Monterey Bay Orca Attack

March 16, 2013  •  Leave a Comment

Spring is a time of intense predation in the waters of California’s Monterey Bay.  After months of fasting in warm southern waters, numerous humpback whales fed on large schools of anchovies near the submarine canyon.  On the first two days of our trip there were humpbacks in every direction, up to 30 each day.  Our fish finder suggested that the anchovies began at about 100 feet and went right to the bottom at 280 feet extending for hundreds of yards.  The immensity of this school seemed beyond imagination.  Groups of sea lions dove and surfaced in unison feeding on the school as birds circled overhead and mighty humpbacks dived into the feast.

On the third day, things began differently as we headed out from Moss Landing.  The sky was covered in thin grey clouds and the water was flat like glass.  Whereas the area had been alive with hundreds of California sea lions, birds and humpbacks in the previous days, that morning all seemed very quiet.  We met a lone humpback as we left the harbour.  This whale was swimming lazily near the boat without actively feeding.  We soon came across a second pair of humpbacks sleeping at the water surface.  They alternately floated and pushed themselves forward with slow beats of their mighty tails, half of their brains remaining alert to watch for danger and to drive them back to the surface to breath.  The calm was peaceful but eerie compared with the vigorous feeding of the preceding days.  

I had come to Monterey hoping to photograph transient orcas hunting grey whale calves as they migrate with their mothers to northern waters.  The mothers and calves must make this long and dangerous 6 000 mile journey to feed in the rich arctic waters after the calves are born in the warm but nutrient poor waters of Mexico during the winter months.  Through much of the journey, grey whales remain in the relative safety of shallow nearshore waters.  However, the whales reach a point of particular vulnerability when they reach Monterey Bay with its deep and complex submarine canyon system.  While in nearshore waters, the grey whales can hide their infants in kelp beds that help to cloak the calves and disguise them from the echolocation of hunting orcas.  Upon reaching Monterey Bay, the grey whale pairs either follow the long but comparatively safe path around the bay or cut directly across the deep canyon.  Some have proposed that it is the young and least experienced mothers that will chance this direct and dangerous path across the deep waters of the canyon.  Most attacks occur at the canyon’s edge.  It has been suggested that the grey whale’s orienting vocalizations or even inappropriate vocalizations by the calves near the canyon may provide a hunting advantage to the passively listening orcas.  Orca attacks on adult grey whales are rare.  Most predation is focused on the calves which are an attractive prey if they can be separated from their mother’s protection.  If the young whale can be separated from its mother it can be fatigued and drowned by the orcas in a brutal struggle that can last 5 hours and longer.

Killer whales (orca) attack a grey whale

Unfortunately, few if any grey whales had yet been seen this April and word from researchers in Mexico told that the grey whales were late in leaving their southern calving grounds.  Hope renewed with word that a single mother and calf had been sited on the edge of the bay the previous day.  

As we left the sleeping humpbacks, our spotter sited the tall dorsal fin of a large bull orca in the distance, perhaps a mile and a half ahead.  The boat sped ahead to join the animal.  When we approached it was clear that there were an unexpected number of orcas spread around the mouth of the bay.  At first it seemed that a group of residents may be coming through but closer examination of the saddle patches confirmed that these were transients.  The resident and transient orca populations seem to have diverged a hundred thousand years ago developing differences in social structure as well as diet and hunting strategy.  Resident orcas live in larger, life long groups of a mother and her generations of offspring.  These highly vocal orcas seem to feed entirely on fish.  Transient orcas on the other hand have a more fluid social structure and silently hunt primarily mammalian prey in smaller groups, vocalizing only after or between hunts.  

As we approached, the transients milled around in small groups without apparent direction or purpose.  Suddenly, the orcas came together into tight groups and began to travel rapidly to the southwest.  They were split into two groups that travelled close together.  Our spotter counted 23 individuals including two large bulls.  Their path led towards the blows of great whales in the distance.  It appeared that they may be hunting the mother and calf sited the day before.  However, the orcas changed direction several times cutting long transects across the bay clouding our perception of their destination.  Nevertheless it seemed that they must be hunting.

