Vol. 29: 201–209, 2016 ENDANGERED SPECIES RESEARCH Published January 21 doi: 10.3354/esr00712 Endang Species Res

OPENPEN ACCESSCCESS Migrating humpback whales show no detectable response to whale alarms off Sydney,

Vanessa Pirotta1,*, David Slip1,2, Ian D. Jonsen1, Victor M. Peddemors3, Douglas H. Cato4,5, Geoffrey Ross6, Robert Harcourt1

1Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia 2Taronga Conservation Society Australia, Bradley’s Head Road, Sydney, NSW 2088, Australia 3Fisheries NSW, NSW Department of Primary Industries, Sydney Institute of Marine Science, Chowder Bay Road, Sydney, NSW 2088, Australia 4Defence Science and Technology Group, Eveleigh, NSW 1430, Australia 5School of Geosciences, University of Sydney, NSW 2006, Australia 6NSW National Parks & Wildlife Service, Bridge Street, Sydney, NSW 1481, Australia

ABSTRACT: Migratory Group V (Stock E1) humpback whales Megaptera novaeangliae are at risk of entanglement with fishing gear as they migrate north and south along the east coast of Aus- tralia. This study investigated the effectiveness of 2 distinct tones for use as an alarm to acousti- cally alert whales to fishing gear presence and therefore reduce the chance of entanglement. We compared how whales responded in terms of changes of surface behaviour and changes in direc- tion of travel in response to 2 acoustic tones and when there was no alarm. These 2 acoustic tones were a 5 kHz tone (5 s emission interval and 400 ms emission duration, similar to but higher fre- quency than the signal from a Future Oceans F3TM 3 kHz Whale Pinger®) and a 2−2.1 kHz swept tone (8 s emission interval and 1.5 s emission duration). A total of 108 tracks (focal follows) were collected using a theodolite at Cape Solander, Sydney, Australia, during the whales’ 2013 north- ern migration. Linear mixed effects models were used to determine the effect of the different acoustic tones on whale direction (heading), and behaviour (dive duration and speed). Whales showed no detectable response to either alarm. Whale direction and surfacing behaviour did not differ whether the alarm was ‘on’ or ‘off’. Although the response may have been different if the alarms were attached to fishing gear, the lack of measurable response suggests that the types of tones used are not likely to be effective in alarms intended to reduce entanglement of northward migrating Australian humpback whales.

KEY WORDS: Fisheries · Entanglement · Megaptera novaeangliae · Mortality · Bycatch · Acoustic deterrents

INTRODUCTION can inflict a number of life threatening injuries upon whales, including restricted movement, emaciation, Baleen (Mysticeti) whale entanglement in fishing rope trauma, infection, tissue damage and death gear is an expensive, current and potentially serious (Moore & van der Hoop 2012). Unlike commercial global problem (Clapham et al. 1999, Read et al. whaling, entanglements with fishing gear are an un- 2006, Cassoff et al. 2011). Interactions between intentional source of baleen whale mortality (Cassoff baleen whales and fisheries are likely to increase as et al. 2011, Moore 2014), and pose a serious threat to whale populations recover in the post-whaling period species such as the Endangered North Atlantic right (Carroll et al. 2011, Gales et al. 2011). Entanglements whale Eubalaena glacialis (Knowlton et al. 2012,

© The authors 2016. Open Access under Creative Commons by *Corresponding author: [email protected] Attribution Licence. Use, distribution and reproduction are un - restricted. Authors and original publication must be credited. Publisher: Inter-Research · www.int-res.com 202 Endang Species Res 29: 201–209, 2016

