Australia’s east coast humpback whales: Satellite tag-derived movements on breeding grounds, feeding grounds and along the northern and southern migration

Abstract Background Satellite tags were deployed on 50 east Australian humpback whales (breeding stock E1) between 2008 and 2010 on their southward migration, northward migration and feeding grounds in order to identify and describe migratory pathways, feeding grounds and possible calving areas. At the time, these movements were not well understood and calving grounds were not clearly identified. To the best of our knowledge, this dataset details all long-term, implantable tag deployments that have occurred to date on breeding stock E1. As such, these data provide researchers, regulators and industry with clear and valuable insights into the spatial and temporal nature of humpback whale movements along the eastern coastline of Australia and into the Southern Ocean. As this population of humpback whales navigates an increasingly complex habitat undergoing various development pressures and anthropogenic disturbances, in addition to climate-mediated changes in their marine environment, this dataset may also provide a valuable baseline. New information At the time these tracks were generated, these were the first satellite tag deployments intended to deliver long-term, detailed movement information on east Australian (breeding stock E1) humpback whales. The tracking data revealed previously unknown migratory pathways into the Southern Ocean, with 11 individuals tracked to their Antarctic feeding grounds. Once assumed to head directly south on their southern migration, five individuals initially travelled west towards New Zealand. Six tracks detailed the coastal movement of humpback whales migrating south. One tag transmitted a partial southern migration, then ceased transmissions only to begin transmitting eight months later as the animal was migrating north. Northern migration to breeding grounds was detailed for 13 individuals, with four tracks including turning points and partial southern migrations. Another 14 humpback whales were tagged in Antarctica, providing detailed Antarctic feeding ground movements. Broadly speaking, the tracking data revealed a pattern of movement where whales were at their northern limit in July and their southern limit in March. Migration north was most rapid across the months of May and June, whilst migration south was most rapid between November and December. Tagged humpback whales were located on their Antarctic feeding grounds predominantly between January and May and approached their breeding grounds between July and August. Tracking distances ranged from 68 km to 8580 km and 1 to 286 days. To the best of our knowledge, this dataset compiles all of the long-term tag deployments that have occurred to date on breeding stock E1.


Introduction
Humpback whales are globally distributed, occupying each of the ocean basins (Jackson et al. 2014).Like most rorqual whale species, humpback whales were targeted by the industrial whaling industry, with around 220,000 humpback whales killed in the Southern Hemisphere between 1904and 1973(Jackson et al. 2015)).In order to manage humpback whale stocks, the International Whaling Commission assigned seven Southern Hemisphere breeding stocks (A-G) and six Southern Ocean feeding areas (Donovan 1991).The two breeding stocks (D and E1) that move along Australia's west and east coasts annually were likely reduced to just hundreds of individuals each when industrial and illegal whaling ceased (Chittleborough 1965, Bannister andHedley 2001).However, despite the devastation caused by whaling, Australia's humpback whales have demonstrated a remarkable population recovery and, in 2022, the Australian Government removed their threatened species listing under the Environment Protection and Biodiversity Conservation Act 1999.Australia's eastern population of humpback whales was estimated to number 24,545 in 2015, with full recovery of the population expected to occur in 2016 (Noad et al. 2019).A contemporary population estimate for Australia's western population of humpback whales is lacking.However, in 2008, the population was conservatively estimated to be 17,810 individuals (Hedley et al. 2011).
Humpback whales undertake the longest mammalian migration on the planet (Rasmussen et al. 2007), moving seasonally between their winter breeding/calving grounds located in tropical and subtropical waters to their high-latitude summer feeding grounds, with the exception of the resident Arabian Sea population (Mikhalev 1997).Whilst some of this migration occurs along populated coastline, which facilitates the spatial and temporal monitoring of movements (for example, Noad et al. 2019 andPirotta et al. (2020)), the majority of movement is far removed from land (for example, Andrews-Goff et al. (2018), Bestley et al. (2019)).Satellite tags are the primary technology used to detail movement over biologically relevant time scales (Dingle 2014) and are especially essential to determine long-term, large-scale, detailed movements.Satellite tag-derived data are critical for identifying habitat use (Reisinger et al. 2021), overlap with threats (Weinstein et al. 2017) and novel behaviour (Garrigue et al. 2015) and is an essential tool for conservation and management of an animal that spends very little time at the surface (Nowacek et al. 2016) and in remote areas with no survey effort (Mate et al. 2007).
We present here a dataset detailing the satellite tag-derived movements of 50 humpback whales from Australia's eastern breeding stock E1.To the best of our knowledge, this dataset compiles all of the long-term tag deployments (type C implantable satellite tags; Andrews et al. ( 2019)) that have occurred to date on breeding stock E1.The dataset details movements on coastal breeding grounds, along northern and southern migrations and on Antarctic feeding grounds.These tracks have been compiled in their raw form, with a basic speed distance angle filter applied and also as a state space model output that accounts for Argos location error.These data provide researchers, regulators and industry with clear and valuable insights into the spatial and temporal nature of humpback whale movements along the eastern coastline of Australia.Managing and protecting species that cross ocean basins and jurisdictions is a challenge (Asaro 2012, Geijer and Jones 2015, Miller et al. 2018).As humpback whales navigate an increasingly complex habitat undergoing various development pressures and anthropogenic disturbances (Bolin et al. 2020, Indeck et al. 2021, Mayaud et al. 2022), as well as a marine environment changing under a shifting climate regime (Tulloch et al. 2019, Pallin et al. 2023), this dataset may also provide valuable baseline data.

