View source for Culling

{{Short description|Process of segregating organisms in biology}}
{{Other uses}}
{{Redirect|Cull|people with the surname "Cull"|Cull (surname)}}
{{For|the rendering techniques in computer graphics|Hidden-surface determination#Culling and visible-surface determination}}
{{Use mdy dates|date=June 2017}}

[[File:At the drafting race from The Powerhouse Museum Collection.jpg|thumb|300px|Drafting out culled sheep]]

'''Culling''' is the process of segregating organisms from a group according to desired or undesired characteristics. In [[animal breeding]], it is removing or segregating animals from a breeding stock based on a specific trait. This is done to exaggerate desirable characteristics, or to remove undesirable characteristics by altering the genetic makeup of the population. For [[livestock]] and [[wildlife]], culling often refers to [[animal slaughter|killing removed animals]] based on their characteristics, such as their sex or species membership, or as a means of preventing [[Transmission (medicine)|infectious disease transmission]].

In [[fruit]]s and [[vegetable]]s, culling is the sorting or segregation of fresh harvested produce into marketable lots, with the non-marketable lots being discarded or diverted into [[food processing]] or non-food processing activities. This usually happens at collection centres located at, or close to farms.

==Etymology==
The word ''cull'' comes from the Latin verb {{wikt-lang|la|colligo|colligere}}, meaning "to gather". The term can be applied broadly to mean partitioning a collection into two groups: one that will be kept and one that will be rejected. The cull is the set of items rejected during the selection process. The culling process is repeated until the selected group is of proper size and consistency desired.

==Pedigreed animals==
{{Further|Selective breeding}}

''Culling'' is: {{quote|... the rejection or removal of inferior individuals from breeding. The act of selective breeding. As used in the practice of breeding pedigree cats, this refers to the practice of spaying or neutering a kitten or cat that does not measure up to the show standard (or other standard being applied) for that breed. In no way does culling, as used by responsible breeders, signify the killing of healthy kittens or cats if they fail to meet the applicable standard.|''Robinson's Genetics for Cat Breeders and Veterinarians'', Fourth  Edition<ref>Carolyn M. Vella, Lorraine M. Shelton, John J. McGonagle, Terry W. Stanglein, ''Robinson's Genetics for Cat Breeders and Veterinarians'', Fourth  Edition, page 212</ref>}}

In the breeding of [[pedigreed]] animals, both desirable and undesirable traits are considered when choosing which animals to retain for breeding and which to place as pets. The process of culling starts with examination of the conformation standard of the animal and will often include additional qualities such as health, robustness, temperament, color preference, etc. The breeder takes all things into consideration when envisioning their ideal for the breed or goal of their breeding program. From that vision, selections are made as to which animals, when bred, have the best chance of producing the ideal for the breed.<ref name=Robinson>{{cite book |first=Roy |last=Robinson |author2=Carolyn M. Vella |author3=Lorraine M. Shelton |author4=John J. McGonagle |author5=Terry W. Stanglein |title=Robinson's Genetics for Cat Breeders and Veterinarians |edition=Fourth |publisher=Butterworth Heinemann |location=Great Britain |isbn=0-7506-4069-3 |date=1999}}</ref>

Breeders of pedigreed animals cull based on many criteria. The first culling criterion should always be health and robustness. Secondary to health, temperament and conformation of the animal should be considered. The filtering process ends with the breeder's personal aesthetic preferences on pattern, color, etc.

===Tandem method===
The tandem method is a form of selective breeding where a breeder addresses one characteristic of the animal at a time, thus selecting only animals that measure above a certain threshold for that particular trait while keeping other traits constant. Once that level of quality in the single trait is achieved, the breeder will focus on a second trait and cull based on that quality.<ref name=Robinson/> With the tandem method, a minimum level of quality is set for important characteristics that the breeder wishes to remain constant. The breeder is focusing improvement in one particular trait without losing quality of the others. The breeder will raise the threshold for selection on this trait with each successive generation of progeny, thus ensuring improvement in this single characteristic of his breeding program.

For example, a breeder that is pleased with the muzzle length, muzzle shape, and eye placement in the breeding stock, but wishes to improve the eye shape of progeny produced may determine a minimum level of improvement in eye shape required for progeny to be returned into the breeding program. Progeny is first evaluated on the existing quality thresholds in place for muzzle length, muzzle shape, and eye placement with the additional criterion being improvement in eye shape. Any animal that does not meet this level of improvement in the eye shape while maintaining the other qualities is culled from the breeding program; i.e., that animal is not used for breeding, but is instead [[neutered]] and placed in a pet home.

===Independent levels===
Independent levels is a method where any animal who falls below a given standard in any single characteristic is not used in a breeding program. With each successive mating, the threshold culling criteria are raised thus improving the breed with each successive generation.<ref name=Robinson/>

This method measures several characteristics at once. Should progeny fall below the desired quality in any one characteristic being measured, it will not be used in the breeding program regardless of the level of excellence of other traits. With each successive generation of progeny, the minimum quality of each characteristic is raised thus ensuring improvement of these traits.