Reeves et al. 2012, van der Hoop et al. 2013). Entan- quency alarm was unlikely to deter migrating hump- glement has been implicated in injury or death of back whales from approaching fishing gear (Har- members of most baleen whale species (IWC 2010), court et al. 2014) and reinforced the need to investi- including the Arctic bowhead Balaena mysticetus gate alternatives. (Reeves et al. 2012), fin Balaenoptera physalus (Lien Migrating humpback whales encounter a range of 1994), minke B. acutorostrata (Northridge et al. 2010, fishing activities as they travel along the east coast of Song et al. 2010), humpback Megaptera novaeanglia Australia each year from their high latitude summer (Lien 1980, Neilson et al. 2009) and southern right feeding grounds to their low latitude breeding whale E. australis (Best et al. 2001). Entanglement in grounds (Chittleborough 1965). Several types of fish- fishing gear may also be a limiting factor in the recov- ing equipment can potentially entangle whales along ery of threatened baleen whale species such as the this path, including longlines, gillnets, shark nets and Critically Endangered western gray whale Es- single units like lobster and crab pots (Groom & chrichtius robustus (Bradford et al. 2009). Coughran 2012). In , entangle- Measures that have been used to reduce whale ments of humpback whales in fishing gear comprise entanglements in fishing gear have included modify- the highest proportion of negative anthropogenic ing fishing equipment, seasonal fishery closures interactions with cetaceans documented between (Knowlton & Kraus 2001, Kraus et al. 2005), and 1970 and 2013 (Lloyd & Ross 2015). Although the east using acoustic alarms that function to alert whales to Australian shark net (bather protection) programs in the presence of fishing gear (Lien 1980, Lien et al. and New South Wales currently use 1995). A major advantage of using alarms over more whale alarms on their nets, there have been ongoing active fisheries management is that they have the humpback whale entanglements, some fatal, and this potential to reduce the risk of entanglement without suggests the alarms may not be deterring all whales. severely impacting the fishery itself. However, for These alarms were the same model as that tested by alarms to be effective in preventing entanglement, Harcourt et al. (2014), who found no detectable whales must notice the sound source and also associ- response to the alarms. ate it with nets or lines (Lien et al. 1992). Southerly migrating humpback whales in southern Acoustic alarms have had mixed success in mitigat- Queensland are reported to show a consistent behav- ing entanglement for odontocetes (toothed whales), ioural response to an upsweeping tone from 2− being most successful in reducing bycatch of harbour 2.1 kHz over 8 s (Dunlop et al. 2013). The robustness porpoises, common dolphins, beaked whales and of this response suggested that this tone might poten- fran ciscana in gill nets (Barlow & Cameron 2003, tially provide an effective alarm. Therefore, we as - McPherson 2011, Berg Soto et al. 2013, Dawson et sessed whether broadcasting this upswept 2−2.1 kHz al. 2013). Acoustic alarms have been specifically de- tone would alter the path of migrating whales and signed to target the hearing range of the animals potentially be useful as an alarm for re ducing the they are intended to deter (Ketten 1994). Odontocete chance of entanglement. We also assessed the re - acoustic alarms typically produce higher frequency sponse to a higher frequency (5.3 kHz) signal with tones (10 kHz) compared with the lower frequency similar temporal characteristics to the 3 kHz Whale alarms used for the non-echolocating baleen whales Pinger®. This new alarm was moored in the middle (3 kHz). of the humpback whale migratory corridor off Syd- Since the initial work developing whale alarms ney, Australia. The aim of the study was to test (Lien 1980), alarm technology has improved, but un- whether the migratory path of northward migrating til recently there has been little systematic re search whales deviated sufficiently in the presence of either in situ to test the efficiency of whale alarms in deter- of these alarm tones to reduce the likelihood of ring whale entanglement from fishing gear (Jeffer- whales swimming into the alarm. son & Curry 1996, Harcourt et al. 2014). A systematic assessment of the effect of a single moored, commer- cially available whale alarm (3 kHz Whale Pinger®; MATERIALS AND METHODS with source level specified as 135 dB ± 4 dB re 1 µPa at 1 m) on the movements of migrating east coast Study site Aus tralian humpback whales M. novaeangliae found that whales showed no detectable response to the The study was conducted at Cape Solander in Bo - alarm over audible ranges (Harcourt et al. 2014). This tany Bay National Park, Sydney, Australia (34° 01’ S, suggested that a simple, monotonic, 3 kHz low fre- 151° 14’ E; Fig. 1). Humpback whales were tracked Pirotta et al.: Migrating humpback whales unresponsive to whale alarms 203

from an observation platform that was located 30 m above sea level and has been used for observing whales during their northern migration for over 18 yr.

