Tag Archives: dolphin

Of Sponges and Bananas and Romance

Marine biology is hard. We (scientists!) literally cannot know what our subjects are doing all the time- we (Tim and Team Sousa) are lucky enough to have marine subjects that have to breathe air and come to the surface fairly frequently, but in a rather neat and frustrating exchange they also have a wide home range and can only be spotted effectively during the day, and really only days with good weather. So much of what they’re doing goes unnoticed or unseen, underwater or under cover of darkness or simply when we’re not looking directly at them. Sousa sahulensis has never, to my knowledge, been kept in captivity, nor could we ever say we’d seen them behaving “normally” and/or with a complete range of behaviors if they were to be so kept. Marine biology- it’s like detective work, following incomplete bits of information to try to piece together a whole story. It’s constructing specific questions, ones that we can answer given the limited observations we can get.

However, we’re out on the water as much as we possibly can be- every relatively windless day, five to ten hours at a time- and we see a lot of interesting behavior. For example, “banana pose,” in which a dolphin arches its back, rostrum (nose) and dorsal fin in the air. It’s a goofy-looking behavior, potentially adopted by males as a social or courtship display. Another example is one that I’ve heard about but haven’t yet seen- “sponging,” which in this case* is another potential courtship behavior, in which a male dolphin selects a sponge on the reef (quite a large one, too) and presents it (at the surface, presumably, since Tim’s seen it) to a female. He then adopts a banana pose. How romantic.

 

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I don’t know that I’d consider any of this to be weirder than human courtship behavior, though. If you liked it, then you should have put a sponge on it- what’s the difference? After actually having visited a bar last Friday on my birthday (WHO AM I) I really could not argue for any sort of logic in the ways that young humans choose to behave (and I’m including myself here, don’t get me wrong). Presenting alcoholic beverages to other individuals or groups, rhythmic full-body movements to pre-recorded vocalizations, displays of colors and other physical attributes… Sponges seem more straightforward. Take note, lads.

 

*”Sponging” can also refer to another really cool dolphin thing- down in Shark Bay, where some other dolphin researchers have been conducting exhaustive focal follows and continuous analysis of several individuals’ behavior, Tursiops aduncus have been seen with sponges over their rostrums, using the squishy animals as shields against anything poky they might encounter while searching the benthos (the bottom, in this case sandy) for food. They actually teach this technique through generations, demonstrating cultural inheritance and general braininess. Ahh, I remember the days when my mom taught me how to forage successfully and keep my nose out of trouble. As far as I recall, grocery store watermelons are supposed to sound hollow, cantaloupes are supposed to be heavy (as is corn on the cob) and most everything else is just supposed to be unbruised. Put my hand under cold water if it gets burned, and while traveling on airplanes, always wear a scarf. Thanks Mom!

Why

So the new official species name Sousa sahulensis has supplied me with sibilant alliterative opportunities, but has also changed the nature of the research we’re doing here on the North West Cape. There has been some research done on Indo-Pacific humpback dolphins, but the humpback dolphins that live their lives around the continent of Australia (and maybe Papua New Guinea?) may have less in common with their relatives than we had previously thought.

According to Science News (shame on me for not reading the actual paper yet…), skull morphology and DNA sequencing were used to determine the separation of S. sahulensis from their northern cousins, S. chinensis. Our dolphins cannot cross Wallace’s Line, a deep ocean barrier separating Australia from the rest of the world and, incidentally, explaining in part why Australia and its waters contain so many endemic (local only) species- as the Line formed, these coastal dolphins could no longer cross between the home waters of S. chinensis and the Australian continental shelf. Those on the southern side of the barrier evolved through genetic drift and natural selection such that they are significantly different from the northern side, and have now been recognized as their own unique group. But why does that matter?

Well, first of all Tim has to change all the abbreviations we’ve been using on spreadsheets (Sc to Ss) and the title of his PhD…

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Okay, the real reason why it matters is that, having proven significantly different from their relatives Up Above, S. sahulensis is now virtually unknown. We can’t assume they behave the same, use space in the same way, or require the same resources or protection as S. chinensis, nor can we rely on the larger population size of both species combined to buffer any human-caused losses or stresses. As oil, gas, and mining operations descend upon Australia’s coastal waters, coral reefs begin to feel the impacts of global climate change, and fishing and ocean recreation continue to increase, we need as much knowledge as we can get about these animals. Their impact on coral reefs and surrounding ecosystems could be a key part of healthy seas around Australia, and we don’t even have a good population estimate, nor any indication of whether the population is growing, shrinking, or neither. Tim’s working hard to break open the wealth of information that the North West Cape dolphins have to offer, but they’re elusive and research requires a lot of time and patience.