For example, a breeder has a view of what the minimum requirements for muzzle length, muzzle shape, eye placement, and eye shape they are breeding toward. The breeder will determine what the minimum acceptable quality for each of these traits will be for progeny to be folded back into their breeding program. Any animal that fails to meet the quality threshold for any one of these criteria is culled from the breeding program.

===Total score method===
The total score method is a selection method where the breeder evaluates and selects breeding stock based on a weighted table of characteristics. The breeder selects qualities that are most important to them and assigns them a weight. The weights of all the traits should add up to 100. When evaluating an individual for selection, the breeder measures the traits on a scale of 1 to 10, with 10 being the most desirable expression and 1 being the lowest. The scores are then multiplied by their weights and then added together to give a total score. Individuals that fail to meet a threshold are culled (or removed) from the breeding program. The total score gives a breeder a way to evaluate multiple traits on an animal at the same time.<ref name=Robinson/>

The total score method is the most flexible of the three. it allows for weighted improvement of multiple characteristics. It allows the breeder to make major gains in one aspect while moderate or lesser gains in others.

For example, a breeder is willing to make a smaller improvement in muzzle length and muzzle shape in order to have a moderate gain in improvement of eye placement and a more dramatic improvement in eye shape. Suppose the breeder determines that she would like to see 40% improvement in eye shape, 30% improvement in eye placement, and 15% improvement in both muzzle length and shape. The breeder would evaluate these characteristics on a scale of 1 to 10 and multiply by the weights. The formula would look something like: 15 (muzzle length) + 15 (muzzle shape) + 30 (eye placement) + 40 (eye shape) = total score for that animal. The breeder determines the lowest acceptable total score for an animal to be folded back into their breeding program. Animals that do not meet this minimum total score are culled from the breeding program.

==Livestock and production animals==
{{see also|Chick culling}}
[[Livestock]] bred for the production of meat or milk may be culled by farmers. Animals not selected to remain for breeding are sold, killed, or sent to the [[slaughterhouse]].

Criteria for culling livestock and production animals can be based on population or production (milk or egg). In a domestic or [[farming]] situation, the culling process involves the selection and selling of surplus stock. The selection may be done to improve breeding stock—for example, for improved production of eggs or milk—or simply to control the group's population for environmental and species preservation. In order to increase the frequency of preferred [[Phenotype|phenotypes]], agricultural practices typically involve using the most productive animals as breeding stock.<ref name=":3" />

With dairy cattle, culling may be practised by [[Insemination|inseminating]] cows—considered to be inferior—with beef breed semen and by selling the produced offspring for meat production.<ref>{{Cite journal|last1=Ettema|first1=J. F.|last2=Thomasen|first2=J. R.|last3=Hjortø|first3=L.|last4=Kargo|first4=M.|last5=Østergaard|first5=S.|last6=Sørensen|first6=A. C.|date=2017-05-01|title=Economic opportunities for using sexed semen and semen of beef bulls in dairy herds|journal=Journal of Dairy Science|language=en|volume=100|issue=5|pages=4161–4171|doi=10.3168/jds.2016-11333|pmid=28237584|issn=0022-0302|doi-access=free}}</ref>

Approximately half of the chicks of [[Poultry farming#Egg-laying chickens|egg-laying chickens]] are males who would grow up to be roosters. These individuals have little use in an industrial egg-producing facility as they do not lay eggs, so the majority of male chicks are killed shortly after hatching.<ref>{{Cite web|url=http://www.independent.co.uk/life-style/food-and-drink/hatched-discarded-gassed-what-happens-to-male-chicks-in-the-uk-10088509.html|title=Hatched, discarded, gassed: What happens to male chicks in the UK|last=Saul|first=Heather|date=2015-03-05|website=The Independent|language=en|access-date=2020-02-22}}</ref> 

Culling of farmed animals is considered a necessary practice to prevent the spread of damaging and fatal diseases such as [[foot-and-mouth disease]], [[avian flu]], [[Influenza A virus subtype H5N1]] and [[bovine spongiform encephalopathy]] ("mad cow disease").<ref >{{cite web | title=Avian Flu: Questions & Answers | website=Food and Agriculture Organization of the United Nations | date=29 November 2006 | url=http://www.fao.org/avianflu/en/qanda.html | access-date=12 February 2020}}</ref><ref>{{cite web | title=Prevention and Control: OIE | website=World Organisation for Animal Health | url=https://www.oie.int/en/animal-health-in-the-world/avian-influenza-portal/prevention-and-control/ | access-date=12 February 2020}}</ref><ref>{{cite web | title=Avian Influenza: Questions & Answers | website=Food and Agriculture Organization of the United Nations | date=29 November 2006 | url=http://www.fao.org/avianflu/en/qanda.html | access-date=12 February 2020}}</ref>

==Wildlife==
{{Main article|Animal population control}}
{{Further|Nuisance wildlife management}}

