and diet for each group were estimated or extrapolated from the literature. Fisheries landings and discards were also included. Temporal trajectories were simulated using Ecosim. The model was fitted with time-series data for the most important groups from 1964 to 2006. Simulations highlighted a decline of top predators and of most of the commercial species since the late 1970s. The model shows that the decline of fish resources was mainly caused by an intensive fishing pressure that occurred in the area until the end of the 1990s and also by changes in primary production that impacted the trajectories of the main functional groups. In particular, simulated changes through time in PP impacted the abundance trends of all the commercial species, showing a cascade-up effect through the ecosystem. The application of Ecopath with Ecosim was a useful tool for understanding the trends of the main functional groups of the northeastern Ionian Sea. The model underlined that management actions are needed to restore and protect target species including marine mammals, pelagic and demersal fishes. In particular, measures to reduce overfishing, illegal fishing activities and to respect existing legislations are in need. Moreover, the adoption of marine protected areas could be an effective management measure to guarantee prey survival and to sustain marine predators.

CSI: Crime Scene Investigation (in the Pliocene)

Four million years ago a Pliocene dolphin Astadelphis gastaldii died. Its skeleton was recovered, then stored in an Italian museum where it lied unstudied for more than a century... until some researchers decided to have a deep look at it. The result was amazing.

Carved into the old dolphin bones, researcher Giovanni Bianucci and his colleagues from the University of Pisa, Italy, found visible shark bite marks. By carefully studying the morphology and disposition of the tooth marks, the authors managed to attribute the bites to the predation of a single shark, most likely a Cosmopolitodus hastalis.

Then Bianucci and colleagues reconstructed what probably happened during the attack:

"… the shark attached from below, biting into the abdomen. Caught in the powerful bite, the dolphin would have struggled, and the shark probably detached a big amount of flesh by shaking its body from side to side. The bite would have caused severe damage and intense blood loss, because of the dense network of nerves, blood vessels and vital organs in this area. Then, already dead or in a state of shock, the dolphin rolled onto its back, and the shark bit again, close to the fleshy dorsal fin".

This study reveals how much can be inferred from skeletal remains, and offers a glimpse on ancient animal behaviour.

Silvia Bonizzoni

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Drawing: Attack sequence as hypothesized by Bianucci et al.
A) the shark approached the prey; B) the shark bitted the abdomen of the dolphin; C) the dolphin, mortally injured, rolled to the left and the shark bitted adjacent to dorsal fin area.

For more information:
http://www.sciencedaily.com/releases/2010/03/100316142519.htm

Bianucci G., Sorce B., Storai T., Landini W. 2010. Killing in the Pliocene: shark attack on a dolphin from Italy. Palaeontology 53(2):457–470.
Abstract - Shark bite marks, including striae, sulci and abrasions, in a well-preserved fossil dolphin skeleton referred to Astadelphis gastaldii (Cetacea, Delphinidae) from Pliocene sediments of Piedmont (northern Italy), are described in detail. The exceptional combination of a fossil dolphin having a significant part of the skeleton preserved and a large number of bite marks on the bones represents one of the few detailed documentations of shark attack in the past. Most bite marks have been referred to a shark about 4 m long with unserrated teeth, belonging to Cosmopolitodus hastalis, on the basis of their shape and their general disposition on the dolphin skeleton. According to our hypothesis, the shark attacked the dolphin with an initial mortal bite to the abdomen from the rear and right, in a similar way as observed for the living white shark when attacking pinnipeds. A second, less strong, bite was given on the dorsal area when the dolphin, mortally injured, probably rolled to the left. The shark probably released the prey, dead or dying, and other sharks or fishes probably scavenged the torn body of the dolphin.

Foodball team

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.

Silvia Bonizzoni

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Photo: a fish ball, at http://www.sea-way.org/blog/Beneath14.JPG

For more information:
http://news.bbc.co.uk/2/hi/science/nature/8530116.stm

Bottlenose dolphins as human-health sentinels?

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.

SB

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For more information:
http://www.noaanews.noaa.gov/stories2010/20100218_dolphins.html
http://www.sciencedaily.com/releases/2010/02/100218173114.htm