title: Spatial and temporal extinction dynamics in a freshwater cetacean.
abstract: Geographical range contraction is a fundamental ecological characteristic of species population decline, but relatively little investigation has been conducted into general trends in the dynamic properties of range collapse. The Yangtze River dolphin or baiji (Lipotes vexillifer), probably the first large mammal species to have become extinct in over 50 years, was believed to have experienced major range collapse during its decline through progressive large-scale range contraction and fragmentation. This range-collapse model is challenged by a new dataset of 406 baiji last-sighting records collected from across the baiji's historical range during an interview survey of Yangtze fishing communities. Although baiji regional abundance may have varied across its range, analyses of the extensive new sighting series provide comprehensive evidence that baiji population decline was not associated with any major contraction in geographical range across the middle-lower Yangtze drainage, even in the decade immediately before probable global extinction of the species. Extinction risk in baiji was therefore seemingly not related to evidence of range collapse. Baiji apparently underwent large-scale periodic and seasonal movements across their range, and we propose that range contraction and fragmentation may not be general biogeographic characteristics for declining populations of mobile species in connected landscapes.
authors.affiliation: Institute of Zoology, Zoological Society of London, Regent's Park, London, UK. samuel.turvey@ioz.ac.uk
authors.forename: Samuel T
authors.initials: ST
authors.lastname: Turvey
authors.forename: Leigh A
authors.initials: LA
authors.lastname: Barrett
authors.forename: Tom
authors.initials: T
authors.lastname: Hart
authors.forename: Ben
authors.initials: B
authors.lastname: Collen
authors.forename: Hao
authors.initials: H
authors.lastname: Yujiang
authors.forename: Zhang
authors.initials: Z
authors.lastname: Lei
authors.forename: Zhang
authors.initials: Z
authors.lastname: Xinqiao
authors.forename: Wang
authors.initials: W
authors.lastname: Xianyan
authors.forename: Huang
authors.initials: H
authors.lastname: Yadong
authors.forename: Zhou
authors.initials: Z
authors.lastname: Kaiya
authors.forename: Wang
authors.initials: W
authors.lastname: Ding
mesh_terms: D000818:Animals; D003247:Conservation of Natural Resources; D004289:Dolphins / Q000502:physiology*; D053476:Extinction, Biological; D005843:Geography; D006801:Humans; D011157:Population Dynamics; D045483:Rivers; D013997:Time Factors