The temporal and spatial spread of a novel foraging behavior among sperm whales (Physeter macrocephalus) in the Gulf of Alaska: Evidence for cultural transmission.

摘要

Culture is well documented in humans and believed to have promoted the global spread of the human species across multiple ecological niches. "Culture" encompasses the behaviors or information obtained from conspecifics through social learning. However, early reports of cultural behavior in animals, such as potato washing by Japanese macaques or the spread of milk bottle opening among British tit species were criticized, precipitating a debate over methodologies and definitions of culture. Early research into animal culture remained segregated disciplinarily (biology, anthropology and psychology), with no conceptual consensus. Recently, evidence of animal culture has accumulated from experimental studies and long-term studies of inter-population variation in behavior across a range of species. Here I review the evidence and methodologies for examining animal culture. As a case study for cultural transmission, I investigated the spread of a novel foraging behavior in Gulf of Alaska sperm whales ( Physeter macrocephalus).;Longline fishing in the Gulf of Alaska has altered the costs and benefits of sperm whale foraging by creating novel concentrations of prey at shallow depths. Despite anecdotal observations of depredation from fisherman (Straley pers comm.), National Marine Fisheries Service observers first reported anecdotal accounts of sperm whales depredating the fish from the longlines in 1997. Since 1997, this behavior has spread through the Gulf of Alaska population of sperm whales. Negative consequences on local communities have included economic loss for fishers, reduced fish stocks, and increased potential for whale entanglement. The complexity of the behavior and its spread through the Gulf of Alaska make sperm whale depredation from longlines an ideal system in which to examine cultural innovation and transmission within a wild population.;To acquire fish from longlines, sperm whales must locate specific vessels, time their arrival to the hauling period, negotiate obtaining fish from the lines, and avoid entanglement. In this thesis, I will attempt to answer the following questions: First, how did depredation of fish by sperm whales from longline fisheries become a common behavior observed in the GOA? I will test two competing hypotheses: the behavior (a) spread via cultural transmission among the whale population, or (b) arose independently among multiple individuals. Second, how do patterns of depredation vary between killer and sperm whales? Data on sperm whale depredation collected during sablefish assessment surveys conducted by National Marine Fisheries Service (NMFS) using longline gear in coastal waters off Alaska from 1998 to 2010 were analyzed by populating two types of models of cultural transmission, the diffusion curve and wave of advance, to test the hypotheses listed above.;Results are consistent with the wave of advance model of cultural transmission and equivocal with regards to the diffusion curve. Additionally, the survey data suggest that depredation in killer whales has been observed for decades, yet remains localized spatially, and highly successful in terms of volume of fish removed. Conversely, sperm whale depredation diffused over the Gulf of Alaska in just several years. This project demonstrates how human fishing and whale foraging behavior overlap in space and time and how behaviors spread among wildlife populations.