In the United States, hunting licenses and hunting seasons are a means by which the population of game animals is maintained. Each season, a hunter is allowed to kill a certain amount of wild animals, determined both by species and sex. If the population seems to have surplus females, hunters are allowed to take more females during that hunting season. If the population is below what is desired, hunters may not be permitted to hunt that particular species, or only hunt a restricted number of males.<ref>{{Cite web|url=https://www.nationalgeographic.com/magazine/2017/10/trophy-hunting-killing-saving-animals/|archive-url=https://web.archive.org/web/20170921085412/http://www.nationalgeographic.com/magazine/2017/10/trophy-hunting-killing-saving-animals/|url-status=dead|archive-date=September 21, 2017|title=Trophy Hunting: Should We Kill Animals to Save Them?|last=Paterniti|first=Michael|date=2018-10-15|website=National Geographic|language=en|access-date=2020-02-22}}</ref>

Populations of game animals such as [[elk]] may be informally culled if they begin to excessively eat winter food set out for domestic cattle herds. In such instances the rancher will inform hunters that they may hunt on their property in order to thin the wild herd to controllable levels. These efforts are aimed to counter excessive depletion of the winter feed supplies.<ref>{{Cite web|url=https://extension.usu.edu/rangelands/pages/please-dont-feed-the-elk|title=Please Don't Feed The Elk: An Applied Management Experiment|website=extension.usu.edu|access-date=2020-02-22|archive-date=February 22, 2020|archive-url=https://web.archive.org/web/20200222140309/https://extension.usu.edu/rangelands/pages/please-dont-feed-the-elk|url-status=dead}}</ref> Other managed culling instances involve extended issuance of extra hunting licenses, or the inclusion of additional "special hunting seasons" during harsh winters or overpopulation periods, governed by state fish and game agencies.<ref>{{Cite journal|last=Heusmann|first=H. W.|date=1999|title=Special Hunting Seasons and Resident Canada Goose Populations|journal=Wildlife Society Bulletin |volume=27|issue=2|pages=456–464|issn=0091-7648|jstor=3783914}}</ref>

Culling for population control is common in wildlife management, particularly on [[Africa]]n [[game farm]]s and [[Australia]]n national parks. In the case of very large animals such as [[elephants]], adults are often targeted. Their orphaned young, easily captured and transported, are then relocated to other reserves. Culling is controversial in many African countries, but reintroduction of the practice has been recommended in recent years for use at the [[Kruger National Park]] in [[South Africa]], which has experienced a swell in its elephant population since culling was banned in 1995.<ref>{{cite news|last=Nduru|first=Moyiga|url=http://www.ipsnews.net/interna.asp?idnews=31297|title=Is 'Cull' a Four-Letter Word?|date=December 5, 2005|access-date=May 12, 2006|url-status=dead|archive-url=https://web.archive.org/web/20060728051326/http://www.ipsnews.net/interna.asp?idnews=31297|archive-date=July 28, 2006|publisher=Inter Press Service|df=mdy-all}}</ref>

===Arguments against wildlife culling===
Culling acts as a strong selection force and can therefore impact the [[population genetics]] of a species. For example, culling based on specific traits, such as size, can enforce [[directional selection]] and remove those traits from the population. This can have long-term effects on the [[genetic diversity]] of a population.<ref name=":3" />

However, culling can act as a selection force intentionally implemented by humans to counteract the selection force of [[trophy hunting]]. Hunting typically enforces selection towards unfavorable phenotypic traits because of the strong hunting bias for specific traits, such as large antler size. Culling "low-quality" traits can counteract this force.<ref>{{Cite journal|last1=Mysterud|first1=Atle|last2=Bischof|first2=Richard|date=2010|title=Can Compensatory Culling Offset Undesirable Evolutionary Consequences of Trophy Hunting?|journal=The Journal of Animal Ecology|volume=79|issue=1|pages=148–160|doi=10.1111/j.1365-2656.2009.01621.x|pmid=19840171|pmc=2810430|bibcode=2010JAnEc..79..148M }}</ref>

[[Animal rights]] activists argue that killing animals for any reason (including hunting) is cruel and unethical.<ref name=":4">{{Cite web|url=https://www.peta.org/issues/wildlife/wildlife-factsheets/sport-hunting-cruel-unnecessary/|title=Why Sport Hunting Is Cruel and Unnecessary|date=2003-12-15|website=PETA|language=en-US|access-date=2020-02-22}}</ref><ref name=":5">{{Cite web|url=https://www.animal-ethics.org/animal-exploitation-section/animals-used-for-entertainment-and-as-companions-introduction/hunting/|title=Hunting|website=Animal Ethics|access-date=2020-02-22|archive-date=September 9, 2017|archive-url=https://web.archive.org/web/20170909161316/https://www.animal-ethics.org/animal-exploitation-section/animals-used-for-entertainment-and-as-companions-introduction/hunting/|url-status=dead}}</ref>

