Editing Cetacea (section)

== Threats ==
The primary threats to cetaceans come from people, both directly from whaling or [[Dolphin drive hunting|drive hunting]] and indirect threats from fishing and pollution.<ref name="wdcs">{{cite book|author=Cara E. Miller|title=Current State of Knowledge of Cetacean Threats, Diversity, and Habitats in the Pacific Islands Region|publisher=Whale and Dolphin Conservation Society|year=2007|access-date=5 September 2015|isbn=978-0-646-47224-9|url=http://uk.whales.org/sites/default/files/whales-and-dolphins-in-the-pacific-islands.pdf|archive-url=https://web.archive.org/web/20150908003502/http://uk.whales.org/sites/default/files/whales-and-dolphins-in-the-pacific-islands.pdf|archive-date=8 September 2015|url-status=dead}}</ref>

=== Whaling ===
{{Main|Whaling|History of Whaling|Dolphin drive hunting}}
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| alt1 = Mother and calf minke whales are pulled through the rear of a Japanese research ship.
| caption1 = Japanese research ship whaling mother and calf [[minke whales]].
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| alt2 = A dolphin caught in a drive hunt is transported away by a forklift.
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Whaling is the practice of hunting whales, mainly baleen and sperm whales. This activity has gone on since the [[Stone Age]].<ref>{{Cite web |date=2024-10-11 |title=Whaling - Commercial, Industrial, Japan {{!}} Britannica |url=https://www.britannica.com/topic/whaling |access-date=2024-10-28 |website=[[Britannica Online Encyclopedia]] |language=en}}</ref>

In the [[Middle Ages]], reasons for whaling included their [[whale meat|meat]], [[whale oil|oil]] usable as fuel and the jawbone, which was used in house construction. At the end of the Middle Ages, early whaling fleets aimed at [[baleen whales]], such as [[bowhead whales|bowheads]]. In the 16th and 17th centuries, the Dutch fleet had about 300 whaling ships with 18,000 crewmen.{{citation needed|date=October 2024}}

In the 18th and 19th centuries, baleen whales especially were hunted for their [[baleen]], which was used as a replacement for wood, or in products requiring strength and flexibility such as [[corset]]s and [[crinoline]] skirts. In addition, the [[spermaceti]] found in the [[sperm whale]] was used as a machine lubricant and the [[ambergris]] as a material for pharmaceutical and perfume industries. In the second half of the 19th century, the explosive [[harpoon]] was invented, leading to a massive increase in the catch size.{{citation needed|date=October 2024}}

Large ships were used as "mother" ships for the whale handlers. In the first half of the 20th century, whales were of great importance as a supplier of raw materials. Whales were intensively hunted during this time; in the 1930s, 30,000 whales were killed. This increased to over 40,000 animals per year up to the 1960s, when stocks of large baleen whales collapsed.{{citation needed|date=October 2024}}

Most hunted whales are now threatened, with some great whale populations exploited to the brink of extinction. Atlantic and Korean [[gray whale]] populations were completely eradicated and the [[North Atlantic right whales|North Atlantic right whale]] population fell to some 300–600. The [[blue whale]] population is estimated to be around 14,000.{{citation needed|date=October 2024}}

The first efforts to protect whales came in 1931. Some particularly endangered species, such as the [[humpback whale]] (which then numbered about 100 animals),<ref>{{Cite web |title=A History of the International Whaling Commission (IWC) |url=https://wwf.panda.org/discover/knowledge_hub/endangered_species/cetaceans/cetaceans/iwc/history |access-date=2024-08-08 |website=wwf.panda.org |language=en}}</ref> were placed under international protection and the first protected areas were established. In 1946, the [[International Whaling Commission]] (IWC) was established, to monitor and secure whale stocks. Whaling of 14 large species for commercial purposes was prohibited worldwide by this organization from 1985 to 2005, though some countries do not honor the prohibition.{{citation needed|date=October 2024}}
[[File:Whales caught recently.png|left|thumb|300px|Whales caught 2010–2014, by country]]
The stocks of species such as humpback and blue whales have recovered, though they are still threatened. The United States Congress passed the [[Marine Mammal Protection Act of 1972]] sustain the marine mammal population. It prohibits the taking of marine mammals except for several hundred per year taken in Alaska. Japanese whaling ships are allowed to hunt whales of different species for ostensibly scientific purposes.{{citation needed|date=October 2024}}

