Humpback Whales in Tonga 2010

It's been another eventful week or so in Vava'u. The weather has been mostly unhelpful, with winds running at least 20 knots on most days, over 30 knots yesterday.

Despite the challenging conditions, we have had several interesting encounters with humpback whales, including two more ID-ed calfs, another mating pair, a friendly single whale, and a four-whale heat run. One of my boats also came across a whale shark in crystal-clear blue water…when I wasn't on the boat (of course).

Lone humpback whale, probably a sexually immature male

Humpback Whale Calf IDs
Getting photo identification of mother and calf pairs has been difficult so far. The wind and sea conditions have made the task of finding and approaching whales challenging, and the whales themselves seem more active than normal…meaning they've been travelling at high speed more often than they've been settled and approachable.

I wondered for some time if this wasn't just a string of bad luck for me. After all, I've had such incredibly good fortune with whale encounters to date that it wouldn't surprise me if I had a bit of a dry spell…the Law of Averages as applied to cetacean encounters, so to speak.

After checking around with many of my friends and other whale watch boats here however, I think it's reasonable to state that everyone has had the same experience.

This isn't to say there haven't been some terrific encounters. It's just that on the whole, such experiences seem to be more the exception than the rule…for the moment at least.

Anyway, we did manage to ID two more calfs this week, both on 9 August.

One was a relatively young baby that we named "Mali Mali", which means "to smile" in Tongan. The calf and its mother were constantly on the go, so were difficult to approach.

Mali Mali and mother

The other was a much bigger calf, perhaps a month old or more. We named this one "Bimyo", which means something along the lines of "strange", "uncertain", "difficult to ascertain", etc. in Japanese, though I don't think there is an exact translation in English.

The reason we named this calf "Bimyo" is because the calf presented us with a head-scratching, mind-bending conundrum.

We came across Bimyo early in the morning, east of an island named Euakafa. There were five whales in total, Bimyo plus four adults. Eventually, one of the adults left, and then another peeled off, leaving Bimyo plus two adults.

When we entered the water (with really poor visibility), we could see that one of the adults was mostly dark in colouration, while the other had a lot of white on its body.

Bimyo with two adult whales during the morning encounter

The dark whale was initially aggressive/ protective, in the classic escort fashion. It swam between the more white adult + calf and us, and it was easy to read the "This is my female!" look in the whale's eyes. Or so I thought.

After getting a few calf ID photos, we left the whales, as the dark one seemed overly hyped-up on testosterone, perhaps from fending off the other two challengers earlier in the morning.

It wasn't until night time that I realised that things might not have been as clear as I had assumed.

Later that same afternoon, we came across another mother/ calf/ escort group, once again in piss-poor visibility. We managed to get a few photos and see them in the water, but the encounters were fly-bys, not extended ones. The whales were completely relaxed…just not in the mood to hang around and play.

This mother was dark all over, and the escort (trailing behind and somewhat below…classic escort behaviour) had a lot of white on its body. The calf was a relatively big one.

I and everyone else assumed this was a third calf. Location, behavior and even appearance was different.

Second encounter with Bimyo, this time calf swimming with the dark whale

But…as I was keywording and captioning images that night, something nagged at me. Given that I was practically comatose from exhaustion, I wanted to finish as soon as possible and get to sleep. I tried ignoring the little voice in my head…to no avail.

I stared at the images, scrolling up and down, over and over again, until I had one of those apple-hitting-me-on-the-head moments: One of the calfs in the morning (i.e., Bimyo) was exactly the same as the calf in the late afternoon.

But…in the morning, it was riding on the nose of the whiter adult, and the dark adult was aggressive and fending off other whales and people. In the afternoon, the calf was riding on the nose of the dark whale, which was placid and mommy-like, while the whiter whale was following in a classic escort-like fashion.

It was too late to show anyone else, so I had to wait until the next morning to share this observation.

I'm not sure what was going on, but some possibilities include: (a) the dark whale is the mom and the baby is equally comfortable with either adult…mom or escort (I've seen babies hang out with escorts before, but never while swimming); (b) the white whale was the escort and was trying to separate the baby from the mother (dark whale) in the morning…perhaps accounting for the dark whale's aggressiveness (I've seen babies separated from their mothers on several occasions), (c) both whales are females and there's cooperative parenting taking place (unlikely, but just a thought).

If anyone has any insight or has seen something similar, please let me know!

Unfortunately, none of us were able to take upskirt photos of either of the adult whales, so we can't determine either whale's sex…meaning the "Who's Your Mommy?" mystery will remain unsolved unless we happen to come across the calf again, and/ or someone else sends photos to sex the adult whale(s).

Speculation
This encounter sparked a cascade of thoughts in my mind.

It's still quite early in the season, and having what appeared to be four male whales vying for a female with a calf at this early stage in the season is relatively unusual.

Sure…it happens, but if you were a horny male leviathan…wouldn't you target the single females first before going for the ones requiring child support? Most of the time, this is exactly what happens.

