Editing Groundhog (section)

==Behavior==
[[File:Groundhog-Standing2.jpg|thumb|A motionless individual, alert to danger, will whistle when alarmed to warn other groundhogs.]]
W.J. Schoonmaker reports that groundhogs may hide when they see, smell, or hear an observer.<ref name=Schoonmaker/>{{rp|41–43}} Marmot researcher Ken Armitage states that the social biology of the groundhog is poorly studied.<ref>Special feature "The Study of Groundhogs: A Real Life Look at Marmots", Movie "Groundhog Day" 15th Anniversary Edition.</ref>
Despite their heavy-bodied appearance, groundhogs are accomplished swimmers and occasionally climb trees when escaping predators or when they want to survey their surroundings.<ref name="chapman">{{cite book|last=Chapman|first=J. A.|author2=Feldhammer, G. A.|title=Wild Mammals of North America, Biology, Management, Economics|year=1982|publisher=Johns Hopkins University Press|isbn=0801823536|url-access=registration|url=https://archive.org/details/wildmammalsofnor0000unse}}</ref> They prefer to retreat to their burrows when threatened; if the burrow is invaded, the groundhog tenaciously defends itself with its two large [[incisor]]s and front claws. Groundhogs are generally [[Agonistic behaviour|agonistic]] and territorial toward each other and may skirmish to establish dominance.<ref name="whitaker"/><ref name="Schoonmaker"/>{{rp|93}}
Outside their burrow, individuals are alert when not actively feeding. It is common to see one or more nearly motionless individuals standing erect on their hind feet watching for danger. When alarmed, they use a high-pitched whistle to warn the rest of the colony, hence the name "whistle-pig".<ref name="adweb" /><ref name="CWS">[https://web.archive.org/web/20110205231246/http://www.hww.ca/hww2.asp?pid=1&id=109&cid=8 Hinterland Who's Who ("Canadian Wildlife Service: Mammals: Woodchuck")]. Hww.ca. Retrieved on September 15, 2011.</ref> Groundhogs may squeal when fighting, seriously injured, or caught by a predator.<ref name="CWS"/> Other vocalizations include low barks and a sound produced by grinding their teeth.<ref name="CWS"/> [[David P. Barash]] wrote that he witnessed only two occasions of upright play-fighting among woodchucks and that the upright posture of play-fighting involves sustained physical contact between individuals that may require a degree of social tolerance virtually unknown in ''M. monax''. Alternatively, upright play-fighting may be a part of the woodchuck's behavioral repertoire that rarely is shown because of physical spacing and/or low social tolerance.<ref name="BarashMarmots">{{Cite book |last=Barash |first=David P. |title=Marmots: social behavior and ecology |date=1989 |publisher=Stanford University Press |isbn=978-0-8047-1534-8 |location=Stanford, California}}</ref>{{rp|97}}

===Diet===
[[File:Juvenile Groundhog in a Field of Clover.jpg|thumb|Clover is a preferred food source for groundhogs.]]
[[File:20240611 groundhog south meadows wm.webm|thumb|Eating wild vegetation]]
Mostly [[herbivory|herbivorous]], groundhogs eat primarily wild grasses and other vegetation, including berries, bark, leaves, and agricultural crops, when available.<ref name="whitaker">{{cite book|title=Mammals of the Eastern United States|last=Whitaker|first=John O|author2=Hamilton, W J.|year=1998|publisher=Cornell University Press|isbn=0-8014-3475-0|url-access=registration|url=https://archive.org/details/mammalsofeastern00whit}}</ref><ref name="auto">{{cite web | url=https://animaldiversity.org/accounts/Marmota_monax/ | title=Marmota monax (Woodchuck) | website=[[Animal Diversity Web]] }}</ref> In early spring, [[dandelion]] and [[Tussilago|coltsfoot]] are important groundhog food items. Some additional foods include [[sheep sorrel]], [[timothy-grass]], [[Ranunculus|buttercup]], [[persicaria]], [[agrimony]], red and black [[Raspberry|raspberries]], [[mulberries]], [[buckwheat]], [[Plantain cultivars|plantain]], [[wild lettuce]], [[alfalfa]], and all varieties of [[clover]]. Groundhogs also occasionally eat small animals, such as [[larva|grubs]], [[grasshopper]]s, [[snail]]s, and even bird eggs and baby birds, but are not as [[omnivore|omnivorous]] as many other [[squirrel|Sciuridae]].<ref name="auto"/><ref>Canadian Wildlife Federation, Groundhog</ref>

