Rescue of a Bryde's Whale Balaenoptera edeni entrapped in the Manning River, New South Wales: unmitigated success or unwarranted intervention?
David Priddel' and Robert Wheeler1
INS\.\' National Parks and Wildlife Service, P.O. Box 196'7, HUI-stville.New South Walcr, 2220
ABSTRACT In August 1994 a Btyde's Whale Balaenoptera edeni entered and became entrapped in the Manning River, New South Wales. The individual was an immature male of the rare pygmy form of
Btyde's Whale: it was 10.3 rn long and weighed approximately 7.7 tonnes. The whale remained in the Downloaded from http://meridian.allenpress.com/australian-zoologist/article-pdf/30/3/261/1475562/az_1997_002.pdf by guest on 30 September 2021 river for 100 days, during which time observations were made of its movements, diving habits, feeding behaviour and body condition. Apart from the risk of stranding, the entrapped whale also faced the potential threats of starvation, entanglement in fishing nets, collision with boat traffic, and exposure to low salinity and high acidity. In view of these threats, a rescue bid was launched to return the whale
to the ocean. Five rescue~~~~ attemots ~ were made. the last culminated in the whale beina successfuilv .. ,~ ~
tnwerl --~-sea ~ ~ --~------~~ ~ ~ ~ ~ ~- to and released several kilometres offshore. Desoite-~--- its -- emaciated ~~ condition ihe whale was rescdd from the r ver ~eforetne onset of I heath or irreparaoe physooglca damage. Tne wale snam array slrongly on reease, and ts cnances of sLrv.va appeareo to De goo0 Tne success ot the operat on togetner w th tne pnys ca slate ol tne an ma1 on re ease ,Lst fy the aeasson taken to mom! such an ambitious rescue bid, even though such action was itself life-threatening.
INTRODUCTION whale was successfully manoeuvred on to a pontoon, towed out to sea and released several Bryde's Whales Balaenoptera edeni occur in kilometres offshore. The whale had been tropical, subtropical and warm temperate waters entrapped in the Manning River for 100 days, around the world (Cummings 1985), often near during which time observations were made of shore in areas of high productivity (Leathemrood its movements, diving habits, feeding behaviour and Reeves 1983). In Australian waters they are and body condition. most often observed north of 40"s (Watson 1981; Leatherwood and Reeves 1983). Reported Since the rescue, debate has ensued regarding strandings, as shown in Figure 1, have been the need for such intervention and the worth of confined to the southern and southeastern such operations. This paper examines the coast of the Australian mainland (Dixon 1970; incident in relation to similar historical events, Llewellyn el a/. 1994; Marine Mammal Strandings discusses the potential threats to the whale in Database, Biodiversity Group, Environment the river, and reports on the biological and Australia). behavioural information gathered. The On 16 August 1994 a 10.3 m long Bryde's findings, and the benefits of hindsight, are used Whale entered the Manning River on the central to appraise the decision to mount a rescue bid. coast of New South Wales. The whale remained entrapped in the river for 100 days, apparently THE MANNING RIVER unable to negotiate its way back out to sea through the shallow, narrow channel at the river The Manning River is a short coastal river, mouth. In view of the potential threats to the rising in the foothills of Mount Barrington in the Great Dividing Range about 150 km from whale whilst in the river (see below), a bid was made to rescue the whale and return it to the the coast and meandering for its final 50 km ocean. across a coastal plain until forming an estuary, out of which it enters the Pacific Ocean. It is a Several rescue strategies were tried. The first typical estuarine river, as described by Morrisey was to drive the whale downstream, through the (1995), of which there are many on the New mouth of the river, across the bar and out to sea. South Wales coast. Several factors influence the When this failed, a second strategy aimed to form of these estuaries. Rainfall in Australia is capture the whale then tow it to sea on an erratic, and river flows are highly variable and inflatable pontoon. Three attempts to capture unpredictable. The ocean swell is consistently the whale were made; all failed. On 24 November substantial and virtually parallel to the coast. As 1994, before another capture attempt could be a result, estuaries of this kind tend to have initiated, the whale grounded on a sand shoal convoluted and shallow passages, a bar across close to the river mouth. While stranded, the the mouth and a narrow channel, the location
March 1997 Australian Zwlogist 30(3) 261 less than 20 000 ML (New South Wales Depart- ment of Land and Water Conservation, unpubl. data). Discharge volumes for the corresponding periods in 1990-93 were substantially greater: up to 140 000 ML. Low river flows in recent times resulted in the constriction and further redirection of the channel in Harrington Inlet. The channel was not expected to widen or deepen until the next major river flow.
