grey whale diet

Still, they may find and eat schooling squid, krill, crab larvae, herring eggs, ghost shrimp, and small bait fish such as capelin. But some whales are now eating herring and krill as well, just like their baleen whale relatives, which include the humpback and the blue.Some whales are even dropping out of the migratory rat race. Gray whales are opportunistic feeders and their diet include a wide range of crustaceans including ghost shrimp and amphipods, as well as herring eggs, polychaete worms, and various kinds of … That would have left bottlenecking evidence in their DNA.”.Bottlenecking is when populations drop so low that inbreeding becomes common, decreasing the genetic diversity in the species and making them less able to adapt to environmental change.The new assessment is good news for gray whales, which appear to have “a lot more evolutionary plasticity than anyone imagined,” Lindberg said.

He and Lindberg urge other scientists to focus on the historical ecology of species to fully understand their complex interactions with a changing environment.“We really make a lot of conservation decisions without a lot of data,” Lindberg said. They thought that an understanding of how gray whales adapted to climate change over the past 3 million years, the period called the Pleistocene, might provide insight into how they will adapt to climate change today.Since gray whales arose – the oldest fossils date from 2.5 million years ago – Earth has gone through more than 40 major cycles of warming and cooling, each of which significantly affected the world’s flora and fauna. That estimate, by Stephen Palumbi of Stanford University and his collaborators, was based on an analysis of gray whale genetic diversity.The numbers clash, however, with claims by some ecologists that populations of between 15,000 and 20,000 are likely the most that the Pacific Coast – specifically along the whales’ 11,000 kilometer (6,900 mile) migratory route from Baja California to the Bering Sea – could support, today or in the past.“Our data say that, if the higher estimates are right, gray whales would have made it through the Ice Ages in numbers sufficiently large to avoid bottlenecking,” Pyenson said. Pyenson and Lindberg looked closely at only the past 120,000 years, during which Earth transitioned from a warm period to a glacial period and then to today’s warmer climate.During the glaciated period, ocean water became locked up in land-based glaciers, drawing down the sea level by about 120 meters, or nearly 400 feet. During the breeding season, it is common for females to have several mates. The marine realm, however, experienced almost no extinctions and very few new originations during that same period.The California, or eastern, gray whale, one of two surviving populations of gray whale, can be traced back about 150,000-200,000 years.
This single ovulation event is believed to coincide with the species’ annual migration patterns, when births can occur in warmer waters. All rights reserved.Gray whales likely survived the Ice Ages by changing their diets,Bone bed tells of life along California’s ancient coastline,Whales evolved biosonar to chase squid into the deep,Ancient whale fall found from Año Nuevo Island. During the last glacial cold spell, between 50,000 and 10,000 years ago, most of the large terrestrial mammals disappeared through a combination of climate change and human depredation, Lindberg noted. Gray whales eat very little while on migration. Prominent among the amphipods is Ampelisca macrocephala which makes up 95% of the whale’s diet.

If gray whales also exploited non-benthic organisms, such as krill, the populations could have been even higher.If gray whales do respond well to the rising temperatures and sea levels predicted for the future, that may not be true for the birds and other marine mammals that feed in the Bering Sea, one of the most productive marine ecosystems during the summer.“If this environment disappears in glacial maxima, we really need to rethink what we know about the ecological history of all the other organisms that make a living in the Bering Sea,” Pyenson said. “If gray whale populations were at the lower levels, they would only have squeaked through the ice ages with populations of hundreds or a few thousand. In general, baleen whales feed low on the food chain, primarily eating zooplankton and small fishes, which they encounter in large swarms or schools. Gray whales can engage in benthic feeding no deeper than about 75 meters (250 feet), Pyenson said, and during the glacial period, waters offshore of the Bering platform would have been much deeper than that.“If gray whales were primarily feeding on the Bering Platform, it’s hard to see how they could have avoided a population crash,” Lindberg said.By calculating the amount of food lost because of dropping sea levels, and combining this with estimates of the food needed to keep a whale alive, the two researchers calculated the impact of global cooling on gray whale populations and the populations that would have had to exist in order for the whales to survive.They concluded that populations would have had to have alternative feeding modes sufficient to support a population of around 70,000 during warm periods so that population drops during glacial periods wouldn’t be below 5,000-10,000 whales. Depending on species, th…

Right whales eat zooplankton (animal plankton). Most fem… Females show highly synchronized reproduction, undergoing oestrus in late November to early December.

According to Lindberg, gray whales were once thought to feed only by suctioning seafloor sediment and filtering out worms and amphipods – so-called benthic organisms. Rorquals generally eat larger prey than do right whales.

One group hangs out year-round off Vancouver Island in Canada, where they chase herring and krill.“We propose that gray whales survived the disappearance of their primary feeding ground by employing generalist filter-feeding modes, similar to the resident gray whales found between northern Washington State and Vancouver Island,” the scientists wrote in their paper.“A combination of low population numbers and a species migrating between places where humans didn’t bother them gave us the impression that gray whales have a stereotypical migratory and feeding behavior that may not be historically correct,” Lindberg said.The new population numbers accord with a 2007 estimate that the California gray whale population was likely 76,000 to 120,000 before humans began hunting them.

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