Whale Migration Research Articles

A statistical acoustics approach for estimating population-scale bowhead whale migration speed and direction.

Bowhead whales vocalize during their annual fall migration from the Beaufort Sea to the Bering Sea, but the calling rates of individual animals are so low that tracking an individual trajectory is impractical using passive acoustic methods. However, the travel speed and direction of the migrating population can be inferred on a statistical basis by cross-correlating time sequences of call density measured at two locations spaced several kilometers apart. By using the triangulation abilities of a set of vector sensors deployed offshore the Alaskan North Slope between 2008 and 2014, call density time sequences were generated from 1-km wide and 40-km tall rectangular "zones" that were separated by distances ranging from 3.5 to 15 km. The cross-covariances between the two sequences generate a peak corresponding to the average time it takes for whales to travel between the zones. Consistent westward travel speeds of ∼5 km/h were obtained from four different locations on 6 of the 7 years of the study, independent of whether the zones were separated by 3.5, 7, or 15 km. Some sites, however, also revealed a less prominent eastern movement of whales, and shifts in migration speed were occasionally detectable over week-long time scales.

Basin‐Wide Shift in Bowhead Whale Migration in the Pacific Arctic

AbstractIn a rapidly changing Arctic, multiple lines of evidence suggest that bowhead whale migration is changing. To explore these changes further, we used passive acoustic data to examine bowhead whale presence in the western Beaufort Sea (12 years) and Chukchi Plateau (11 years) spanning 2008 to 2022. Departure from the western Beaufort Sea shifted 45 days later over the 12‐year period. Summer presence increased at both sites, suggesting feeding areas within the Chukchi Sea are becoming more favorable. Likewise, findings from the Bering Strait suggest that some whales are remaining north of the Bering Strait for the winter instead of in the Bering Sea. These Pacific Arctic‐wide changes to migration have occurred over only one decade. Questions remain about prey availability in the Chukchi Sea, implications of migratory changes, such as a northward shift in the core overwintering area, and impact to communities south of the Bering Strait.

Avoidance, confusion or solitude? Modelling how noise pollution affects whale migration

Many baleen whales are renowned for their acoustic communication. Under pristine conditions, this communication can plausibly occur across hundreds of kilometres. Frequent vocalisations may allow a dispersed migrating group to maintain contact, and therefore benefit from improved navigation via the “wisdom of the crowd”. Human activities have considerably inflated ocean noise levels. Here we develop a data-driven mathematical model to investigate how ambient noise levels may inhibit whale migration. Mathematical models allow us to simultaneously simulate collective whale migration behaviour, auditory cue detection, and noise propagation. Rising ambient noise levels are hypothesised to influence navigation through three mechanisms: (i) diminished communication space; (ii) reduced ability to hear external sound cues and; (iii) triggering noise avoidance behaviour. Comparing pristine and current soundscapes, we observe navigation impairment that ranges from mild (increased journey time) to extreme (failed navigation). Notably, the three mechanisms induce qualitatively different impacts on migration behaviour. We demonstrate the model’s potential predictive power, exploring the extent to which migration may be altered under future shipping and construction scenarios.

A novel RT-qPCR health assay reveals differential expression of stress and immunoregulatory genes between the seasonal migrations of humpback whales (Megaptera novaeangliae).

Health information is essential for the conservation management of whale species. However, assessing the health of free-ranging whales is challenging as samples are primarily limited to skin and blubber tissue. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) offers a method to measure health from blubber RNA, providing insights into energetic status, stress and immune activity. To identify changes in health, natural differences in baseline gene expression linked to an individual's sex, reproductive status and life-history stage must first be quantified. This study aimed to establish baseline gene expression indices of health in migrating humpback whales (Megaptera novaeangliae). To do this, we developed an assay to quantify seven health-related gene transcripts (Leptin, Leptin Receptor, Adiponectin, Aryl Hydrocarbon Receptor, Tumour Necrosis Factor-α, Interleukin-6, Heat Shock Protein-70) and used Bayesian mixed effect models to assess differential baseline expression based on sex, lactation status and migration stage (northbound to and southbound from the annual breeding grounds). Results showed no significant contribution of sex to differential baseline expression. However, lactating individuals exhibited downregulated AhR and HSP-70 compared to non-lactating conspecifics. Additionally, southbound individuals demonstrated significantly upregulated HSP-70 and downregulated TNF-alpha, suggesting a relationship between these inflammation-linked transcripts and migratory fasting. Our results suggest that baseline differences due to migratory stage and lactation status should be considered in health applications of this assay. Future monitoring efforts can use our baseline measurements to better understand how gene expression is tied to population-level impacts, such as reduced prey availability or migratory stressors.