An adult groundhog can eat more than {{Convert|1|lb|kg|abbr=on}} of vegetation daily.<ref>DNR, Indiana Department of Natural Resources, Groundhog</ref> In early June, woodchucks' [[metabolism]] slows, and while their food intake decreases, their weight increases by as much as 100% as they produce fat deposits to sustain them during hibernation and late winter.<ref>{{Cite news |last=Line |first=Les |date=29 January 1997 |title=Woodchucks Are in the Lab, but Their Body Clocks Are Wild |url=https://www.nytimes.com/1997/01/28/science/woodchucks-are-in-the-lab-but-their-body-clocks-are-wild.html |work=The New York Times}}</ref> Instead of storing food, groundhogs stuff themselves to survive the winter without eating.<ref>Discovery Nature Encyclopedia, Groundhog</ref> Thought not to drink water, groundhogs are reported to obtain needed liquids from the juices of edible plants, aided by their sprinkling with rain or dew.<ref name="Schoonmaker"/>{{rp|85}}<ref>The Virtual Nature Trail at Penn State New Kensington Species Pages Scientific name: Marmota monax Common name: woodchuck.</ref><ref name="Seton1928"/>{{rp|308}}

===Burrows===
[[File:Marmota monax UL 07.jpg|thumb|Groundhog gathering nesting material for its warm [[burrow]]]]
Groundhogs are excellent burrowers, using burrows for sleeping, rearing young, and [[hibernation|hibernating]]. Groundhog burrows usually have two to five entrances, providing groundhogs their primary means of escape from predators. The volume of earth removed from groundhog burrows in one study averaged {{convert|6|cuft|m3}} per den. The longest burrow measured {{convert|24|ft|m}} in addition to two short side galleries.<ref name="Schoonmaker"/>{{rp|108-109}} 

Though groundhogs are the most solitary of the marmots, several individuals may occupy the same burrow.

Burrows can pose a serious threat to agricultural and residential development by damaging farm machinery and even undermining building foundations.<ref name="adweb">{{cite web |last=Light |first=Jessica E. |title=Animal Diversity Web: Marmota monax |url=http://animaldiversity.ummz.umich.edu/site/accounts/information/Marmota_monax.html |url-status=dead |archive-url=https://web.archive.org/web/20110518042717/http://animaldiversity.ummz.umich.edu/site/accounts/information/Marmota_monax.html |archive-date=May 18, 2011 |access-date=July 14, 2009 |publisher=University of Michigan Museum of Zoology}}</ref> In a June 7, 2009, Humane Society of the United States article, "How to Humanely Chuck a Woodchuck Out of Your Yard" by John Griffin, director of Humane Wildlife Services, stated you would have to have a lot of woodchucks working over a lot of years to create tunnel systems that would pose any risk to a structure.{{cn|date=May 2024}}

