Editing Kangaroo (section)

== Biology and behaviour ==
{{see also|Red kangaroo#Behaviour|Eastern grey kangaroo#Behaviour}}
[[File:Kangaroo-in-flight.jpg|thumb|left|upright=0.7|A [[Eastern grey kangaroo#Taxonomy|Tasmanian eastern grey kangaroo]] in motion]]
[[File:Kangaroos Maranoa.JPG|thumb|upright=0.7|Kangaroos in their native grassland habitat]]
[[File:Kangur.rudy.drs.jpg|thumb|left|upright=0.7|A [[red kangaroo]] grazing]]
[[File:Group of Macropus fuliginosus Darling Range 05010.JPG|thumb|upright=0.7|[[Western grey kangaroo]]s]]

=== Locomotion ===
Kangaroos are the only large mammals to use [[Jumping|hopping]] on two legs as their primary means of [[Animal locomotion|locomotion]].<ref>{{cite news |last1=Briggs |first1=Helen |title=When did the kangaroo hop? Scientists have the answer |url=https://www.bbc.co.uk/news/science-environment-47130734 |access-date=5 February 2023 |work=BBC News |date=6 February 2019 |quote=Living kangaroos are the only large mammal to use hopping on two legs as their main form of locomotion.}}</ref> The comfortable hopping speed for a red kangaroo is about {{convert|20–25|kph|abbr=on}}, but speeds of up to {{convert|70|kph|abbr=on}} can be attained over short distances, while it can sustain a speed of {{convert|40|kph|abbr=on}} for nearly {{convert|2|km|abbr=on}}.<ref name="secret">{{cite book | last = Penny | first = Malcolm | title = The Secret World of Kangaroos | publisher = Raintree Steck-Vaughn | year = 2002 | location = Austin TX | isbn = 978-0-7398-4986-6 | url = https://books.google.com/books?id=NNLpLfdP5GwC&q=%2270+km%22 | access-date = 8 May 2020 | archive-date = 16 August 2021 | archive-url = https://web.archive.org/web/20210816140648/https://books.google.com/books?id=NNLpLfdP5GwC&q=%2270+km%22 | url-status = live }}</ref> During a hop, the powerful [[gastrocnemius muscle]]s lift the body off the ground while the smaller [[plantaris muscle]], which attaches near the large fourth toe, is used for push-off. Seventy percent of potential energy is stored in the elastic tendons.<ref>{{cite book |last1=Jackson |first1=S |last2=Vernes |first2=K |year=2010|title=Kangaroo: Portrait of an Extraordinary Marsupial|publisher=Allen and Unwin|pages=139–140|isbn=9781741759037}}</ref> At slow speeds, it employs pentapedal locomotion, using its tail to form a tripod with its two [[forelimb]]s while bringing its hind feet forward. Both pentapedal walking and fast hopping are energetically costly. Hopping at moderate speeds is the most energy efficient, and a kangaroo moving above {{convert|15|kph|abbr=on}} maintains energy consistency more than similarly sized animals running at the same speed.<ref name="Dawson 1995"/>

=== Diet ===
Kangaroos have single-chambered stomachs quite unlike those of [[cattle]] and [[sheep]], which have four compartments.<ref name=Hume1984>{{cite journal | last = Hume | first = I.D. | year = 1984 | title = Principal Features of Digestion in Kangaroos | journal = Proceedings of the Nutritional Society of Australia | volume = 9 | url = http://apjcn.nhri.org.tw/server/apjcn/ProcNutSoc/1980-1989/1984/1984%20p76-81.pdf | pages = 76–81 | access-date = 15 October 2017 | archive-date = 15 October 2017 | archive-url = https://web.archive.org/web/20171015150859/http://apjcn.nhri.org.tw/server/apjcn/ProcNutSoc/1980-1989/1984/1984%20p76-81.pdf | url-status = live }}</ref><ref name=VB>{{cite book |author=Romer, Alfred Sherwood|author2=Parsons, Thomas S.|year=1977 |title=The Vertebrate Body |publisher=Holt-Saunders International |location= Philadelphia, PA|page= 347|isbn= 978-0-03-910284-5}}</ref> They sometimes regurgitate the vegetation they have eaten, chew it as [[cud]], and then swallow it again for final digestion. However, this is a different, more strenuous, activity than it is in [[ruminant]]s, and does not take place as frequently.<ref name=Vendl2017>{{cite journal | author = Vendl, C. | display-authors = etal | year = 2017 | title = Merycism in western grey (''Macropus fuliginosus'') and red kangaroos (''Macropus rufus'') | journal = Mammalian Biology | volume = 86 | pages = 21–26 | doi = 10.1016/j.mambio.2017.03.005| doi-access = free | bibcode = 2017MamBi..86...21V }}</ref>