Examining environmental conditions that influence long-term Antarctic blue whale migration patterns in the Southern Hemisphere using an 18-year passive acoustic dataset

Antarctic blue whales (Balaenoptera musculus intermedia) are difficult to study due to the low numbers and cryptic behaviour. The largest subspecies of blue whale migrates from Antarctic feeding areas to temperate and tropical breeding grounds every year. Their use of these remote areas makes it difficult to detect them using visual survey methods. However, blue whales are vocal animals and sing throughout the year especially during their annual migration. By using passive acoustic monitoring, we can study the long-term migration patterns of Antarctic blue whales across the Southern Hemisphere. Using an 18-year passive acoustic dataset from the CTBTO, we examined the migration patterns of Antarctic blue whales across four different locations spread across all three major ocean basins. We modelled blue whale acoustic detections with environmental variables including El Niño Southern Oscillation, the Southern Annular Mode, and yearly Antarctic sea-ice extent. We also examined krill abundance estimates from Krill Base in our models. We found that the whale call detections at the four sites were correlated with different variables. The variables were also correlated with various degrees of lag. Our study provides evidence that these whales vary their migration patterns from year-to-year with respect to changing oceanic, and climatic conditions.

A trans-Pacific movement reveals regular migrations of humpback whales Megaptera novaeangliae between Russia and Mexico

Humpback whalesMegaptera novaeangliaeundertake extensive annual migrations, have complex migratory patterns, and have held several mammalian long-distance movement records. Here, we report on a whale known to feed in the Russian Far East that was sighted in breeding areas on either side of the North Pacific, the Mariana Islands and Mexico, in less than 1 yr (357 d apart). This is the longest published distance (11261 km great-circle route) between 2 unique sightings of a photo-identified humpback whale to date. To understand the context of this movement, we investigated records of whales that had been sighted in Russian feeding areas and Mexican breeding areas using historic and newly available photo-identification data. We found 117 humpback whales documented in both countries between 1998 and 2021, revealing a substantial increase from the only 11 matches that were previously known. These whales exhibited high site fidelity to Mexico, with one-third seen in multiple years, and up to 10 yr. However, we also found that they changed breeding areas more frequently than Mexico whales matched to other feeding areas, illustrating how the Mariana Islands-Mexico movement may have occurred. We document the first complete round-trip migrations between Mexico and Russia, a journey of >16400 km, the longest known migration of Northern Hemisphere humpback whales. Our data demonstrate regular trans-Pacific movements of humpback whales in the North Pacific, highlighting the importance of Mexico for the species ocean-basin-wide and the need for effective local management to aid in the conservation of multiple at-risk distinct population segments.

Distribution, hosts and long-term decline in abundance of the Patagonian lamprey inferred from diet assessment of albatrosses

