IUCN Red List Assessment
Red List Category Year Assessed
Data Deficient Red List Criteria Version
Reilly, S.B., Bannister, J.L., Best, P.B., Brown, M., Brownell Jr., R.L., Butterworth, D.S., Clapham, P.J., Cooke, J., Donovan, G.P., UrbÃ¡n, J. & Zerbini, A.N. Reviewer/s
Taylor, B.L. & Notarbartolo di Sciara, G. (Cetacean Red List Authority) Contributor/s Justification
Although there is no accepted estimate of current abundance, the population size is clearly in the hundreds of thousands. The data analysed by standard methods suggest a reduction of approximately 60% between the 1978â91 period and the 1991â2004 period. However, alternative hypotheses to explain the apparent decline are still under investigation. If the decline is real, its extent and causes are currently unknown, and it may still be continuing. The corresponding population reduction thresholds (criterion A2) are 30% for Vulnerable and 50% for Endangered, measured over a 3-generation time window, which in this case is estimated to be approximately 66 years (22 years per generation). If the decline proves to be largely or mainly an artefact, or proves to have been transient in the light of analyses of more recent data, the species would qualify as Least Concern. If it were real, the species would qualify as Endangered. Pending resolution of the uncertainties relating to the apparent decline, however, the species is listed as Data Deficient (DD).