Mysticete migration revisited: are Mediterranean fin whales an anomaly?

Abstract

1.The generally accepted model of Mysticete whale migration is that most individuals undertake seasonal migrations between high and low latitudes. Although numerous exceptions have been described in the literature, the traditional model remains unexamined. This paper represents the first 'official' challenge to the traditional model of Mysticete migration. 2. We set out to review the current state of knowledge on the Mediterranean fin whale migratory pattern, and to examine whether the small, resident population in the Mediterranean is an anomaly within the framework of the traditional model of Mysticete migration. We investigated the prevalence of alternative migratory strategies among the Mysticete whales, reviewing the migratory habits of the Mediterranean fin whales and those of other fin whale and baleen whale populations. 3. We reach three main conclusions. First, the seasonal behaviour of the resident Mediterranean fin whales is highly dynamic, and a decade of research has not clarified prevailing uncertainties regarding migration patterns. Second, migration strategies similar to those observed in the Mediterranean fin whales are commonly seen in other populations of baleen whales. Third, the traditional model of whale migration is too simplified to describe the repertoire of Mysticete migratory behaviours accurately. 4. We argue that the paradigm of baleen whale migration warrants further scrutiny to account for more complex movement strategies. We suggest that Mysticete migration should be thought of as a continuum of different strategies that have evolved in the face of different selective pressures. Instead of representing an exception to the rule, the resident Mediterranean fin whales may in fact fall towards one end of a larger spectrum of migratory behaviours. A greater knowledge of ecological factors, reproductive patterns, and local adaptations will be needed to understand the evolutionary mechanisms behind the diversity of migratory habits. bs_bs_banner

Foraging areas, migratory movements and winter destinations of blue whales from the western North Atlantic

“…Reilly & Thayer 1990, Mate et al 1999, Visser et al 2011, Silva et al 2013, Owen et al 2015. A closer look at seasonal movements within and across baleen whale populations has revealed that dynamic migration strategies do not conform with a feast and famine yearly cycle (Geijer et al 2016). For instance, blue whales in the northeastern Pacific exhibit ARS behaviour throughout the migratory cycle (Bailey et al 2009).…”

“…These include several areas along the slope of the Laurentian Channel, the continental shelf edge, and sectors within shelf habitats (depth <100 m) of the SLE and GSL (Simard & Lavoie 1999, Lavoie et al 2000, Sourisseau et al 2006, Plourde et al 2016. The classical depiction of the annual cycle of capital breeding mysticetes involves alternating feast and famine as the animals move from their feeding to breeding areas (Lockyer & Brown 1981, Clapham 1996; although see exceptions in Geijer et al 2016). However, migrating animals likely encounter zones of heightened productivity in the open ocean, where intermittent feeding may occur during winter and spring (Silva et al 2013).…”

“…Another aspect to consider when studying seasonal habitat is that not all individuals or populations migrate (Geijer et al 2016). Habitat requirements are poorly understood for blue whales, but likely vary according to energy requirements, which may depend on age, sex, size, and reproductive state (Corkeron & Connor 1999, Ford & Reeves 2008.…”

“…In blue and other baleen whales, seasonal movements are traditionally thought to occur be tween productive high-latitude feeding areas in summer, and oligotrophic, tropical or sub-tropical calving and mating areas in the winter, where feeding is absent (Kellogg 1929, Norris 1967. A recent review of the literature indicates that while this traditional model prevails for some species, sub-species or populations, other movement strategies may also apply, including partial or differential migration, and flexible feeding throughout the migratory range (Geijer et al 2016). While summer feeding areas have been described for some blue whale aggregations (e.g.…”

“…The blue whale Balaenoptera musculus is a species for which our understanding of movement ecology has been limited in some regions by the conflict be tween technology and conservation status (re viewed in Geijer et al 2016). While movement patterns have been well studied in some populations, such as in the eastern Pacific using implantable tags (e.g.…”