General description
Purpose: Satellite tags were deployed on humpback whales on their southward migration, northward migration and feeding grounds in 2008, 2009 and 2010 to describe migratory pathways and movements on Antarctic feeding grounds and to identify possible calving areas.At the time, these movements were not well understood and calving grounds were not clearly identified.
Additional information: This dataset revealed the following key results:

Sampling methods
Description: Satellite tags were deployed on humpback whales located off east Australia (2008,2009,2010) and in east Antarctica (2010).Locations were transmitted via the Argos satellite system and processed to account for erroneous locations and the spatial error associated with Argos locations.

Sampling description: Satellite tag deployment
Type C implantable satellite tags (Andrews et al. 2019) were deployed on humpback whales in good body condition using a modified version of the Air Rocket Transmitter System (ARTS), Restech (Heide-Jorgensen et al. 2001) and a purpose-designed projectile carrier at a pressure of 7-12 bar.Deployment details are given within the Data Resources package, with additional information capturing tracking duration, deployment location, behaviour and type of movement described in Table 1.The satellite tag employed was comprised of a stainless-steel cylindrical housing containing a location-only SPOT-5 transmitter manufactured by Wildlife Computers (Redmond, Washington, USA) or a Kiwisat 202 Cricket (Sirtrack, Havelock North, New Zealand) plus an anchor section (320 mm in length).The tag was designed to penetrate the skin and blubber with retention via a springloaded, articulated anchor and passively deployed petals.This articulated design is now superseded.Deployment of the tag using the ARTS was aided by a purpose-designed projectile carrier, often referred to as a 'rocket' or 'sabot'.Retention teeth on the projectile carrier are gripped to a metal ring secured to the end of the tag.When the tag came into contact with the whale, the rapid deceleration of the tag and the projectile carrier withdrew the retention teeth, releasing the projectile carrier.The metal ring then fell off in time to reduce the drag of the tag.Satellite tags were sterilised with ethylene oxide prior to deployment and implanted up to a maximum of 290 mm into the skin, blubber, interfacial layers and outer muscle mass of the whale.Each tag was deployed from the bow-sprit of a purpose-built 6.3 m aluminium Naiad RHIB and was positioned high and forward on the body.Satellite tags transmitted data via the Argos satellite system once the tag was immersed in salt water, activating the salt water switch.Tags were programmed to transmit at various duty cycles to extend battery life and tag deployment duration.Tag transmissions were relayed to processing centres to calculate the transmitter's location by measuring the Doppler Effect on transmission frequency.Transmitted data were processed using least squares analysis and each location was assigned an estimated error and one of seven associated location classes (LC; see CLS ( 2023)).Briefly, LC 3 has an estimated error of 250 m, LC 2 has an estimated error between 250 and 500 m and LC 1 has an estimated error between 500 and 1500 m.LC 0 has an open-ended error of 1500 m, whilst LC A and B have no accuracy estimation and LC Z is an invalid location.Tags ceased transmitting when they were either naturally shed, damaged, experienced sensor fouling or the battery was exhausted.
Upon tag deployment, a small amount of skin and blubber was simultaneously collected for genetic analyses.These were collected using a biopsy dart fired from a modified 0.22 Paxarms system (Krutzen et al. 2002).Biopsy samples were stored in 70% ethanol and DNA subsequently extracted using a Tissue DNA purification kit for the Maxwell 16 DNA extraction robot (Promega Corporation).The sexes of the tagged whales were determined using a 5′ exonuclease assay of the polymorphisms in the sex-linked Zinc Finger genes as described by Morin et al. (2005).This research was conducted using non-lethal methods that are designed to learn about whales without harming them.The research was approved by the Australian Antarctic Ethics Committee (under Australian Antarctic Science Project 2941) and complied with all relevant permits, including the Australian Government Environment Protection and Biodiversity Conservation Act Cetacean Permit (2007-0007).