Different species of kangaroos have different diets, although all are strict [[herbivores]]. The eastern grey kangaroo is predominantly a [[Grazing|grazer]], and eats a wide variety of grasses, whereas some other species such as the red kangaroo include significant amounts of [[shrub]]s in their diets. Smaller species of kangaroos also consume [[hypogeal]] fungi. Many species are [[nocturnal]],<ref name="archive">{{cite web|last=McGuinness|first=Keith|title=Re: Kangaroos|url=http://www.madsci.org/posts/archives/dec96/845059250.Zo.r.html|work=MadSci Network|access-date=2 October 2011|date=25 November 1996|archive-date=18 October 2011|archive-url=https://web.archive.org/web/20111018075222/http://www.madsci.org/posts/archives/dec96/845059250.Zo.r.html|url-status=live}}</ref> and [[crepuscular]],<ref name="colzoo">{{cite web|title=From Boomers to Blue fliers: Fun facts About Kangaroos!!|url=http://www.colszoo.org/animalareas/austral/kangfact.html|work=Columbus Zoo and Aquarium|archive-url=https://web.archive.org/web/20040226032907/http://www.colszoo.org/animalareas/austral/kangfact.html|archive-date=26 February 2004}}</ref><ref name="nocturn2">{{cite web|url=http://www.dfat.gov.au/facts/kangaroos.html |title=About Australia: Kangaroos |publisher=Department of Foreign Affairs and Trade |access-date=6 June 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120527162537/http://www.dfat.gov.au/facts/kangaroos.html |archive-date=27 May 2012 }}</ref> usually spending the hot days resting in shade, and the cool evenings, nights and mornings moving about and feeding.

==== Absence of digestive methane release ====
Despite having herbivorous diets similar to [[ruminant]]s such as cattle, which release large quantities of digestive [[methane]] through [[Breathing|exhaling]] and [[eructation]] (burping), kangaroos release virtually none. The [[hydrogen]] byproduct of [[fermentation]] is instead converted into [[acetate]], which is then used to provide further energy. Scientists are interested in the possibility of transferring the bacteria responsible for this process from kangaroos to cattle, since the [[greenhouse gas]] effect of methane is 23 times greater than [[carbon dioxide]] per molecule.<ref>{{cite journal |last1=Vendl |first1=C. |last2=Clauss |first2=M. |last3=Stewart |first3=M. |last4=Leggett |first4=K. |last5=Hummel |first5=J. |last6=Kreuzer |first6=M. |last7=Munn |first7=A. |title=Decreasing methane yield with increasing food intake keeps daily methane emissions constant in two foregut fermenting marsupials, the western grey kangaroo and red kangaroo |journal=Journal of Experimental Biology |date=4 November 2015 |volume=218 |issue=21 |pages=3425–3434 |doi=10.1242/jeb.128165 |pmid=26538176 |doi-access=free |bibcode=2015JExpB.218.3425V }}</ref>

