\nToday we saw Risso’s<\/a>, common<\/a> and bottlenose dolphins.<\/a> We are always happy to find all kind of species but seeing Rissos is always cause of joy as we don’t see them that often, even thought it is considered as a resident specie of the A\u00e7ores.<\/div>\n
\n<\/div>\n
\nHere some detailed information about our beautiful Risso’s:<\/b><\/div>\n
\n<\/div>\n
\n<\/div>\n
\n<\/div>\n
\nThe Risso\u2019s dolphins (in Portuguese known as Grampo) <\/span>is the fifth largest of the delphinids and<\/span>
\none of the 3 resident species in Azores.<\/span>
\nIts anterior body is extremely robust, tapering to a relatively narrow tail
\nstock and its dorsal fin is one of the tallest in proportion to body length of
\nany cetacean, exceeded only by that of the adult male killer whale (Orcinus
\norca<\/i>). <\/span>A cetacean that can reach 4 meters long and weight as
\nmuch as 500kg. <\/span>They have a morphological characteristic
\nthat results in an adaptation to the feed, which consists in a square design of
\nthe head that facilitates the catching of squids.<\/span> <\/span>They c<\/span>an be found in a wide range of colors, because they are
\nborn with a dark color and as they grow older, they gain a whiter color and the
\nbody full of scars (<\/span>Colour patterns change dramatically
\nwith age<\/span>). <\/span>Older
\nanimals can appear completely white on the dorsal surface. This is a widely
\ndistributed species, inhabiting deep oceanic and continental slope waters 400-
\n1,000 m deep from the tropics through the temperate regions in both
\nhemispheres. Sighting records indicate this species occurs roughly between 60\u00b0N
\nand 60\u00b0S latitudes, where surface water temperature are above 10 \u00b0C. Risso’s
\ndolphins are pelagic, mostly occurring seaward of the continental slope. They
\nfrequent subsurface sea-mounts and escarpments where they are thought to feed
\non vertically migrant and mesopelagic cephalopods. In the North Atlantic and
\nwestern Pacific, there appears to be a summer calving peak and a winter calving
\npeak in the eastern Pacific. They are are often seen surfacing slowly, although
\nthey can be energetic, sometimes breaching or porpoising, and occasionally
\nbowriding. Normally Risso\u2019s associate in groups tend to be small to moderate in
\nsize, from 2-100 individuals, averaging 30 animals, but groups of up to 4,000
\nhave been reported, presumably in response to abundant food resources. Risso’s
\ndolphins prey on a mix of neritic, oceanic, and occasionally bottom dwelling
\ncephalopods and they normally feed at day. Risso\u2019s are often seen surfacing
\nslowly, although they can be energetic, sometimes breaching or porpoising, and
\noccasionally bowriding <\/span><\/div>\n
\none of the 3 resident species in Azores.<\/span>
\nIts anterior body is extremely robust, tapering to a relatively narrow tail
\nstock and its dorsal fin is one of the tallest in proportion to body length of
\nany cetacean, exceeded only by that of the adult male killer whale (Orcinus
\norca<\/i>). <\/span>A cetacean that can reach 4 meters long and weight as
\nmuch as 500kg. <\/span>They have a morphological characteristic
\nthat results in an adaptation to the feed, which consists in a square design of
\nthe head that facilitates the catching of squids.<\/span> <\/span>They c<\/span>an be found in a wide range of colors, because they are
\nborn with a dark color and as they grow older, they gain a whiter color and the
\nbody full of scars (<\/span>Colour patterns change dramatically
\nwith age<\/span>). <\/span>Older
\nanimals can appear completely white on the dorsal surface. This is a widely
