In the company of Short-finned Pilot Whales

Written by Simon Mustoe

Tongatapu, Tonga’s main island, is encircled by ocean over 4,000m deep. The island is an oasis, a place where the deserted sea buts up against a submarine coastline. 

The island is tectonically active. In the week we spent here there is an earth tremor.  In 2009, Tonga made world headlines when a nearby oceanic volcano erupted and created a new island. 

Deep ocean water streams surfaceward, mixing nutrients in the sunlit shallows, creating conditions for a thriving portfolio of wildlife to co-exist.

As this happens only a few miles offshore, it was with anticipation and excitement that we rose to a still-calm day and headed north out of the Capital’s harbour Nuku’Alofa, past the outer reef, on our search for whales.  

A becalmed sea shows its internal machinations. Like the cogs in a glass-fronted watch, the surface is criss-crossed by eddying currents. The largest might be hundreds of miles across, the smallest whip around the faces of the individual reefs, where shoaling waves break, staining the white sand seafloor a brilliant turquoise.

Our boat is just a speck and to us, the currents appear as flat silvery lines but these are three-dimensional superhighways for marine wildlife. 

A Sailfish breaches in the distance. We catch glimpse of a small, hooked dorsal fin - most likely a rarely seen (though abundant) Pygmy Sperm Whale.

The walls of these currents are often characterised by differences in temperature or salinity. As areas of ocean spin, tiny food particles spread outwards, colliding with the outer surface, becoming concentrated into a soup. 

It’s here that filter-feeing flying fish swarm. They are one of the most protein-rich fish on the planet and a staple in the diet of voracious predators like the gleaming yellow and glistening Mahi Mahi. The current’s vertical facades might even break up the movement of sound, providing predators like the Pygmy Sperm Whale, with acoustic camouflage to both foil prey and avoid predators themselves. 

Far from being a desert, this is a dynamic, lively environment where literally anything can happen and today we are heading out to an almost perfect calm sea; conditions we know can turn up the unexpected. 

So we start searching.   

While Humpback Whales make their homes here and were the focus of our attention, we soon start spotting other smaller dorsal fins. A pod of Bottlenose Dolphins are flanking a pod of whales, leaping clear of the water, as they make haste towards our vessel and spend a minute or two bow-riding. 

The relationship between Humpback Whales and dolphins is curious. Skipper David Donnelly says he’s watched them playing together. On another occasion we observe a pod of a dozen or so marauding Rough-toothed Dolphins (another rarely seen oceanic cetacean) among Humpback Whales, appearing to be attacking Remora fish, suckered to the whales’ underside. The whales are vocalising together and swimming fast. 

Just before lunchtime we spot more dorsal fins at the surface. This time, they are moving slowly, almost hanging there, suspended above the blue. On closer inspection, we have a pod of Short-finned Pilot Whales.  

While technically a dolphin, Pilot Whales are one of several species closely related to Killer Whales and are one of the most abundant. They travel in harems of females and juveniles, with one dominant male taking the lead. He would appear occasionally, sporting a larger humped dorsal fin than the rest. 

The pod was mildly curious so we idled a little before a few youngsters came over for a look and there was some spy-hopping, where they would ascend vertically, eyes above the surface, gleaning a quick look at us. We decided to chance a swim and see if they would maintain their interest. 

Swimming with cetaceans is a difficult activity, often challenging and potentially fraught. We were drifting in ocean about 900m deep. There have been incidents of aggression in Pilot Whales (though in one notable case, the swimmers approached and harassed an adult male) and any swimming in ‘blue water‘ has to done in a deliberate, controlled and safely measured way. 

The conditions were ideal. The whales were relaxed and everyone on the vessel was comfortable in bottomless ocean. So we slipped very quietly in and paddled gently towards a group of females and juveniles logging nearby. 

What followed, we agreed, was possibly one of the most memorable marine wildlife encounters we’ve ever had. 

For about 45 minutes, we swam gently alongside a group of five whales. At any point they could have dove to 600m or more but instead they swam slowly beneath us, rolling over to eyeball our silhouetted shapes above. 

The pod would gently caress each other - the social cohesion and relationships among pilot whales are complex. Groups can contain the grandparents of offspring long-since past breeding. This is almost unique in mammals other than humans.

The trick to spending time with any animal - whether swimming with whales or getting close to the birds in your garden - is patience. There’s a moment when animals stop viewing you as a threat. It usually doesn’t take very long but all of a sudden, you find yourself almost accepted as part of the environment and as long as you maintain a respectful demeanour, the wildlife can surprise you.

So when we were photographing four Pilot Whales moving quietly ahead of us, we momentarily looked around and one of the pod suddenly appeared from behind and below - an arms-length away - and surfaced right next to us, seemingly undetterred by us being there. 

A couple of our group dived down to a few metres and rolled in the water. The whales mimiced the movement by spiralling together before turning to take a ‘look’ - and started bombarding us with their scanning sonar.        

These are the privileged moments we yearn for but they are also earnt moments. They are unpredictable. 

The approach to swimming with Humpback Whales is just the same. It’s obvious when there is interest and there is no point in pursuing a group of whales for the sake of a swim. By contrast, when animals seek you out, the experience is nothing short of extraordinary. On another day we had two Humpback Whales curious enough to keep coming back and visiting swimmers in the water, sometimes down to just a few metres.   

When you reach this point and there is a feeling of serenity as the minutes pass and your mind is enveloped by the world around you. For a short while you are in the moment and it’s an intensely and uniquely enjoyable thing.

Wildiaries • October 2016