ENTRY OF THE WHALE INTO THE RIVER
At approximately 1300 h on 16 August 1994, Downloaded from http://meridian.allenpress.com/australian-zoologist/article-pdf/30/3/261/1475562/az_1997_002.pdf by guest on 30 September 2021 the whale grounded on a sandbar at the mouth of the Manning River (Fig. 3). The tide was l.l m, peaking at 1.65 m around 1600 h. The whale .Fig. 1. Australia, showing locations of reported strandings of remained grounded on the sandbar until, on the Bryde's Whales. Key: l, Corny Point (1883); 2, Cape Banks rising tide, it refloated and was swept by waves (19a5); 3, Manning River Quly 1948); 4, Corio Bay (July 1968); 5, Port Wakefield (April 1972); 6, Younghusband off the sandbar into the river. It ran aground Peninsula (anuary 1982); 7, Great Sandy Strait (October again on a sand shoal approximately 2 km 1982); 8, Valla Beach (October 1983); 9, Red Cliff Point upstream (Fig. 3) where it floundered for 20 min. (September 1985); 10, North Brighton (July l986); 11, before again being refloated by the incoming Hayward's Beach (November 1989); 12, Manning River (August to November 1994). tide. Minimum water depth between the heads when the whale crossed was 4.6 m on the of which is very changeable. The European northern side and 2.2 m on the southern side settler has, on virtually every such river, (Hydrographic Office, Royal Australian Navy, endeavoured to deepen and stabilize the passage unpubl. data). Dy varlous measures. Local fishers followed the whale upstream for The Manning River estuary is shown in several kilometres before it disappeared. It Figure 2 and has two entrances to the ocean. was next sighted the following morning in the The main channel flows to Harrington Inlet South Passageat the mouth of Blackfords Bay (31'53'S; 152'41'E) and the smaller South approximately 23 km upstream (Fig. 2). The Channel and Scotts Creek flow to Farquar Inlet whale remained in this vicinity for several weeks, (31'57'S; 152'36'E). Harrington Inlet, where rarely venturing upstream of Dumaresq Island extensive sand shoals extend almost 3 km or downstream of Blackfords Bay. upstream from the river mouth, is the major Why the whale entered the river is unclear, passage for boat traffic entering or leaving the although it appeared to be due to miscalculation river. The narrolv channel, which has been rather than intention. A local fisher who witnessed redirected by a long training wall (Fig. 3), is the event believed that the whale got into convoluted and shallow and can be difficult to difficulties while feeding at the river entrance navigate. where schools of young Tailor Pomatomussalt- The whale entered the Manning River during atrix were plentiful around the time of the a period when protracted drought conditions incident. The whale ran aground while feeding prevailed over most of eastern Australia. The in shallow water and, once grounded, could not Manning River catchment was severely affected, turn around. It was subsequentlyswept over the and was drought declared from August to shoals and into the river by breaking waves. A November 1994 (New South Wales Department pod of Bottlenose Dolphins Tursiops truncatus of Agriculture, unpubl. data). The annual rain- was also present nearby and preceded the whale fall at Taree during 1994 was 555 mm, 46% of upriver. They too appeared to be hunting the long-term (1O9-year)average (Meteorological shoaling fish. Records Database, Australian Bureau of Meteor- ology). The I l0 mm of rain that f'ellduring the THE RESCUE OF THE WHALE four-month period encompassing the whale's FROM THE RIVER entrapment (August to November) was 39% of The Drive the long-term mean for this period. River flows were substantially reduced because of the The first strategy to remove the whale from protracted drought. Total stream discharge the river was to drive the animal downstream by from August to November 1994, as measured at producing a noise barrier created by banging Killawarra (32 km upstream from Taree), was metal pipes suspended in water from a flotilla
262 AustralianZoologist 30(3) March 1997 Downloaded from http://meridian.allenpress.com/australian-zoologist/article-pdf/30/3/261/1475562/az_1997_002.pdf by guest on 30 September 2021
Fig. 2.Th'e lower reaches of the Manning River showine locations mentioned in the text
Pacific Ocean
Flg. J. Harrington Inlet at the mouth of the Manning River showing sites of groundings of the entrapped whale. Heavy stippling, land; light stippling, sand shoals; circles, sites of grounding on 16 August 1994; triangle, site of grounding on l3 September 1994; square, site of grounding on 24 November 1994. of small boats. The drive took place on l0 unwilling to venture into an area where it had October 1994, 55 days after the whale entered grounded previously. the river. The rescue attempt drove the whale approximately 19 km downstream to within Deepening of the channel by mechanical I km of the network of sand shoals at the river means would have involved the dredging of mouth. In spite of a determined effort to drive massive quantities of sand. An operation of such it through the narrow channel to the ocean, the magnitude would be subject to several planning whale would go no further downstream. It was and environmental regulations and would, either unable to navigate the narrow channel therefore, require considerable government and between the many shoalsin the river mouth, or public scrutiny. The protracted nature of such
