Species News

Our final Risso's dolphin blog takes us on our first (and last) journey to the southern hemisphere to meet researcher Oli Yates who is as far as literature suggests, conducting the only dedicated southern hemisphere research on this species. Being able to understand more about Risso's dolphins in different areas of their distribution is crucial (and fascinating) to the future conservation of the species and WDCS is proud to support Oli in his endeavours ... and after reading his blog, I'm off to book my ticket to Chile!

Enjoy ... and come back in October for some harbour porpoise madness!!

At eight thirty on Sunday morning the phone rang. Who could possibly be calling at this time on a Sunday I wondered aloud? It might be family, calling from England and getting the time difference wrong… In Chile we are four hours behind GMT but with daylight saving hours we end up with three to five hours difference – who can keep track?

I answer the phone and it’s not family but Señora Ana María, who lives on the eighth floor of the department block that looks over the bay. “Hello, good morning!” she says happily, “the dolphins are in the bay again, lots of them today and they seem very active!”

Since we began this project we have depended on volunteers from the local village to help us monitor the presence of Risso’s dolphin in La Herradura Bay (Horse Shoe Bay). Several people whose houses look out over the bay let us know when they see the dolphins, which greatly supports our opportunistic data collection.

The bay is about two kilometres across and is enclosed on all sides but for a narrow entrance that opens out into the Pacific Ocean. The calm waters of the bay allow us to use kayaks to approach the dolphins and take photos for the study without impacting the population with noise from an outboard motor.

Once the dolphins arrive I know I have about an hour to get the kayak in the water and paddle out to them. The group today included around 65 individuals, which is about average for the population we are studying in Chile. On some days two or three different groups come together and all of a sudden you can find yourself in the middle of 300 or so dolphins!

Whilst in the kayak the dolphin behaviour is typically inquisitive, they frequently pass under the kayak looking up through the clear water at what must look like a giant banana floating at the surface (the kayak is yellow!). By staying close to the centre of the bay, I can generally wait while they pass by repeatedly as they relax and socialise in the relatively shallow water.

This way we sample (take photos of) as much of the group as possible while they pass by without having to exert too much energy following them. This is greatly facilitated when the group is calm as they move much more slowly, so it is in our best interest to avoid any disturbance.



Today they only stayed for 45 minutes while they breached and slapped the water with their flukes. The Risso’s tend to breach often, almost always turning in the air to impact with the water on their side. They continued to display like this as they left the bay heading north and left me to go and find my breakfast.

Taking our leave of the Mediterranean, we head south to meet up with Risso's researcher, Karin Hartman from Nova Atlantis Foundation. Karin is studying the Risso's dolphins to be found in and around the island archipelago known as the Azores. Once again I have to note how jealous i am of their weather conditions (that make for outstanding photographs) ... I guess that's what being closer to the equator does for you!!

Hello!

A message from a big rock in the Atlantic Ocean: Pico Island, Azores archipelago.

I am currently living here to study Risso’s dolphins and am conducting a PhD project titled: “Long term patterns of social behaviour and ecology of Risso’s dolphins, (Grampus griseus) off Pico Island. More than a decade ago we “discovered” a Risso dolphin hot spot by chance in the Bay of Ribeiras off the south coast of Pico. A Dutch based Foundation was created two years later in order to study and protect this cetacean rich area. Besides Risso’s dolphins, a variety of about 20 other cetacean species can be observed both from land and at sea. The reason for this species’ richness is related with the presence of food! The upwelling from deep-sea waters against the steep marine (volcanic) walls, the nutrient run off from the Islands itself and the circulation of the Gulf Stream along the Islands in general provides and creates food in a relatively poor high sea. In general we started working on Risso’s since there is not a lot know of their social behaviour and life history patterns and they seemed to be one of the most seen species in our study area.

Risso’s dolphins feed predominantly on squid just like pilot, sperm and beaked whales. In the Bay and around the Azores, it seems that there is food for all, and everybody can be observed feeding at their own “depth” line. Due to the availability of prey in a relatively deep but coastal place we were able to observe the animals (land-based) from dawn to dusk, following them at rather strange hours. This method gave us general insights in how and when the dolphins use the area.

But to answer more detailed questions like: How do males and females life? How is their social structure? Who is with whom? When and where are they here? How long stays a calve with the mother? - you need to go to the ocean and identify the dolphins. Photo Identification has therefore been our main research method and after the digital camera’s were introduced we were able to study the group compositions directly. Until today, we have identified 1248 individuals during eleven years of research. This is the largest ID catalogue in the world for this species. After taking thousands of pictures, cropping the dorsal fins, matching these with the catalogue and finally analyzing the connecting behavioral and spatial data, it seems that Risso’s dolphins off Pico Island cluster in highly stable pods of 3 to 12 individuals.