=== Social and sexual behavior ===
[[File:Fighting red kangaroos 1.jpg|thumb|upright=1|Two male [[red kangaroo]]s boxing]]
Groups of kangaroos are called ''mobs'', ''courts'' or ''troupes'', which usually have 10 or more kangaroos in them. Living in mobs can provide protection for some of the weaker members of the group.<ref name="Kidcyber"/> The size and stability of mobs vary between geographic regions,<ref name = "McCullough 2000">{{harvnb|McCullough|2000}}</ref><ref>{{cite journal |last1=Green-Barber |first1=JM |last2=Old |first2=JM |year=2018 |title=Town roo, country roo: a comparison of behaviour in eastern grey kangaroos (''Macropus giganteus'') in developed and natural landscapes |journal=Australian Zoologist |volume=39 |issue=3 |pages=520–533 |doi=10.7882/AZ.2018.019|s2cid=134213663 |doi-access=free }}</ref><ref>{{cite journal |last1=Green-Barber |first1=JM |last2=Old |first2=JM |year=2018 |title=The genetic relatedness of a peri-urban population of eastern grey kangaroos |journal=BMC Research Notes |volume=11 |issue=1 |pages=856 |doi=10.1186/s13104-018-3969-2|pmid=30514393 |pmc=6280538 |doi-access=free }}</ref> with eastern Australia having larger and more stable aggregations than in arid areas farther west.<ref name="McCullough 2000"/> Larger aggregations display high amounts of interactions and complex social structures, comparable to that of [[ungulate]]s.<ref name="McCullough 2000"/>

One common behavior is nose touching and sniffing, which mostly occurs when an individual joins a group.<ref name="Dawson 1995">{{cite book |author=Dawson, Terence J. |title=Kangaroos: Biology of the Largest Marsupials |publisher=Cornell University Press/Comstock Publishing |year=1995 |isbn=978-0-8014-8262-5 |url-access=registration |url=https://archive.org/details/kangaroosbiology00daws }}</ref> The kangaroo performing the sniffing gains much information from smell cues. This behavior enforces social cohesion without consequent aggression. During mutual sniffing, if one kangaroo is smaller, it will hold its body closer to the ground and its head will quiver, which serves as a possible form of submission.<ref name="Dawson 1995"/> Greetings between males and females are common, with larger males being the most involved in meeting females. Most other non-antagonistic behavior occurs between mothers and their young. Mother and young reinforce their bond through grooming. A mother will groom her young while it is suckling or after it is finished suckling.<ref name="Dawson 1995"/>  A joey will nuzzle its mother's pouch if it wants access to it.

{{Anchor|Sexual behavior}}
[[Animal sexual behavior|Sexual activity]] of kangaroos consists of consort pairs.<ref name = "Gansloßer 1995"/> [[Estrus|Oestrous]] females roam widely and attract the attention of males with conspicuous signals.<ref name = "Gansloßer 1995">{{cite journal |author=Gansloßer, Udo |title=Courtship behaviour in Macropodoidea (kangaroos, wallabies and rat kangaroos)&nbsp;– phylogenetic and ecological influences on ritualization |journal=Mammal Review |volume=25 |issue=3 |pages=131–157 |year=1995 |doi=10.1111/j.1365-2907.1995.tb00453.x |bibcode=1995MamRv..25..131G }}</ref> A male will monitor a female and follow her every movement. He sniffs her urine to see if she is in oestrus, a process exhibiting the [[flehmen response]]. The male will then proceed to approach her slowly to avoid alarming her.<ref name = "McCullough 2000"/> If the female does not run away, the male will continue by licking, pawing, and scratching her, and [[copulation (zoology)|copulation]] will follow.<ref name = "McCullough 2000"/> After copulation is over, the male will move on to another female. Consort pairing may take several days and the copulation is also long. Thus, a consort pair is likely to attract the attention of a rival male.<ref name = "Gansloßer 1995"/> As larger males are tending bonds with females near oestrus, smaller males will tend to females that are farther from oestrus.<ref name = "McCullough 2000"/> [[dominance (ethology)|Dominant]] males can avoid having to sort through females to determine their reproductive status by searching for tending bonds held by the largest male they can displace without a fight.<ref name = "McCullough 2000"/>

