Migratory vertebrates adjust their movements in response to environmental change. Throughout their migrations, they gather information, integrate environmental and internal state data, and make decisions about the timing and orientation of migratory movements. Understanding this class of animal decision-making has both basic and applied interest because migratory animals face unique challenges adjusting to anthropogenic environmental changes worldwide. Evolved changes in decision mechanisms necessarily lag behind environmental changes, as their evolution is driven by the consequences of resulting actions, and this raises the possibility of major mismatches between behaviour and environmental circumstances when the latter change faster than the pace of natural selection. Yet, migration-decision systems have the capacity for considerable flexibility at the phenotypic level. Distinguishing the evolution of fixed genetic changes from changes that can occur in individual phenotypes often requires a better understanding of the mechanisms underlying organismal response. We reflect on such issues, hoping to engender new thinking about the special difficulties that long-distance migrants face in times of rapid environmental change. We focus on three key aspects: (1) We distinguish between variations in migratory paths forced upon the migrants by overwhelming environmental changes and those that arise from individual "strategic" variation in decision-making. (2) We examine how the availability and reliability of information about environmental quality determines optimal cue choice and cue-response, highlighting how changes in the correlations between cues and environmental parameters can lead to detrimental departure timing and negative fitness consequences on the breeding grounds. (3) We highlight how adjustments of individual migration strategies can be made by changes in the decision-making machinery during development, dramatically increasing the rate at which migratory strategies can adjust to environmental change.

/pdf/cues-strategies-and-outcomes-how-migrating-vertebrates-track-2xp40776l3.pdf

Cues, strategies, and outcomes: how migrating vertebrates track environmental change

Humpback whales Megaptera novaeangliae are seasonal migrants that mate and calve at low latitudes and feed at mid- to high latitudes. Connections between most Southern Hemisphere breeding and feeding areas are not well understood, but are critical for assessing stock structure and human impacts. Photo-identification was performed to identify the feeding grounds of an Endan- gered sub-population that breeds in the central South Pacific Ocean (CSP). Identification pho- tographs were obtained from 159 ind. at American Samoa and compared to 3508 Southern Hemi- sphere humpback whales in the Antarctic Humpback Whale Catalogue (AHWC), including 1352 from Antarctic feeding grounds. Two individuals from American Samoa were seen on 3 occasions at the Antarctic Peninsula. This is the first known feeding site for American Samoa and one of few reli- ably identified for the CSP. AHWC #2950 was confirmed to have undertaken a round-trip movement of no less than 18 840 km, spanning 108 longitudinal degrees. This represents the largest mammalian migration known to date and a departure from historical assumptions about CSP migratory patterns. The frequency, causes, and fitness implications of such movements have yet to be determined. How- ever, distance is the only known extrinsic barrier to humpback whale movement within oceans, and so maximum individual range is 1 factor potentially affecting population exchange and colonization of new habitats. The movement documented here may place this Endangered sub-population at risk if conservation efforts are relaxed in unidentified parts of its range. Yet, the ability of humpback whales to undertake such extensive movements may have also contributed to the apparent recovery of some populations versus other historically exploited whale species.

/pdf/return-movement-of-a-humpback-whale-between-the-antarctic-2unicad6ei.pdf

Return movement of a humpback whale between the Antarctic Peninsula and American Samoa: a seasonal migration record

We examine the scientific evidence for the assertion that commercial fisheries are negatively impacted by whales in tropical breeding areas.

Should Whales Be Culled to Increase Fishery Yield

Data on distribution and behaviour of mother-calf pairs of humpback whales Megaptera novaeangliae obtained during the breeding season (June to October) off Ecuador were analysed. The study was carried out between 2001 and 2009 aboard whale-watching boats. A total of 187 groups containing mother-calf pairs were recorded: 124 pairs alone (MC), 44 with an escort whale (MCE) and 18 with 2 or more whales (MC + n). Five environmental variables were used to assess mother-calf distribution with a principal component analysis (PCA). Two variables, depth and time of day, were sufficient to explain heterogeneity. Average depths increased significantly with group size from MC to MC + n groups (p < 0.001), showing that mother-calf social condition would be a function of the depth at which they moved. MC groups were distributed in shallower waters dur- ing afternoon hours (p = 0.035), indicating a preference for shelter areas when sea conditions wors- ened. The proportion of the 3 female-calf group classes remained fairly constant during the season. In 2 MCE groups, the same escort accompanied the pair after 1 and 4 d, indicating some level of sta- bility and/or guarding behaviour. Twenty resightings of 14 different mother-calf groups were recorded, 90% of resightings occurred within 10 d, showing low site fidelity. In coastal waters, a lower proportion of mother-calf pairs was associated with competitive groups than in other breeding areas located in oceanic archipelagos. This is probably because whales breeding in continental shores do not have to enter oceanic waters when moving between sites within the breeding area. Coastal distribution exposes mother-calf pairs to a greater extent than other age classes to anthro- pogenic activities in coastal waters, which must be taken into account when considering coastal man- agement.