Since the presence of calves of most long term followed pods were missing we assumed that these animals were males. These pods may work together (second order alliances) with other stable groups but mainly if they feel the need to defend their habitat towards other squid eating species. This already indicates that we are dealing with a resident population! But… many times we see some guys hanging behind groups of females. Sometimes they escort a female or a female and calf. When the female is fertile more male pods may come and sometimes they fight and get very wild. During these social events they wound each other and leave their tooth marks in the rival’s or the female’s skin. In general the females seem to life separated from the males, clustering together in nursery groups. They babysit for each other when it’s time to forage in the deep. Sometimes one female is taking care of 3 calves! A newborn baby is a fragile and under serious threat: pelagic sharks do attack and eat them! The coastal waters around Pico seems a very important nursery ground since they also find some shelter (to lactate and rest) and have food available in near shore and shallow waters.





I am currently trying to come up with proof and numbers that we indeed have a resident population around Pico. This is very important since Risso’s and 4 other species’ are locally targeted for swimming with dolphin tourism. In other words: our residents are frequently exposed to very close and long encounters of the commercial whale watching industry. In another study we found that the Risso’s change their resting schedule during high season: They rest only between 13:00 and 15:00, when all boats are back in the harbours for lunch… In low season they rest at other hours, over the day. Since this species’ is feeding mainly at night they need to rest during the day. Wasting their energy by travelling away from vessels may have a serious impact on their day to day survival.





In general Risso’s deserve special attention: They show the social aspects of bottlenose dolphins and chimps, are driven by the diet of a deep diving beaked whale and have their own special looks! Because they are so well recognizable and tolerant we have been able to study them intensively and part by part the secrets of their complex social life are becoming visible. And of course: more questions are arising since we cannot follow them to the bottom of the ocean or on their inner or outside island migrations.

Keep on Gramping!

Greetings form Pico,
Karin
Nova Atlantis Foundation

As promised, I now hand over to Sabina Airoldi from Tethys Research Institute in Italy, who explains in more detail the work of her and her colleagues on Risso's dolphins in the Mediteranean Sea. Having had the pleasure of joining them in the field during previous seasons, I can attest to the quality and professionalism with which they operate. I can also only dream of similar environmental conditions within which to conduct our own Risso's research ...! Scotland may be beautiful and magical but it's not the tropics - at least not for more than a few days a year!

Since 1990 the Tethys Research Institute has been carrying out a long term project focusing on the ecology of the cetacean species living in the Pelagos Sanctuary, an international Sanctuary for the protection of the Mediterranean marine mammals. In order to provide a scientific basis for management recommendations to the policy makers, the final goal of Tethys' research is to gain a basic understanding of this complex ecosystem, studying the distribution, abundance, habitat use and ecology of the different cetacean species inhabiting the Ligurian Sea, together with their social organization, behaviour and foraging ecology. One of the eight species investigated is the Risso’s dolphin (Grampus griseus).

In the Mediterranean Sea Risso’s dolphins are relatively widespread, but not abundant and their occurrence can be unpredictable. This factor, together with generally low densities, has precluded sustained and focused investigations, therefore, information on this cetacean species remains relatively scant and the distribution, ecology, status and trends of this species in the Mediterranean remain somewhat mysterious. A regional IUCN Red List assessment workshop in March 2006 concluded that the Mediterranean subpopulation is Data Deficient.

Risso's dolphins are usually about 3 m long but can reach 4 m, with no significant sexual size dimorphism. The adults are heavily scarred, mostly from superficial wounds caused by the teeth of conspecifics. Depigmentation can persist for a long time, and this facilitates species identification at sea and also allows single individuals to be photo-identified. During the surveys conducted in the western Ligurian Sea by the Tethys Research Institute over the last 20 years, more than 350 individuals have been photo-identified in an area of approximately 24.000 km2. These data suggest relatively wide movements but do not preclude some degree of fidelity or regular use of specific areas.





Risso’s dolphins can be energetic and active at the sea surface, breaching, porpoising and occasionally riding the bow of a vessel. In the Mediterranean Sea they are often seen ‘head-standing’, i.e. staying almost motionless in a vertical position with the tail stock out of the water, sometimes for 10-20 sec. The reason behind this behaviour is unknown. In the Ligurian Sea, during daytime, Tethys researchers observed Risso’s dolphins moving mostly at about 6-7 km h-1, with surfacings of about 7-15 sec followed by dives lasting 5-7 min, and occasionally longer.







