Editing Porpoise (section)

==Behaviour==
[[File:Two Dalls Porpoises.JPG|thumb|right|"Rooster tail" spray around swimming [[Dall's porpoise]]s]]

===Life cycle===
Porpoises are fully aquatic creatures. Females deliver a single calf after a [[gestation period]] lasting about a year.  Calving takes place entirely under water, with the foetus positioned for tail-first delivery to help prevent drowning.  Females have mammary glands, but the shape of a newborn calf's mouth does not allow it to obtain a seal around the nipple—instead of the calf sucking milk, the mother squirts milk into the calf's mouth.<ref>{{citation|editor=Kenneth Stafford Norris|author=E. J. Slijper|title=Whales, Dolphins, and Porpoises|chapter=Functional morphology of the reproductive system in Cetecea| chapter-url=https://books.google.com/books?id=x-iptRSGHIQC&pg=PA310|year=1966|publisher=University of California Press|isbn=978-0-520-03283-5|page=310}}</ref> This milk contains high amounts of fat, which aids in the development of blubber; it contains so much fat that it has the consistency of toothpaste. The calves are weaned at about 11 months of age.  Males play no part in rearing calves.  The calf is dependent for one to two years, and maturity occurs after seven to ten years, all varying between species. This [[R/K selection theory|mode of reproduction]] produces few offspring, but increases the probability of each one surviving.<ref name=r.reeves>{{cite book|first1=Randall|last1=Reeves|first2=Brent|last2=Stewart|first3=Phillip|last3=Clapham|first4=James|last4=Powell|year=2002|title=National Audubon Society Guide to Marine Mammals of the World|publisher=Knopf Doubleday Publishing |isbn=978-0-375-41141-0|url=https://archive.org/details/guidetomarinemam00folk}}</ref>

===Diet===
Porpoises eat a wide variety of creatures. The stomach contents of harbour porpoises suggests that they mainly feed on [[Demersal fish#Benthic fish|benthic fish]], and sometimes [[pelagic fish]]. They may also eat benthic invertebrates. In rare cases, algae, such as ''[[Ulva lactuca]]'', is consumed. Atlantic porpoises are thought to follow the seasonal migration of [[bait fish]], like [[herring]], and their diet varies between seasons. The stomach contents of Dall's porpoises reveal that they mainly feed on [[cephalopod]]s and bait fish, like [[capelin]] and [[sardine]]s. Their stomachs also contained some deep-sea benthic organisms.<ref name="Porpoise"/>

The finless porpoise is known to also follow seasonal migrations. It is known that populations in the mouth of the [[Indus River]] migrate to the sea from April through October to feed on the annual spawning of [[prawn]]s. In Japan, sightings of small pods of them herding [[sand lance]] onto shore are common year-round.<ref name="Porpoise"/>

Little is known about the diets of other species of porpoises. A dissection of three Burmeister's porpoises shows that they consume shrimp and [[euphausiid]]s (krill). A dissection of a beached Vaquita showed remains of squid and [[grunt (fish)|grunts]]. Nothing is known about the diet of the spectacled porpoise.<ref name="Porpoise"/>