Editing Wildebeest (section)

===Migration===
{{See also|Serengeti#Great migration}}
{{Multiple image | perrow = 2
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| header = Migration in wildebeest
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| caption1 = Wildebeest herding and following zebra in the Serengeti National Park
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| caption2 = Wildebeest in Masai Mara during the [[Serengeti#Great Toms|Great Migration]]
| image3 = Wildebeest_Jumping_Into_the_Mara_River.jpg
| caption3 = Wildebeest leaping into the Mara River during their [[Serengeti#Great Toms|Great Migration]]
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Not all wildebeest are migratory. Black wildebeest herds are often nomadic or may have a regular home range of {{convert|1|km2|sqmi|lk=in|abbr=on}}. Bulls may occupy territories, usually about {{convert|100|to|400|m|-2|abbr=on}} apart, but this spacing varies according to the quality of the habitat. In favourable conditions, they may be as close as {{convert|9|m|ft|abbr=on}}, or they may be as far apart as {{convert|1600|m|ft|abbr=on}} in poor habitat.<ref name=nowak>{{cite book|last=Nowak|first=R. M.|title=Walker's Mammals of the World |url=https://archive.org/details/walkersmammalsof0002nowa|url-access=registration|year=1999 |publisher=Johns Hopkins University Press |isbn=978-0-8018-5789-8 |pages=[https://archive.org/details/walkersmammalsof0002nowa/page/1184 1184–6] |edition=6th}}</ref> Female herds have home ranges of about {{convert|250|acre|ha sqmi|}} in size. Herds of nonterritorial bachelor males roam at will and do not seem to have any restrictions on where they wander.<ref name=uu>{{cite web|last=Huffman |first=B. |title=''Connochaetes gnou'': White-tailed gnu, Black wildebeest |url=http://www.ultimateungulate.com/Artiodactyla/Connochaetes_gnou.html |publisher=Ultimate Ungulate |access-date=19 January 2014}}</ref>

Blue wildebeest have both migratory and sedentary populations. In the [[Ngorongoro]], most animals are sedentary and males maintain a network of territories throughout the year, though breeding is seasonal in nature. Females and young form groups of about 10 individuals or join in larger aggregations, and nonterritorial males form bachelor groups.<ref name=Leuthold>{{cite book |author=Leuthold, Walter |title=African Ungulates |year=1977 |chapter=The Influence of Environmental Factors on the Spatial and Social Organization |series=Zoophysiology and Ecology|volume=8 |pages=227–235 |doi=10.1007/978-3-642-81073-2_18 |isbn=978-3-642-81075-6}}</ref> In the [[Serengeti]] and [[Tarangire Ecosystem|Tarangire]] ecosystems, populations are mostly migratory, with herds consisting of both sexes frequently moving, but resident subpopulations also exist.<ref name=":0">{{Cite journal|last1=Morrison|first1=Thomas A.|last2=Link|first2=William A.|last3=Newmark|first3=William D.|last4=Foley|first4=Charles A. H.|last5=Bolger|first5=Douglas T.|date=2016-05-01|title=Tarangire revisited: Consequences of declining connectivity in a tropical ungulate population|journal=Biological Conservation|volume=197|pages=53–60|doi=10.1016/j.biocon.2016.02.034|url=http://eprints.gla.ac.uk/117078/1/117078.pdf}}</ref> During the rutting season, the males may form temporary territories for a few hours or a day or so, and attempt to gather together a few females with which to mate, but soon they have to move on, often moving ahead to set up another temporary territory.<ref name=Leuthold/>

In the [[Maasai Mara]] game reserve, a non-migratory population of blue wildebeest had dwindled from about 119,000 animals in 1977 to about 22,000 in 1997. The reason for the decline is thought to be the increasing competition between cattle and wildebeest for a diminishing area of grazing land as a result of changes in agricultural practices, and possibly fluctuations in rainfall.<ref>{{cite journal |author1=Ottichiloa, Wilber K. |author2=de Leeuwa, Jan |author3=Prins, Herbert H. T. |year=2001 |title=Population trends of resident wildebeest [''Connochaetes taurinus hecki'' (Neumann)] and factors influencing them in the Masai Mara ecosystem, Kenya |journal=Biological Conservation |volume=97 |issue=3 |pages=271–282 |doi=10.1016/S0006-3207(00)00090-2}}</ref>

Each year, some East African populations of blue wildebeest have a long-distance migration, seemingly timed to coincide with the annual pattern of rainfall and grass growth.<ref>{{Cite journal|last1=Bond|first1=Monica L.|last2=Bradley|first2=Curtis M.|last3=Kiffner|first3=Christian|last4=Morrison|first4=Thomas A.|last5=Lee|first5=Derek E.|date=2017-05-26|title=A multi-method approach to delineate and validate migratory corridors|journal=Landscape Ecology|volume=32|issue=8|language=en|pages=1705–1721|doi=10.1007/s10980-017-0537-4|s2cid=24743662|issn=0921-2973|url=http://eprints.gla.ac.uk/143652/1/143652.pdf}}</ref> The timing of their migrations in both the rainy and dry seasons can vary considerably (by months) from year to year. At the end of the [[wet season]] (May or June in East Africa), wildebeest migrate to dry-season areas in response to a lack of surface (drinking) water. When the rainy season begins again (months later), animals quickly move back to their wet-season ranges. Factors suspected to affect migration include food abundance, surface water availability, predators, and phosphorus content in grasses. Phosphorus is a crucial element for all life forms, particularly for lactating female bovids. As a result, during the rainy season, wildebeest select grazing areas that contain particularly high phosphorus levels.<ref name=ulfstrand /> One study found, in addition to phosphorus, wildebeest select ranges containing grass with relatively high nitrogen content.<ref name=benshahar>{{cite journal|last=Ben-Shahar|first=Raphael|author2=Coe, Malcolm J. |title=The relationships between soil factors, grass nutrients, and the foraging behaviour of wildebeest and zebra |journal=Oecologia |year=1992 |volume=90 |issue=3 |pages=422–428 |doi=10.1007/BF00317701|pmid=28313531|bibcode=1992Oecol..90..422B|s2cid=25556587}}</ref>

Aerial photography has revealed that a level of organisation occurs in the movement of the herd that cannot be apparent to each individual animal; for example, the migratory herd exhibits a wavy front, and this suggests that some degree of local decision-making is taking place.<ref>{{cite journal |author1=Gueron, Shay |author2=Levin, Simon A. |year=1993 |title=Self-organization of front patterns in large wildebeest herds |journal=Journal of Theoretical Biology |volume=165 |issue=4 |pages=541–552 |doi=10.1006/jtbi.1993.1206 |bibcode=1993JThBi.165..541G}}</ref> Numerous documentaries feature wildebeest crossing rivers, with many being eaten by [[Nile crocodile|crocodile]]s or drowning in the attempt. While having the appearance of a frenzy, recent research has shown a herd of wildebeest possesses what is known as a "[[swarm intelligence]]", whereby the animals systematically explore and overcome the obstacle as one.<ref>{{cite book |author1=Corne, David W. |author2=Reynolds, Alan |author3=Bonabeau, Eric |title=Handbook of Natural Computing |chapter=Swarm Intelligence |year=2012 |pages=1599–1622 |doi=10.1007/978-3-540-92910-9_48 |isbn=978-3-540-92909-3}}</ref>