The sound repertoire of Risso’s dolphins includes a variety of pulsed and whistle-like sounds, used for both echolocation and communication. Echolocation clicks in free-ranging animals average 40 ?s with peak frequencies around 50 kHz and source levels of 202–222 dB re 1 ?Pa. Risso’s dolphins may be capable of hearing frequencies above 100 kHz.

Based on mitochondrial DNA analyses, Risso’s dolphins in the Mediterranean Sea are genetically differentiated from those in U.K. waters, with limited gene flow between the two areas and genetic analyses on 33 samples from the Mediterranean region (27 collected by Tethys from the Ligurian Sea) suggested relatively high diversity.

Risso’s dolphins have reduced dentition that is specialised to capture cephalopods, their main prey. They seem to feed predominantly during the night, probably to take advantage of the circadian vertical movements of their prey. Diet consists primarily of cephalopods, with a clear preference for mesopelagic squids.

In the Mediterranean Sea, similarly to other areas around the world, Risso’s dolphins prefer steep slopes and submarine canyons and are observed over mean bottom depths of 1280 m. Most observations come from the northwestern part of the basin. During the summer Risso’s dolphins are found regularly in continental slope waters of the Ligurian-Corso-Provençal basin, in the Alborán Sea and in the Gulf of Vera, where their range includes deep offshore waters. In the eastern Mediterranean, most information comes from the Greek seas.

In the western Ligurian Sea, where the continental shelf is particularly narrow, Risso’s dolphins have been described to be distributed along steep sections of the upper continental slope, a few km from the coast, and the Tethys researches observed this species at depths ranging between 370 and 1100 m. Their occurrence in this area during the summer months has not changed across years or months, but encounter rates were higher during certain shorter intervals, suggesting some sort of ‘transient’ use of the study area. This may indicate a strategy to exploit the temporary availability of food resources induced by zooplankton accumulation. Tethys researchers also found a correlation between Risso’s dolphin presence and stormy sea conditions in the preceding days, and speculated that moving along the slope area would be an efficient strategy to exploit prey attracted by the wind-driven accumulation of zooplankton. The frequency of occurrence of Risso’s dolphins in and near the Pelagos Sanctuary was similarly higher near the 1000 m isobaths, but sightings were also made far offshore and in deeper pelagic waters.

Risso’s dolphin groups tend to be small to moderate in size (up to around 100 individuals), averaging perhaps 30 animals. Risso's dolphins in the Ligurian Sea were characterised by low levels of relatedness, and kin-based affiliations were found only within groups of females.



A variety of human activities threaten cetaceans and many of those activities are expected to increase in the foreseeable future. In the Mediterranean, most bycatch of Risso’s dolphins is caused by pelagic gillnets (also called driftnets). These are large, floating nets that target primarily swordfish and tunas. Driftnets can be up to 50 km long and hang vertically 20-30 m from the surface. Because these nets indiscriminately kill protected species such as whales, dolphins, sharks, turtles, rays and sea birds, they have been banned in the European Union (EU) since 2002. The ongoing illegal use of driftnets in several parts of the Mediterranean, including areas where Risso’s dolphins occur, means that incidental mortality almost certainly continues at some scale. Risso’s dolphin mortality in driftnets deployed by the Italian fleet was significant and probably unsustainable in the early 1990s and it likely remains high, although there have been no focused investigations in recent years.

In the Mediterranean Sea there has been a great expansion of recreational boat traffic and shipping in recent decades and there is growing evidence that prolonged direct disturbance and noise caused by boat traffic can affect the behaviour and habitat use of cetaceans. However, the implications for disrupting behaviour and excluding Risso’s and other dolphins from important habitat have never been investigated. Noise from human activities including seismic surveys, marine construction and the use of military or other sonars is a cause for concern for Risso’s dolphins and other cetacean species. However, so far no deaths of Risso’s dolphins have been linked definitively to noise.



As a predominantly teuthophagous species that feeds in continental slope waters, the Risso’s dolphin may be less vulnerable to the prey depletion caused by overfishing in the Mediterranean Sea, since most fishing occurs in continental shelf waters and targets bony fishes. Few of the main cephalopod prey species of Risso’s dolphins are commercially important. Two factors, however, are of concern: 1) the possible expansion of Mediterranean deep-water fisheries and 2) the tendency of fisheries to target species lower and lower in the food web, as populations of higher trophic level species are depleted. These trends could lead to reductions in key prey populations or otherwise disrupt food webs in continental slope waters, where Risso’s dolphins mainly forage.