Whale alarm

We installed a fixed mooring with a sur- face float 1.3 km offshore from the obser- vation platform in 53 m of water with the prototype whale alarm secured at 5 m depth. The whale alarm consisted of a rolled aluminum housing enclosing a bat- tery pack, iPod nano®, amplifier and loudspeaker (Altronics PA Compression Driver C6115) fitted to the end of the rolled aluminum housing, at a depth of 5 m. This depth was chosen to be similar to that used by the fishing industry to deter whales from entanglement in set nets and lines (Erbe & McPherson 2012, Harcourt et al. 2014). The whale alarm mooring was anchored in the midpoint of the peak migration route as determined from previous research conducted at the same study site in the years 2006−2008 (Gulesserian et al. 2011). A randomised playlist was preset on an iPod nano® that played 1 of 2 tones or a control of no tone for 11 h each day (07:00−16:30 h, daylight hours). The 2 tones were (1) a 2−2.1 kHz swept tone (8 s emission interval and 1.5 ms emission duration, adapted from Dunlop et al. 2013) and (2) a 5.3 kHz tone of 5 s emis- sion interval and 400 ms emission dura- tion. The 5.3 kHz tone was actually the second harmonic of the signal, which had a fundamental frequency at 2.65 kHz, but the level was about 10 dB lower than the 5.3 kHz harmonic, so it was effectively a 5.3 kHz tone.

Data collection Fig. 1. All tracks that passed within 1000 and 500 m of the alarm moor- ing. Whale alarm location indicated by star (depth of 53 m). All focal Data were collected between 28 June follows that passed through the study site when the alarm was (a) off 2013 and 4 August 2013 to coincide with (control) and focal follows when the alarm emitted either the (b) the peak of the northern migration (Ni - 5.3 kHz tone or (c) 2−2.1 kHz swept tone. Each dot represents a single whale surfacing along individual focal follows. Triangle represents cholls et al. 2000, Vang 2002, Gulesserian the location of the theodolite. A black 1000 m (outer) and 500 m (inner) et al. 2011) using the method described in radius around the alarm mooring represents the likely acoustic range Harcourt et al. (2014). Whale observations of detectability 204 Endang Species Res 29: 201–209, 2016