Fighting has been described in all species of kangaroos. Fights between kangaroos can be brief or long and ritualised.<ref name="Dawson 1995"/> In highly competitive situations, such as males fighting for access to oestrous females or at limited drinking spots, the fights are brief.<ref name="Dawson 1995"/> Both sexes will fight for drinking spots, but long, ritualised fighting or "boxing" is largely done by males. Smaller males fight more often near females in oestrus, while the large males in consorts do not seem to get involved. Ritualised fights can arise suddenly when males are grazing together. However, most fights are preceded by two males scratching and grooming each other.<ref name="Dawson 1995"/> One or both of them will adopt a high standing posture, with one male issuing a challenge by grasping the other male's neck with its forepaw. Sometimes, the challenge will be declined. Large males often reject challenges by smaller males. During fighting, the combatants adopt a high standing posture and paw at each other's heads, shoulders and chests. They will also lock forearms and wrestle and push each other as well as balance on their tails to kick each other in the abdomen.<ref name="Dawson 1995"/>

Brief fights are similar, except there is no forearm locking. The losing combatant seems to use kicking more often, perhaps to parry the thrusts of the eventual winner. A winner is decided when a kangaroo breaks off the fight and retreats. Winners are able to push their opponents backwards or down to the ground. They also seem to grasp their opponents when they break contact and push them away.<ref name="Dawson 1995"/> The initiators of the fights are usually the winners. These fights may serve to establish dominance hierarchies among males, as winners of fights have been seen to displace their opponent from resting sites later in the day.<ref name="Dawson 1995"/> Dominant males may also pull grass to intimidate subordinate ones.<ref name = "McCullough 2000"/>

=== Predators ===
Kangaroos have a few natural [[predator]]s. The [[thylacine]], considered by palaeontologists to have once been a major natural predator of the kangaroo, is now [[Extinction|extinct]]. Other extinct predators included the [[marsupial lion]], ''[[Megalania]]'' and ''[[Wonambi]]''. However, with the arrival of humans in Australia at least 50,000 years ago and the introduction of the [[dingo]] about 5,000 years ago, kangaroos have had to adapt.

Along with dingoes, [[Invasive species, Australia|introduced species]] such as foxes, [[feral cat]]s, and both domestic and feral dogs, pose a threat to kangaroo populations. Kangaroos and wallabies are adept [[Aquatic locomotion|swimmers]], and often flee into waterways if presented with the option. If pursued into the water, a large kangaroo may use its forepaws to hold the predator underwater so as to [[Drowning|drown]] it.<ref name="camuseum">{{cite web|title=Kangaroos|url=http://www.nature.ca/notebooks/english/kanga.htm|work=Natural History Notebooks|publisher=Canadian Museum of Nature|access-date=2 October 2011|date=3 May 2011|archive-date=9 January 2016|archive-url=https://web.archive.org/web/20160109223806/http://www.nature.ca/notebooks/english/kanga.htm|url-status=live}}</ref> Another defensive [[Tactic (method)|tactic]] described by witnesses is catching the attacking dog<!--Just dogs, or other predators as well?--> with the forepaws and [[disembowel]]ling it with the hind legs.

=== Adaptations ===
[[File:Kangaroo and joey03.jpg|thumb|upright=0.7|Kangaroo and joey in pouch]]
[[File:Kaenguru Hinterfuss-drawing.jpg|thumb|upright=0.7|The hind leg of a kangaroo]]
Kangaroos have developed a number of adaptations to a dry, infertile country and highly variable climate. As with all [[marsupial]]s, the young are born at a very early stage of development—after a [[gestation]] of 31–36 days. At this stage, only the forelimbs are somewhat developed, to allow the newborn to climb to the [[Pouch (marsupial)|pouch]] and attach to a [[teat]]. In comparison, a human [[embryo]] at a similar stage of development would be at about 7 weeks gestation (even in a modern intensive care unit, [[Premature birth|premature babies]] born at less than 23 weeks gestation are usually not mature enough to survive). When the joey is born, it is about the size of a [[Phaseolus lunatus|lima bean]]. The joey will usually stay in the pouch for about 9 months (180–320 days for the Western Grey) before starting to leave the pouch for small periods of time. It is usually fed by its mother until reaching 18 months.

