Moko's death remains a mystery

Boat strike and drowning through net entanglement have been ruled out as potential causes of death of the dolphin carcass believed to be Moko, washed up on Matakana Island, near Tauranga last week.

In the post mortem report released today, Massey University pathologists state that “there were no obvious signs of extensive bruising or of any skeletal fractures, making blunt trauma an unlikely cause of death” and that none of the usual signs of drowning (from accidental capture in a net) were present.

Whilst ruling out these potential causes, the report also states that the pathologists have been “unable to establish cause of death due to post mortem decomposition”. The only potential contributing factor that has been identified is evidence of liver disease; however the specifics around type and severity of this disease cannot be identified due to the degraded state of the dolphin’s body.

Although DNA results could still be eight weeks away, the pathologists have made careful examination of the bent and broken teeth of the dolphin carcass, comparing them to photos of Moko, and concluded that they are in exactly the same positions and angles; therefore it is highly unlikely to be the body of any other dolphin.

Announcements were made yesterday that Moko’s final resting place will be Matakana Island and a memorial service is to be held in Whakatane. DOC spokesperson, Katrina Knill says that the exact timing and details have yet to be confirmed by local iwi but the public service at Mataatua Reserve in Whakatane is likely to take place at midday tomorrow (Friday). We’ll continue to keep people informed as information is available”.

Ms Knill also says that the Department is grateful for the assistance and co-operation they have received from the universities, iwi, business and the wider community “many people have gone above and beyond the call of duty to help us work through this”.

“We’re sorry that we can’t shed any more light on the cause of Moko’s death but we share the community’s grief at his loss and hope that his legacy will be an increased level of consideration and care for the marine environment and its inhabitants by all New Zealanders.” 

DIAGNOSIS
1. Unable to establish cause of death due to post mortem decomposition
COMMENTS
The advanced state of decay of this dolphin means that it is not possible to determine the cause of death.
There were no obvious signs of extensive bruising or of any skeletal fractures, making blunt trauma an
unlikely cause of death. Moko was known to have had pre-existing damage to his teeth, and based on
comparisons with photos taken several months ago it appears that he has sustained further tooth damage in
the intervening period. There was, however, no evidence of infection of the remaining teeth or of the bone
surrounding the damaged teeth, so it is unlikely that this was associated with his death.
Drowning is also unlikely, as in most cases of drowning (for example due to accidental capture in nets)
dolphins will have freshly ingested prey in their stomachs, as well as congested, fluid-filled lungs with
abundant froth in the airways and net marks on the surface of their snout or flukes. Moko had none of the
lesions that are characteristic of drowning. Establishing a natural cause of death, such as infection for
example, usually requires microscopic examination of tissues. In this case however, although these
examinations are currently underway, the marked decomposition of the internal organs means that we are
unlikely to be able to detect any disease processes that could have been present.
Addendum report: results of ancillary investigations.
Radiographs of the jaw did not show evidence of infection of the broken teeth or of the mandible.
Microscopic evaluation of sections of lung, liver, kidney, spleen, stomach, muscle, intestine and brain was
generally unrewarding due to the extensive autolysis. No cellular detail remained in the majority of the
tissues examined. The liver contained a large amount of gold/orange pigment, which was negative on iron
stains and was interpreted as bile. This pigment was present both within cells and between cells,
presumably in small bile ductules. No further evaluation of the nature of any underlying liver disease was
possible. This change within the liver is likely to be due to obstructed excretion of bile, which can occur in a
number of liver diseases. Unfortunately, due to the extent of post mortem degeneration of the tissues, it is
not possible to determine what the liver disease was, or how severe it was. It is possible though that this
may have contributed to the death of the dolphin.
GROSS PATHOLOGY
The animal was in an advanced state of post mortem decomposition (code 3-4). The entire epithelium of the
skin had sloughed and the underlying soft tissue was soft, wrinkled, and covered in large amounts of foul
smelling, viscous, dark red material. The blubber was partially liquefied. On the right lateral thorax there
were two holes within the remaining skin, measuring approximately 25-30mm in diameter. There was no
evidence of haemorrhage into the surrounding superficial tissues (likely to be a post mortem lesion).
On the left mandible, teeth 10, 11, 12, and 13 were either obliquely or transversely fractured, with the pulp
cavity of each tooth exposed. Tooth 15 was enveloped in a moderate amount of firm, dark brown,
proliferative tissue, with only the proximal half of the tooth visible. The right mandible was similarly but more
severely affected, with tooth loss or fracture of the majority of the teeth in the cranial half of the jaw. No
abnormalities were noted in the bony tissues of either mandible or maxilla, and there was no exudate
associated with the damaged teeth.
Within the lateral, superficial and deep muscles of the neck, and in the muscles dorsal to the pharynx there
were several areas (up to 10 x 5cm) that were slightly reddened and gelatinous (possible bruising).
All internal organs were in a moderarate to advanced state of post mortem decomposition. The stomach
compartments were devoid of ingesta, while the small and large intestine contained only small amounts of
tubid, drak brown material. Most of the stomach mucosa had sloughed into the lumen. The lungs were
collapsed, with no evidence of pulmonary oedema, and no froth in the airways. The blowhole and larynx
were clear, and the mucosa normal.
No other abnormalities were noted on gross post-mortem.