Question: What animal subject to the Foster's rule is the smallest North American deer?

full_context: Document 1: Key deer: The Key deer ("Odocoileus virginianus clavium") is an endangered deer that lives only in the Florida Keys. It is a subspecies of the white-tailed deer ("O. virginianus"). It is the smallest North American deer.
Document 2: Foster's rule: Foster's rule (also known as the island rule or the island effect) is an ecogeographical rule in evolutionary biology stating that members of a species get smaller or bigger depending on the resources available in the environment. For example, it is known that pygmy mammoths evolved from normal mammoths on small islands. Similar evolutionary paths have been observed in elephants, hippopotamuses, boas, deer (for example Key deer) and humans.
Document 3: Seneca white deer: The Seneca White Deer are a rare herd of deer living within the confines of the former Seneca Army Depot in Seneca County, New York. When the 10600 acre depot was created in 1941, a 24 mi fence was erected around its perimeter, isolating a small herd of White-tailed deer, some of whom had white coats. These deer are not albino, but instead carry a set of recessive genes for all-white coats. Isolation of the herd causes high levels of inbreeding.
Document 4: Cope's rule: Cope's rule, named after American paleontologist Edward Drinker Cope, postulates that population lineages tend to increase in body size over evolutionary time. It was never actually stated by Cope, although he favoured the occurrence of linear evolutionary trends. It is sometimes also known as the Cope-Depéret rule, because Charles Depéret explicitly advocated the idea. Theodor Eimer had also done so earlier. The term "Cope's rule" was apparently coined by Bernhard Rensch, based on the fact that Depéret had "lionized Cope" in his book. While the rule has been demonstrated in many instances, it does not hold true at all taxonomic levels, or in all clades. Larger body size is associated with increased fitness for a number of reasons, although there are also some disadvantages both on an individual and on a clade level: clades comprising larger individuals are more prone to extinction, which may act to limit the maximum size of organisms.
Document 5: American mountain deer: Odocoileus lucasi, historically incorrectly confused with "Navahoceros fricki", and known as the American mountain deer, is an extinct species of North American deer.
Document 6: Elk: The elk, or wapiti ("Cervus canadensis"), is one of the largest species within the deer family, Cervidae, in the world, and one of the largest land mammals in North America and Eastern Asia. This animal should not be confused with the still larger moose ("Alces alces") to which the name "elk" applies in British English and in reference to populations in Eurasia. Apart from the moose, the only other member of the deer family to rival the elk in size is the south Asian sambar ("Rusa unicolor").
Document 7: Founder effect: In population genetics, the founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. It was first fully outlined by Ernst Mayr in 1942, using existing theoretical work by those such as Sewall Wright. As a result of the loss of genetic variation, the new population may be distinctively different, both genotypically and phenotypically, from the parent population from which it is derived. In extreme cases, the founder effect is thought to lead to the speciation and subsequent evolution of new species.
Document 8: List of rodents of the Caribbean: The Caribbean region is home to a diverse and largely endemic rodent fauna. This includes the endemic family Capromyidae (hutias), which are largely limited to the Greater Antilles, and two other groups of endemic hystricognaths, the heteropsomyines and giant hutias, including the extinct bear-sized "Amblyrhiza inundata". Lesser Antillean rodent faunas mostly consist of oryzomyines, members of a distantly related group of rodents, and include two of the largest known oryzomyines, "Megalomys desmarestii" and ""Oryzomys hypenemus"". Various other rodents are limited to land-bridge islands such as Trinidad, which were connected to the mainland during glacial-period lowered sea levels in the Pleistocene, or to smaller portions of the Caribbean archipelago. Much of the native rodent fauna of the Caribbean are extinct because of human influences, particularly following the introduction of invasive species such as Old World rats.
Document 9: Pudú: The pudús (Mapudungun "püdü" or "püdu", Spanish: pudú , ] ) are two species of South American deer from the genus Pudu, and are the world's smallest deer. The name is a loanword from Mapudungun, the language of the indigenous Mapuche people of southern Chile and south-western Argentina. The two species of pudús are the northern pudú ("Pudu mephistophiles") from Venezuela, Colombia, Ecuador, and Peru, and the southern pudú ("Pudu puda"; sometimes incorrectly modified to "Pudu pudu") from southern Chile and south-western Argentina. Pudús range in size from 32 to tall, and up to 85 cm long. As of 2009, the southern pudu is classified as near threatened, while the northern pudu is classified as vulnerable in the IUCN Red List.
Document 10: Pampas deer: Pampas deer ("Ozotoceros bezoarticus") live in the grasslands of South America at low elevations. They are known as "venado" or "gama" in Spanish and as "veado-campeiro" in Portuguese. Their habitat includes water and hills, often with winter drought, and grass that is high enough to cover a standing deer. Many of them live on the Pantanal wetlands, where there are ongoing conservation efforts, and other areas of annual flooding cycles. Human activity has changed much of the original landscape. They are known to live up to 12 years in the wild, longer if captive, but are threatened due to over-hunting and habitat loss. Many people are concerned over this loss, because a healthy deer population means a healthy grassland, and a healthy grassland is home to many species, some also threatened. Many North American birds migrate south to these areas, and if the Pampas deer habitat is lost, they are afraid these bird species will also decline. There are approximately 80,000 Pampas deer total, with the majority of them living in Brazil.
Document 11: Columbia Basin pygmy rabbit: The Columbia Basin pygmy rabbit is an isolated population of pygmy rabbit ("Brachylagus idahoensis"), that is native only to a single Columbia Basin area of Washington state. The Columbia Basin pygmy rabbit is the smallest North American rabbit. While the IUCN considers the species as a whole to be of least concern, the US Fish & Wildlife Service considers this a distinct population segment, and as thus merits protections under the Endangered Species Act. The last purebred Columbia Basin pygmy rabbit died in 2008, marking the end of the pure genetic line.
Document 12: Genomic evolution of birds: Birds are the group of amniotes with the smallest genomes. Whereas mammal and reptilian genomes range between 1.0 and 8.2 giga base pairs (Gb), bird genomes have sizes between 0.91 Gb (black-chinned hummingbird, "Archilochus alexandri") and 1.3 Gb (common ostrich, "Struthio camelus"). Just as happens to any other living being, bird genomes’ reflect the action of natural selection upon these animals. Their genomes are the basis of their morphology and behaviour.
Document 13: Caspian red deer: The Caspian red deer ("Cervus elaphus maral"), is one of the easternmost subspecies of red deer that is native to areas between the Black Sea and Caspian Sea such as Crimea, Asia Minor, the Caucasus Mountains region bordering Europe and Asia, and along the Caspian Sea region in Iran. The Caspian red deer is sometimes referred to as maral, noble deer, or eastern red deer.
Document 14: Majorcan giant dormouse: The Majorcan giant dormouse ("Hypnomys morpheus") is an extinct animal from Majorca, Spain in Europe. It is considered an example of island gigantism. The closest extant relative is considered to be the genus "Eliomys", which includes the garden dormouse. It is believed to have been omnivorous, and may have been terrestrial rather than arboreal. The arrival of humans on the island is believed to have been a major factor in its extinction. "H. morpheus" was described by the palaeontologist Dorothea Bate in 1919. A 2011 study estimated its body weight as between 173 and 284 g, with a head and body length of 179 mm and a total body length of 295 mm.
Document 15: On Being the Right Size: "On Being the Right Size" is a 1926 essay by J. B. S. Haldane which discusses proportions in the animal world and the essential link between the size of an animal and these systems an animal has for life.
ground_truth: Key deer