March1997 Australian Zoologist 30(3) 263 a process rendered this option as impracticable the world. In Australia, a young male stranded considering the urgency of the situation. and died at the mouth of Lime-burner Creek, Corio Bay, Victoria on 25 July 1968 (Dixon Attempts at Capture 1970). The first attempt to net the whale was made Newspaper accounts report four previous on 8 November 1994, 84 days after it had instances of a large whale in the Manning River. entered the river. The nets were deployed from A Sperm Whale Physeter mmocephulw entered Chinamans Beach (Fig. 2) where the whale had and left the river on New Year's Day 1932 been making regular passes close to shore. Two (Manning Times 6 Jan. 1932). At this time the nets were used, one deployed upstream of the river entrance was navigable by larger vessels whale, the other downstream. On the initial than at present, presumably because the channel attempt (0745 h), the whale escaped between the was deeper and wider than it is currently. nets before the boats deploying the nets had Individual Humpback Whales Megaptera nouae- passed each other. On a second attempt (1 115 h) angliae entered the river in 1944 and 1945. In the whale evaded capture by swimming under a 1948 a whale described as "being of the black Downloaded from http://meridian.allenpress.com/australian-zoologist/article-pdf/30/3/261/1475562/az_1997_002.pdf by guest on 30 September 2021 portion of the net where the lead-line was variety" (Mannzng Tzmes 21 July 1948) was also inadvertently tangled in the float-line. sighted in the river. These three whales survived in the river for three months, four months, and A subsequent endeavour to net the whale was one week respectively, before each stranded and made on 12 November 1994. The nets were died on a mudflat or sand shoal. deployed from the shoreline immediately downstream of the entrance to Cattai Creek Local residents also recounted two, or possibly (Fig. 2). As in the previous attempt, the nets three, whales entering the Manning River in were readied where the whale had been making 1942, but this incident could not be verified by regular passes close to shore. Again, two nets published historical records. Reputedly, one were set, but these were deployed more quickly whale became stranded and died, one was than before by the use of more powerful boats. allegedly shot, and the third (if it existed) The whale was successfully encircled, but apparently found its way back to sea. escaped by breaking through both ners. A A photograph taken in the 1940s depicts a sample of skin and epidermal tissue, lodged in whale with three longitudinal ridges on the one of the nets, was collected for pathological dorsal surface of its head stranded in the and DNA analvsis. Manning River. Such ridges are a diagnostic characteristic of Bryde's Whale. Although it is The Final Rescue uncertain as to exactly when the photograph was On 24 November 1994, preparations were taken, it demonstrates unequivocally that the afoot for a fourth attempt to net the whale the recent entrapment is not the first time that a following day. Fortunately, at around 0530 h, Bryde's Whale has entered the Manning River. and just approaching low tide, the whale again grounded on the sand shoals at the mouth of POTENTIAL THREATS TO THE WHALE the river (Fig. 3). An immediate response was Stranding initiated. The stranded whale was successfully positioned on to an inflatable pontoon, towed to The whale grounded twice on sand shoals at sea without incident over difficult sandbars and the river mouth while entering the river (Fig. 3). released several kilometres offshore. The whale Twenty-eight days later, at around 1000 h on 13 swam away strongly in a southerly direction. September 1994, the whale again ran aground on sand shoals near the river entrance (Fig. 3). It refloated before any rescue attempt could be HISTORICAL PERSPECTIVE initiated or blood samples taken. A subsequent Historically, the stranding of a whale was grounding in the same vicinity (Fig. 3) on 24 a welcome event and an occasion for local November 1994 eventually led to the animal's Aboriginal people to eat to repletion. Nowadays rescue and return to the ocean. such events are viewed with solemnity and Although on three occasions the grounded invoke great concern for the welfare of the whale refloated on the rising tide, these ground- distressed animal. ings were potentially life-threatening. Three of Strandings of Bryde's Whales are relatively the other four whales known to have entered uncommon, but the occurrence of this species the Manning River stranded and died, each up a river is not without precedent. The type taking several days to succumb. specimen was found stranded about 32 km up a A depth profile of the estuary, prepared by small river in Burma (Anderson 1878). Since the New South Wales Department of Public then, there have been several incidences of Works, revealed a raised river floor across the Bryde's Whales in rivers and estuaries around narrow channel between the sand shoals. Visual