===Birds===
{{Further|Cormorant culling}}

[[File:Double Crested Cormorant in the Sunset.jpg|alt=Double crested cormorant|thumb|143x143px|Double-crested cormorant]]
Some bird species are culled when their populations impact upon human property, business or recreational activity, disturb or modify habitats or otherwise impact species of conservation concern. Cormorants are culled in many countries due to their impact on commercial and recreational fisheries and habitat modification for nesting and [[guano]] deposition. They are culled by shooting and the smothering of eggs with oil. Another example is the culling of [[silver gull]]s in order to protect the chicks of the vulnerable [[banded stilt]] at ephemeral inland salt lake breeding sites in South Australia. The gulls were culled using bread laced with a narcotic substance.<ref>{{Cite news|url = http://www.abc.net.au/7.30/content/2004/s1195030.htm|title = Seagulls cost cities 'millions'|last = Sexton|first = Mike|date = September 8, 2004|work = 7.30 Report|access-date = January 7, 2015|publisher = ABC|archive-url = https://web.archive.org/web/20150124212634/http://www.abc.net.au/7.30/content/2004/s1195030.htm|archive-date = January 24, 2015|url-status = dead}}</ref> In the Australian states of Tasmania and South Australia, [[Cape Barren geese]] are culled to limit damage to crops and the fouling of waterholes.<ref>{{Cite web|url =http://www.rockjawtours.com.au/geese.htm|title =Cape Barren Geese|access-date =January 13, 2015|website =Flinders Island Hunting Tours|archive-url =https://web.archive.org/web/20150227095103/http://rockjawtours.com.au/geese.htm|archive-date =February 27, 2015|url-status =dead|df =mdy-all}}</ref> Cape Barren Geese remain one of the rarest geese in the world, though much of their habitat is now regarded as secure.<ref>{{Cite web|url=https://dpipwe.tas.gov.au/wildlife-management/fauna-of-tasmania/birds/complete-list-of-tasmanian-birds/cape-barren-goose|title=Cape Barren Goose|website=dpipwe.tas.gov.au|publisher=[[Department of Primary Industries, Water and Environment (Tasmania)]]|access-date=2020-02-22|archive-date=February 22, 2020|archive-url=https://web.archive.org/web/20200222141815/https://dpipwe.tas.gov.au/wildlife-management/fauna-of-tasmania/birds/complete-list-of-tasmanian-birds/cape-barren-goose|url-status=dead}}</ref>

===Seals===
[[File:NZ Fur Seal - 1231 2013 002 (14184250871).jpg|alt=New Zealand fur seal|thumb|186x186px|New Zealand fur seal]]
In [[South Australia]], the recovery of the state's native population of New Zealand fur seals (''[[Arctocephalus forsteri]]'') after severe depletion by sealers in the 1800s has brought them into conflict with the fishing industry. This has prompted members of Parliament to call for [[seal culling in South Australia]].<ref>{{Cite web |title = Liberal MP campaigns to shoot 'booming' fur seal population in SA |url= http://www.abc.net.au/news/2015-07-01/shooting-fur-seals-coorong-lower-lakes-private-members-bill/6585088 |website = ABC News |access-date=July 5, 2015|date= June 30, 2015 }}</ref> The State Government continues to resist the pressure<ref>{{Cite web |title= Aggressive seals attacking rare birds, pelicans and fishing nets, SA fishermen warn |url=http://www.abc.net.au/news/2015-04-24/fur-seals-attack-rare-birds-pelicans-fishing-nets-coorong-lower/6418046|website= ABC News |access-date=July 5, 2015|date=April 24, 2015}}</ref> and as of July 2015, the animals remain protected as listed Marine Mammals under the state's ''[[National Parks and Wildlife Act 1972]]''.<ref>{{Cite web|url = http://www.legislation.sa.gov.au/LZ/C/A/NATIONAL%20PARKS%20AND%20WILDLIFE%20ACT%201972/CURRENT/1972.56.UN.PDF |title=South Australia National Parks and Wildlife Act 1972|date=July 1, 2015 |access-date=July 5, 2015 |publisher=Parliament of South Australia }}</ref>

===Sharks===
[[File:Great white shark south africa.jpg|alt=Great white shark|thumb|186x186px|Great white shark]]
{{Main article|Shark culling}}