Toxic contamination can affect reproduction and health at the individual and population level. There is evidence to suggest a causal link between organochlorine exposure and reproductive, endocrine and immunological disorders in cetaceans. Levels of organochlorine compounds in Risso’s dolphins from the Mediterranean Sea have been described as ‘high’, and so have levels of trace metals. It is uncertain, however, whether recent and current levels of exposure to any of these contaminants are affecting Risso’s dolphins in the region. Cephalophods in the stomach of one Risso’s dolphin stranded in Corsica had mercury concentrations about 25 times higher than those of fish found in the stomachs of other delphinid species in the same sample, and 50 times higher than concentrations recommended for human consumption.

Some of the effects of global warming have become dramatically apparent in recent years and they have the potential to affect a range of biological processes and cause significant shifts in marine and other biota. Increased temperature has been observed in Mediterranean deep and surface waters and there is increasing evidence of biological responses to such warming. The effects of climate change on cetaceans, often mediated via changes in prey abundance and distribution, may include shifts in distribution and grouping behaviour but it is uncertain how they might apply to Risso’s dolphins.

Data on abundance, distribution, movements, population dynamics and trends, as well as better information on threats, are still needed to inform conservation efforts and ensure that Risso’s dolphins remain a functioning part of marine ecosystems in the Mediterranean region.

Text extracted from: Bearzi, G., Reevs, R., R., Remonato, E., Pierantonio, N., Airoldi, S. Risso’s dolphin Grampus griseus in the Mediterranean Sea. Mammal. Biol. (2010), doi:10.1016/j.mambio.2010.06.003

I am writing this blog with a very heavy heart. Two days ago we attended the live stranding of a juvenile Risso's dolphin here on the Isle of Lewis and despite our best efforts the decision was taken (by the vet at the scene) to end the animals life. Attending the post-mortem the following day was difficult but important. The chances of us being at the right place at the right time for this dolphin were very slim (it was only due to high winds and dogs to walk that we were on that particular beach) but we intend to make sure that lessons are learnt from this unfortunate tragedy.

Further details can be found in our fieldwork blog.

This incident has only strengthened our resolve as to the importance of studying this population of animals. No population-level information is available on trends in abundance, incidental mortality rates or even the distributional range of the populations of Risso’s dolphins in Scotland or the UK. Risso’s dolphins are oceanic dolphins that feed primarily on squid, octopus and cuttlefish and seem predominantly to feed in deeper waters. They are often found around interesting topographical features, where productivity is enhanced by mixing waters, such as seamounts and escarpments. The species only inhabit a handful of coastal sites where the continental shelf is narrow and close to shore and because Scotland is in the process of designating a network of marine protected areas by 2012, to meet its international obligations – we think this population of Risso’s deserves to be included!

More information on our research here can be found by following the fieldwork blog!

More photos can also be found on the fieldwork blog ... but i'll leave you with a selected few of the best from here so far .... !

Next time we'll hear from researchers studying Risso's dolphins in the Mediterranean Sea.

Welcome to September's Species of the Month - the Risso's dolphin!

I'm aware that we're already almost a week into September but i have a very good reason for being a bit late to start this particular blog ... I'm currently in the field in the northwest corner of Scotland (on the beautiful Isle of Lewis) conducting our very own WDCS Risso's research project and they've been keeping us busy! More on our work in a later blog and in the meantime, check out our blog from the field!

Risso's dolphins or Grampus griseus (always makes me think of a grizzly, grey Grandpa!) are possibly one of the most charismatic of all the dolphin species. They are large dolphins with no perceptible beak, and as their name implies the dominant colour is grey, although this changes with age as the animal becomes paler over time. A very sociable animal, the Risso's dolphin bears the scars from it's close interactions with fellow Risso's. Tooth rake marks and other scratches make individuals easy to recognise helping researchers learn more about these enigmatic creatures lives.

Although the Risso's dolphin is one of the less well studied odontocetes due to it being a predominantly offshore species (their main prey item is squid), there are several long-term projects focusing on the species and over the next month we'll be hearing from all of the researchers from various locations around the world, including of course from here in Scotland.

Interestingly, the first dolphin in the world to be protected by law was a Risso's dolphin called Pelorus Jack. Pelorus Jack accompanied ships travelling between Wellington and Nelson in New Zealand and was first noticed in 1888 when he joined a steamer bound for Nelson. Pelorus Jack spent the next 24 years escorting boats from Pelorus Sound to the treacherous French Pass and due to the fact that in the early 1900s someone fired at him from a steamer an Order in Council was drawn up in 1904, declaring him protected. His ultimate fate was never established. Rumours told of Norwegian whalers killing him, but others claimed to have seen his body on a beach.

I'll leave you for the moment to read up on the background to this species and be back soon with our first research installment.