Quality control: Argos data processing to remove erroneous locations and account for Argos location error
Using the raw Argos tracking dataset and for all tracks containing > 5 Argos locations, we accounted for the spatial error associated with Argos locations by fitting a correlated random walk state-space model to generate a location estimate at each observed location time (fit_ssm function in the aniMotum package; Jonsen et al. ( 2023)) within R (R Core Team 2023).Within this state-space model, we applied the sdafilter function, which is an algorithm based on swimming speed, distance between successive locations and turning angles (sdafilter function in the Argosfilter package; Freitas et al. ( 2008)) to remove unlikely position estimates (speed of 10 ms , spike angles of 15° and 25°, spike lengths of 2,500 m and 5,000 m).Individual tracks were split into track segments for processing where data gaps exceeded 24 hours. −1

Geographic coverage
Description: The geographic range of the bulk of the dataset is along the east coast of Australia and broadly through the east Antarctic sector of the Southern Ocean, concentrating in IWC Management Area V (Fig. 1).The tracking data captured various geographic ranges of movement, including southern migration along the east coast of Australia into the Southern Ocean (n = 10), southern migration towards New Zealand (n = 4) and southern migration via New Zealand into the Southern Ocean (n = 1).Six of the tags only transmitted coastal movement on the southern migration.Of these, one tag transmitted a partial southern migration to approximately 50°S, then ceased transmissions only to begin transmitting eight months later at approximately 37°S as the animal was migrating north.Northern migration to breeding grounds was also captured (n = 13), including turning points and partial southern migrations (n = 4).Movement restricted solely to Antarctic feeding grounds was captured by another 14 tracks.Tracking distances ranged from 68 km to 8,580 km (Table 1).
Notes: Tags transmitted data over 1 to 286 days; however, not all tags transmitted continuously (Fig. 2).Tags transmitted locations for each month of the year with the exception of September (Table 2; Fig. 3).The temporal pattern of movement can be broadly described by assessing mean latitude against month, acknowledging that there is individual variability in the dominant direction of travel in each month.On average, tagged humpback whales were at their northern limit in July and their southern limit in March.Migration north was most rapid across the months of May and June, with mean latitude in May at 64.0°S and mean latitude in June at 27.1°S.Migration south was most rapid between November (mean latitude of 44.6°S) and December (mean latitude of 58.7°S).Tagged humpbacks were located on their Antarctic feeding grounds predominantly between January and May and approach their breeding grounds between July and August (noting that there are no location data for September).Table 2.
Monthly track summary detailing the number of tracks occurring in that month, the number of state space modelled location estimates generated by those tracks, the mean latitude of the location estimates and the dominant direction of travel.

Usage licence
Usage licence: Other IP rights notes: CC BY: This licence allows reusers to distribute, remix, adapt and build upon the material in any medium or format, so long as attribution is given to the creator.The licence allows for commercial use.