The burrow is used for safety, retreat in bad weather, hibernating, sleeping, mating, and nursery. In addition to the nest, there is an excrement chamber. The hibernation or nest chamber is lined with dead leaves and dried grasses.<ref>{{Cite journal |last=Kwiecinski |first=Gary G. |date=1998-12-04 |title=Marmota monax |url=https://academic.oup.com/mspecies/article-lookup/doi/10.2307/3504364 |journal=Mammalian Species |issue=591 |pages=1–8 |doi=10.2307/3504364|jstor=3504364 }}</ref> The nest chamber may be about twenty inches to three feet ({{convert|20|-|36|in|cm|disp=out}}) below ground surface. It is about {{convert|16|in|cm}} wide and {{convert|14|in|cm}} high. There are typically two burrow openings or holes. One is the main entrance, the other a spy hole. Description of the length of the burrow often includes side galleries. Excluding side galleries, Schoonmaker reports the longest was {{convert|24|ft|m}}, and the average length of eleven dens was {{convert|14|ft|m}}.<ref name="Schoonmaker"/>{{rp|104-105}} W. H. Fisher investigated nine burrows, finding the deepest point {{convert|49|in|cm}} down. The longest, including side galleries, was {{height|ft=47|in=11.5}}.<ref name="Seton1928"/>{{rp|306}} Numbers of burrows per individual groundhog decrease with [[urbanization]].<ref name="watson"/><ref>{{Cite journal |last1=Lehrer |first1=E.W. |last2=Schooley |first2=R.L. |last3=Whittington |first3=J.K. |date=2011-12-14 |title=Survival and antipredator behavior of woodchucks ( Marmota monax ) along an urban–agricultural gradient |url=http://www.nrcresearchpress.com/doi/10.1139/z11-107 |journal=[[Canadian Journal of Zoology]] |language=en |volume=90 |issue=1 |pages=12–21 |doi=10.1139/z11-107 |issn=0008-4301|url-access=subscription }}</ref>

Bachman mentioned when young groundhogs are a few months old, they prepare for separation, digging a number of holes in the area of their early home. Some of these holes were only a few feet deep and never occupied, but the numerous burrows gave the impression that groundhogs live in communities.<ref name="Seton1928"/>{{rp|318}}

Abandoned groundhog burrows benefit many other species by providing shelter. They are used by [[Cottontail rabbit|cottontail rabbits]], [[Raccoon|raccoons]], [[Fox|foxes]], [[River Ottter|river otters]], [[Eastern chipmunk|eastern chipmunks]], and a wide variety of small mammals, snakes, and birds.<ref>{{cite web|url=https://njaes.rutgers.edu/e361/|title=Ecology and Management of the Groundhog (Marmota monax)|access-date=August 7, 2024}}</ref>

===Hibernation===
[[File:Baby groundhogs - 05-17-2020.jpg|thumb|Two baby groundhogs]]
Groundhogs are one of the few species that enter into true [[hibernation]], and often build a separate "winter burrow" for this purpose. This burrow is usually in a wooded or brushy area and is dug below the [[frost line]] and remains at a stable temperature well above freezing during the winter months. In most areas, groundhogs hibernate from October to March or April, but in more temperate areas, they may hibernate as little as three months.<ref name="rhodeisland">[http://www.dem.ri.gov/programs/bnatres/fishwild/pdf/woodchuck.pdf Woodchucks in Rhode Island] {{Webarchive|url=https://web.archive.org/web/20070412090734/http://www.dem.ri.gov/programs/bnatres/fishwild/pdf/woodchuc.pdf |date=April 12, 2007 }}. (PDF) dem.ri.gov. Retrieved on September 15, 2011.</ref> Groundhogs hibernate longer in northern latitudes than southern latitudes.<ref>{{Cite journal |last1=Zervanos |first1=Stam M. |last2=Maher |first2=Christine R. |last3=Waldvogel |first3=Jerry A. |last4=Florant |first4=Gregory L. |date=January 2010 |title=Latitudinal Differences in the Hibernation Characteristics of Woodchucks (Marmota monax ) |url=https://www.journals.uchicago.edu/doi/10.1086/648736 |journal=[[Physiological and Biochemical Zoology]] |language=en |volume=83 |issue=1 |pages=135–141 |doi=10.1086/648736 |pmid=19958172 |issn=1522-2152|url-access=subscription }}</ref><ref>{{cite web|website=berks.psu.edu|date=January 23, 2014|title=Professor sheds light on groundhog's shadowy behavior|url=https://berks.psu.edu/story/2398/2014/01/23/professor-sheds-light-groundhogs-shadowy-behavior|access-date=June 11, 2021|archive-date=June 11, 2021|archive-url=https://web.archive.org/web/20210611180103/https://berks.psu.edu/story/2398/2014/01/23/professor-sheds-light-groundhogs-shadowy-behavior|url-status=live}}</ref> To survive the winter, they are at their maximum weight shortly before entering hibernation.<ref name="ReferenceA">Woodchucks in Rhode Island, dem.ri.gov</ref> When the groundhog enters hibernation, there is a drop in body temperature to as low as {{convert|35|°F|°C|abbr=out}}, heart rate falls to 4–10 beats per minute and breathing rate falls to one breath every six minutes.<ref>{{Cite web|url=https://www.uwsp.edu/biology/VertebrateCollection/Pages/Vertebrates/Mammals%20of%20Wisconsin/Marmota%20monax/Marmota%20monax.aspx|title= Marmota monax - Vertebrate Collection &#124; UWSP|access-date=October 13, 2018|archive-date=October 13, 2018|archive-url=https://web.archive.org/web/20181013053816/https://www.uwsp.edu/biology/VertebrateCollection/Pages/Vertebrates/Mammals%20of%20Wisconsin/Marmota%20monax/Marmota%20monax.aspx|url-status=live}}</ref> During hibernation, they experience periods of torpor and arousal.<ref>Penn State news, January 22, 2014, ''Professor sheds light on groundhog's shadowy behavior ''</ref> Hibernating woodchucks lose as much as half their body weight by February.<ref>Groundhog Day facts and factoids, Cornell Chronicle, February 1, 1996</ref> They emerge from hibernation with some remaining body fat to live on until the warmer spring weather produces abundant plant materials for food.<ref name="ReferenceA"/> Males emerge from hibernation before females.<ref>{{cite journal|doi=10.2307/3504364|jstor=3504364|title=Marmota monax|last1=Kwiecinski|first1=Gary G.|journal=Mammalian Species|year=1998|issue=591|pages=1–8|doi-access=free}}</ref><ref name="Schoonmaker"/>{{rp|50}} Groundhogs are mostly [[diurnality|diurnal]] and are often active early in the morning or late afternoon.<ref>[http://web.extension.illinois.edu/wildlife/directory_show.cfm?species=woodchuck Woodchuck] {{Webarchive|url=https://web.archive.org/web/20140421064626/http://web.extension.illinois.edu/wildlife/directory_show.cfm?species=woodchuck |date=April 21, 2014 }}, Illinois University</ref>