The female kangaroo is usually pregnant in permanence, except on the day she gives birth; however, she has the ability to freeze the development of an embryo until the previous [[Joey (marsupial)|joey]] is able to leave the pouch. This is known as [[embryonic diapause]] and will occur in times of drought and in areas with poor food sources. The composition of the milk produced by the mother varies according to the needs of the joey. In addition, the mother is able to produce two different kinds of milk simultaneously for the newborn and the older joey still in the pouch.

Unusually, during a dry period, males will not produce sperm and females will conceive only if enough rain has fallen to produce a large quantity of green vegetation.<ref name="animal">{{cite book | last = Burnie | first = David |author2=Don E. Wilson | title = Animal | publisher=DK | year = 2001 | location = New York NY | pages = 99–101 | isbn = 978-0-7894-7764-4}}</ref>

Kangaroos and wallabies have large, elastic tendons in their hind legs. They store elastic strain energy in the [[tendon]]s of their large hind legs, providing most of the energy required for each hop by the spring action of the tendons rather than by any muscular effort.<ref name="tendons & hopping">{{cite book| last=Dawson| first=Terence J. (Professor UNSW)| title=Kangaroos: Biology of the largest marsupials| year=1998| publisher=Comstock Pub. Associates| location=Ithaca, N.Y.| isbn=9780801482625| pages=7–11| url=https://books.google.com/books?id=KNxIlprcmTYC&q=ancestors+of+kangaroos&pg=PA6| edition=2nd| access-date=3 August 2013| format=Paperback| archive-date=16 May 2021| archive-url=https://web.archive.org/web/20210516185428/https://books.google.com/books?id=KNxIlprcmTYC&q=ancestors+of+kangaroos&pg=PA6| url-status=live}}</ref> This is true in all animal species which have muscles connected to their skeletons through elastic elements such as tendons, but the effect is more pronounced in kangaroos.

There is also a link between the hopping action and breathing: as the feet leave the ground, air is expelled from the lungs; bringing the feet forward ready for landing refills the lungs, providing further energy efficiency. Studies of kangaroos and [[Wallaby|wallabies]] have demonstrated, beyond the minimum energy expenditure required to hop at all, increased speed requires very little extra effort (much less than the same speed increase in, say, a horse, dog or human), and the extra energy is required to carry extra weight. For kangaroos, the key benefit of hopping is not speed to escape predators—the top speed of a kangaroo is no higher than that of a similarly sized quadruped, and the Australian native predators are in any case less fearsome than those of other countries—but economy: in an infertile country with highly variable weather patterns, the ability of a kangaroo to travel long distances at moderately high speed in search of food sources is crucial to survival.

New research has revealed that a kangaroo's tail acts as a third leg rather than just a balancing strut. Kangaroos have a unique three-stage walk where they plant their front legs and tail first, then push off their tail, followed lastly by the back legs. The propulsive force of the tail is equal to that of both the front and hind legs combined and performs as much work as what a human leg walking can at the same speed.<ref>{{cite news|title=Kangaroos use tail like a leg to walk|url=http://www.australiangeographic.com.au/news/2014/07/kangaroos-use-tail-to-walk|access-date=18 November 2014|website=Australian Geographic|date=2 July 2014|archive-date=10 November 2014|archive-url=https://web.archive.org/web/20141110100429/http://www.australiangeographic.com.au/news/2014/07/kangaroos-use-tail-to-walk|url-status=live}}</ref>

