Island gigantism

This is itself one aspect of the more general phenomenon of island syndrome which describes the differences in morphology, ecology, physiology and behaviour of insular species compared to their continental counterparts.

Large mammalian carnivores are often absent on islands because of insufficient range or difficulties in over-water dispersal.

In their absence, the ecological niches for large predators may be occupied by birds, reptiles or smaller carnivorans, which can then grow to larger-than-normal size.

[4] Thus, island gigantism is usually an evolutionary trend resulting from the removal of constraints on the size of small animals related to predation and/or competition.

[6] In contrast, insular dwarfism among predators more commonly results from the imposition of constraints associated with the limited prey resources available on islands.

[citation needed] Increased leaf and seed size was also reported in some island species regardless of growth form (herbaceous, bush, or tree).

Size comparison of the giant gymnure (moonrat) Deinogalerix from the Late Miocene of Gargano , Italy, with a European hedgehog
Diagram displaying the change in size of weta species in two ecosystems. The size and population of weta are affected by predation. Rats introduced on the mainland began to prey on weta, reducing their population; weta shrank in response. On an island isolated from predation, such as Little Barrier Island , weta have a dense population and have grown to a massive size. Insular species of giant weta are the only ones not facing extinction. As weta grow over time, bird predation declines. [ citation needed ]
Leithia melitensis
Leithia melitensis
Komodo dragon ( Lesser Sundas )
Galápagos giant tortoise