Abstract
BackgroundDwarfism is a condition characterized by shorter stature, at times accompanied by differential skeletal growth proportions relative to the species-typical physical conformation. Causes vary and are well-documented in humans as well as certain mammalian species in captive or laboratory conditions, but rarely observed in the wild.Case presentationWe report on a single case of apparent dwarfism in a free-ranging adult male Asian elephant in Sri Lanka, comparing physical dimensions to those of other males in the population as well as in previous literature. The subject M459 was found to have a shoulder height of approximately 195 cm, is shorter than the average height of typical mature males, with a body length of 218 cm. This ratio of body length to height deviates from what is typically observed, which is approximately 1:1, but was similar to the attributes of a dwarf elephant in captivity documented in 1955. We report on behavior including the surprising observation that M459 appears to have a competitive advantage in intrasexual contests. We discuss how this phenotype compares to cases of dwarfism in other non-human animals.ConclusionM459 exemplifies a rare occurrence of disproportionate dwarfism in a free-ranging wild mammal that has survived to reproductive maturity and appears otherwise healthy.
Highlights
Dwarfism is a condition characterized by shorter stature, at times accompanied by differential skeletal growth proportions relative to the species-typical physical conformation
Anecdotal historic accounts exist of apparent dwarfism occurring in the wild in various parts of this species’ range [4], these are not substantiated
We report on the case of dwarfism exhibited by a fully-grown male Asian elephant (E. maximus maximus) in Uda Walwe National Park, Sri Lanka [5]
Summary
Reduced stature is a shared attribute among individuals exhibiting various forms of dwarfism, though this alone is not diagnostic of dwarfism. The young tusker captured from the wild in Sri Lanka in 1933 (Figure 1b, Table 1) is a candidate for the first known case of dwarfism and is the only instance for which measurements are available This individual was stated to have a shoulder height of 183 cm and a back length of 198 cm (measured from behind the ear rather than from the ear canal, to the base of the tail). From the anterior view proportions of the young tusker are more similar to wild type individuals than to M459 (Table 1), while the height is again slightly shorter than back length. The former may represent a case of proportionate dwarfism. Such cases may be rarely documented due to publication biases resulting from the lack of venues for reporting them
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