Data resources
Data package title: East Australian (breeding stock E1) humpback whale tracking datasatellite tag-derived Argos locations and associated information, reference data detailing tag deployments and state-space model location estimates that provide a dataset that

Column label Column description
tag-id A unique identifier for the deployment of a tag on animal.
animal-id An individual identifier for the animal.

Figure 1 .
Figure 1.State-space model location estimates for 48 east Australian (breeding stock E1) humpback whales.Two tracks contained < 5 Argos locations so were not included in the state-space model.The boundary between IWC Management Areas IV and V is depicted by the vertical black line at 130°E.

Figure 2 .
Figure 2. Deployment duration (x axis) for each of the deployed satellite tags (unique Argos PTT on the y axis).Deployments span 2009, 2010 and 2011.Satellite tags transmitted locations continuously (for example, 88741) or sometimes intermittently (for example, 88755).

Figure 3 .
Figure 3.State-space model location estimates generated by satellite tagged east Australian (breeding stock E1) humpback whales in each year and coloured according to month.
sensor-typeThe type of sensor with which data were collected.Argos Doppler shift = The sensor location is estimated by Argos using Doppler shift.individual-taxon-canonical-nameThescientific name of the species on which the tag was deployed, as defined by the Integrated Taxonomic Information System (ITIS).tag-local-identifierAn identifier for the tag.individual-localidentifierAn individual identifier for the animal.study-nameThename of the study in Movebank.Data set name: Movements of Australia's east coast humpback whales-reference-data Download URL: https://www.movebank.org/cms/webapp?gwt_fragment=page= studies,path=study3030068329Data format: csv Description: Reference data detailing satellite tag deployments on Australia's east coast humpback whales (n = 50).

Table 1 .
Satellite tag-derived movements of breeding stock E1 humpback whales.Additional deployment information can be found in Data Resources.Argos PTT = the unique tag identification number; Tracking duration = duration of tag deployment from tag deployment date to last location date; Deploy location = broad geographic location where satellite tag was deployed; Stage of annual cycle upon deployment = migration direction or feeding grounds; Initial activity = whale behaviour at tagging; Retained for SSM = whether the state-space model was applied to the Argos locations generated to account for Argos location error; SSM-derived track distance esimate = the length of the satellite track from the state-space model location estimates in kilometres; Movement captured = the types of movement and behaviour detailed in each satellite track.Australia's east coast humpback whales: Satellite tag-derived movements o ... Australia's east coast humpback whales: Satellite tag-derived movements o ...
Megaptera novaeangliae (Borowski, 1781) (Balaenopteridae, order Artiodactyla), which is categorised as Least Concern in the IUCN Red List (Cooke 2018).This dataset details the east Australian humpback whale breeding stock/population E1.The Australian Government categorises this population as vulnerable.
Description: This dataset focuses exclusively on the humpback whale - accounts for erroneous locations and Argos location error.Datasets are freely available and are published in the Movebank data repository and the Australian Antarctic Data Centre.This file contains all Argos locations generated by satellite tags deployed on 50 humpback whales, as detailed in Table 1 and the reference data within Data Resources.Using the raw Argos tracking dataset, but only for tracks containing > 5 locations (n = 48), we accounted for the spatial error associated with Argos locations by fitting a correlated random walk state-space model to generate a location estimate at each observed location time.Within this state-space model, we applied the sdafilter to remove unlikely position estimates (speed of 10 ms , spike angles of 15° and 25°, spike lengths of 2500 m and 5000 m).The associated state-space model locations for 48 humpback whales are also contained within this file and are identified within the columns 'comments' ('state-space model location estimate -see citation for details') and 'modelled' ('TRUE').Australia's east coast humpback whales: Satellite tag-derived movements o ... geographic longitude location estimate.Positive values are east of the Greenwich Meridian, negative values are west of it.Units: decimal degrees, WGS84 reference system.argos:lon2 Argos' alternative geographic longitude location estimate.Positive values are east of the Greenwich Meridian, negative values are west of it.Units: decimal degrees, WGS84 reference system.comments Additional information -identifies state-space model locations.modelled Identifies locations that are modelled (marked as TRUE). −1