264 Australian Zoologist 30(3) inspection confirmed the existence of a sub- Boat Traffic merged ridge extending the full width of the The Manning River is a popular holiday channel, which at low tide was covel-ed only by destination and a haven for recreational activities about 1 m of water. This ridge in the river Hoar such as fishing, sailing and water skiing. The together with the configuration of sand shoals river is a busy waterway for all kinds of small either side of the narrow, shallow channel (Fig. boat craft including speedboats, cruisers, house- 3) was thought to be preventing the whale from boats and fishing trawlers. The lower reaches I-etul-ningto sea. are commercially fished and also support a substantial oyster farming industry. The Insufficient Food potential for collision with boats or entangle- Bryde's Whales are less migratory than other ment in fishing nets was a threat to the whale Baleen Whales (Best 1960; Carwardine 1995), and a risk to public safety. and do not undertake annual migrations to Shol-tly after entering the Manning River, the the Antarctic. There is no evidence that whale took up residence in South Passage of the Downloaded from http://meridian.allenpress.com/australian-zoologist/article-pdf/30/3/261/1475562/az_1997_002.pdf by guest on 30 September 2021 Bryde's Whales fast like those species that river near Dumaresq Island. On advice from the feed predominantly in the polar regions. On the National Parks and Wildlife Service, the South contrary, Bryde's Whales have been recorded Passage was immediately closed to all recreational feeding throughout the year (Watson 1981; tmffic. A few weeks later, as the whale became Carwardine 1995), and at least twice or perhaps more wide-ranging, this restriction was revoked as many as five times daily (Best 1977). The diet in favour of establishing an exclusion zone consists primarily of small shoaling fish such as around the whale wherein vessels were required pilchard, mackerel, herring, anchovy and sardine to maintain at least 100 m between themselves (Chittlehorough 1959; Nemoto 1959; Best 1967, and the animal. Although the whale was legally 1977). Crustaceans constitute an important protected from interference from river traffic, component of the diet in some areas. particularly its safety in the river could not be assured. in offshore waters where cold-water upwellings support plankton blooms (Best 1977; Watson Salinity 1981). Cephalopods have also been reported in the diet (Best 1977). 'The farthest upstream stretch of the Manning River occupied by the rvhale during its period of Sergeant (1969) postulated that adult Baleen entrapment was between the western end of Whales need to consume, on average, the Dumaresq Island and the road bridge across the equivalent of 34% of theil- body weight daily. river at Taree (Fig. 2). Water salinity in this area Gaskin (1982) considered this estimate to be too was 29% compared to 3570 in oceanic waters high, claiming that the minimum quantity of outside the heads. Although the Ions-term food needed to sustain an adult rorqual whale effects of exposure to low salinity are unknown, is around 2.5-3.0% of body weight per day. the level of salinity in the river was not From this more conservative estimate and the considered dangerous for the whale in the short assessment of body size (see below), the food term. Of greatest concern was the potential requirements of the Bryde's Whale entrapped threat that local heavy rains could cause a in the Manning River was calculated to be substantial and rapid reduction in salinity. Salinity approximately 200 kg per day. levels as low as 5% have been recorded in the Several areas frequented by the whale during river just off Manning Point (Fig. 2) during its entrapment in the Manning River were times of significant fresh water How (McCotter trawled to assess local potential food stocks. The 1993). trawls were made with an otter prawn net Low salinity may potentially disrupt the comprising a 30 mm mesh with a 3 m mouth. A whale's normal osmotic process, causing body 20 min. trawl off Chinamans Beach (Fig. 2) and salts to leach out of tissues and water to seep in another of similar duration several kilometres (Roletto 1986). The effect of this osmotic process upstream netted nothing. The mouth of Cattai is water-logging of the skin with potentially Creek (Fig. 2) was trawled for 30 min., netting lethal consequences. The skin may change only three fish. A 15 min. trawl further colour and eventually slough. Reduced salinity upstream in Cattai Creek, an area where prawns will also make the aninla1 less buoyant, causing were thought most likely to occur, produced the animal to expend excessive energy when nothing. Although the whale was observed swimming and when surfacing. attempting to feed, the apparent dearth of fish and crustacea in the river raised concerns that it Acidity may have been unable to catch sufficient food to sustain itself in the long term. The length of During the whale's entrapment, the pH of the time a Bryde's Whale can abstain from food river was between 7.6 and 7.8, commensurate without causing irreparable physiological with oceanic waters, and posing no immediate damage is unknown. threat to the whale. The prevailing drought,