Knowledge of lampreys during their marine phase is limited, and for the southern hemisphere species was gleaned from their predators (albatrosses) in the 1970s. Taking advantage of new methodologies and long-term data on predator diet and distributions, we infer diverse aspects of lamprey distribution and ecology. DNA analyses indicated that albatrosses at South Georgia prey on Patagonian lamprey Geotria macrostoma, originating from Argentina. Their core pelagic distribution when free swimming appears to be the Antarctic Polar Frontal zone (APFZ), and not South Georgia waters as assumed previously. If so, the APFZ would be the first known hotspot in abundance of an anadromous lamprey in oceanic waters. We could not identify a teleost fish that would be a likely host. Instead, we infer that the lamprey may prey on baleen whales, based on comparison of stable isotope ratios in lamprey with candidate host species, timing of appearance in albatross diets coincident with whale migrations, and circumstantial evidence (unexplained scarring recorded during the whaling era). We suggest that the lamprey do not tolerate cold Antarctic waters, and detach from southerly-migrating whales at the thermal boundary of the APFZ, where they become accessible to albatrosses in surface waters. Given strong evidence that relative importance of prey in seabird diets reflects availability in foraging areas, the steep decrease in the annual consumption of lamprey by albatrosses at South Georgia from > 550 tonnes in 1975–1976 and 1986, to very low levels in most years since 2012, is likely to indicate a major population decrease. Despite our unconventional means of assessing the population trend, there is a compelling case for listing of Patagonian lamprey at least as Near threatened by the International Union for the Conservation of Nature, and an urgent need to better understand anthropogenic threats in Argentina.

Spatial and temporal structure of the western North Pacific minke whale distribution inferred from JARPN sightings data

The density of minke whales (Balaenoptera acutorostrata) in the western North Pacific was examined using a generalized additive model in order to investigate the spatial and temporal distribution patterns. The data used were a subset of JARPN sightings data collected from 1994 to 1999. The process for estimating the density was divided into two parts: the detection process for the estimation of the effective search half-width; and the encounter process for the estimation of the encounter rate. Model selection was carried out using information criteria. The selected model for the detection process included ‘sightability’, a synthetic index of detectability, as a covariate, and for the encounter process included the interaction between latitude and longitude and the interaction between month and latitude. The trend surface of the transformed density predicted by each month revealed no clear gaps. The monthly transition of the density distribution also suggested the northward seasonal feeding migration of the minke whales.

Evaluation of high-powered binoculars to detect inter-year changes in offshore distribution of eastern North Pacific gray whales

Paired, independent searches for gray whales (Eschrichtius robustus) were conducted through fix-mounted, 25-power binoculars during January 1995 and 1996 at Granite Canyon, California. The study was a test of an efficient method for documenting inter-year changes in the offshore distribution of the migration. The research site has been used most years since 1975 by the National Marine Mammal Laboratory to make counts for abundance estimates of gray whales. Matching sightings between the paired observation efforts showed a very high agreement between observers (detection probability 0.97) for whale groups apparently of more than one animal within 1-3 n.miles of shore and a fairly high agreement (0.87) for animals travelling alone (5% of the sampled population) within 1-3 n.miles of shore. Sighting probability thus remained high up to 3 n.miles, a distance which includes most (98.7%) of the whale migration. For the critical sighting range of 1-3 n.miles, the method applied here is considered a feasible, cost-effective technique for detecting inter-year differences in the offshore tail of the distribution.

Simultaneous tracking of multiple whales using two fiber-optic cables in the Arctic

Climate change is impacting the Arctic faster than anywhere else in the world. As a response, ecosystems are rapidly changing. As a result, we can expect rapid shifts in whale migration and habitat use concurrent with changes in human patterns. In this context, responsible management and conservation requires improved monitoring of whale presence and movement over large ranges, at fine scales and in near-real-time compared to legacy tools. We demonstrate that this could be enabled by Distributed Acoustic Sensing (DAS). DAS converts an existing fiber optic telecommunication cable into a widespread, densely sampled acoustic sensing array capable of recording low-frequency whale vocalizations. This work proposes and compares two independent methods to estimate whale positions and tracks; a brute-force grid search and a Bayesian filter. The methods are applied to data from two 260 km long, nearly parallel telecommunication cables offshore Svalbard, Norway. First, our two methods are validated using a dedicated active air gun experiment, from which we deduce that the localization errors of both methods are 100 m. Then, using fin whale songs, we demonstrate the methods' capability to estimate the positions and tracks of eight fin whales over a period of five hours along a cable section between 40 and 95 km from the interrogator unit, constrained by increasing noise with range, variability in the coupling of the cable to the sea floor and water depths. The methods produce similar and consistent tracks, where the main difference arises from the Bayesian filter incorporating knowledge of previously estimated locations, inferring information on speed, and heading. This work demonstrates the simultaneous localization of several whales over a 800 km area, with a relatively low infrastructural investment. This approach could promptly inform management and stakeholders of whale presence and movement and be used to mitigate negative human-whale interaction.