were made using the naked eye and 7 × 50 magnitude We took recordings of the received level from the binoculars. All data were recorded using a theodolite alarm and the background noise at regular distances set up on the Cape Solander observation deck that along transects — the distance between recording stands 30 m above sea level. A Sokkia DT510A positions was 50 m — creating a 300 × 300 m grid over theodolite was connected to a laptop computer run- the position of the alarm. A Garmin GPSMAP® 78sc ning custom written software VADAR© (Version GPS to locate the start of each transect line. At the 1.51.02 Eric Kneist, University of Newcastle, Australia, start of a transect line, the boat motor was switched http://cyclops-tracker.com/). The theodolite simulta- off and the hydrophone was lowered to 30 m and neously measured horizontal and vertical angles to a recording started. We selected transect lines based target whale and fed to a computer that calculated the on wind conditions that would allow drifting along whale position using VADAR©. The horizontal angle the transect, and once recordings commenced, the was calibrated using a known reference object, Cape boat was allowed to drift over the entire transect. Banks (the headland north of the field site). Recordings ceased once the boat had reached the At least 2 people constantly scanned to the south for end of the transect line. The boat then motored up to approaching humpback whale groups. A group was the start of the new transect and the recording pro- defined as either a lone whale or more than one indi- cess was repeated. vidual. Groups were selected as far south as possible The frequencies of the alarm tones were expected relative to the alarm to allow the approach to be to be audible to humpback whales as they are within recorded. All whales that passed through the study the range of humpback whale vocalisations (Ketten site were on their annual northern migration, and 1992, 1997, Au et al. 2006, Dunlop et al. 2008). The therefore each focal follow was considered independ- threshold of audibility will depend on the received ent. Once a group was seen, a focal animal, distin- signal to noise ratio, specifically the critical ratio for guishable by the natural variation in markings and tonal signals, which is the difference between the dorsal fin shape, was chosen to track within a group. level of the tone (i.e. the received level of the alarm) We recorded every surface event for the focal animal, and the noise spectrum level at the same frequency, as well as any associated behaviour with every surfac- at the threshold of audibility. Based on the reasoning ing, from the moment the group was first sighted until given by Dunlop et al. (2013) and drawing on meas- it left the study area (>4000 m north of the theodolite) urements of critical ratios for a range of terrestrial or could no longer be seen. Common causes of poor and marine mammals (Richardson et al. 1995, visibility included intense sunlight and mist. Once a Southall et al. 2007), the best estimate of the critical group moved out of the study site, the next southern- ratio for humpback whales is that it would lie in the most group was selected for tracking (if present). We range of the ratios for other mammals, i.e. 19−26 dB monitored all vessels using a 15 min scan of vessel for 2 kHz and 20−27 dB for 5.3 kHz. activity (Martin & Bateson 1998). The received signal to noise ratio of a tone was Observations were made from dawn until dusk measured as the difference in the level of the tone (subject to daylight, usually 06:20−17:20 h Australian (corrected for background noise) and the noise spec- Eastern Daylight Time, AEDT) when weather condi- trum level at the same frequency as the tone. The tions were favourable (no rain and Beaufort of <4). We measurements of the noise were made in the inter- recorded weather conditions throughout the day and vals between the transmission of the tone and cor- included: Beaufort, swell, cloud coverage and rain. rected for the measurement bandwidth to give the spectrum level, i.e. the level in a 1 Hz band. Meas- urements of the alarm tones showed that the signal to Whale alarm recordings noise ratios were consistently within the range of crit- ical ratios for distances up to about 500 m and on To estimate the audible range of the prototype some measurements beyond 500 m. The alarm was whale alarm, we made acoustic recordings as de - audible to humans at similar distances. Some exam- scribed in Harcourt et al. (2014) at various distances ples of the measured signal to noise ratios for the from the alarm. We used a hydrophone (High Tech 2 kHz alarm are: 30−32 dB at 150 m, 23 dB at 500 m, Inc.) attached to 30 m of line suspended from a drift- 19−20 dB at 850 m and 15−16 dB at 1.5 km. For the ing boat and recorded the signal directly onto an 5.3 kHz alarm, measured levels were 22−23 dB at M-Audio Micro Track 24/96 Professional 2-Channel 150 m, 23 dB at 500 m, 10 dB at 930 m. Noting that Mobile Digital Recorder. The frequency response the noise varies with wind speed, the wind conditions was 20 Hz−20 kHz. during these measurements were chosen to be simi- Pirotta et al.: Migrating humpback whales unresponsive to whale alarms 205