March 1997 Aushalian Zoologist 30(3) 265 'SM~N'lax0 a~uax~e~dq o~oqd .aIq!s!A Xlnap SI 'xaleM MolIeqs u! Bu!uru~!~sjo qnsax aqi 'axnu ~!saqi jo a8pa Burpea1 aqq oi uo!sexqv .uooiuod aqi uryl!~pIaq seM aFqM aql al!qM uaxel axaM sa~duresanssq pue poo~g
I I SMJN 'law a~uame7kq o~oqd .g wsal03 Xpmpyps aleqm aqi pasmua uooluod ayl 'pa~~px~ pm paisnFpe Xpuanbasqns uaqM .uoo~uodaql p q puokaq pa~nno~daVB P s,@FIM l Downloaded from http://meridian.allenpress.com/australian-zoologist/article-pdf/30/3/261/1475562/az_1997_002.pdf by guest on 30 September 2021 however, had caused many of the tributaries of and Wheeler, in press). This form appears to the Manning River to stop flowing, and several have a restricted distribution and is known from swamps were dry for the first time in living only a handful of specimens (Dizon et a1 1996). memon7. Exposure and drying of underlying acid-sulphate pyrite soils can cause a substantial Sex increase in soil acidity (Dent and Pons 1993). The acid arises from oxidized pyrite that was Molecular analysis of epidermal tissue also originally buried under wet sediment but which, revealed that the entrapped whale was a male due to altered drainage patterns and drought, (Priddel and Wheeler, in press). The absence may become exposed to the air. After heavy rain of testostel-one in the blood indicated sexual the first run-off from these soils will flush large immaturity (ibid). quantities of highly acidic leachate from the soil into the river. The extent of the resultant rise in Size acidity is unpredictable. In the nearby Tweed Measurements of the whale entrapped in the River catchment, heavy rain after a two-year Manning River were taken while it was Downloaded from http://meridian.allenpress.com/australian-zoologist/article-pdf/30/3/261/1475562/az_1997_002.pdf by guest on 30 September 2021 drought led to a discharge of acidic water into grounded on 24 November 1994 (Table 1). the Tweed River. More than 20 km of river Total body length, tip of upper jaw to centre of system was affected by increased acidity which eye, and tip of upper jaw to tip of dorsal fin caused the death of substantial numbers of fish were measured in a straight line parallel to the and crustacea (Tunks 1993). longitudinal axis of the whale. Height of dorsal fin and the distance from notch to tip of fluke Pesticide Residues were also recorded. The prolonged use of chemical pesticides for agriculture and the presence of riverside industry Table I. Morphometric measurements of the entrapped Bryde's Whale. % BL, measuremenr as a percentage of body have the potential to lead to the accumulation lengrh. of pesticide residues in the river. River water was tested for the presence of a broad range of Measuremenr Length (m) %BI. organochlorine pesticides, including DDT, Body length 10.30 DDE, DDD, BHC, chlordane, heptachlor, aldrin, 'Tip of upperiaw to centre of eye 1.98 19.2 endosulphan, dieldrin and endrin. None was Tip of upperjaw ro rip of dorsal fin 7.58 73.6 present in detectable quantities. Height of dorsal fin 0.38 3.7 Notch of fluke to tip of fluke 1.32 12.8 BIOLOGY AND BEHAVIOUR OF THE ENTRAPPED WHALE The length of the entrapped whale was 10.3 m. The weight of a healthy Bryde's whale Taxonomy can be estimated from the following equation: Morphometric variation between different W = 0.50 X x L2-j4;where W = weight in tonnes, and L = body length in feet (Fujino - 1955, amended by Gamhell 1977). With this 1959; Omura 1959; Masaki 1975; Kawamum Sormula, the weight of the whale was estimated and Satake 1976; Best 1977; Privalikhin and to be approximately 7.7 tonnes. Berzin 1978; Leatherwood and Reeves 1983). Male Bryde's Whales of the coastal race of the By measuring the genetic differentiation among standard form attain sexual maturity at 9-10 years species, Wada and Numachi (1991) identified of age when they reach the length of 11.&12.2 m two broadly divergent forms; a standard form (Best 1977); offshore races are approximately and a smaller or pygmy form. They estimated 10% larger. The numerical relationship between that the two forms diverged about 4.1 million size and age has not been determined for the years ago and are so dissimilar that they should pygmy form ofthe Bryde's Whale. be regarded as distinct and separate species. Based on the phylogeny of mitochondria1 DNA, Dizon et al. (1996) also concluded that the Movements pygmy Bryde's Whale may be a separate species, Within hours of entering the nver, the whale more distinct from the standard form of the confined itself to the western end of' the Bryde's Whale than is the Sei Whale Balaenoptera South Passage alongside Dumaresq Island borealir. approximately 23 km upstream from the river A sample of the whale's skin and epidermal mouth (Fig. 2). As far as could he ascertained, tissue was recovered from one of the nets the whale remained in this vicinity for several penetrated by the whale during an unsuccessful weeks. Although the whale disappeared for attempt to capture it. Molecular genetic analysis significant periods of time each day, it was rarely of this material identified the animal as belong- seen upstream of the island or downstream of ing to the pygmy form of Bryde's Whale (F'riddel Blackfords Bay. Noise ernanating from pile
