Recovery from severe cutaneous injury in two free ranging

bottlenose dolphins (Tursiops spp.)

Michael I Bossley

& Michelle A Woolfall

Whale & Dolphin Conservation, Adelaide, South Australia.

School of Animal & Veterinary Sciences, University of Adelaide, South Australia.

Abstract

Bottlenose dolphins (Tursiops spp.) inhabiting the Port

Adelaide estuary in South Australia have been studied since 1989.

Here we present the cases of a female and calf which sustained

severe localized burn-like injuries of unconfirmed aetiology. The

remarkable recovery of the two dolphins was carefully documented

photographically from the time of first sighting (April 11, 2010)

through to the present (June, 2014). No invasive tissue sampling to

investigate pathology was undertaken, nor was any form of

medication administered. This paper chronologically presents

images and commentary of the phases of wound healing seen in

these two unique cases. The unaided recovery of these dolphins

from severe trauma has implications for evaluating the need for

veterinary intervention in these animals in certain situations. In

addition, the topics of dolphin behaviour and the value of citizen

science in documenting the events are discussed.

[JMATE. 2014;7(1):12-16]

Keywords: Cetacean, injury, integument, intervention, healing,

Tursiops

Introduction

Bottlenose dolphins (Tursiops spp.) inhabit the

Port Adelaide estuary in South Australia. These dolphins

have been studied since 1989 using photo identification

techniques to monitor the behaviour and health of indi-

viduals. There are approximately 30 resident dolphins

and numerous others that visit the area, which is close to

a city of a million people and thus subject to numerous

human impacts. These impacts include habitat damage

caused by pollution and direct impacts on the dolphins

from deliberate attack and accidents. In 2005, the South

Australian government declared the waters around the

Port Adelaide estuary a dolphin sanctuary. Two of the

resident dolphins are an adult female (F351, estimated to

have been born in 1992) and her male calf (M501, born

in March 2009). F351 had previously given birth to two

calves (a male in 2002 and a female in 2006) which have

remained in the estuary. F351 is identifiable by the shape

and configuration of her dorsal fin. F351 is known

locally as “Wave” and her calf (M501) as “Tallula.”

At some time between the 2nd and 11th of April

2010, the two dolphins received severe, burn-like skin

injuries, F351 on her right flank and her calf M501 on

his left flank. The aetiology of these injuries is

unknown, but most marine mammal experts who

viewed photographs of the injuries suggested sunburn

arising from being stranded as the most likely cause. We

have no way of verifying this aetiology but the local

geography includes extensive intertidal mudflats which

could increase the potential for standings.

Communication with port authorities indicated no

evidence of chemical spills or other anthropogenic

incidents which might have caused the injuries. The

recovery of the two dolphins from this severe trauma

was documented photographically from the time of first

sighting (April 11, 2010) through to the present (June

2014). However, no invasive tissue sampling to

investigate pathology was undertaken, nor was any form

of medication administered. This paper documents the

phases of wound healing seen in these dolphins.

Dolphins possess remarkable wound healing

abilities (1, 4). Many sustain large gaping wounds from

boat propeller strikes and predators (1). Nevertheless,

even severe wounds exposing deep muscle tissue have

been observed to heal almost completely within five

months (4). Humans sustaining similar injuries relative

to body size would likely encounter serious

complications without surgical or therapeutic

intervention. The wound healing physiology of the

bottlenose dolphin therefore represents an interesting

area of inquiry.

Case report

The two dolphins were sighted on April 2, 2010

with no abnormal lesions. Nine days later, on April 11,

Received February 18, 2014; Accepted September 19, 2014

Correspondence: Michael Bossley

Whale and Dolphin Conservation, PO Box 720, Port Adelaide BC, Port

Adelaide, South Australia, Australia 5015.

