DOI: 10.5061/dryad.v9s4mw71g
title: Differences in the functional use of two migratory stopovers by humpback whales (Megaptera novaeangliae)

description: Humpback whale migration between tropical breeding grounds and polar
 feeding grounds is an energy-intensive activity undertaken on finite
 energy stores. The use of stopover sites to rest reduces energetic
 expenditure and provides enhanced opportunity for calves to nurse during
 migration. Moreton Bay is a newly identified migratory stopover for
 Australia’s east coast humpback whale population. Understanding the
 functional roles of stopovers is essential for a holistic understanding of
 population dynamics and connectivity. Therefore, contextualising the
 significance of Moreton Bay relative to a well-established stopover like
 Hervey Bay can provide valuable insights into their functional roles
 within the broader migratory network, helping to inform targeted
 conservation efforts. To investigate this, we conducted a total of 865km
 of systematic, boat-based line transects across the two distinct
 geographical regions during temporally staggered periods (August and
 September – October) of the 2021 humpback whale migration. We examined
 population structure, behaviour, and habitat segregation, and developed
 spatial density surface models to predict density distribution patterns at
 each respective site. Our results show that Hervey Bay supports a more
 heterogeneous mix of demographic groups, while Moreton Bay had a
 significantly greater number of calf-groups (z = 4.53, p = 0.017). Both
 bays exhibited similar resting behaviours, but social interactions among
 juveniles were unique to Hervey Bay. These findings suggest Moreton Bay
 serves a more utilitarian role as a stopover, functioning primarily as a
 resting site for mother-calf pairs, rather than the multifaceted use
 described in Hervey Bay. As lactating females and their calves are
 particularly vulnerable to anthropogenic threats like vessel strike, it is
 imperative to understand how different habitats contribute to the success
 of migration and ensure adequate protection is maintained.
description: This data was collected using randomly placed systematic line
 transects onboard a 7-meter research vessel. The vessel transited along
 these transect lines at a speed of ~8 knots, and humpback whale sightings
 were collected using the Distance sampling methodology. Briefly, these
 notes the distance and angle of the sighting relative to the vessel's
 center line. Both on effort (sighting made whilst on transect) and
 off-effort (sightings made whilst the vessel was going between
 transects/sightings/start-point), sightings were collected and noted.
 Sightings were then used to build density surface models. This was done in
 R using the packages "distance" and "dsm".
description: # Differences in the functional use of two migratory stopovers by humpback
 whales (*Megaptera novaeangliae*)” 1. Co-authors: Raphael Mayaud*, Joshua
 N. Smith, David Peel, Craig Wilson, Wally Franklin, Tim Stevens, and Susan
 Bengtson Nash *contact:
 [Raphael.mayaud@griffithuni.edu.au](mailto:Raphael.mayaud@griffithuni.edu.au) 2. Data collection: Queensland, Australia (2021) 3. Data citation: Mayaud, Raphael; Smith, Joshua, N.; Peel, David et al. (2025). Differences in the functional use of two migratory stopovers by humpback whales (Megaptera novaeangliae) [Dataset]. Dryad. [https://doi.org/10.5061/dryad.v9s4mw71g](https://doi.org/10.5061/dryad.v9s4mw71g) ## DATA OVERVIEW The data consists of raw data collected from boat-based line transects during the field season in 2021. Two study regions were sampled, and each region had two different survey areas (1 & 2 for one region and A & B for the second region). There are two Excel tabs: the effort data (data regarding transect effort) and the sightings data (data regarding sightings of humpback whales, behaviour, location, etc.). ### EFFORT DATA This data records whenever the vessel started and left a line transect, as well as environmental variables associated with each transect. • Number of variables: 13 • Number of rows: 76 • Missing data: none Variable list: 1. Area: Area from which transects were performed. 2. Date: Date of when the transect was performed. 3. TimeOn: Time the boat started the transect. 4. TimeOut: Time when the boat exited the transect. 5. Transect: Transect label 6. Lat0: Latitude location of where the research vessel started the transect.* 7. Lon0: Longitude location of where the research vessel started the transect.* 8. Lat1: Latitude location of where the research vessel exited the transect* 9. Lon1: Longitude location of where the research vessel exited the transect.* 10. Seastate: Measure of the seastate when on a transect (using the Beaufort Sea State measure). 11. Wind(kt): Measure of the wind in knots on transect (derived from websites such as Seabreeze, Windy App at the time of survey). 12. WindDir: Wind direction(N = North, E = East, S = South, W = West etc.) 13. Fog: Presence of fog or not ### SIGHTINGS DATA These data represent each sighting made whilst on the research vessel. This includes both whilst the vessel was on effort (i.e., on the transect) and off-effort (not on the transect). Each row represents a new humpback whale sighting. Sightings that were made on effort were recorded following distance sampling methodology, and so the distance and angle relative to the vessel's centre line were recorded for these sightings. • Number of variables: 13 • Number of rows: 126 • Missing data: none Variable list: 1. Area: Area from which transects were performed. 2. Date: Date of when the transect was performed. 3. Sighting: Sighting number for that day. Each new day leads to a sighting number starting from one again 4. Time: Time sighting was made 5. Transect: Transect sighting was made on (if on effort, otherwise if off-effort, this is left blank) 6. Latitude: Latitude location of sighting* 7. Longitude: Longitude location of sighting* 8. Angle: Angle of the sighting relative to the vessel centre line. An angle of 0 is a sighting that is made dead ahead of the vessel, and sightings were recorded up to 90 degrees port/starboard of the beam of the vessel 9. Dist: The distance (in metres) with which the sighting was made. Please note, this is not the radial distance. 10. Count: Total count of humpback whales within that sighting 11. Comp: The humpback whale group compositions of the sighting. The following symbols represent the pod compositions: S = Singleton; M = Member of a pair; MC = Mother calf; MCE = Mother calf escort; N(n) = Non-competitive pod of n individuals. 12. Behaviour: The behaviour of the humpback whales at the time of the sighting. Codes here represent: B = Breach; T = Travel; TS = Tail slapping; FS = fin slapping; Sparring Pod; see manuscript for definition, but briefly when two or more whales were half competing with one another without the high intensity energy behaviours associated with competitive groups and no obvious fight for female (resembling play fighting); L = Logging; R = resting; N = nursing. 13. Effort: Either on or off effort *Please note, locations of data have been reduced to 1 decimal place to reduce the precision of sighting locations as per Dryad guidelines. If more precise locations are needed, please contact the authors directly.