Much has been written about the importance of coral reefs for economic and environmental reasons, and much has been written about wildlife in general having inherent importance to humanity. I support all those reasons, and can give you pages and pages of arguments on why it’s important to maintain diverse and stable ecosystems of all types. However, I also think simply that we humans, as a species (yes, one global and multiplying species), ought to tread lightly on the world.

Yes, it’s important to understand and preserve the world around us because without diversity we and our world will be more easily overcome by change, because reefs and mangroves and wetlands provide storm shelter and water filtration to human habitations, because icy tundras and redwood forests and tigers and whales and tiny colorful fishes inspire us and make us wonder. But that all presupposes that it’s our right to choose to destroy or save those wonderful things. We approach the world assuming that we can manipulate it at will, but we are just students of systems much larger and more complex than the ones we have created.

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Species-ous Allegations

 

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As I’ve mentioned before, our focal animal, Sousa sahulensis or the Australian humpback dolphin, has only recently entered the official rolls of described species. In a recent report, scientists named this newly-identified species and thus spake Science- a species was born. Does that sound sort of arbitrary to you? Good, it probably ought to.

Let’s talk about species definitions for a second:

 

I love species names. I love using those distinct descriptions to identify the organism I’m looking at, and I love the way the fake-Latin words (so science! Very officialness) feel in my mouth. There’s a pleasing elegance to the system through which you can categorize groups of related species, like nested folders or bags-within-bags (kingdom, phylum, class, order, family, genus, species, subspecies). But do I trust species boundaries as absolutes? No, I do not. 

A “species” can be defined quite a few different ways, is part of the problem. For example, the biological definition states that for a species to be valid, the population that makes it up must not be able (for reasons of geography, genetic change, or physical incompatibility, among other potential reasons) to produce viable, or fertile, offspring with the group from which it is being separated. Several issues arise with this definition.

 

First, we consider many animals to be part of one species despite the fact that they’re almost certainly never going to meet and exchange genetic material without the aid of humans. For example, northern and southern hemisphere killer whales in all oceans are still listed officially as Orcinus orca, which is absurd. They can reproduce in captivity, probably, but even groups of killer whales (for example, Southern Residents and the area’s Transients) that live in the exact same bays and straits avoid each other completely in the wild, and probably haven’t exchanged genes for tens of thousands of years. I could go on and on about killer whales and species definitions but I will spare you (for now, mwa-ha-ha) and move on to the next problem.

Second, some domestic animals like farmed turkeys, certain cows, and many dogs cannot reproduce without human assistance. Are they species? They can’t reproduce at all, in reality, so they don’t pass the “fertile offspring” test unless people intervene quite a bit (artificial insemination, cesarean section, etc.).

Some people don’t hold with the biological definition. They prefer to define a species based on the percentage of functional genes that are different between two groups (which varies wildly depending on the age and genetic purity of a presumed species), or physical characteristics that show distance between populations. There isn’t really a definition that captures the flawed system we have (understandably) superimposed on the natural world, and the flawed system doesn’t even capture the nuance that the evolutionary process constantly creates and changes.

Meanwhile, what do you do with mushrooms and plants that can self-fertilize, or other less-identifiable organisms like bacteria, constantly passing genes from one individual to another. How about viruses, just tiny packets of DNA and self-replication machines? People think of things in groups that feel natural (haha, biology = natural…) but that’s not very scientific. It is, however, very convenient and intuitive. We group things to make them study-able, understandable, explainable, referable. For the most part, the species definition really does work to distinguish different types of organisms. We just can’t explain exactly why.

 

So anyways, it’s a bit tricky to explain why Sousa sahulensis has been officially designated a new group within that system. In this case, a combination of geographic separation, physical characteristics, and genetic difference added up to the split of the Australian humpback dolphins from Sousa chinensis, the Indo-Pacific humpback dolphin. Tomorrow’s post will explain exactly how our Sousa have earned their species stripes- this is likely enough of a biology-nerd’s rant for today.

Stay posted, dearest readers! I’m going to go track down some more cute photos of our resident charismatic megafauna and then turn in- today was long, but wonderful. I’ll dream of manta rays and humpback whales and leaping dolphins- I hope you do too.

The Science of Sousa

Despite all the photos of us smiling and drinking tea on boats, looking at the pretty little dolphins and later playing with baby kangaroos, we are actually here in Exmouth for Scientific Research (note the Important Capitals denoting the Realness of our Science).

Anyways, the research bit is cool too. Out on the boat, we drive transects around the tip of the North West Cape, collecting data on dolphin species, numbers, age classes and groupings, locations, environmental conditions, and the ever-important photographs for identifying individual dolphins from the catalogue Tim’s assembled over the past two years.