Australian Zoologist 30(3) 267 driving at a bridge construction site approximately extremes of around 1 min. and 20 min. Similar 1 km downstream from Blackfords Bay may extremes have been observed by Cummings have deterred the whale from moving down- (1985). Two types of swimming behaviour were stream through the South Passage. distinguishable. The first involved movements which generally followed a predictable circuit Throughout its period of entrapment, the over an area of relatively deep water. Such whale's &vements &ere regular andmethodical, behaviour was accompanied by respiratory rates eenerallv followine a oredictable circuit that was 0- ~ ~~ , .2 1 that were reasonably constant. The second often confined to a small stretch of the river. behaviour involved more extensive and less The whale repetitively swam the same circuit, predictable movements, the whale often travers- seldom venturing beyond discernible boundaries. ing broad expanses of shallow water. This The predictability of its movements was the behaviour was characterized by comparatively essential element of the whale's behaviour that longer dives and erratic respiratory rates. made it vulnerable to capture.
Unsuccessful attempts to rescue the whale had Feeding Beha viom Downloaded from http://meridian.allenpress.com/australian-zoologist/article-pdf/30/3/261/1475562/az_1997_002.pdf by guest on 30 September 2021 a marked effect on its movements. After each rescue attempt the whale deserted its previous Several attempts at feeding were observed. Feedinz benan with the whale swimming slowlv locale and swam to another section of the river. n '7 <, Prior to intervention, the whale spent most of its in pr~,grcssivelydec.rc:a.;ing tirl:les, ay)parcr~tl\to time in the South Passage near Dumaresq herd smalLsh~valir~gfish. 'l'he whale then 111ngrrl Island. After the drive, the whale adopted a new several times (wirh sudden accelerations and haunt downstream of Cattai Creek (Fig. 2). It changes in direction) and rolled to one side, on was occasionally observed downstream as far as occasion exposing the baleen. The quantity of Manning Point. After an attempt to capture the food ingested, if any, is unknown. whale at Chinamans Beach, the whale moved upstream to the area between Cattai Creek and Vocalizations Lansdowne River. After a second attempt to capture the whale in this area it initially moved While submerged, Bryde's Whales can into the South Passage, and shortly after it again produce simple but powerful vocalizations often relocated, this time farther downstream to referred to as moans (Thompson el al. 1979; within a few kilometres of the river mouth. Clark 1990). Underwater sounds in the vicinity of the entrapped whale were investigated. The most spectacular response of the whale Ambient sounds and boats were heard hut no to any intervention occurred immediately after distinguishable whale vocalizations were detected. the first attempt to net it. After eluding the nets, The lack of vocalizations may have been due to the whale swam rapidly upstream approximately the absence of other members of its kind. 2 km then breached out of the water on six occasions in rapid succession. During the first two breaches, the whale reared entirely out of Body Condition the water, arching its back in mid-air and twist- Throughout the period of the whale's entrap- ing before crashing back into the river. The ment uncertainty existed as to the whale's remaining breaches were successively less general condition and state of health. Although spectacular, and in the last, only half of the every opportunity was taken to observe the whale left the water, the animal lunging onto its whale as it swam at the surface or rose to back and side. On its first breach, the whale left breathe, assessments of the whale's well-being the water almost vertically despite a water depth varied. Several veterinarians and marine of only 6.8 m. Breaching is common in Bryde's mammal biologists thought the whale was losing Whale in some areas, and often follows periods of condition. Apparent hollowing of the flanks and strenuous activity such as high-speed swimming back was interpreted as a sign of weight loss and (Carwardine 1995). deterioration of body condition. However, over the period of the whale's entrapment, there Diving Behaviour was no discernible lateral body instability, no While undisturbed in the river, the whale discernible change in the whale's behaviour or exhibited a quiet temperament. Exhalation and speed of travel, nor in the height and strength inhalation at the surface were unhurried and of the blow. Both nares seemed to be operating the subsequent submergence was slow and efficiently and equally. methodical. The only few instances of vivacious Pathological analysis of the epidermal tissue behaviour witnessed were what appeared to be recovered from the net holed by the whale attempts to feed (see below). found no physiological abnormalities or any The whale spent only a few seconds at the evidence of active inflammation. Close examina- surface to exchange air, and dived for periods tion of the animal was possible only when the generally lasting 4-7 min., with infrequent whale eventually grounded. The whale was