Shark culling occurs in four locations {{as of|lc=yes|2018}}: [[New South Wales]], [[Queensland]], [[KwaZulu-Natal]] and [[Réunion]].<ref name=":6">{{Cite web|url=https://www.marineconservation.org.au/pages/shark-culling.html|title=Shark culling|website=Australian Marine Conservation Society|url-status=dead|archive-url=https://web.archive.org/web/20181002102324/https://www.marineconservation.org.au/pages/shark-culling.html|archive-date=October 2, 2018|access-date=December 2, 2018}}</ref><ref name=":7">{{Cite web|url=https://sharkangels.org/news-media/latest-news/157-shark-nets|title=Shark Nets: A tangled web of destruction|last=Andersen|first=Julie|website=Shark Angels|language=en-gb|access-date=2020-02-22|archive-date=February 22, 2020|archive-url=https://web.archive.org/web/20200222140308/https://sharkangels.org/news-media/latest-news/157-shark-nets|url-status=dead}}</ref><ref name=":8">{{Cite news|url=https://www.nzherald.co.nz/world/news/article.cfm?c_id=2&objectid=11847758|title=Man who devoted life to sharks, killed off the coast of Reunion|date=2017-04-29|work=[[The New Zealand Herald]] |access-date=2020-02-22|language=en-NZ|issn=1170-0777}}</ref> Between 1950 and 2008, 352 tiger sharks and 577 great white sharks were killed in the [[shark nets|nets]] in New South Wales—also during this period, a total of 15,135 marine animals were caught and killed in the nets, including whales, turtles, rays, dolphins, and dugongs.<ref name=":6" /> From 2001 to 2018, a total of 10,480 sharks were killed on lethal [[drum line (shark control)|drum lines]] in Queensland.<ref>{{Cite web |title=Queensland Government Kills Sharks, Faces Court Challenge |url=https://www.maritime-executive.com/article/queensland-government-kills-sharks-faces-court-challenge |access-date=2024-08-27 |website=The Maritime Executive |language=en}}</ref> In a 30-year period up to early 2017, more than 33,000 sharks were killed in [[KwaZulu-Natal]]'s shark-killing program—during the same 30-year period, 2,211 turtles, 8,448 rays, and 2,310 dolphins were killed.<ref name=":7" /> Authorities on Réunion kill about 100 sharks per year.<ref name=":8" /> All of these culls have been criticized by environmentalists, who say killing sharks harms the [[marine ecosystem]].<ref name=":6" /><ref>{{Cite web|url=https://hsi.org.au/blog/2016/12/08/shark-nets-death-traps-for-marine-animals/|title=Shark nets – death traps for marine animals|last=Morris|first=Jessica|publisher=[[Humane Society International Australia]]|url-status=dead|archive-url=https://web.archive.org/web/20181002103912/https://hsi.org.au/blog/2016/12/08/shark-nets-death-traps-for-marine-animals/|archive-date=October 2, 2018|access-date=December 2, 2018}}</ref><ref>{{Cite web|url=https://pursuit.unimelb.edu.au/articles/sharks-how-a-cull-could-ruin-an-ecosystem|title=Sharks: How a cull could ruin an ecosystem|last=Schetzer|first=Alana|date=2017-05-08|website=Pursuit|publisher=University of Melbourne|language=en|access-date=2020-02-22}}</ref>

In 2014, a controversial policy was introduced by the [[Western Australia]]n state government which became known as the [[Western Australian shark cull]].<ref>{{Cite web |url=http://fish.wa.gov.au/About-Us/Media-releases/Pages/New-measures-to-combat-WA-shark-risks.aspx|title=New measures to combat WA shark risks |date=March 16, 2014|access-date=June 2, 2017|url-status=bot: unknown|archive-url=https://web.archive.org/web/20140316231459/http://fish.wa.gov.au/About-Us/Media-releases/Pages/New-measures-to-combat-WA-shark-risks.aspx |archive-date=March 16, 2014|df=mdy-all}}</ref> Baited hooks known as [[drum lines]] were to be set over several consecutive summers to catch and kill otherwise protected [[great white sharks]]. The policy's objective was to protect users of the marine environment from fatal shark attack. Thousands of people protested against its implementation, claiming that it was indiscriminate, inhumane and worked against scientific advice the government had previously received.<ref>{{Cite journal |last=Cressey |first=Daniel |title=Australian shark-cull plan draws scientists' ire |url=http://www.nature.com/news/australian-shark-cull-plan-draws-scientists-ire-1.14373 |journal=Nature |language=en |doi=10.1038/nature.2013.14373|year=2013 |s2cid=131232906 |url-access=subscription }}</ref> Seasonal setting of drum lines was abandoned in September 2014 after the program failed to catch any great white sharks, instead catching 172 other [[elasmobranchii]], mostly [[tiger sharks]].<ref>{{Cite news |url=http://www.abc.net.au/news/2014-05-07/shark-catch-and-kill-data-released/5435682 |title=WA shark cull: 172 caught on drum lines off popular beaches |last1=Bembridge |first1=C. |last2=Weber |first2=D |date=May 7, 2014 |work=ABC News, Australia |access-date=June 3, 2017}}</ref>