[[Aboriginal whaling]] is still permitted. About 1,200 pilot whales were taken in the [[Faroe Islands]] in 2017,<ref name="faroe">{{Cite web |url=http://heimabeiti.fo/default.asp?menu=400 |title=Hagar & seyðamark |website=heimabeiti.fo |access-date=2018-04-07 |archive-date=2014-09-24 |archive-url=https://web.archive.org/web/20140924041544/http://www.heimabeiti.fo/default.asp?menu=400 |url-status=dead }}</ref> and about 900 [[narwhal]]s and 800 [[beluga whale|belugas]] per year are taken in Alaska, Canada, Greenland, and Siberia. About 150 minke are taken in Greenland per year, 120 gray whales in Siberia and 50 bowheads in Alaska, as aboriginal whaling, besides the 600 minke taken commercially by Norway, 300 minke and 100 sei taken by Japan and up to 100 fin whales taken by Iceland.<ref name="iwcatch">{{Cite web |url=https://iwc.int/total-catches |title=Total Catches |website=iwc.int |language=en |access-date=2018-04-07}}</ref> Iceland and Norway do not recognize the ban and operate commercial whaling. Norway and Japan are committed to ending the ban.{{citation needed|date=October 2024}}

Dolphins and other smaller cetaceans are sometimes hunted in an activity known as dolphin drive hunting. This is accomplished by driving a pod together with boats, usually into a bay or onto a beach. Their escape is prevented by closing off the route to the ocean with other boats or nets. Dolphins are hunted this way in several places around the world, including the [[Solomon Islands]], the [[Faroe Islands]], [[Peru]] and Japan (the most well-known practitioner). Dolphins are mostly hunted for their [[whale meat|meat]], though some end up in [[dolphinarium|dolphinaria]]. Despite the controversy thousands of dolphins are caught in drive hunts each year.{{citation needed|date=October 2024}}

=== Fishing ===
{{See also|Cetacean bycatch}}
[[File:Domino whale-bone hg.jpg|thumb|[[Dominoes]] made of baleen]]
Dolphin pods often reside near large tuna shoals. This is known to fishermen, who look for dolphins to catch tuna. Dolphins are much easier to spot from a distance than tuna, since they regularly breathe. The fishermen pull their nets hundreds of meters wide in a circle around the dolphin groups, in the expectation that they will net a tuna shoal. When the nets are pulled together, the dolphins become entangled under water and drown. Line fisheries in larger rivers are threats to [[river dolphins]].{{citation needed|date=October 2024}}

A greater threat than by-catch for small cetaceans is targeted hunting. In Southeast Asia, they are sold as fish-replacement to locals, since the region's edible fish promise higher revenues from exports. In the Mediterranean, small cetaceans are targeted to ease pressure on edible fish.<ref name="wdcs" />

=== Strandings ===
{{Main|Cetacean stranding}}
A stranding is when a cetacean leaves the water to lie on a beach. In some cases, groups of whales strand together. The best known are mass strandings of [[pilot whale]]s and sperm whales. [[Cetacean stranding|Stranded]] cetaceans usually die, because their as much as {{convert|90|MT|ST}} body weight compresses their lungs or breaks their ribs. Smaller whales can die of heatstroke because of their thermal insulation.{{citation needed|date=October 2024}}
[[File:Ecomare - gestrande bultrug op Razende Bol (bultrug2012-razende-bol-412-sw).jpg|thumb|Beached humpback whale]]
The causes are not clear. Possible reasons for mass beachings are:<ref name="wdcs" />
* toxic contaminants
* debilitating parasites (in the respiratory tract, brain or middle ear)
* infections (bacterial or viral)
* flight from predators (including humans)
* social bonds within a group, so that the pod follows a stranded animal
* disturbance of their magnetic senses by natural anomalies in the Earth's magnetic field
* injuries
* [[Noise pollution#Wildlife|noise pollution]] by shipping traffic, seismic surveys and military sonar experiments

Since 2000, whale strandings frequently occurred following military [[sonar]] testing. In December 2001, the US Navy admitted partial responsibility for the beaching and the deaths of several marine mammals in March 2000. The coauthor of the interim report stated that animals killed by active sonar of some Navy ships were injured. Generally, underwater noise, which is still on the increase, is increasingly tied to strandings; because it impairs communication and sense of direction.<ref>{{cite journal |author=Schrope, Mark. |title=Whale deaths caused by US Navy's sonar |journal=Nature |volume=415 |issue=106 |pages=106 |year=2003  |doi=10.1038/415106a|bibcode = 2002Natur.415..106S |pmid=11805797|s2cid=52827761 |doi-access=free }}</ref>