A [[DNA sequencing]] project of the [[genome]] of a member of the kangaroo family, the [[tammar wallaby]], was started in 2004. It was a collaboration between Australia (mainly funded by the [[Victoria (Australia)|State of Victoria]]) and the [[National Institutes of Health]] in the US.<ref name="genome">{{Cite press release|author=Spencer, Geoff |title=Kangaroo Hops in Line for Genome Sequencing |url=http://www.nih.gov/news/pr/jun2004/nhgri-08.htm |work=National Human Genome Research Institute |publisher=National Institutes of Health |access-date=2 October 2011 |date=8 June 2004 |url-status=dead |archive-url=https://web.archive.org/web/20111002020057/http://www.nih.gov/news/pr/jun2004/nhgri-08.htm |archive-date=2 October 2011 }}</ref> The tammar's genome was fully sequenced in 2011.<ref name="Renfree/Papenfuss">{{cite journal |author=Renfree M. B. |author2=Papenfuss, A. T. |author3=Deakin, J. E. |display-authors=etal | title=Genome sequence of an Australian kangaroo, ''Macropus eugenii'', provides insight into the evolution of mammalian reproduction and development.| journal=Genome Biology| volume=12| issue=8| pages=R81| pmid=21854559| doi=10.1186/gb-2011-12-8-r81| pmc=3277949 | date=19 August 2011 |doi-access=free }}</ref> The genome of a marsupial such as the kangaroo is of great interest to scientists studying [[comparative genomics]], because marsupials are at an ideal degree of evolutionary divergence from humans: [[mouse|mice]] are too close and have not developed many different functions, while birds are genetically too remote. The dairy industry could also benefit from this project.<ref>{{cite journal|title=The tammar wallaby: A model to examine endocrine and local control of lactation|journal=IUBMB Life|last1=Brennan|first1=A. J.|last2=Sharp|first2=J. A.|last3=Digby|first3=M. R.|last4=Nicholas|first4=K. R.|volume=59|issue=3|pages=146–150|year=2007|doi=10.1080/15216540701335724|doi-access=free|pmid=17487685}}</ref>

=== Blindness ===
Eye disease<!--Proper name(s)?--> is rare but not new among kangaroos. The first official report of kangaroo blindness took place in 1994, in central [[New South Wales]]. The following year, reports of blind kangaroos appeared in Victoria and South Australia. By 1996, the disease had spread "across the desert to Western Australia".<ref name=nwf/> Australian authorities were concerned the disease could spread to other livestock and possibly humans. Researchers at the Australian Animal Health Laboratories in [[Geelong]] detected a virus called the Wallal virus in two species of [[midge]]s, believed to have been the carriers.<ref>{{cite journal |last=Hooper |first=P |title=Kangaroo blindness and some other new viral diseases in Australia |journal=Australian Veterinary Journal |volume=77 |issue=8 |pages=514–5 |date=August 1999 |url=http://www.ava.com.au/avj/9908/99080514.pdf |access-date=31 December 2006 |doi=10.1111/j.1751-0813.1999.tb12122.x |pmid=10494397 |archive-url=https://web.archive.org/web/20060917145454/http://www.ava.com.au/avj/9908/99080514.pdf |archive-date=17 September 2006 |url-status=dead }}</ref><ref>{{cite journal | doi = 10.1071/EC87p36 | title = Viruses on the hop | journal=Ecos | issue = 87 |date=Autumn 1996 | author1 = <!-- Please add first missing authors to populate metadata. --> | volume=1996 | page=36| doi-broken-date = 2 May 2025 }}</ref> [[Veterinarians]] also discovered fewer than 3% of kangaroos exposed to the virus developed blindness.<ref name=nwf>{{cite web | last = Harrison | first = George | title = Everything You Always Wanted to Know About Kangaroos | date = September–October 1997 | publisher=National Wildlife Federation | archive-url  = https://web.archive.org/web/20051230075601/http://www.nwf.org/internationalwildlife/kangaroo.html | archive-date = 30 December 2005 | url = http://www.nwf.org/internationalwildlife/kangaroo.html}}</ref>