===Deer===
[[White-tailed deer]] (''Odocoileus virginianus'') have been becoming an issue in suburbs across the United States due to large population increases.<ref name=":0">{{Cite journal |jstor = 3783476|title = An Adaptive Management Approach to Controlling Suburban Deer|last1 = Nielsen|first1 = Clayton K.|last2 = Porter|first2 = William F.|last3 = Underwood|first3 = H. Brian|journal = Wildlife Society Bulletin |volume = 25|issue = 2|pages = 470–477|year = 1997}}</ref> This is thought to be caused mainly by the [[Local extinction|extirpation]] of most of their major predators in these areas.<ref>{{Cite web|url=http://www.science.smith.edu/msi/pdf/i0076-3519-388-01-0001.pdf|title=Mammalian Species Odocoileus virginianus |archive-url=https://web.archive.org/web/20120620063955/http://www.science.smith.edu/msi/pdf/i0076-3519-388-01-0001.pdf |archive-date=June 20, 2012|url-status=dead|df=mdy-all}}</ref> In response to these population booms, different management approaches have been taken to decrease their numbers mainly in the form of culls.<ref name=":0" /><ref>{{Cite journal |doi = 10.1890/03-0009|title = The Demographic Consequences of Releasing a Population of Red Deer from Culling|year = 2004|last1 = Coulson|first1 = Tim|last2 = Guinness|first2 = Fiona|last3 = Pemberton|first3 = Josephine|last4 = Clutton-Brock|first4 = Tim|journal = Ecology|volume = 85|issue = 2|pages = 411–422| bibcode=2004Ecol...85..411C |url = https://www.pure.ed.ac.uk/ws/files/7992329/ECOLOGY_2004_Pemberton_J.pdf|hdl = 20.500.11820/b36d587f-9c7a-4ca4-b8d9-6902c5f0fb87| s2cid=62815482 |hdl-access = free}}</ref> Culls of deer are often partnered with exclusions with fencing and also administering contraceptives.<ref name="Husheer, Sean W. 2005">{{Cite journal | doi=10.1071/WR04006| title=High-intensity deer culling increases growth of mountain beech seedlings in New Zealand| year=2005| last1=Husheer| first1=Sean W.| last2=Robertson| first2=Alastair W.| journal=Wildlife Research| volume=32| issue=4| pages=273}}</ref>

[[File:White-tailed deer.jpg|thumb|White-tailed deer buck]]
The effectiveness of these deer culls has been debated and often criticized as only a temporary fix to the larger problem of deer overpopulation and argue that the use of culling will increase fertility of remaining deer by reducing competition.<ref>{{Cite news |url=https://www.usatoday.com/story/news/nation/2015/03/07/deer-culls-stir-debate-metro-detroit/24567687/ |title=Deer culls stir debate in Detroit metro area |work=USA TODAY |access-date=June 2, 2017 |language=en}}</ref> Those in favor of the culls argue that they can be used to combat the [[Selective breeding|selection pressure]] that is imposed by hunting that creates smaller antler and body sizes in deer.<ref name=":3">{{Cite journal | doi=10.1073/pnas.0901069106| pmid=19528656| pmc=2702803| title=Human-induced evolution caused by unnatural selection through harvest of wild animals| year=2009| last1=Allendorf| first1=F. W.| last2=Hard| first2=J. J.| journal=Proceedings of the National Academy of Sciences| volume=106| issue=Suppl 1| pages=9987–9994| doi-access=free}}</ref> People in favor of the culls recommend that they not be random and actively select for smaller individuals and bucks with smaller antlers, specifically "button bucks" or bucks with only spiked antler in their first year as opposed to forked antlers.<ref>{{Cite journal | doi=10.1002/jwmg.741| title=Age-related patterns of antler development in free-ranging white-tailed deer| year=2014| last1=Hewitt| first1=David G.| last2=Hellickson| first2=Mickey W.| last3=Lewis| first3=John S.| last4=Wester| first4=David B.| last5=Bryant| first5=Fred C.| journal=The Journal of Wildlife Management| volume=78| issue=6| pages=976–984| bibcode=2014JWMan..78..976H}}</ref><ref>{{Cite journal |jstor = 3784175|title = Effects of Selective-Harvest Strategies on White-Tailed Deer Antler Size|last1 = Strickland|first1 = Bronson K.|last2 = Demarais|first2 = Stephen|last3 = Castle|first3 = Larry E.|last4 = Lipe|first4 = Jim W.|last5 = Lunceford|first5 = William H.|last6 = Jacobson|first6 = Harry A.|last7 = Frels|first7 = Don|last8 = Miller|first8 = Karl V.|journal = Wildlife Society Bulletin |volume = 29|issue = 2|pages = 509–520|year = 2001}}</ref>

Culling of deer can also have benefits in the form of disease prevention<ref name=":1">{{Cite journal | doi=10.1111/j.1365-2664.2008.01576.x| pmid=19536340| pmc=2695855| title=Host culling as an adaptive management tool for chronic wasting disease in white-tailed deer: A modelling study| year=2009| last1=Wasserberg| first1=Gideon| last2=Osnas| first2=Erik E.| last3=Rolley| first3=Robert E.| last4=Samuel| first4=Michael D.| journal=Journal of Applied Ecology| volume=46| issue=2| pages=457–466| bibcode=2009JApEc..46..457W}}</ref> and in places that the white-tailed deer is an invasive species such as New Zealand culling of deer has added benefits for native species.<ref name="Husheer, Sean W. 2005"/> Diseases are [[Density dependence|density dependent factors]] and decreases in the density of the deer populations through culling causes diseases, such as [[chronic wasting disease]] and [[Lyme disease]], to spread less quickly and effectively.<ref name=":1" />