Estimates of large whale abundance in Greenlandic waters from a ship-based survey in 2005

A ship-based line transect survey of large whales in East and West Greenland was conducted in September 2005. The survey platform primarily targeted capelin, Mallotus villosus, using acoustic methods and systematically covered the east and west coasts of Greenland from the coast to the shelf break (approximately 200m). The surveyed area comprised 81,000km2 in East Greenland and 225,000km2 in West Greenland. A total of 194 sightings of 13 cetacean species were obtained and standard line transect methods were used to derive abundance estimates of the four most commonly encountered large cetaceans. Fin whales, Balaenoptera physalus, were most abundant in East Greenland (3,214, 95% CI=980-10,547) with lower abundances estimated for West Greenland (1,980, 95% CI=913-4,296). Sei whales, B. borealis, were frequently encountered in the same areas as fin whales, but the estimated abundance in East Greenland (763, 95% CI=236- 2,465) was lower than in West Greenland (1,599, 95% CI=690-3,705). Humpback whales, Megaptera novaeangliae, were found both in offshore and coastal areas of West Greenland (1,306, 95% CI=570-2,989) and in low numbers in East Greenland (347, 95% CI=48-2,515). Finally, common minke whale, B. acutorostrata, abundance was estimated at 1,848 (95% CI=197-17,348) for East Greenland and 4,479 (95% CI=1,760-11,394) for West Greenland. Inclusion of sightings of unidentified large baleen whales in West Greenland distributed in proportion to species and strata increased abundance estimates for fin, sei, and humpback whales to 2,824 (95% CI=1,346-5,925), 2,009 (95% CI=948-4,260), and 1,514 (95% CI=560-4,089), respectively. Despite good conditions and considerable effort, few cetaceans were observed in the northernmost strata in West Greenland. This suggests that the southbound fall migration of large whales from North West Greenland had already started by the time the survey was initiated. The abundance estimates presented in this study are negatively biased. No corrections were applied for whales missed by observers or for whales submerged during the passage of the survey platform, which should cause a particularly large negative bias, for the estimates of common minke whale abundance.

Abundance of Bering-Chukchi-Beaufort bowhead whales (Balaena mysticetus) in 2004 estimated from photo-identification data

Ice-based surveys near Point Barrow, Alaska, have been used to obtain most estimates of abundance for the Bering-Chukchi-Beaufort (B-C-B) stock of bowhead whales, but global warming has raised concerns that ice-based surveys may not be practical in the future. Aerial photographic surveys provide an alternative method for obtaining abundance estimates and may replace ice-based surveys. Aerial photographic surveys were conducted near Point Barrow during the spring migrations of bowhead whales in 2003 and 2004 and, in 2005, in the northern Bering Sea in spring and near Barrow in fall. The 2003 survey was the most complete photographic survey of the population conducted to date. These surveys provided photo-identification data for use in capture-recapture analyses. A screening procedure was used to define which whales captured in 2003, 2004 and/or 2005 were marked and could be reidentified if photographed on another occasion. An estimate of the number of marked whales was obtained using a closed population model for capture-recapture data. Several models were investigated, including models that accounted for heterogeneity in capture probabilities, but a simple model with no covariates produced the most precise estimate. To account for unmarked whales, the estimate of marked whales was divided by an estimate of the proportion of the bowhead population that was marked based on the 1989–2004 spring photographic surveys near Point Barrow. Abundance of the B-C-B bowhead population in 2004 (excluding calves) was estimated to be 12,631 with CV 0.2442, 95% bootstrap percentile confidence interval (7,900; 19,700) and 5% lower limit 8,400. These results were compared with results that used approximate variance expressions for the estimates of the number of marked whales, the proportion of the population that was marked and population abundance instead of using the bootstrap. The estimates of abundance in 2004 computed for comparison included one based on a modified Petersen estimate of the number of marked whales that omitted the 2005 data as well as the estimate of 12,631 described above. The comparison estimates also included estimates of abundance in 1985 computed from 1984–87 photographic survey data using the same methods. All the abundance estimates computed from photographic data were consistent with expectations based on independent abundance and trend estimates from the ice-based surveys conducted from 1978 to 2001.

