Ontogenetic development of migration : Lagrangian drift trajectories suggest a new paradigm for sea turtles

Long distance migration occurs in a wide variety of taxa including birds, insects, fishes, mammals and reptiles. Here, we provide evidence for a new paradigm for the determinants of migration destination. As adults, sea turtles show fidelity to their natal nesting areas and then at the end of the breeding season may migrate to distant foraging sites. For a major rookery in the Mediterranean, we simulated hatchling drift by releasing 288 000 numerical particles in an area close to the nesting beaches. We show that the pattern of adult dispersion from the breeding area reflects the extent of passive dispersion that would be experienced by hatchlings. Hence, the prevailing oceanography around nesting areas may be crucial to the selection of foraging sites used by adult sea turtles. This environmental forcing may allow the rapid evolution of new migration destinations if ocean currents alter with climate change.

Ontogeny of long distance migration

The movements of some long-distance migrants are driven by innate compass headings that they follow on their first migrations (e.g., some birds and insects), while the movements of other first-time migrants are learned by following more experienced conspecifics (e.g., baleen whales). However, the overall roles of innate, learned, and social behaviors in driving migration goals in many taxa are poorly understood. To look for evidence of whether migration routes are innate or learned for sea turtles, here for 42 sites around the world we compare the migration routes of >400 satellite-tracked adults of multiple species of sea turtle with ∼45 000 Lagrangian hatchling turtle drift scenarios. In so doing, we show that the migration routes of adult turtles are strongly related to hatchling drift patterns, implying that adult migration goals are learned through their past experiences dispersing with ocean currents. The diverse migration destinations of adults consistently reflected the diversity in sites they would have encountered as drifting hatchlings. Our findings reveal how a simple mechanism, juvenile passive drift, can explain the ontogeny of some of the longest migrations in the animal kingdom and ensure that adults find suitable foraging sites.

Migration, unemployment and trade

Migration, Unemployment and Trade focuses on the issues of migration, welfare and unemployment in a trade and development framework. Several chapters of the book analyze the implications of internal labor mobility in a model designed to highlight its implications for regional welfare, urban unemployment, rural-urban dichotomy and structural adjustment. An important innovation in this work is the disaggregation of the economy and the use of separate utility functions to highlight non-homogeneity of preferences. The book also deals with international mobility of factors in different frameworks. In particular it concentrates on the highly emotive issue of legal and illegal migration. Thus this work incorporates interesting and important features of labor economics and factor mobility into trade and distortion theory.

The relationships between migration, social support and social integration on quality of Life

Past research indicates that humans have a remarkable ability to maintain normal levels of subjective wellbeing despite adverse objective circumstances. This suggests that such wellbeing may be held under homeostatic control. This paper investigates some of the potential factors
that may contribute to this homeostatic mechanism, in response to the major life event of migration. Three groups were examined: Persian immigrants to Australia (Persian- Australians), non-Persian Australians, and Persians residing in Iran. A total of 330 subjects were recruited. A notable finding was that all three groups did not differ in regard to subjective wellbeing, despite the Persian-Australians being a minority ethnic group in Australia, and the Persians having significantly lower objective life quality. The Persian-Australians who migrated at an older age reported lower subjective quality of life, while the number of years of residence in Australia did not appear to be related to the extent of social integration. Subjective life quality was, however, related to subjective social support for the Australian and Persian samples, and to reciprocality of support for the Persian-Australians.