Heat runs (i.e., male competition for mates) generally revolve around single females earlier in the season, while escorts attached to females with babies become relatively more common later in the season. This is not a set-on-stone rule, just a general pattern.

I'm going to climb far, far out on a limb here and speculate, starting with a few observations:

1. We saw what appeared to be four males vying for a female with a calf on 9 August, i.e., very early in the season.

2. We've seen four male/ female pairs so far, i.e., females that have already chosen mates, again, early in the season.

3. There seem to be many more young whales (as singles, as pairs, or in pairs with mature whales) than would be normally expected.

4. I counted over 60 babies in the past three seasons. Since there's no possibility I counted every baby, there quite probably were more than 100 babies in that time.

5. It's commonly believed that there are 500 +/- whales that regularly visit Tonga during the winter season.

6. All the whale watch boats are reporting fewer whale encounters in comparison to a hypothetical "average" year.

So here's my bit of speculation, drawing upon the statements above.

Let's assume there are 500 whales in this group, and let's say half of them are female, and half of those are able to mate at any given time. This (overly) simple calculation suggests a breeding-capable population of around 125 female whales at any given time.

If there were more than 100 babies in this group in the past three years, then it would be reasonable to conclude that a large proportion of the breeding-capable females have had babies in the recent past.

I know for a fact that humpback females can have babies two years in a row, but most evidence and common sense suggests that they're relatively unlikely to do so, and more likely to wait a couple/ few seasons before having a baby.

Giving birth to a four-metre baby and raising it requires a lot of energy, so it's perfectly reasonable for mommy whales to take a bit of time off to rest and build-up fat reserves before trying again.

So what this suggests is that there might be a relative abundance of young, sexually immature whales showing up here, with fewer females ready for mating than there were in the past few years...exactly what appears to be taking place.

If this is the case, it might help explain why we've seen four mated pairs already…the strongest males have already claimed the few available, single females. They've mated, and the females have headed back south to fatten up for birth.

It may also help to explain the cluster of males around Bimyo and mom so early in the season…there may just not be that many females around.

It may also explain my earlier encounter with the young whale vocalising non-song, song-like sounds (that I wrote about in Part 1.)

And finally, it may help explain why there seem to be fewer whales around in general…those that have mated have gone back, while the immature ones will hang out for a bit, do some stuff around Vava'u, then travel to other places to explore. The young are always restless.

I realise that I don't have anywhere near sufficient evidence to "prove" a storyline like this, but I think it's important to draw together strands of personal experience and collective wisdom from my friends to try to piece together what's going on.

As the season progresses, I'll update and amend my speculation when new information becomes available. It's entirely possible that everything I wrote above is proven wrong. But as George E. Hale once observed: "he who would launch great ships must live in deep waters,". I'm not afraid of the deep.

Other Highlights
Among the other highlights this week were an encounter (on 11 August) with what appeared to be another mated pair (the 4th this season), with the female once again demonstrating a penchant for hanging tail up in the water, with fluke protruding out of the water.

We've only come across this behaviour once before, a few years ago with a single female that might have been pregnant.

This season, we've now seen two different female whales (accompanied by males) doing the "tail-out-of-the-water" pose (See Part 2).

We also had a four-whale heat run on 12 August, that I first spotted travelling at super-duper high speed in the distance far offshore. They eventually came toward the islands, allowing us to follow and drop in a few times for a closer look.

High-energy, testosterone-driven heat runs are my absolute favourite whale encounters, so I hope we see more this season. If my speculation above is correct, however, there may not be too many.

One of the four heat-run whales, cruising at depth

On the same day, one of my boats had an amazing encounter with a whale shark in perfect water. I gather that there were many shrieks of joy and lots of high-fives going around. Plus a group picture when the boat got back to the dock with everyone saying "whale shark!" instead of "cheese!".

Whale shark outside Hunga

And finally, we came across an interesting pair of whales on 14 August. The whales were on the move, so we weren't able to get into the water with them, but we watched for an hour-and-a-half or more.

One of the two whales had the unusual habit of tail-slapping once and only once each time before the pair dived. Tail-slapping isn't unusual, but doing it only once, continuously for an extended period of time over an extended distance, is. I've never seen this behaviour before.

It was the first day out on the water for the people on the boat (Colin, Cary, J, Geri, CC, Jenny), so it was entertaining watching everyone get frustrated trying to get topside photos of the tail slaps.

With repeated tail slaps (or other surface behaviour), it's much easier to get good photos because you know where the action is happening. Since this whale executed only one slap at a time, you basically had to guess the time and place, plus get the framing correct, have the right light, and not have the boat rocked by a swell when you hit the trigger. No simple task.

Let's just say there was an abundance of groaning and muttering, along with some good-natured shrieks of agony.

I'm not sure what the whales were, but they did appear relatively small. I think they were young whales, but since I wasn't able to get into the water to get a closer look, it was impossible to be certain.

That's it for now.

Humpback whale doing one and only one tail slap before diving