MOBBING IN HAWAIIAN MONK SEALS (MONACHUS-SCHAUINSLANI) - THE VALUE OFSIMULATION MODELING IN THE ABSENCE OF APPARENTLY CRUCIAL DATA

Several small populations of Hawaiian monk seals (Monachus schauinslan i) exhibit male-biased adult sex ratios and ''mobbing,'' an aggressive behavior in which adult males injure and often kill adult females and immature seals of both sexes during mating attempts Mobbing appears t o be limiting the growth of some populations of this endangered specie s. The frequency of mobbing deaths appears to increase as a population 's sex ratio becomes increasingly male-biased although the exact relat ionship between these two variables (the mobbing response) is unknown We developed a stochastic demographic model of a small Hawaiian monk s eal population using several different assumption about the mobbing re sponse. We used the model to explore the origins of male-biased sex ra tios in monk seal populations and to determine whether it was possible , given the lack of data on the mobbing response: to evaluate the prob able effects of alternative management strategies to address the mobbi ng problem. Small populations (100 to 200 seals) and those with slower growth rates were more likely to develop male-biased adult sex ratios . Almost all of our modeling scenarios supported the immediate removal of males from populations where mobbing occurs. Our conclusions were relatively unaffected when the assumptions regarding the mobbing respo ne were varied Thus, a model was helpful even when apparently crucial data were unavailable.