===Reproduction===
Groundhogs are considered the most [[Sociality#Presociality|solitary]] of the [[Marmot|marmot species]]. They live in aggregations, and their social organization also varies across [[populations]]. Groundhogs do not form stable, long-term pair-bonds, and during [[mating season]] male-female interactions are limited to [[copulation (zoology)|copulation]]. Groundhogs in [[Ohio]], however, have been observed to have different social organization than groundhogs elsewhere, with adult males and females associating with each other throughout the year and often from year to year.<ref name="mating system">{{Cite journal |last1=Maher |first1=Christine R. |last2=Duron |first2=Melissa |date=June 16, 2010 |title=Mating system and paternity in woodchucks (Marmota monax) |journal=Journal of Mammalogy |volume=91 |issue=3 |pages=628–635 |doi=10.1644/09-MAMM-A-324.1 |s2cid=56472630 |doi-access=free}}</ref><ref name="Kwiecinski" /> Usually groundhogs [[biological reproduction|breed]] in their second year, but a small proportion may breed in their first. The [[breeding season]] extends from early March to mid- or late April, after hibernation. Woodchucks are polygynous<ref name=ADW/> but only alpine and woodchuck marmot females have been shown to mate with multiple males.<ref name="mating system"/> A mated pair remains in the same den throughout the 31- to 32-day [[gestation period]].<ref>[https://web.archive.org/web/20100619014532/http://www.ncwildlife.org//Wildlife_Species_Con/Profiles/woodchuck.pdf Woodchuck. ''Marmota monax'']. (PDF). North Carolina Wildlife.</ref> As birth of the young approaches in April or May, the male leaves the den. One litter is produced annually. Female woodchucks give birth to one to nine offspring, with most litters ranging between 3 and 5 pups.<ref name=ADW/> Groundhog mothers introduce their young to the wild once their fur is grown in and they can see. At this time, if at all, the father groundhog comes back to the family.<ref name="Seton1928"/>{{rp|316}} By the end of August, the family breaks up; or at least, the larger number scatter, to burrow on their own.<ref name="Seton1928"/>{{rp|318}}