Phone: + 61 8 84403700

Email: [email protected]

Journal of Marine Animals and Their Ecology

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JMATE

Case Report

2010, they were observed with marked epidermal

sloughing, seen on F351’s right flank and on her calf’s

left flank (Figure 1a and 1b).

sloughing from the lesion (Figure 3a). Pink tissue

discoloration could be seen caudally. In addition, the

cranial aspect had a diffusely nodular appearance (Figure

3b, arrow). By April 21, 2010 all areas that initially

appeared necrotizing and pale were now pink, which

was likened to the appearance of granulation tissue.

Lesion borders remained hyper-pigmented and there was

some yellow-brown discolouration to the wound cra-

nially (Figure 3c, arrow).

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Recovery from cutaneous injuries in wild bottlenose dolphins

Figure 2: F351’s lesion on the 13th of April 2010. This figure

depicts the tissue lobulation described. Reproduced with permission.

F351’s lesions - These appeared more extensive

than her calf’s. At this time, she had a focally extensive,

well demarcated, elliptical lesion that resembled

ulceration and necrosis. This spanned across the dorsal

third of the body wall on the right side of the midline,

and extended cranially to the cervical region, caudally to

the peduncle, and tapered at both ends. The lesion was

widest beneath the dorsal fin. Epidermis at the lesion

borders appeared hyper-pigmented (darkened), and a

white layer of what could have been necrotic epidermis,

dermis or underlying blubber was exposed (Figure 1a).

Two days later, this layer appeared raised and lobulated

(Figure 2), and on April 17, 2010, was seen to be

Figure 1: Lesions on April 11, 2010 of (a) mother F351. (b) calf

M501. Arrows indicate the position of two small areas of

hypopigmentation and thickening on the calf’s dorsal fin.

Reproduced with permission.

Figure 3: F351’s lesions (a) on April 17, 2010 showing sloughing of

pale white tissue and caudal granulation. (b) on April 17, 2010 there

was a nodular appearance to the cranial aspect of the lesion (arrow).

cranial discolouration (arrow), necrotic tissue and granulation.

Reproduced with permission.

JMATE

as F351’s. While F351’s dorsal fin appeared normal, the

calf had two small focal areas of hypopigmentation and

thickening (interpreted as dermal sloughing) on his

dorsal fin (Figure 1b, arrows; 6b). Like F351,

hyper-pigmentation was observed along the borders of

sloughed and un-sloughed epidermis (Figures 1b, 6a,

6b), and a yellow-brown discoloration became

progressively evident over the surface of ulcerated tissue

(Figure 6b, arrow). By April 22, 2010, tissue resembling

blubber in the caudal aspect of the lesion was slightly

protruding from the level of surrounding healthy

epidermis and appeared broadly lobular (Figure 6c).

There was also a focal area of papular appearance

cranially (Figure 6c, arrow). By May 22, 2010, the entire

lesion had almost completely contracted, with pale grey

discolouration remaining on the affected regions for the

remainder of the year (Figure 6d). Scarring did not occur

in the same manner as with F351.

Behaviour and reproduction

F351 had regularly exhibited a behaviour known

as “tail walking” since 2008, a behaviour that appears to

have been learned from another local dolphin who had

spent time in a local dolphinarium. This was a high

energy behaviour which involved rising out of the water

until only her flukes were submerged and then crashing

back onto the water surface dorsal side first. She did not

perform this behaviour for three months after acquiring

her injury. While activities such as feeding did not seem

to change, certain social activities may have also been

altered as neither dolphin presented with rakings

(markings from social scraping of the teeth by other

dolphins) throughout the duration of their healing

processes. The minor lesion previously discussed

(Figure 5b) was the first potential raking since the major

injury, which had by then reduced to a scar. There did

not appear to be a change in home range or frequency of

Recovery from cutaneous injuries in wild bottlenose dolphins

Figure 4: F351’s lesion on (a) April 26, 2010. (b) May 7, 2010.

images demonstrates the progression of re-epithelialization and

wound contraction. Reproduced with permission.