lar to those of the behavioural studies. Noise levels out (i.e. Null models) alarm status as a fixed effect. measured from a drifting boat tend to be higher than We also used likelihood ratio (LR) tests to assess true background noise because of the additional whether differences between these model pairs were noise of waves splashing against the boat. Hence, significant (p < 0.05). All statistical analyses were actual noise levels would have been lower than performed using the nlme library (Pinheiro et al. measured and signal to noise ratios would have been 2014) in the statistical software package R (R Foun- higher than measured, so these distance estimates dation for Statistical Computing). are conservative. However, to ensure that the tones were always within the range of audibility, we lim- ited the analysis to those whale groups that passed RESULTS within 500 m of the alarms. A total of 108 focal follows were recorded over 300 h of observation. Observations were made for Analysis 12 d while the source was silent (control), 10 d for the upswept 2−2.1 kHz tone, and 11 d for the 5.3 kHz Only focal follows collected via the theodolite that tone. Each group was considered independent as were at least 15 min in duration, included multiple whales were on their annual northern migration. For (2 or more) dives, and passed within 1000 and 500 m focal follows that passed within 1000 m of the alarm, of the alarm were included in the analysis. We ana- 52% (n = 57) occurred during the control treatment, lysed whale behaviour during focal follows accord- 27% (n = 28) occurred during the 2−2.kHz treatment, ing to 3 response variables: (1) heading (degrees); (2) and 21% (n = 23) occurred during the 5.3 kHz treat- dive duration (s); and (3) travelling speed (m s−1). We ment. For focal follows that passed within 500 m of calculated heading as the bearing between consecu- the alarms, 48% (n = 30) occurred during the control, tive surfacings measured in relation to north. Dive 28% (n = 18) occurred during the 2−2.1 kHz treat- duration was calculated as the time (s) between the ment, and 24% (n = 15) occurred during the 5.3 kHz last respiration before each dive and the first after treatment. The surface plots of whale movements that dive. Whales typically remained at the surface under the 2 treatments and the control were visually respiring a number of times after a dive. To avoid cal- similar (Fig. 1). culating sequential surfacing respirations after a The direction whales were heading did not differ dive, all surfacing events less than 120 s apart were between the control and treatments within both 1000 excluded from the analysis. Travelling speed was measured as the time taken to travel the distance Table 1. Comparison of linear mixed-effects models that between consecutive sightings (m s−1). To measure used the Akaike information criterion (AIC) and likelihood the potential effects of the alarm, we assessed whale ratios (LR) to assess differences in whale response variables behaviour between 2 treatments (2−2.1 kHz tone and among treatments (2−2.1 kHz, 5.3 kHz and control) within a 1000 m radius of the alarm 5.3 kHz tone) and a control (no tone). As we could not observe whale behaviour under- water, these 3 behavioural responses were chosen on Response variable Null AIC AIC LR p-value the basis of being observable through the methodol- Downtime (min) 603.419 606.201 1.219 0.544 ogy used in this study. If the alarm was to have any Speed (m s−1) 786.931 789.977 0.954 0.621 effect on an individual whale, we tested whether Heading (°) 2704.267 2707.613 0.654 0.721 travel speed, dive duration or directional movements differed between the treatment and the control. We used a cosine transformation to account for the circu- Table 2. Comparison of linear mixed-effects models that used the Akaike information criterion (AIC) and likelihood lar nature of the heading data and a logit transforma- ratios (LR) to assess differences in whale response variables tion to normalize the cosines of the headings. among treatments (2−2.1 kHz, 5.3 kHz and control) within a Linear mixed-effects models (Pinheiro & Bates 500 m radius of the alarm 2000) were used to assess differences between treat- ments for the 3 response variables. We treated the Response variable Null AIC AIC LR p-value focal follow as a random effect to account for the repeated measures within individual whales. For Downtime (min) 397.086 399.909 1.177 0.555 Speed (m s−1) 357.515 359.289 2.227 0.329 each response variable, we compared the Akaike Heading (°) 1671.231 1675.202 0.028 0.986 information criterion (AIC) of models with and with- 206 Endang Species Res 29: 201–209, 2016

Heading and 500 m of the alarm (Tables 1 & 2, Fig. 2a). Whales followed a similar northeast path as they travelled a through the study site. Collectively, these results 150 suggest that the directionality of whale movements was independent of the alarm. Movements may be most likely influenced by other factors, such as the 100 topography. Whale speed (Tables 1 & 2, Fig. 2b) and dive dura- tion (downtime) (Tables 1 & 2, Fig. 2c) did not differ Course (°) between the alarm treatments and the control within 50 both 1000 and 500 m of the alarm. The mean speed across both treatments and the control was similar, 2 kHz: 2 m s−1 (SD = 1.08 m s−1, n = 28), 5.3 kHz: 2 m 0 s−1 (SD = 1.08 m s−1, n = 23) and control: 2 m s−1 (SD = 1.17 m s−1, n = 57). This suggests that speed and dive duration were not influenced by the alarm. Speed 5 b DISCUSSION 4

