Critically low abundance and limits to humanrelated mortality for the Maui's dolphin

Abstract

The New Zealand endemic Maui's dolphin Cephalorhynchus hectori maui is characterized by several life history traits thought to be important predictors of extinction risk in marine mammals, including a slow rate of reproduction, small geographic range, small group size, and coastal distribution. We continued the genetic monitoring of the remnant population of Maui's dolphins using DNA profiles to identify 39 individuals from 73 skin biopsy samples collected during dedicated boat surveys in the austral summers of 2010 and 2011. Using a 2-sample, closed-population model with the genotype recapture records, we estimated the current abundance to be N = 55 individuals approximately age 1+ (95% confidence limits = 48, 69; coefficient of variation = 0.15). The endangered species potential biological removal that would permit the recovery of the Maui's dolphin was calculated to be 1 dolphin every 10 to 23 yr. Despite this, the Maui's dolphin is not necessarily doomed to extinction. It appears to be maintaining an equal sex ratio and connectivity within its remnant range and has the potential for rescue by interbreeding with Hector's dolphin C. h. hectori migrants.