Identification and Estimation of Sensitive Life History Parameters for Cetaceans in Response to Acoustic Disturbances with Implications for Conservation

Meta-analyses of published cetacean life history data and original modeling efforts have been conducted to determine which vital rates are most important in determining the growth and sustainability of both odontocete and mysticete populations. In particular, the role of anthropogenic sound in the ocean was examined in relation to cetacean population trends, with specific implications for life functions, vital rates, and population sustainability. Elasticity and sensitivity analyses of Leslie matrices suggested that most cetacean populations appear to be most sensitive to changes in the adult female survival rate, and least sensitive to calf survival. A secondary factor to which whale populations are sensitive is a change in juvenile survival or growth. With the exception of the North Atlantic right whale (Eubalaena glacialis), most cetaceans are not sensitive to changes in fecundity at any age stage. Of particular concern for depleted cetacean species, adult females may be sensitive to changes in foraging success which limit their ability to acquire sufficient body fat to reproduce and raise calves successfully. These results are similar to those for other species with similar life histories, such as terrestrial vertebrates and non-mammalian marine predators.The resulting model outputs have direct implications for the management of marine mammals, particularly in regions where acoustic disturbances are likely in the future or are currently prevalent. Additionally, information gained from these modeling exercises may aid in the transition of the Population Consequences of Acoustic Disturbances (PCAD) model from qualitative to quantitative, as well as provide useful values for the parameterization of population viability analyses (PVAs) in cetacean management. The implications of these model findings to cetacean conservation are many, and include: 1) Increases in anthropogenic noise in the marine environment which have the capacity to limit adult female survival should be avoided at all costs, 2) Due to the inexact nature of cetacean population modeling, changes in vital rates may induce undetectable or unpredictable changes in population growth rate, so use of the precautionary principle is strongly advised in management decisions, 3) There are likely thresholds within which population vital rates can change without a resulting change in the growth rate, but these are not indicated by traditional sensitivity and elasticity analyses. Future studies are needed focusing on the likely intricate relationships between anthropogenic ocean noise and both adult female and juvenile cetacean survival. Additionally, improvements in cetacean modeling resulting in more precise and robust population and vital rate estimates would prove invaluable to the conservation of these species.