We aim for good-quality, zoomed-in, in-focus, and well-lit photographs where the fin is parallel to the plane of focus on the camera and fully out of the water, for maximum potential to identify them. Glare, spray, waves, animal movements, boat lurches, poorly angled light or backlight, focus problems- any of these things and many more can disrupt the camera and leave us with a big pile of crappy photos that we later have to sort through. But occasionally we get a photo like this:

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It’s clear and sharp, all four fins are fully out of the water, the lighting and contrast are good, and the dolphins are nearly exactly at a right angle to the direction of the lens. As a bonus, the two farthest dolphins are surfacing “in position,” meaning that their positioning along with the relative small size of the middle dolphin indicates that they are possibly a mother-juvenile pair (or in boat slang, MJ). From this photo, then, we can identify probably three out of four dolphins in the catalogue, note that the group cohesion is less than 2 meters, observe their traveling behavior, determine likely relationships, and enjoy lovely memories of how blissfully flat the water was that day.

When processing this photo, we first zoom in. Most of our photos (not sure about this one in particular) are shot with the lens fully extended to 400mm. We then have to crop out most of the photo, anything that is just water or unidentifiable parts like flukes or pectoral fins. This photo, since it’s got four good fins in it, will be copied into up to five different files, one for each dolphin and one to demonstrate the MJ pair’s positioning and relationship in the water and in the group.

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The small fin in the middle (a PJ, or potential juvenile) looks fairly unmarked. The edges are smooth, and though there is some spray obscuring a tiny part of the fin, there don’t seem to be any scars that would last from sighting to sighting and allow us to match this dolphin with photos from another time and place. Dolphins heal absurdly fast and absurdly well, sustaining shark attack wounds and other injuries that would seem fatal to a human while continuing to swim around the friggin’ ocean. And their scars often go away really fast, so they can’t regularly be used to tell one fin from another. Therefore, we go mainly on nicks and notches, the unique shapes and textures of a dolphin’s fin. For example:

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In this way-zoomed-in photo, you can see a notch about the middle of the fin, another toward the top, plus two at the tip. By searching the catalogue for a fin with exactly this shape (fairly distinctive, though not nearly the most distinctive fin I’ve seen) we can determine who’s who with relative ease, especially once we get to know the different fins throughout the season. These ones are Tursiops aduncus, Indo-Pacific bottlenose dolphins, not the main study species Sousa sahulensis, and there are more than 250 recognizable individuals in the catalogue, so we probably won’t know all of these really quickly. But there are a few, like “Steps,” that we can recognize immediately.

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Her scarring is even more distinctive from the other side, and we’ve spotted her a fair number of times since I’ve been in Exmouth. That’s part of the benefit of photo-ID though- we recognize her every time we see her and her juvenile, but just because the other dolphins in her ever-changing group aren’t as obvious, they can still be recorded and identified at a later and more leisurely (sort of…) time.

So there it is- the first part of the Science! All the analysis and breakdowns of data will come later, as we get even more sightings and process the backlog of photos from past boat days. As a reward for reading all that and hopefully understanding a bit more about why all that foolin’ around on boats and such is important to this study, for you my dear readers I present a really freaking cute photo of a baby bottlenose:

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By Any Other Name

Scientific names are very important- not only are they identifiers for different species that simultaneously differentiate groups and unify them under larger categories, but they also tend to provide some information about that species, even if the information is the name of a researcher who did seminal work in the area, or that Stephen Colbert is awesome (see Aptostichus stephencolberti and Agaporomorphus colberti, a spider and a beetle respectively named for the comedian).

For instance, upon seeing and naming this new friend:IMG_0662

I can be sure that she’s a relative to someone that long-time Agent Red Squirrel readers might recognize. Nephila clavipes was my research subject in Corcovado, Costa Rica, which is why her legs, which look like the graceful result of some dreadful hair-growing (or hair-shaving) experiments, are so familiar. This lady here is a large female Nephila edulis, which translates roughly to “edible spider who is fond of spinning,” which is illuminating if not entirely explanatory or comforting to the Western palate.

The dolphins I’ll be studying here have been, until I think today, actually, been officially known as Sousa chinensis, but have acquired independence from their northerly cousins and become recognized as Sousa sahulensis. Though not named after me, as they should have been, S. sahulensis do gain potential protection due to their smaller numbers, which brings me to my point: S. chinensis, S. chinensis, wherefore are you S. chinensis? For a research project by any other name would be as wicked sweet.Screen Shot 2014-08-03 at 12.25.46 AM