In the late morning we had to return to port leaving the hunters.  It was disappointing to pull away as, with the intense change in the mood of the bay, it seemed clear that something was soon to happen.  However, an hour and half later, our boat sped back towards the edge of the submarine canyon, returning to the spot where we had observed the humpbacks feeding for the past 3 days.  As we approached we were met with frantic activity and large splashes.  The orcas had found the mother and her calf.  Even from a distance it was easy to see the aggressive passes of the large orcas trying to cleave the calf from its mother in order to drown it.  Upon detection by the orcas, mothers and their calves will typically dash towards the safety of shallower waters.  The orcas generally appear unwilling to follow their prey into shallow waters less than sixty feet deep.  This pair had made their way along the canyon’s edge towards the beaches near Moss Landing where we found them again.

 

Grey whale calf seeks protection

As we approached we saw the mother lying on her side holding the calf above the water lying across her exposed flank.  This behaviour helps to lift the calf away from the constant assaults for brief moments of reprieve.  Again and again the orcas hurled themselves at the calf knocking it from its position of relative safety.  The calf appeared strong but the red stain of blood was evident in the spray coming off the calf.  For 20-30 minutes these attacks continued.  At this point a pair of humpbacks appeared in the mix.  The humpbacks began to pass between the grey whales and their attackers close enough to touch the greys.  On several occasions the humpbacks struck the attacking orcas with their great pectoral fins and appeared to swipe at the attackers with their tails.  The humpbacks repeatedly passed over and around the greys but the orca attack was relentless.  As the minutes passed, several more humpbacks appeared.  At this point, strange and haunting humpback vocalizations began to emanate from the sea as the humpbacks would surface.  While the meaning of these vocalizations is impossible to know, one could feel the distress of these animals in the presence of the hunting orcas.  Similar “wheezing” blows have been described previously during an orca attack on humpbacks in Canadian waters and these differ markedly from their vocalizations under normal circumstances.  It seems possible that these sounds function as a humpback distress call and may have contributed to the arrival of additional humpbacks.  As more humpbacks appeared, physical encounters began to occur between humpbacks and orcas away from and surrounding the main struggle involving the calf.  Much was unclear due to the subsurface nature of the events but the orcas and humpbacks would come together with much splashing and the appearance of tails and pectoral fins above the surface.  At one point a large bull orca was engaged with two humpbacks away from the main battleground.

Wounded grey whale calf
The action was intense with large sprays in which one could appreciate the backs and dorsal fins of greys, humpbacks and orcas in very close proximity.  As time came for us to head back to port, groups of orcas continued to hit the calf as its mother tried to position herself between her baby and the attackers and to strike at the orcas with her tail.  The calf still had energy enough for shallow breaches but the attacks seemed without end.  As we pulled away an orca leapt onto the back of the calf as it surged forward trying to escape.  Splashes and struggles continued in the distance as the boat pulled away.

As we returned to the harbour, both the outcome and the significance of what we had seen were still unclear.  What was clear was that such involvement of humpback whales in the predatory interaction between orcas and grey whales was something that none of the observers had seen or heard of before.  While only a small number of predatory attacks by orcas on humpbacks have been described worldwide in the past 200 years, in fact, up to 20% of humpbacks on the California feeding grounds bear rake marks from the teeth of orcas.  However, I can not find any published description of an event like the one we witnessed.  It is difficult to be certain of all that transpired due to the cryptic nature of the watery environment but it is absolutely clear that a group of humpback whales became closely involved in this predatory event, placed themselves repeatedly between the attacking orcas and the vulnerable grey whales and had many dramatic and close interactions with the orcas throughout the event.  While it is possible that the humpbacks themselves were independently under attack, they seemed to approach the site of the attack from elsewhere putting themselves into danger.  The orcas’ energies seemed focused on the grey whale calf and the humpbacks placed themselves in a position near to the grey whale mother and calf increasing their personal vulnerability.  Further, we did not see any direct assaults on the humpbacks and while both the mother grey whale and calf had wounds with exposed blubber, none of the humpbacks had any obvious injuries.