) Baleen whale entanglement in fishing gear is an –1 3 international problem that is likely to increase with the growth of fishing effort alongside the recovery of some whale populations post-whaling (Read 2008, 2 Pauly 2009). A recent study that tested the effective- Speed (m s (m Speed ness of a 3 kHz commercial whale alarm that is 1 already widely used on fishing nets found that north- ward migrating humpback whales showed no de - 0 tectable behavioural response to the alarm, suggest- ing that either the tone was too faint in a noisy ocean or that the whales were indifferent to the tone Downtime (Harcourt et al. 2014). In the present study we tested the response of humpback whales to different to- 14 c nal signals, a higher frequency tone (5.3 kHz) and a more complex tone (swept from 2.0−2.1 kHz) that 12 humpback whales were found to respond to during 10 the southern migration (Dunlop et al. 2013). Even with these differences we could not detect any 8 responses from whales in directionality, speed or dive duration as a result of either alarm being pres- 6 ent, consistent with the results of the study by Downtime (min) Downtime Harcourt et al. (2014). 4 There may be a number of reasons why whales did not respond to either the swept tone or the higher 2 frequency version of an existing alarm signal. The 2 kHz 5.3 kHz Control swept 2 kHz tone was adopted because there were clear and consistent responses reported for south- Treatment ward migrating humpback whales (Dunlop et al. Fig. 2. Boxplots of each response variable for whales that 2013). However, most of the responding whales in passed within a 500 m radius of the alarm between treat- that study were females with newborn calves, some- ments (2−2.1 kHz, 5.3 kHz and control): (a) heading, (b) trav- times accompanied by escorts (Dunlop et al. 2013), elling speed and (c) downtime. Grey boxes: inner quartile ranges; black lines: median of each treatment; whiskers: whereas in our study the whales were predominantly lower and upper quartiles of the data; single dots: outliers adults including near-term pregnant females. Whale Pirotta et al.: Migrating humpback whales unresponsive to whale alarms 207