Sea ice directs changes in bowhead whale phenology through the Bering Strait

BackgroundClimate change is warming the Arctic faster than the rest of the planet. Shifts in whale migration timing have been linked to climate change in temperate and sub-Arctic regions, and evidence suggests Bering–Chukchi–Beaufort (BCB) bowhead whales (Balaena mysticetus) might be overwintering in the Canadian Beaufort Sea.MethodsWe used an 11-year timeseries (spanning 2009–2021) of BCB bowhead whale presence in the southern Chukchi Sea (inferred from passive acoustic monitoring) to explore relationships between migration timing and sea ice in the Chukchi and Bering Seas.ResultsFall southward migration into the Bering Strait was delayed in years with less mean October Chukchi Sea ice area and earlier in years with greater sea ice area (p = 0.04, r2 = 0.40). Greater mean October–December Bering Sea ice area resulted in longer absences between whales migrating south in the fall and north in the spring (p < 0.01, r2 = 0.85). A stepwise shift after 2012–2013 shows some whales are remaining in southern Chukchi Sea rather than moving through the Bering Strait and into the northwestern Bering Sea for the winter. Spring northward migration into the southern Chukchi Sea was earlier in years with less mean January–March Chukchi Sea ice area and delayed in years with greater sea ice area (p < 0.01, r2 = 0.82).ConclusionsAs sea ice continues to decline, northward spring-time migration could shift earlier or more bowhead whales may overwinter at summer feeding grounds. Changes to bowhead whale migration could increase the overlap with ships and impact Indigenous communities that rely on bowhead whales for nutritional and cultural subsistence.

Observations of bowhead whales along the Northern Chukotka peninsula 2010–2012 with comparisons to 1994–1996 and 2002–2005

This paper contains information on the seasonal distribution of bowhead whales (Balaena mysticetus) in coastal waters of Chukotka (northeast Russia) in 2010–2012. Data from shore-based observation posts provides spatial and temporal information about whale distribution and migration in the coastal zones, as well as information about their relative numbers. The spring migration was observed only from Uelen, Russia (66°N, 149°W), near the northwestern entrance to the Bering Strait, and extended from the end of May through the first half of June. Some year-to-year differences in numbers and migration dynamics were observed. During summer, bowhead whales were sighted in the waters of the northern coast of Chukotka Peninsula in July and August. In 2010–2012, single whales and small groups of up to 4–8 whales were observed in the area for days making non-directed movements. Our observations in 2010–2012 demonstrated that many bowhead whales visited Chukotka coast in the autumn (September) before sea ice formation. From past observations, it appears that the autumn migration begins 2–3 weeks earlier on the northwestern coast of the Chukotka Peninsula than in the (northern) entry of the Bering Strait. The autumn migration of bowhead whales began with ice formation and ended with the complete freezing of the waters. Ice conditions appear to drive high variability in timing of the bowhead autumn migration. The northeastern Chukotka coast is one of the most important feeding areas for the Bering-Chukchi-Beaufort (BCB) bowhead whale population.

Stable isotope analysis of baleen from North Atlantic right whales Eubalaena glacialis reflects distribution shift to the Gulf of St. Lawrence

