Island gigantism 3658014 225751691 2008-07-15T06:22:22Z Socal gal at heart 4316556 [[Image:Giant Haasts eagle attacking New Zealand moa.jpg|thumb|right|200px|The large [[Haast's Eagle]] and [[Moa]] from [[New Zealand]].]] '''Island gigantism''' is a biological phenomenon where the size of animals isolated on an island increases dramatically over generations. It is a form of natural selection in which bigger size provides a survival advantage (see [[Bergmann's Rule]]). Large size in [[herbivore]]s usually makes it harder to escape or hide from predators, but on islands, these are often lacking. Thus, island gigantism is not an evolutionary trend due to fundamentally new parameters determining fitness (as in [[insular dwarfism|island dwarfing]]), but rather the removal of constraints. With the arrival of humans and associated predators (dogs, cats, rats, pigs), many giant island endemics have become [[Extinction|extinct]]. As opposed to [[island dwarfing]], island gigantism is found in most major [[vertebrate]] groups and in [[invertebrates]]. == Examples == Examples of island gigantism include: === [[Mammal]]s === * Rodents ** [[Flores Giant Rat]]s ** [[Giant hutia]]s from the [[West Indies]] (extinct) ** [[Majorcan Giant Dormouse]] and [[Minorcan Giant Dormouse]] (extinct) Many rodents grow larger on islands, whereas [[lagomorph]]s, [[carnivore]]s, [[proboscidean]]s and [[artiodactyl]]s usually become smaller. *Primates **the extinct giant [[lemur]] genera ''[[Archaeoindris]], [[Palaeopropithecus]]'' and ''[[Megaladapis]]'' of [[Madagascar]]. * [[Giant rabbit]]s and [[shrew]]s from [[Mediterranean]] islands (extinct) === [[Bird]]s === *Ratites **the [[elephant bird]], among the largest birds ever, formerly living on Madagascar (extinct) **the extinct [[moa]] of [[New Zealand]]. *Waterfowl **[[Moa-nalo]]s, extinct giant ducks from [[Hawaii]]. *Wildfowl **''[[Sylviornis neocaledoniae]]'' a huge extinct [[megapode]]-like bird from [[New Caledonia]] **some extinct [[Polynesia]]n megapodes. *Rails **the [[takahē]]s from New Zealand and other ''[[Porphyrio]]'' as well as many ''[[Gallirallus]]'' species from [[Melanesia]] and [[Polynesia]] and a few other [[Rallidae]]. *Seabirds **the extinct [[Spectacled Cormorant]] from [[Bering Island]]. *Pigeons **[[Dodo]] and [[Rodrigues Solitaire]] from the [[Mascarenes]] **the extinct flightless [[Viti Levu Giant Pigeon]]. *Birds of prey ** the extinct [[Haast's Eagle]] and [[Eyles' Harrier]] of New Zealand. *Parrots **the extinct [[Broad-billed Parrot]] from Mauritius, an undescribed huge extinct parrot from [[Easter Island]], and the [[Kakapo]] of New Zealand. *Owls **[[Cuba]]n ''[[Ornimegalonyx]]'' true owls and several ''[[Tyto]]'' barn owls from the [[Mediterranean]], [[Caribbean]] and [[Melanesia]]. === [[Reptiles]] === *Turtles **[[Giant tortoise]]s on the [[Seychelles]], [[Galápagos Islands]] and formerly the Mascarenes *Lizards **[[Komodo dragon]] and a similar (extinct) giant [[monitor lizard]] from [[Timor]], rare examples of giant insular carnivores. Since islands tend to offer limited food and territory, their carnivores are usually smaller than continental ones. These cases may be unusual because they involve [[cold-blooded]] carnivores on islands too small to support much [[warm-blooded]] competition. (However, these lizards are not as large as their extinct Australian relative ''[[Megalania]]''.) **[[San Esteban Chuckwalla]] (''Sauromalus varius'') of islands off [[Baja California]] **''[[Leiolopisma mauritiana]]'' and ''[[Macroscincus coctei]]'', two extinct [[skink]]s from [[Mauritius]] and [[Cape Verde]], and the rare New Caledonian skink ''[[Phoboscincus bocourti]]'' ** the extinct [[Rodrigues giant day gecko]] and [[New Zealand giant gecko]], and the extant [[Rhacodactylus leachianus|New Caledonian giant gecko]] === [[Insects]] === *[[Madagascar hissing cockroach]] *[[St. Helena Earwig]] *[[Conant's Giant Nihoa Tree Cricket]] *[[Lord Howe Island phasmid]] *[[Giant weta]] of New Zealand === [[Flora]] === *[[Megaherb]] ==In popular culture== The movie [[King Kong]] provides a fictional (and exaggerated) example of Island gigantism. The animals, bugs and plants found on [[Skull Island]] all present monstrous sizes. == See also == *[[Insular dwarfism|Island dwarfing]] *[[Island rule]] *[[Deep-sea gigantism]] == External links == *[http://www.pbs.org/wgbh/nova/eden/giants.html PBS NOVA: Why Do Islands Breed Giants (And Sometimes Dwarfs)?] [[Category:Zoology]] [[Category:Evolutionary biology]] [[es:Gigantismo insular]] [[fr:Gigantisme insulaire]] [[hr:Otočni gigantizam]] [[id:Gigantisme pulau]] [[it:Gigantismo insulare]]