behaviour may differ depending on the direction of volves active feeding and searching (Stimpert et migration and the social category. For example, al. 2012). Foraging whales may be more mindful to southward migrating mothers may be more cautious any acoustic presence in comparison to migrating and responsive in order to protect their calves in humpback whales (Noad & Cato 2007, Silva et al. comparison to northerly migrators still anticipating 2013). While we do not know whether the whales reproduction and competing to mate (Noad & Cato were actually detecting the alarm tone, our results 2007, Smith et al. 2012). Possibly, whale responses to suggest even if whales were alerted by the alarm, the alarm used in this study may have been too subtle they did not alter behaviour even when passing to detect by means of a theodolite. within 500 m of it and simply continued on their As humpback whales move along the east coast of northward journey. Australia, they are exposed to many different natural Currently there is no single solution to reducing and anthropogenic sounds during their migration whale entanglement in fishing gear. While acoustic (Cato & Bell 1992, Cato & McCauley 2002, Cato alarms may alert humpback whales to nets in feeding 2010). Whether humpback whales are able to associ- areas (Lien 1980, Lien et al. 1990a,b, 1992), they do ate the sound of an alarm with a threat is unclear. It is not appear to be effective for northerly migrating reasonable to assume that whales migrating along humpback whales (Harcourt et al. 2014, present the east coast of Australia are accustomed to a wide study). Approaches to reducing entanglements there- variety of noises, in which case the alarm sounds may fore require a more targeted approach rather than appear simply as another, minor, component of this attempting one-size-fits-all. In areas where animals modified acoustic environment (Dunlop et al. 2010). are moving slowly with calves, or feeding, the results In addition, ambient noise along the east coast of of Dunlop et al. (2013) indicate that alarms may still Australia may also have the potential to mask the be beneficial even if not foolproof. It is possible that alarm’s output (Cato & McCauley 2002, Erbe & other types of acoustic signals may be more effective McPherson 2012). To be effective, any acoustic alarm as alarms. For example, Götz & Janik (2010) found must be functional in noisy areas not just quiet ones. that signal rise time had an effect on response of pin- We suggest that lack of audibility was not the prob- nipeds. Further research directions may examine the lem in our case. Our in situ measurements of the effect of different types of alarms, the potential of an received levels of the alarms and the background array of complex alarm acoustics incorporating lower ambient indicated that the signal to noise ratios and higher frequency tones, as well as swept and should have been adequate for the alarms to have modulated tones, with longer emission durations. been consistently audible at distances up to at least However, in areas of directed migration a mixture of 500 m and beyond 500 m for some of the time. management strategies such as fishing gear modifi- If we assume acoustic detectability, it is possible cations, e.g. breakaways and sinking ground lines that whales may have been ‘alerted’ but simply did (Moore 2014), or seasonal fishery area closures may not deviate away from the alarm. Initial experiments be effective. Preventing unintentional mortality of by Lien (Lien 1980, Lien et al. 1990a,b, 1992) demon- baleen whales (Moore 2014), unacceptable cruelty, strated that in different cases whales could be both prolonged suffering (Moore & van der Hoop 2012) attracted and deterred from acoustic devices. In some and loss of fishing gear has widespread interest instances whales slowed and turned in the direction within the global fishing community, government of the sound to investigate, while others turned away agencies, NGOs and the scientific community. from the sound source and increased speed (Lien Future efforts to reduce entanglement should be at 1980, Lien et al. 1990a,b, 1992). However, these trials the forefront of baleen whale conservation biology were conducted on humpback whales within feeding research. areas as opposed to the humpback whales in mid- migration tested in our study. Baleen whales devote a Acknowledgements. This research was conducted under the large proportion of time and energy each year to Macquarie University Animal Ethics Committee Animal Research Authority 2012-016 and the NSW Office of Envi- migration (Corkeron & Connor 1999, Silva et al. 2013, ronment and Heritage Scientific Research permit SL 100953. Braithwaite et al. 2015). Often these migrations in - This research was made possible through funding from the volve competitive breeding or calving, all while mov- Department of Environment, Water, Heritage and the Arts, ing with direct (or near direct) navigational orienta- the Australian Marine Mammal Centre, Australian Antarctic Division, the Commonwealth Environment Research Facili- tion (Corkeron & Connor 1999, Horton et al. 2011, ties (CERF) programme, and the Taronga Conservation Sci- Waugh et al. 2012). Unlike migrating humpback ence Initiative. Vanessa Pirotta was supported by a Mac- whales, foraging humpback whale behaviour in - quarie University Masters of Research scholarship. We 208 Endang Species Res 29: 201–209, 2016

thank Dr. Simon Northridge, Dr. Peter Corkeron and Prof. ping or not to ping: the use of active acoustic devices in Douglas Wartzok for reviewing early drafts of the manu- mitigating interactions between small cetaceans and gill- script. We thank Maryrose Gulesserian, Eric Kneist (author net fisheries. Endang Species Res 19:201−221 of VADAR), Wayne Reynolds, the Cape Solander Whale Dunlop RA, Cato DH, Noad MJ (2008) Non-song acoustic Migration Study Volunteers and the Kamay communication in migrating humpback whales (Mega- National Park Staff for facilitating the field research. Thank ptera novaeangliae). Mar Mamm Sci 24: 613−629 you also to Andrew Boomer for construction of the whale Dunlop RA, Cato DH, Noad MJ (2010) Your attention please: alarm, mooring assemblage, deployment, retrieval and Increasing ambient noise levels elicits change in commu- hydrophone testing along with Andrew Irvine, Phil nication behaviour in humpback whales (Megaptera McDowall and Andre Steckenreuter. 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Editorial responsibility: Louise Chilvers, Submitted: June 15, 2015; Accepted: November 16, 2015 Wellington, New Zealand Proofs received from author(s): January 15, 2016