Seasonal migration of the Critically Endangered North Atlantic right whale Eubalaena glacialis along the eastern seaboard of North America has been well studied. Since 2010, however, right whales have shifted their summer foraging location from the Bay of Fundy to the Gulf of St. Lawrence. There is a need to better understand right whale distribution to manage anthropogenic activities and mitigate impacts on whales. Stable isotope ratios of baleen plates can provide details about migration and foraging behaviour of an individual over a period of several years. We interpreted δ13C and δ15N cycles, examined whether stable isotope ratios of baleen could detect the right whale distribution shift, and compared variation within and among individuals before and after 2010. δ13C and δ15N values were compared between 8 right whales that died between 1992 and 2005 (pre-2010) and 5 right whales that died in 2019 (post-2010). The correlation between δ13C and δ15N varied considerably between individuals, indicating no clear pattern of annual migration in δ13C among whales. We observed a change in both isotope ratios after 2010, whereby the post-2010 whales were enriched in 13C and 15N relative to the pre-2010 whales (mean ± SE: 0.5 ± 0.1 and 0.9 ± 0.2‰, respectively). The isotopic variance among and within whales did not change after 2010. These results suggest that a range shift observed in sighting data is also reflected in the isotope ratios of right whale baleen. Detecting shifts in right whale migration is essential for protecting this species, and stable isotope analyses may be useful in future conservation efforts.

Evidence of likely foraging by pygmy blue whales in the Timor Trough during the late austral winter and early austral spring

Understanding the behavioural context of wildlife movement patterns is imperative to the conservation of migratory species like cetaceans. The traditional model of baleen whale migration entails uninterrupted journeys performed throughout extended periods of fasting, during which individuals sustain the enormous costs of travelling from the poles to the tropics only from energy reserves acquired prior to departure. However, this ‘feast and famine’ paradigm is being challenged by increasing observations of supplemental feeding events along whale migratory routes. In this context, identifying the location of migratory stopovers is key to managing cetacean populations, particularly in data-poor ecosystems subject to changing ocean conditions. We report on likely foraging activity by migrant pygmy blue whales Balaenoptera musculus brevicauda in the Timor Trough (ca. 9.5° S, 126° E), a deep-water habitat south of the species’ presumed breeding grounds. Using photo-identification and generalised additive modelling, we analysed visual sightings collected aboard seismic vessels operating off Timor-Leste in 2007-2008 and demonstrate that (1) whales engage in surface behaviours suggestive of active feeding, (2) some individuals remain within the region for more than 1 d, and (3) whale presence is significantly associated with predictably high chlorophyll a concentrations. Despite previous efforts to examine pygmy blue whale movements at low latitudes using long-term satellite telemetry, knowledge of the species’ behavioural ecology in the tropics remains limited. Our results lend support to previously untested hypotheses about the possible use of the Timor Trough as a foraging site by eastern Indian Ocean pygmy blue whales during the late austral winter and early austral spring.

A First Individual-Based Model to Simulate Humpback Whale (Megaptera novaeangliae) Migrations at the Scale of the Global Ocean

Whale migrations are poorly understood. Two competing hypotheses dominate the literature: 1. moving between feeding and breeding grounds increases population fitness, 2. migration is driven by dynamic environmental gradients, without consideration of fitness. Other hypotheses invoke communication and learned behaviors. In this article, their migration was investigated with a minimal individual-based model at the scale of the Global Ocean. Our aim is to test if global migration patterns can emerge from only the local, individual perception of environmental change. The humpback whale (Megaptera novaeangliae) meta-population is used as a case study. This species reproduces in 14 zones spread across tropical latitudes. From these breeding areas, humpback whales are observed to move to higher latitudes seasonally, where they feed, storing energy in their blubber, before returning to lower latitudes. For the model, we developed a simplified ethogram that conditions the individual activity. Then trajectories of 420 whales (30 per DPS) were simulated in two oceanic configurations. The first is a homogeneous ocean basin without landmasses and a constant depth of −1000 m. The second configuration used the actual Earth topography and coastlines. Results show that a global migration pattern can emerge from the movements of a set of individuals which perceive their environment only locally and without a pre-determined destination. This emerging property is the conjunction of individual behaviors and the bathymetric configuration of the Earth’s oceanic basins. Topographic constraints also maintain a limited connectivity between the 14 DPSs. An important consequence of invoking a local perception of environmental change is that the predicted routes are loxodromic and not orthodromic. In an ocean without landmasses, ecophysiological processes tended to over-estimate individual weights. With the actual ocean configuration, the excess weight gain was mitigated and also produced increased heterogeneity among the individuals. Developing a model of individual whale dynamics has also highlighted where the understanding of whales’ individual behaviors and population dynamic processes is incomplete. Our new simulation framework is a step toward being able to anticipate migration events and trajectories to minimize negative interactions and could facilitate improved data collection on these movements.