\ndistributed species, inhabiting deep oceanic and continental slope waters 400-
\n1,000 m deep from the tropics through the temperate regions in both
\nhemispheres. Sighting records indicate this species occurs roughly between 60\u00b0N
\nand 60\u00b0S latitudes, where surface water temperature are above 10 \u00b0C. Risso’s
\ndolphins are pelagic, mostly occurring seaward of the continental slope. They
\nfrequent subsurface sea-mounts and escarpments where they are thought to feed
\non vertically migrant and mesopelagic cephalopods. In the North Atlantic and
\nwestern Pacific, there appears to be a summer calving peak and a winter calving
\npeak in the eastern Pacific. They are are often seen surfacing slowly, although
\nthey can be energetic, sometimes breaching or porpoising, and occasionally
\nbowriding. Normally Risso\u2019s associate in groups tend to be small to moderate in
\nsize, from 2-100 individuals, averaging 30 animals, but groups of up to 4,000
\nhave been reported, presumably in response to abundant food resources. Risso’s
\ndolphins prey on a mix of neritic, oceanic, and occasionally bottom dwelling
\ncephalopods and they normally feed at day. Risso\u2019s are often seen surfacing
\nslowly, although they can be energetic, sometimes breaching or porpoising, and
\noccasionally bowriding <\/span><\/div>\n
\nThe most threats of Risso\u2019s are:<\/span><\/div>\n
\n\u00b7
\n<\/span><\/span><\/span>Direct
\ncatch <\/span><\/b>(in Sry Lanka); Incidental catch (<\/b><\/span>southern Caribbean, the Azores, Peru);<\/span><\/span><\/div>\n
\n<\/span><\/span><\/span>Direct
\ncatch <\/span><\/b>(in Sry Lanka); Incidental catch (<\/b><\/span>southern Caribbean, the Azores, Peru);<\/span><\/span><\/div>\n
\n\u00b7
\n<\/span><\/span><\/span>Culling
\n<\/span><\/b>(<\/span>Off Japan, Risso’s
\ndolphins were killed in the drive fishery (oikomi<\/i>) in response to
\ncompetition with commercial fisheries);
\n<\/b><\/span><\/span><\/div>\n
\n<\/span><\/span><\/span>Culling
\n<\/span><\/b>(<\/span>Off Japan, Risso’s
\ndolphins were killed in the drive fishery (oikomi<\/i>) in response to
\ncompetition with commercial fisheries);
\n<\/b><\/span><\/span><\/div>\n
\n\u00b7
\n<\/span><\/span><\/span>Pollution
\n<\/span><\/b>(<\/span>Increasing levels of
\nplastics and other refuse at sea may pose a threat to wild populations:
\nNecropsies of specimens from Japan revealed that they had eaten foreign
\nmaterials such as plastic bags, soda cans, and pieces of rope, which may have
\nbeen fatal);<\/span><\/span><\/div>\n
\n<\/span><\/span><\/span>Pollution
\n<\/span><\/b>(<\/span>Increasing levels of
\nplastics and other refuse at sea may pose a threat to wild populations:
\nNecropsies of specimens from Japan revealed that they had eaten foreign
\nmaterials such as plastic bags, soda cans, and pieces of rope, which may have
\nbeen fatal);<\/span><\/span><\/div>\n
\n\u00b7 <\/span><\/span><\/span>Noise pollution <\/span><\/b>(<\/span>In early 2004 and in 2005, several unusual stranding
\nevents including Risso\u2019s dolphins occurred in Taiwan during a period when
\nlarge-scale naval exercises were conducted in and on nearby waters)<\/span><\/span><\/div>\n
\nevents including Risso\u2019s dolphins occurred in Taiwan during a period when
\nlarge-scale naval exercises were conducted in and on nearby waters)<\/span><\/span><\/div>\n
\n<\/div>\n
\nThe IUCN lists G. griseus <\/i>as “Least
\nConcern” <\/span><\/div>\n
\nConcern” <\/span><\/div>\n
\n(Text by Rafael Martins)<\/span><\/span><\/div>\n
\n Some photos of today’s encounter with the Risso’s dolphins<\/span><\/u><\/span><\/span><\/div>\n
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