[[Climate change]] influences the major wind systems and ocean currents, which also lead to cetacean strandings. Researchers studying strandings on the Tasmanian coast from 1920 to 2002 found that greater strandings occurred at certain time intervals. Years with increased strandings were associated with severe storms, which initiated cold water flows close to the coast. In nutrient-rich, cold water, cetaceans expect large prey animals, so they follow the cold water currents into shallower waters, where the risk is higher for strandings. Whales and dolphins who live in pods may accompany sick or debilitated pod members into shallow water, stranding them at low tide.<ref>{{Cite journal |last1=Evans |first1=K |last2=Thresher |first2=R |last3=Warneke |first3=R.M |last4=Bradshaw |first4=C.J.A |last5=Pook |first5=M |last6=Thiele |first6=D |last7=Hindell |first7=M.A |date=2005-06-22 |title=Periodic variability in cetacean strandings: links to large-scale climate events |journal=Biology Letters |volume=1 |issue=2 |pages=147–150 |doi=10.1098/rsbl.2005.0313 |issn=1744-9561 |pmc=1626231 |pmid=17148151}}</ref>

=== Environmental hazards ===
{{See also|Marine mammals and sonar}}
{{Quote box|quote=Worldwide, use of active sonar has been linked to about 50 marine mammal strandings between 1996 and 2006. In all of these occurrences, there were other contributing factors, such as unusual (steep and complex) underwater geography, limited egress routes, and a specific species of marine mammal—beaked whales—that are suspected to be more sensitive to sound than other marine mammals.
|source=—Rear Admiral Lawrence Rice|align=left|width=30%}}

Heavy metals, residues of many plant and insect venoms and plastic waste [[flotsam]] are not biodegradable. Sometimes, cetaceans consume these hazardous materials, mistaking them for food items. As a result, the animals are more susceptible to disease and have fewer offspring.<ref name="wdcs" />

Damage to the [[ozone layer]] reduces plankton reproduction because of its resulting radiation. This shrinks the food supply for many marine animals, but the filter-feeding baleen whales are most impacted. Even the [[Nekton]] is, in addition to intensive exploitation, damaged by the radiation.<ref name="wdcs" />

Food supplies are also reduced long-term by [[ocean acidification]] due to increased absorption of increased atmospheric carbon dioxide. The CO<sub>2</sub> reacts with water to form [[carbonic acid]], which reduces the construction of the [[calcium carbonate]] skeletons of food supplies for zooplankton that baleen whales depend on.<ref name="wdcs" />

The military and resource extraction industries operate strong [[sonar]] and blasting operations. Marine seismic surveys use loud, low-frequency sound that show what is lying underneath the Earth's surface.<ref name="Nowacek">{{cite journal|last1=Nowacek|first1=Douglas|last2=Donovan|first2=Greg|last3=Gailey|first3=Glenn|last4=Racca|first4=Roberto|last5=Reeves|first5=Randall|last6=Vedenev|first6=Alexander|last7=Weller|first7=David|last8=Southall|first8=Brandon|title=Responsible Practices for Minimizing and Monitoring Environmental Impacts of Marine Seismic Surveys with an Emphasis on Marine Mammal|journal=Aquatic Mammals|date=2013|volume=39|issue=4 |pages=356–377|doi=10.1578/am.39.4.2013.356|bibcode=2013AqMam..39..356N }}<!--|access-date=April 2, 2016--></ref> Vessel traffic also increases noise in the oceans. Such noise can disrupt cetacean behavior such as their use of [[biosonar]] for orientation and communication. Severe instances can panic them, driving them to the surface. This leads to bubbles in blood gases and can cause [[decompression sickness]].<ref>{{Cite book|author1=M. Andre|title=Europe Oceans 2005|author2=T. Johansson|author3=E. Delory|author4=M. van der Schaar|publisher=Oceans 2005–Europe|year=2005|volume=2|pages=1028–1032 Vol. 2|doi=10.1109/OCEANSE.2005.1513199|chapter=Cetacean biosonar and noise pollution|isbn=978-0-7803-9103-1|s2cid=31676969}}</ref> Naval exercises with sonar regularly results in fallen cetaceans that wash up with fatal decompression. Sounds can be disruptive at distances of more than {{convert|100|km|mi}}. Damage varies across frequency and species.{{citation needed|date=October 2024}}