The next day began with word that the grey whale calf was seen escaping from the previous day’s attack.  It is easy to speculate that the seemingly heroic involvement of the humpback whale may have evened the score enough to allow the calf’s survival.  Expectation was high as to what the bay might hold this new day.

We set out again into Monterey Bay passing feeding humpback whales on the way out.  As we reached the centre of the bay, the fins of transient orcas again came into view.  As we approached we found that they had surrounded a lone grey whale calf, isolated from its mother.  The calf was swimming slowly spending much of the time lying on its side.  In this position, we could clearly see the extensive wounds on the baby’s flukes and exposed side.  As the boat approached, the calf sought shelter directly under our boat.  A large bull orca vigorously and repeatedly tail slapped in the direction of the boat and the whale cowering under it from mere feet away.  The orcas did not appear particularly dissuaded by the boat and continued to rush under the boat to harass and attack the calf.  This put our boat in a particularly dangerous position.  As the baby whale floated out from under the boat, it gazed upwards making direct eye contact.  This was a sad and striking moment as multiple orcas made passes at it only feet off the side of the boat.  Carefully we moved our boat away to a safer position and allowed the natural event to continue without interference.

Dying grey whale calf

Where was the baby’s mother?  It seems very likely that these were the same mother and calf from the previous day.  Had they finally been separated?  The answer it would seem was likely more sinister.  The orcas continued their assaults on the baby, repeatedly ramming it in coordinated waves for several minutes.  The orcas then moved off several hundred yards to the south where they circled taking dives repeatedly into the same area of sea.  As the orcas left the wounded baby, instead of fleeing, the baby swam slowly towards the orcas.  As we approached this area with our boat, the unmistakable smell of blubber filled the air.  It seems that a whale carcass was likely lying below the surface.  After a kill, the carcass of an adult grey whale sinks to the bottom with the orcas diving as much as 1000 feet in order to feed.  It is likely that the baby felt compelled to return to the site of its dead mother.  Without her, it had little direction or chance of survival.  Having been recently born in the warm waters of Mexico, this baby had never made the northern migration before and surely was not yet weaned.

Around the site of the previous kill, the orcas behaved like a pack of wolves after a successful hunt.  There was a wide variety of social behaviours mixed in with the subsurface forays for feeding.  The orcas breached and tail slapped around the site.  After swimming weakly towards the kill, the baby was not seen again.  We could not be sure whether the baby was killed subsurface or whether it simply swam away.  If it swam on, the hunters would have easily been able to reacquire the baby and kill the helpless and weakened animal later.

Killer whales (orca) after the kill

It is chilling to conjecture about the events that passed between the two predation events.  The mother and calf seemed to have escaped late in the previous afternoon but may have been gravely injured and unable to make much progress out of the bay.  What a long and terrifying night it must have been before the final kill.  Might the injuries that the mother had accumulated in defence of her baby have finally led to her demise?  What a sad and compelling sight to see the baby robbed of its caregiver, alone, directionless and helpless against the predators.

We returned to the same site several hours later and a large oil slick had spread across the surface of the water giving testament to what had come before.  The orcas were now in a different behavioural state moving about in small groups without urgency.  It seemed that this particular tale had come to a sad and compelling conclusion.

The next and final day was very quiet on the bay.  We encountered no whales on our travels out into the centre of the bay where the carcass remained below the surface.  There we found the orcas still circling the hidden remains, intermittently diving to feed.  The oil slick remained across the water surface.  After several hours of feeding, the orcas left en mass, heading with speed to the northwest to parts unknown.

As we headed back to Moss Landing and our time in Monterey Bay came to an end, we encountered three humpback whales that were game for a friendly encounter.  As they frolicked around and below the boat looking up at their human observers, it seemed a quiet, peaceful end to the gripping and bloody events that we had witnessed.


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