F351’s loss of body condition was apparent as

evidenced by prominence of ribs and angular flanks seen

on April 26, 2010. Lesion borders now appeared raised

and pale grey (Figure 4a and 4b). This tissue had

completely extended over the granulation tissue by

August 27, 2010, leaving two distinct white scars

(Figure 5a). Nodules that had been present cranially

completely regressed as the wound contracted (Figure 4c

and 4d).Comparison of the images in Figure 4

demonstrates the progression of re-epithelialization and

wound contraction.

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In early 2011, F351 sustained an injury resembling

tooth rakings from another dolphin. In reference to

Figure 5b, the scar tissue appeared to be more readily

damaged than surrounding epidermis. This minor injury

healed without complication. It would appear the

existing scar will remain for the life of the animal.

For one year following the appearance of the

injury, F351’s dorsal fin leaned approximately 10° in the

direction of the wound. The fin has since returned to

normal. The calf did not display this response.

M501’s lesion - The calf was a dependent 13

month-old (born March, 2009) when injured, yet the

stages and timing of wound healing appeared similar to

F351’s. On April 11, 2010, the calf had an irregular

oblong streak resembling ulceration and necrosis

dorsally, spanning from the blowhole to the caudal

insertion of the dorsal fin, situated along the midline

cranially, and curving to the left of the midline caudally

(Figure 6a). This lesion was not as sharply demarcated

Figure 5: (a) F351 on August 27, 2010 shows two distinct scars

have resulted along the right flank. These have remained similar in

appearance to date (June 2014). (b) A minor injury that F351

sustained in early 2011 (arrow) depicts the relative weakness of the

scar to surrounding normal tissue. Reproduced with permission.

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Recovery from cutaneous injuries in wild bottlenose dolphins

Figure 6: Appearance of M501’s lesion on (a) April 11, 2010. (b)

April 6, 2010 showing hyperpigmentation of lesion borders and

yellow-brown discoloration of ulcerative tissue (arrow).

and protruding blubber. (d) May 22, 2010. Reproduced with

permission.

bow riding associated with the injury.

F351’s first three calves, including M501, survived

to weaning and are regularly sighted in the dolphin

sanctuary today. However, in the years following

F351’s injury, a fourth calf was born in February 2012

and died five days later. On September 22, 2013, F351

was sighted holding a fifth calf that was likely to have

been stillborn or died immediately after birth. It is

unknown whether the deaths of F351’s calves in 2012

and 2013 were related to the injury described in this

paper.

Discussion

This report adds to the small body of literature on

the unassisted recovery from severe trauma of bottlenose

dolphins in the wild. In addition, it highlights the

extraordinary capacity of these animals to not only

recover but also manage the extra energy demands of

providing for a dependent calf at the same time.

Within the first day of a dolphin sustaining

cutaneous injury, blubber from surrounding tissue

migrates over the exposed wound surface (4). The

blubber consists of many collagen bundles, elastic fibres

and adipocytes. It is connected to underlying

musculature by the subcutis, a loose layer of connective

tissue (3). This blubber layer is a complex structure that

undertakes coordinated cellular rearrangements in

healing to form new tissue using adipocytes, collagen

and elastic fibres (4). Two days after injury, pink

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granulation tissue gradually begins to fill the wound in

order to aid in volume restoration while reconstructing

the blood supply to the site of injury. Within the first

week of the injury, non-viable tissues, including the

transposed blubber, are naturally debrided (4).

