Editing Whale (section)

==Ecology==
===Foraging and predation===
{{See also|Beluga whale#Predation}}

[[File:Polar Bear ANWR 10.jpg|thumb|upright|[[Polar bear]] with the remains of a [[beluga whale|beluga]]]]

All whales are carnivorous and predatory. Odontocetes, as a whole, mostly feed on [[fish]] and [[cephalopod]]s, and then followed by [[crustacean]]s and [[bivalve]]s. All species are generalist and opportunistic feeders. Mysticetes, as a whole, mostly feed on [[krill]] and [[plankton]], followed by crustaceans and other [[invertebrate]]s. A few are specialists. Examples include the [[blue whale]], which eats almost exclusively krill, the [[minke whale]], which eats mainly schooling fish, the [[sperm whale]], which specialize on [[squid]], and the grey whale which feed on bottom-dwelling invertebrates.{{sfn|Goldbogen|2010}}{{sfn|Nemoto et al.|1988|pp=292–296}}{{sfn|Lydersen et al.|1991}} The elaborate baleen "teeth" of filter-feeding species, mysticetes, allow them to remove water before they swallow their planktonic food by using the teeth as a sieve.{{sfn|Modern Marvels|2007}} Usually, whales hunt solitarily, but they do sometimes hunt cooperatively in small groups. The former behaviour is typical when hunting non-schooling fish, slow-moving or immobile invertebrates or endothermic prey. When large amounts of prey are available, whales such as certain mysticetes hunt cooperatively in small groups.{{sfn|Defenders of Wildlife}} Some cetaceans may forage with other kinds of animals, such as other species of whales or certain species of [[pinnipeds]].{{sfn|Klinowska|1991|pp=122–162}}{{sfn|Riedman|1991|p=168}}

Large whales, such as mysticetes, are not usually subject to predation, but smaller whales, such as monodontids or ziphiids, are. These species are preyed on by the orca. To subdue and kill whales, orcas continuously ram them with their heads; this can sometimes kill bowhead whales, or severely injure them. Other times they corral the narwhals or belugas before striking. They are typically hunted by groups of 10 or fewer orcas, but they are seldom attacked by an individual. Calves are more commonly taken by orcas, but adults can be targeted as well.{{sfn|Morrel|2012}}

These small whales are also targeted by terrestrial and [[Pagophily|pagophilic]] predators. The polar bear is well adapted for hunting Arctic whales and calves. Bears are known to use sit-and-wait tactics as well as active stalking and pursuit of prey on ice or water. Whales lessen the chance of predation by gathering in groups. This however means less room around the breathing hole as the ice slowly closes the gap. When out at sea, whales dive out of the reach of surface-hunting orcas. Polar bear attacks on belugas and narwhals are usually successful in winter, but rarely inflict any damage in summer.{{sfn|Smith|Sjare|1990}}

===Whale pump===
[[File:Oceanic whale pump - journal.pone.0013255.g001.tiff|thumb|"Whale pump" – the role played by whales in recycling ocean nutrients.{{sfn|Roman|McCarthy|2010}}]]

A 2010 study considered whales to be a positive influence to the productivity of ocean fisheries, in what has been termed a "whale pump." Whales carry nutrients such as nitrogen from the depths back to the surface. This functions as an upward biological pump, reversing an earlier presumption that whales accelerate the loss of nutrients to the bottom. This nitrogen input in the Gulf of Maine is "more than the input of all rivers combined" emptying into the gulf, some {{convert|23000|MT|ST}} each year.{{sfn|University of Vermont|2010}}{{sfn|Roman|McCarthy|2010}} [[Whale faeces|Whales defecate]] at the ocean's surface; their excrement is important for fisheries because it is rich in iron and nitrogen. The whale faeces are liquid and instead of sinking, they stay at the surface where [[phytoplankton]] feed off it.{{sfn|Roman|McCarthy|2010}}{{sfn|Boness|2014}}{{sfn|Roman et al.|2014}}

===Whale fall===
{{Main|Whale fall}}
Upon death, whale carcasses fall to the deep ocean and provide a substantial habitat for marine life. Evidence of whale falls in present-day and fossil records shows that deep sea whale falls support a rich assemblage of creatures, with a global diversity of 407 species, comparable to other [[neritic]] biodiversity hotspots, such as [[cold seep]]s and [[hydrothermal vent]]s.{{sfn|Smith|Baco|2003}}

Deterioration of whale carcasses happens through a series of three stages. Initially, moving organisms such as [[shark]]s and [[hagfish]], scavenge the soft tissues at a rapid rate over a period of months, and as long as two years. This is followed by the colonization of bones and surrounding sediments (which contain organic matter) by enrichment opportunists, such as [[crustaceans]] and [[polychaetes]], throughout a period of years. Finally, sulfophilic bacteria reduce the bones releasing [[hydrogen sulfide]] enabling the growth of [[chemoautotrophic]] organisms, which in turn, support other organisms such as mussels, clams, limpets, and sea snails. This stage may last for decades and supports a rich assemblage of species, averaging 185 species per site.{{sfn|Smith|Baco|2003}}{{sfn|Fujiwara et al.|2007}}