==Zoos==
{{see also|List of animals culled in zoos}}

Many [[zoo]]s participate in an international [[breeding program]] to maintain a genetically viable population and prevent inbreeding.<ref>{{cite web |url=http://www.waza.org/en/site/conservation/conservation-breeding-programmes |title=Conservation Breeding Programmes |publisher=[[World Association of Zoos and Aquariums]] }}</ref> Animals that can no longer contribute to the breeding program are considered less desirable and are often replaced by more desirable individuals.<ref>{{Cite magazine|url=https://www.newyorker.com/magazine/2017/01/16/killing-animals-at-the-zoo|title=Killing Animals at the Zoo|last=Parker|first=Ian|date=January 9, 2017|magazine=The New Yorker|language=en|access-date=2020-02-22}}</ref> If an animal is surplus to a zoo's requirements and a place in another zoo can not be found, the animal may be killed. In 2014, the culling of a young, healthy giraffe [[Marius (giraffe)|Marius]] raised an international public controversy.<ref>{{Cite news|last=Eriksen|first=Lars|url=https://www.theguardian.com/world/2014/feb/09/danish-zoo-outrage-giraffe-marius|title=Copenhagen zoo sparks outrage by killing healthy giraffe named Marius|date=2014-02-09|work=[[The Guardian]] |access-date=2020-02-22|language=en-GB|issn=0261-3077}}</ref>

Zoos sometimes consider female animals to be more desirable than males.<ref>{{Cite web |url=http://www.zoo.dk/BesogZoo/Presse/Pressemeddelelse%20-%20Girafglaede%20i%20Zoo.aspx |title=Pressemeddelelse - Girafglaede i Zoo |access-date=February 14, 2014 |archive-url=https://web.archive.org/web/20140222033239/http://www.zoo.dk/BesogZoo/Presse/Pressemeddelelse%20-%20Girafglaede%20i%20Zoo.aspx |archive-date=February 22, 2014 |url-status=dead |df=mdy-all }}</ref> One reason for this is that while individual males can contribute to the birth of many young in a short period of time, females give birth to only a few young and are pregnant for a relatively long period of time. This makes it possible to keep many females with just one or two males, but not the reverse. Another reason is that the birth of some animal species increases public interest in the zoo.

Germany's [[:de:Tierschutzgesetz_(Deutschland)|''Animal Welfare Act 1972'']] orders that zoo animals cannot be culled without verification by official veterinary institutes of the [[Landkreis]] or [[federated state]].<ref>{{cite web |url=http://www.rijksoverheid.nl/bestanden/documenten-en-publicaties/kamerstukken/2014/03/25/beantwoording-kamervragen-over-fokken-en-doden-van-gezonde-dieren-in-dierentuinen/beantwoording-kamervragen-over-fokken-en-doden-van-gezonde-dieren-in-dierentuinen.pdf |title=Beantwoording vragen over fokken en doden van gezonde dieren in dierentuinen |publisher=[[Ministry of Economic Affairs (Netherlands)]] |date=March 25, 2014 |access-date=June 9, 2014 |language=nl |archive-url=https://web.archive.org/web/20140714161822/http://www.rijksoverheid.nl/bestanden/documenten-en-publicaties/kamerstukken/2014/03/25/beantwoording-kamervragen-over-fokken-en-doden-van-gezonde-dieren-in-dierentuinen/beantwoording-kamervragen-over-fokken-en-doden-van-gezonde-dieren-in-dierentuinen.pdf |archive-date=July 14, 2014 |url-status=dead |df=mdy-all }}</ref>

In the UK, there is no general prohibition on [[animal euthanasia]], which is allowed when overcrowding compromises the well-being of the animals.<ref>{{cite web|url=https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/69596/standards-of-zoo-practice.pdf|title=Secretary of State's Standards of Modern Zoo Practice|date=2012|website=gov.uk|publisher=[[Department for Environment, Food and Rural Affairs]]|access-date=April 16, 2016}}</ref>

==Ethics==
{{see also|Conservation (ethic)}}

[[Jaak Panksepp]], an American neuroscientist, concludes that both animals and humans have brains wired to feel emotions, and that animals have the capacity to experience pleasure and happiness from their lives.<ref>Masson, Jeffrey Moussaieff. 2004. ''The Pig Who Sang to the Moon: The Emotional World of Farm Animals''. New York: Ballantine Books.</ref>

Culling has been criticized on animal rights grounds as [[Speciesism|speciesist]]—it has been argued that killing animals for any reason is cruel and unethical, and that animals have a right to live.<ref name=":4" /><ref name=":5" />