268 Australian Zwlogist 30(3) clearly emaciated. Rather than being smooth DISCUSSION and rotund, the back and flanks dipped away markedly either side of the vertebrae. The As stated, debate has occurred since the dorsal fin was not erect throughout its height, rescue rega.rding the need for such intervention. the apex being flaccid and leaning to one side. A fundamental issue was the question of The emaciated state of the whale supported whether the whale was effectively trapped and predictions that it would be unable to obtain unable to return to the ocean unaided. Repeated sufficient food in the river to maintain body groundings near the river mouth suggested that condition. the whale had difficulty entering the shallow channel running between the training wall and Several patches of skin were discoloured but the network of sand shoals (Fig. 3). Increased there was no evidence of any skin loss or slough- river flonrs following heavy rain would normally ing. Comparison with previous observations enlarge the channel through the river mouth, indicated that these dermal blemishes had perhaps sufficient for the whale to return to the
become more intense during the period of ocean of its own accord. One option, therefore, Downloaded from http://meridian.allenpress.com/australian-zoologist/article-pdf/30/3/261/1475562/az_1997_002.pdf by guest on 30 September 2021 entrapment. Approximately 15 longitudinal was simply to wait and let nature solve the scratches (200-1 200 mm) were evident along problem. With the benefit of hindsight, this the dorsal surface and flanks; one was up to approach would have failed. Although river flow 6 mm deep, the others were largely superficial. has increased in the year since the rescue was These wounds were almost certainly incurred completed, the volume of water has been when the whale broke through the nets. insufficient to scour a deeper channel through The leading edge of both caudal flukes was the river mouth. severely abraded. These wounds, probably The occurrence of a large whale in the caused by ongoing abrasion against the sandy Manning River is a rare but not unprecedented bottom as the whale turned or attempted to event. Most whales that have entered the manoeuvre in shallow water, were raw and river, however, have stranded and died. On bleeding. Best (1977) found long thin scratches the several occasions that the present whale on the undersurface of the caudal flukes became grounded on sand shoals it managed to and along the ventral keel of the peduncle refloat itself on the rising tide. Nonetheless, in several whales of the coastal form and each of these groundings was potentially life- attributed these injuries to contact with the threatening. Thus, judging from previous sea floor. incidents, and from the apparent inability of the Pathological analysis of blood samples taken whale to find its own way out to sea, it was during the final rescue operation provided the reasonable to conclude that the entrapped whale only objective assessment of body condition would probably die if not rescued by human (Priddel and Wheeler, in press). Despite the intervention. visible indications of emaciation and clinical Under the National Parks and Wildlqe Act evidence of malnutrition, there was no discernible (1974) the NSM' National Parks and Wildlife physiological damage due to the protracted Service is charged with a legal responsibility for period of entrapment in the river. Cetaceans the care and protection of all marine mammals. maintain salt and water balance through the The Service also has a responsibility to prevent ingestion of food, which provides both the tree- or alleviate circumstances likely to cause distress formed water and additional water derived to any protected animal. There was clearly a from the oxidation of fats (Geraci 1978). legal obligation to ensure the humane transfer When food intake falls below subsistence levels, of the whale from the unsafe situation it was in water balance ultimately can be compromised to its more familiar oceanic environment. leading to the onset of dehydration and electro- lyte disorder (zbid). The contrast between the At issue was the time, and the extent, of inter- whale's poor body condition and its relatively vention by the Service, particularly when such healthy blood chemistry suggests a state of intervention could itself be life-threatening. The metabolically compensated starvation. Although initial response of the Service had been to close the whale had greatly depleted its energy the stretch of river where the whale first took up reserves, it was rescued from the river before residence. As the whale became more wide- the onset of ill health or irreparable physiological ranging it was clear that such action was no damage. longer appropriate. The restrictions on entering the South Passage were revoked in favour of Some kidney insufficiency was apparent but establishing an exclusion zone around the organ damage was more likely to have been whale. Despite this action the whale remained caused by parasitism rather than entrapment. vulnerable to accidental collision with river The whale showed clear biochemical signs of traffic, as well as to the potential threats of stress during the final rescue attempt but this stranding, starvation, and exposure to low salinity stress was not considered severe. and high acidity.