/pdf/distribution-and-behaviour-of-humpback-whale-mother-calf-1j3oxst17c.pdf

Distribution and behaviour of humpback whale mother-calf pairs during the breeding season off Ecuador

Migrating humpback whales from northern and southern feeding grounds come to the tropical waters near Osa Peninsula, Pacific of Costa Rica, to reproduce and raise their calves. Planning effective marine protected areas that encompass humpback critical habitats require data about which oceanographic features influence distribution during the breeding period. This study examines the relationship between water depth and ocean floor slope with humpback whale distribution, based on sightings during two breeding seasons (2005 and 2006). Data are from the Southern and Northern subpopulations in the Eastern Tropical Pacific (ETP). Analysis followed the basic principles of the Ecological Niche Factors Analysis (ENFA), where indices of Marginality and Tolerance provide insights on the restrictiveness of habitat use. At a fine scale, physical factors such as water depth and slope define the critical breeding and nursing habitat for M. novaeangliae. Divergence in the sub- samples means of depths and slope distribution, with the global mean of the study area in both eco-geographical variables, determine habitat requirements restricted by topographic features such as depths (< 100 m) and slope (< 10%), and locate the key breeding and nursing habitat of the species within the continental shelf domains. Proposed Marine Protected Areas (MPA's) network plans should consider connectivity of Cano island-Drake Bay and the extension of Corcovado National Park maritime borders. Rev. Biol. Trop. 56 (2): 591-602. Epub 2008 June 30.

/pdf/underwater-topography-determines-critical-breeding-habitat-43j5oe7hk3.pdf

Underwater topography determines critical breeding habitat for humpback whales near Osa Peninsula, Costa Rica: implications for marine protected areas.

Migratory destinations of humpback whales from the magellan strait feeding ground, southeast pacific

Seasonal abundance estimates of humpback whales resident during the austral winter in Hervey Bay, Queensland, Australia between 1987 and 2007 were obtained from a capture-mark-recapture study using photo-identification images of 3,155 individual whales. Hervey Bay is a major southbound stopover site for Breeding Stock E humpback whales returning to Antarctic waters from over-wintering in the vicinity of the Great Barrier Reef. Annual survival, recapture and abundance estimates were derived using a Cormack-Jolly-Seber modelling approach and a Horwitz-Thompson type abundance estimator. The best-fit model was a 2-ageclass Brownie-Robson type model that estimated apparent annual survival for the non-transient winter stopover ageclass at approximately 0.945 (95% confidence interval: 0.929-0.957). Apparent annual abundance of winter stopover humpback whales in Hervey Bay was estimated to have increased significantly over the past 21 years at ca. 13.4% per annum (95% CI 11.6-15.2). The most recent Hervey Bay winter stopover population (2007) was estimated to comprise ca. 6,246 post-yearlings (95% CI 5,011-7,482). This estimated rate of population increase is similar to estimates for other surveys along the east Australian coast but significantly higher than the intrinsic rate of increase (rmax) estimated recently for several recovering Southern Hemisphere humpback whale stocks based on the feeding ground sampling.

Long term trends in abundance of humpback whales in Hervey Bay, Australia

Documentation of humpback whale movements between east and west Australian breeding grounds have been restricted to limited historical data from ‘Discovery’ marks, and implied from song analysis and molecular data. We report on the first inter-ocean movement of a humpback whale between the Pacific Ocean, east Australia (BS-E1) and the Indian Ocean, west Australia (BS-D) confirmed by photo-ID. A single humpback whale from BS-E1 (1987) was re-sighted to BS-D (1995) breeding grounds. The identification photographs of this single whale were then compared to fifteen fluke ID catalogues containing 15,011 fluke identifications (not reconciled for duplications between catalogues) collected from 1981 2011, and one catalogue containing 3,555 left and 3,572 right lateral body images collected from 1990 – 2010. Catalogues searched represent individual humpback whale fluke IDs from Breeding Stocks A, B, B1, B2, C1, C2, C3, D, E1, E2, E3, F, F2, G; New Zealand (migratory corridor); and feeding areas of Antarctic Peninsula, Areas I-VI and Chile, and lateral body IDs from BS-D. This re-sight record across breeding stocks provides further evidence of longitudinal movement of humpback whales in the southern hemisphere and highlights the value of both opportunistic data collection and the importance of comparing identified individuals among catalogue holders working in adjacent and non-adjacent breeding regions.

Photographic evidence of interchange between East Australia (BS E-1) and West Australia (BS-D) humpback whale breeding populations

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Migratory destinations of humpback whales from the magellan strait feeding ground, southeast pacific

Long term trends in abundance of humpback whales in Hervey Bay, Australia

Photographic evidence of interchange between East Australia (BS E-1) and West Australia (BS-D) humpback whale breeding populations