First evidence for fin whale migration into the Pacific from Antarctic feeding grounds at Elephant Island.

This study presents the first long-distance tracks of fin whales (Balaenoptera physalus) equipped with satellite transmitters off the Antarctic Peninsula. Southern Hemisphere fin whales were severely depleted by twentieth century industrial whaling, yet recently, they have returned to historical feeding grounds off the northern Antarctic Peninsula, forming large aggregations in austral summers. To date, our knowledge only extended to summer behaviour, while information regarding migration routes and the location of breeding and wintering grounds are lacking. During the austral autumn of 2021, we deployed nsatellite transmitters on four fin whales at Elephant Island. Two transmitters stopped working while the animals were still at the feeding grounds, while two continued to transmit during the transition from feeding activity to migration. Both migrating animals left the feeding ground on 15 April 2021, travelling northward into the Pacific and up along the Chilean coast. The most northerly position received before all tags stopped transmitting on 1 May 2021 was at 48°S. These tracks provide initial evidence of seasonal migratory routes and a first indication toward possible locations of winter destinations. This information, even if preliminary, is critical for investigations of population connectivity, population structure and the identification of breeding grounds of Southern Hemisphere fin whales.

Changes of Oceanic Conditions Drive Chagos Whale Migration Patterns in the Central Indian Ocean

Marine ecosystems are experiencing rapid shifts under climate change scenarios and baleen whales are vulnerable to environmental change, although not all impacts are yet clear. We identify how the migration behaviour of the Chagos whale, likely a pygmy blue whale (Balaenoptera musculus brevicauda), has changed in association with shifts in environmental factors. We used up to 18 years of continuous underwater acoustic recordings to analyse the relationships between whale acoustic presence and sea surface temperature (SST), chlorophyll-a concentration, El-Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). We compared these relationships between two independent sites Diego Garcia southeast (DGS) and Diego Garcia northwest (DGN) where Chagos whales are detected and are suspected to move interannually across the Chagos-Laccadive ridge. We showed that the number of whale songs detected increased on average by 7.7% and 12.6% annually at DGS and DGN respectively. At the DGS site, Chagos whales shifted their arrival time earlier by 4.2 ± 2.0 days/year ± SE and were detected for a longer period by 7.3 ± 1.2 days/year ± SE across 18 years. A larger number of songs were detected during periods of higher chlorophyll-a concentration, and with positive IOD phases. At the DGN site, we did not see an earlier shift in arrival and songs were not detected for a longer period across the 13 years. Whale presence at DGN had a weaker but opposite relationship with chlorophyll-a and IOD. The oceanic conditions in the Indian Ocean are predicted to change under future climate scenarios and this will likely influence Chagos whale migratory behaviour. Understanding how environmental factors influence whale movement patterns can help predict how whales may respond to future environmental change. We demonstrate the value of long-term acoustic monitoring of marine fauna to determine how they may be affected by changing environmental conditions.

The Role of Governance in Promoting the Resilience of Arctic Communities

Abstract Arctic Indigenous communities have faced, and overcome, threats to their lifestyles, livelihoods and communities for thousands of years and in doing so have maintained communities with deep cultural roots and close connections to the land on which they live. Modern Arctic Indigenous communities also face threats to their existence. These threats range from the environmental impacts of climate change forcing wholescale relocation of an entire village to noise from oil and gas exploration causing the relocation of the whale migration out of reach of hunters. The article examines the concept of resilience and the role which governance can play in promoting the resilience of Arctic communities, and therefore their ability not only to survive but also to thrive. The article develops a theory of resilience, dividing types of resilience into in-situ and ex-situ resilience to allow the comparison of seemingly disparate examples. Through the use of a systematic comparative case analysis technique, the article explores the lessons which can be learned about the role of good governance in ensuring the promotion of resilience in Arctic communities in the future.