Australian Zoologist 30(3) 269 About 50 days after the whale entered the The experience gained in this incident will river, the decision was taken to embark on a prove invaluable when the need arises to rescue rescue bid to remove the animal from the river other large whales that may become entangled, and return it to the ocean. The overriding stranded or entrapped in New South Wales consideration underpinning this course of waters. The incident validated the usefulness of action was that the whale was thought to be several techniques untried previously in this unable to return to its normal oceanic environ- part of the world, techniques that can now be ment on its own, and that it was exposed to used with confidence to rescue individuals of several threats to its well-being. Of major more endangered species or, in circumstances concern was the uncertainty about whether the such as entanglement, where the need for inter- whale was able to obtain sufficient food in the vention is urgent. river to sustain itself. Cetaceans have a great It would be of advantage if satellite radio- capacity to live off body reserves but once these transmitters were routinely attached to rescued have been metabolized an individual's health or rehabilitated whales in order to monitor their could be expected to deteriorate rapidly. Body survival after release. The data obtained will not Downloaded from http://meridian.allenpress.com/australian-zoologist/article-pdf/30/3/261/1475562/az_1997_002.pdf by guest on 30 September 2021 organs may be irreparably damaged by the time only serve to assess the merit of the rescue blood chemistry reflects malnutrition (Sweeney operation, but will add to our knowledge of 1990). Considering the emaciated condition of whale behaviour, movements and migratory the whale and the clinical signs of catabolism at patterns, thereby enhancing our ability to the time of its rescue, it was unlikely to have conserve these majestic creatures. survived much longer had it remained in the river. Any rescue attempt initiated after definitive ACKNOWLEDGEMENTS signs of deterioration became evident may have been to late to save the animal. The rescue bid that eventually resulted in the whale being returned to its natural environ- Very little information was available from ment was ultimately successful only through similar incidents to assist in the formulation of the combined efforts of numerous dedicated a rescue plan. Biological and behavioural individuals and with the support of many information for the Bryde's Whale was also organizations. The NSW National Parks and scant. Despite these constraints, the rescue Wildlife Service co-ordinated the rescue. Sea operation eventually culminated in the safe World, Coffs Harbour Pet Porpoise Pool, return of the whale to the ocean. The whale Taronga Park Zoo and the Organization for the swam away strongly on release and its chances Research and Rescue of Cetaceans in Australia of survival appeared to be good. (ORRCA) kindly contributed their expertise and provided considerable logistical support. It may be argued that the rehabilitation of a single individual contributed little to the conserva- Data and observations presented in this paper tion of the species. Bryde's Whales are probably were collected by many people; the authors' role more secure than any other species of Baleen has been largely one of collation and interpreta- Whale, mainly because they inhabit tropical and tion. Notable contributions were made by Eric low latitude waters most of which have been Claussen, Libby Eyre, Andrew Marshall, and closed to pelagic whaling since the 1930s by ORRCA. Water samples were analysed by the measures intended to protect the breeding Australian Laboratory Services, Brisbane. Under- grounds of other, less secure species (Klinowska water sounds were investigated by Jane Taylor 1991). This particular individual, however, was Flemons (Dept of Biophysics, University of New of the rare pygmy form of the Bryde's Whale South Wales). Trawls to assess potential food which has a restricted distribution and is known stocks in the river were co-ordinated by Keny from only a few specimens; its conservation Cree (New South Wales Fisheries, Taree). Jan status in the wild is unknown. Moreover, public Birrell and Stephen Donnellan (South Austra- interest in the plight of the entrapped whale was lian Museum) determined the gender of the enormous. The attempts to rescue the whale whale by DNA analysis of epidermal tissue. received national and international media Andrew Dizon (Southwest Fisheries Science interest and undoubtedly heightened public Centre, California) performed the molecular awareness of the occurrence of whales in Austra- genetic analysis to determine taxonomic status. lian inshore waters. The benefit of such Leighton Llewellyn, Andrew Marshall, Barry increased awareness is that it engenders a Mufford, Mike Bryden and Irina Dunn kindly greater concern for whales, which in turn reviewed the manuscript. provides a greater impetus for governments to act to conserve marine mammals and their REFERENCES marine habitats. Anderson, J., 1878. Anotmnicol and zoolqgical rerearchef: cmnplinng on account of the roological redti of the huo Although the safe and humane return of the expeditiem to WrmYunmn in 1868 and I875; mzd a whale to the ocean was the primary goal of the monograph of Ihe huo rcfnceon genrm. 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