Some argue that culling is necessary when [[biodiversity]] is threatened.<ref>{{Cite web|url=https://www.nbcnews.com/id/wbna10244771|title=S. Africa elephant culling splits wildlife groups|date=2005-11-29|website=msnbc.com|language=en|access-date=2020-02-22}}</ref> However, the protection of biodiversity argument has been questioned by some animal rights advocates who point out that the animal which most greatly threatens and damages biodiversity is humanity, so if we are not willing to cull our own species we cannot morally justify culling another.<ref>Brown, Les. 1988. ''Cruelty to Animals: The Moral Debt''. London, UK: Palgrave Macmillan.</ref><ref>Clarke, Paul A.B. and Linzey, Andrew (eds.). 1990. ''Political Theory and Animal Rights''. Winchester, MA: Pluto Press.</ref>

===Non-lethal alternatives===
There are non-lethal alternatives which may still be considered culling, and serve the same purpose of reducing population numbers and selecting for desired traits without killing existing members of the population. These methods include the use of [[wildlife contraceptive]]s and reproductive inhibitors. By using such methods population numbers might be reduced more gradually and in a potentially more humane fashion than by directly lethal culling actions.

Currently, wildlife contraceptives are largely in the experimental phase and include such products as [[Gonacon]], an [[adjuvant]] vaccine which delivers a high dosage of a competitor ligand of the [[hormone]] [[Gonadotropin-releasing hormone|GnRH]] to female mammals (e.g. whitetail deer). The complex formed of GnRH and the Gonacon molecule promotes production of antibodies against the animal's own GnRH, which themselves complex with GnRH. This encourages an extended duration of the drug's effects (namely, reduction of active/unbound GnRH in the animal's system).<ref name=":2">{{Cite web|url=https://www.aphis.usda.gov/aphis/ourfocus/wildlifedamage/programs/nwrc/research-areas/sa_reproductive_control/ct_gonacon|title=GonaCon™ New GnRH Single Shot|date=November 18, 2019|website=usda.gov|publisher=[[United States Department of Agriculture]]|access-date=February 22, 2020|archive-date=February 22, 2020|archive-url=https://web.archive.org/web/20200222133254/https://www.aphis.usda.gov/aphis/ourfocus/wildlifedamage/programs/nwrc/research-areas/sa_reproductive_control/ct_gonacon|url-status=dead}}</ref> Though the [[endocrinology]] behind Gonacon is sound, the need for multiple lifetime doses for full efficacy make it a less-guaranteed and less-permanent solution for wildlife than lethal culls. Even among domestic animals in controlled conditions, Gonacon cannot ensure 100% reduction in the occurrence of pregnancies.<ref>{{Cite journal|last1=Levy|first1=Julie K.|last2=Friary|first2=John A.|last3=Miller|first3=Lowell A.|last4=Tucker|first4=Sylvia J.|last5=Fagerstone|first5=Kathleen A.|date=November 2011|title=Long-term fertility control in female cats with GonaCon™, a GnRH immunocontraceptive|journal=Theriogenology|volume=76|issue=8|pages=1517–1525|doi=10.1016/j.theriogenology.2011.06.022|issn=1879-3231|pmid=21835455|url=https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=2332&context=icwdm_usdanwrc|url-access=subscription}}</ref>

Reproductive inhibitors need not act on the parental individuals directly, instead damaging reproductive processes and/or developing offspring to reduce the number of viable offspring per mating pair. One such compound called [[Nicarbazin]] has been formulated into bait for consumption by [[Canada goose|Canada Geese]], and damages egg yolk formation to reduce the viability of clutches without harming the adult geese.<ref>{{Cite web|url=https://www.aphis.usda.gov/aphis/ourfocus/wildlifedamage/programs/nwrc/research-areas/sa_reproductive_control|title=Nicarbazin Research|date=February 9, 2018|website=usda.gov|publisher=[[United States Department of Agriculture]]|access-date=February 22, 2020|archive-date=February 22, 2020|archive-url=https://web.archive.org/web/20200222133253/https://www.aphis.usda.gov/aphis/ourfocus/wildlifedamage/programs/nwrc/research-areas/sa_reproductive_control|url-status=dead}}</ref>

==See also==
* [[Australian feral camel]]
* [[Badger culling in the United Kingdom]]
* [[Brumby]] - [[feral horse]]s in Australia
* [[Eugenics]], the selective breeding of human populations
* [[Experimental evolution]]
* [[Cats in Australia|Feral cats in Australia]]
* [[Foam depopulation]]
* [[Ventilation shutdown]]

==References==
{{Reflist|2}}

==External links==
{{Wiktionary|culling}}
* [http://dictionary.reference.com/browse/culling Dictionary.com definition for Culling]
* {{usurped|1=[https://web.archive.org/web/20060211025853/http://www.planetark.com/dailynewsstory.cfm/newsid/29953/story.htm/ Brief description of South African culling controversy]}}
* [https://web.archive.org/web/20121204073853/http://www.awfc.ca/english/works/pub/disposehens.htm The Disposal of Spent Laying Hens]

{{Animal rights}}

[[Category:Animal culling]]
[[Category:Animal killing]]
[[Category:Animal rights]]
[[Category:Animal welfare]]
[[Category:Cruelty to animals]]
[[Category:Intensive farming]]
[[Category:Livestock]]