For both dolphins, there was hyper-pigmentation

observed along the borders of sloughed epidermis. In

terrestrial mammals, this is a result of inflammation

involving some degree of chronicity. An abundance of

blubber infiltration into the exposed areas of dermis is

consistent with normal healing, and would have brought

immune mediators to the affected site along with

additional insulation and protection to underlying tissue

(4). Once the underlying granulation bed was complete,

non-viable tissue that had lost vascularity and was

necrotizing, including transposed blubber, would be

passively sloughed. The aetiology of the yellow-brown

discolouration on both dolphins was unknown. It may

have been a result of colonization by environmental

bacteria, protozoa and/or fungi. The nodular appearance

of F351’s lesion (Figure 3b, arrow) was also of unknown

aetiology. The focal area of papular appearance

(Figure 6c, arrow) on M501’s lesion may have signified

a hyperplastic process or simply finer lobulation of the

blubber that appeared broader caudally. Nevertheless,

these lesions proceeded to regress without obvious

complication or human intervention. Despite exposure to

an industrially polluted environment, it appears the

dolphins’ immune mechanisms against environmental

pathogens were adequate.

The lack of pigmentation in F351’s scars may

predispose her to predation, reduced heat absorption in

colder weather, and damaging ultraviolet radiation. Due

to the rarity of depigmentation or albinism in cetaceans,

it is difficult to ascertain the significance of these risks.

The survival of F351 with her dependent calf under the

circumstances was remarkable. Given the stress

associated with attempting to sample and/or treat free

ranging dolphins, these observations suggest close

monitoring of injuries should be undertaken and

intervention only instigated as a last resort. A case of

similar significant skin lesions of unknown aetiology in

a wild bottlenose dolphin calf was studied in Monterey

Bay (U.S.A.) (2). The Monterey Bay dolphin suffered

severe ulcerative tissue necrosis, emaciation and swam

abnormally. The calf survived this condition and

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Recovery from cutaneous injuries in wild bottlenose dolphins

3. Rommel SA and Lowenstine LJ. Gross and

microscopic anatomy. In: CRC Handbook of

Marine Mammal Medicine, edited by Dierauf LA

and Gulland FMD. 2

edition. CRC Press, Boca

Raton pp. 139. 2001.

4. Zasloff M. Observations on the remarkable (and

mysterious) wound-healing process of the

bottlenose dolphin. Journal of Investigative

Dermatology 131: 2503-2505. 2011.

appeared to be improving in subsequent sightings,

reinforcing the outstanding healing abilities of these

cetaceans (2).

Subsequent to the events described above, in

December 2013, another dolphin U378, a subadult of

unknown gender presented with a set of lesions visually

similar, but less extensive, to those described for F351

and M501. The recovery process proceeded along

identical lines to that for F351 and M501, and we

assume the same aetiology for all three animals.

The unassisted recovery of these dolphins has

implications for triage decision making in relation to

dolphins suffering natural and anthropogenic injuries

and also for decisions concerning the advisability of

interventions.

Comprehensive monitoring of the healing process

of these dolphins was only possible through the

assistance of a group of dedicated volunteer

photographers (see acknowledgments section). Their

involvement highlights the growing contributions of

citizen scientists armed with sophisticated photographic

equipment to field research.

Acknowledgements

Special thanks to the many biologists and veterinarians who

provided their advice on the possible aetiology of these lesions. In

particular we would like to thank Dr P Duignan and Dr J Geraci for

their very helpful assistance. We are also grateful to the following

photographers for permission to use images in this paper: B

Saberton (Figures 1a, 2, 3a, 4c, 6d, 5a), M Boorman (Figures 1b, 3b,

4a, 6a, 5b), O Wieczorek (Figure 4d) and P & D Huxtable (Figure

4b, 6b, 6c) who were also the first to report the dolphins’ injuries.

Without their assistance the documentation of the recovery of these

dolphins would have been incomplete.

References

1. Bloom P and Jager M. The injury and subsequent

healing of a serious propeller strike to a wild

bottlenose dolphin (Tursiops truncatus) resident in

cold waters off the Northumberland coast of

England. Aquatic Mammals Journal 20(2): 59-64.

1994.

2. Riggin JL and Maldini D. Photographic case

studies of skin conditions in wild-ranging

bottlenose dolphin (Tursiops truncatus) calves.

Journal of Marine Animals and Their Ecology

3(1): 5-9. 2010.

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