Marine Mammal Population Recoveries and Critical Factors

Abstract

Of all the marine taxa, marine mammals seem to have benefited the most from a paradigm shift from exploitation to conservation. This thesis provides the first quantitative assessment for marine mammals of (1) global, publicly available population-level abundance data, (2) abundance trends, (3) the relationship between decline and recovery, and (4) critical factors to recovery. I compiled a database of 143 population abundance time series. Using robust linear regression, I found approximately one third (35%) were significantly increasing and recovering. For populations with historical estimates (n=47), I also found a negative relationship between decline and recovery. With the significant population trends (n=43), I used a variety of modeling approaches—classification trees, generalized linear models (GLMs) and generalized additive models (GAMs) —to assess the relationship between hypothesized intrinsic and extrinsic critical factors and recovery. The results suggest the ongoing importance of wildlife proximity and accessibility to humans in determining population recovery.