=== Reproduction and life cycle ===
{{see also|Red kangaroo#Reproduction|Eastern grey kangaroo#Reproduction}}
[[File:Joey in pouch.jpg|thumb|upright=0.7|A newborn joey sucking on a teat in the pouch]]
Kangaroo reproduction is similar to that of [[opossum]]s. The egg (still contained in the shell membrane, a few micrometres thick, and with only a small quantity of yolk within it) descends from the [[ovary]] into the [[uterus]]. There it is fertilised and quickly develops into a [[neonate]]. Even in the largest kangaroo species (the [[red kangaroo]]), the neonate emerges after only 33 days. Usually, only one young is born at a time. It is blind, hairless, and only a few centimetres long; its hindlegs are mere stumps; it instead uses its more developed forelegs to climb its way through the thick fur on its mother's [[abdomen]] into the pouch, which takes about three to five minutes. Once in the pouch, it fastens onto one of the four teats and starts to feed. Almost immediately, the mother's sexual cycle starts again. Another egg descends into the uterus and she becomes sexually receptive. Then, if she mates and a second egg is fertilised, its development is temporarily halted. This is known as [[embryonic diapause]], and will occur in times of drought and in areas with poor food sources. Meanwhile, the neonate in the pouch grows rapidly. After about 190 days, the baby ([[Marsupial#Early development|joey]]) is sufficiently large and developed to make its full emergence out of the pouch, after sticking its head out for a few weeks until it eventually feels safe enough to fully emerge. From then on, it spends increasing time in the outside world and eventually, after about 235 days, it leaves the pouch for the last time.<ref>[http://planet.uwc.ac.za/nisl/biodiversity/loe/page_193.htm Evolution of Biodiversity] {{Webarchive|url=https://web.archive.org/web/20160303182629/http://planet.uwc.ac.za/nisl/biodiversity/loe/page_193.htm |date=3 March 2016 }}, BCB705 Biodiversity, University of the Western Cape</ref> The [[Life expectancy|lifespan]] of kangaroos averages at six years in the wild<ref name="patricia">{{Cite book|last =Miller-Schroeder|first =Patricia|title =Kangaroos|series =The Untamed World|publisher =Raintree Steck-Vaughn|year =2002|url =https://books.google.com/books?id=zO_YyJfjK00C&q=kangaroo++lifespan|isbn =978-0-7398-4972-9|access-date =8 May 2020|archive-date =16 May 2021|archive-url =https://web.archive.org/web/20210516185636/https://books.google.com/books?id=zO_YyJfjK00C&q=kangaroo++lifespan|url-status =live}}</ref> to in excess of 20 years in captivity, varying by the species.<ref name="park">{{cite web|url=http://www.parkweb.vic.gov.au/education/factfiles/06.htm |title=Kangaroo |publisher=Parks Victoria |access-date=20 February 2011 |url-status=dead |archive-url=https://web.archive.org/web/20110208012253/http://www.parkweb.vic.gov.au/education/factfiles/06.htm |archive-date=8 February 2011 }}</ref> Most individuals, however, do not reach maturity in the wild.<ref name="nowak">{{Cite book|last =Nowak|first =Ronald M.|title =Walker's mammals of the world|publisher =Johns Hopkins University Press|volume =2|year =1999|isbn =978-0-8018-5789-8|url =https://books.google.com/books?id=T37sFCl43E8C&q=kangaroo+average+life+span+wild&pg=PA125|access-date =4 October 2020|archive-date =16 May 2021|archive-url =https://web.archive.org/web/20210516185610/https://books.google.com/books?id=T37sFCl43E8C&q=kangaroo+average+life+span+wild&pg=PA125|url-status =live}}</ref><ref name="giganteus">{{cite web|url=http://animaldiversity.ummz.umich.edu/site/accounts/information/Macropus_giganteus.html|title=Macropus giganteus|last2=Wund|last1=Joo|first2=Matthew|first1=Michael S.|publisher=Animal Diversity Web, University of Michigan Museum of Zoology|access-date=20 February 2011|archive-date=29 June 2011|archive-url=https://web.archive.org/web/20110629053809/http://animaldiversity.ummz.umich.edu/site/accounts/information/Macropus_giganteus.html|url-status=live}}</ref>