Wondering about mimics?

I have been meaning to write a blog about the Mimic octopus (Thaumoctopus mimicus) and Wunderpus (Wunderpus photogenicus) for ages, but inspiration has eluded me until I was revisiting some of my earlier research on charismatic muck dive species. Both the mimic octopus and the wunderpus are very popular with critter enthusiasts, but we know surprisingly little about them. Time to change that or at the very least tell you some of the things we know about them!

Wunderpus

A wunderpus (Wunderpus photogenicus) checks out my camera

If you’re not a diver or you have never heard of them, the Mimic and the Wunderpus are very (very!) funky species of octopus. They have a wide range of interesting behaviour, they look amazing, and both are found on sandy habitats in the tropics. What they also have in common is that both were only recognised as new species fairly recently (2005 and 2006).

Just by reading their scientific names you could imagine these are not your average cephalopod. The wunderpus’ species name “Wunderpus photogenicus” says it all and  is probably also one of the easiest scientific names to remember (except maybe for the brilliantly named “Boops boops“). “Thaumoctopus mimicus” tells you that this particular species is good at mimicry, even for octopus standards.

Best of Dauin_Cephalopod_OctopusMimic

Mimic octopus (Thaumoctopus mimicus) foraging on the sand

Both species live on soft sediment (mostly sand) habitats and they have evolved to be perfectly adapted to this lifestyle. They live in holes in the sand, are small, have longer arms than your average octopus, and their colours are quite drab. There are a few subtle physical and behavioural differences between the two though.

Wunderpus (2)

Wunderpus partially in its hidey-hole

One of the things I noticed is that their hunting strategies vary slightly. Wunderpus have more extensive “webbing” between their arms than mimics and they use this webbing when hunting. Crabs are a favourite prey of wunderpus and they catch them by spreading their mantle (the “web” between their arms) over rocks, holes, or other objects like a big parachute. They then use the tips of their arms to poke the crabs out of their holes, after which they run into the parachute-web and are easily collected with one of the other arms.

Mimic octopus seem to forage more actively and (in my experience) use the parachute-technique less often. Instead they poke their long arms into holes in the sand, scaring out any critter that’s in there and then grabbing it directly. This means that mimics spend even more time moving over the sand than wunderpus do, which might be why they evolved some very particular behaviour.

Mimic

Trying to mimic?

Whenever you search for information about the mimic octopus, one of the first things to come up is that they mimic all kinds of other animals. Unlike other octopuses, it does not just mimic colour, but also the behaviour of up to 6 (or 8 or 12 depending on who you ask). The question is, does a mimic really mimic? Their mimicry is supposed to deter or fool predators or prey, but I wonder if this is really the case, or whether we are over-interpreting things from our human perspective.

Many of the behaviours that have been called mimicry could also be explained by simple logic or physics. Take for instance the idea that they mimic toxic flounders/soles while swimming. Yes, they do look very similar when they swim, but it is also a fast and energy-efficient way to swim over any flat area. Which is undoubtedly why this type of swimming is used by most octopus species living in the sand. Another example is the lionfish-mimic, which could also be explained as a way to look as big as possible when threatened. It’s a very common tactic used throughout the animal kingdom, and if you happen to be an octopus with long arms, you’ll look like a spiky lionfish when spreading them out. Other behaviours can similarly be explained, but I wouldn’t want to bore you with long lists right now.

Does this mean they do not mimic or that I am just a mopey cynical bastard who refuses to be amazed by a fantastic animal? Of course not! I love mimics and they show some  of the most extraordinary behaviour in the ocean. It just means that I want to learn more about them to find out what causes it.

OLYMPUS DIGITAL CAMERA

Close up of a mimic octopus

To study them properly, you first need to be able to tell the wunderpus and mimic octopus apart though! These critters look very similar (stripey), so it’s easy to get confused. Here is what to look for:

  • Arm patterns I: The black/white patterns on the arms of Wunderpus are very sharply defined, compared to more blurry with the mimic. Imagine the patterns on the wunderpus were drawn by a German painter using a pen and ruler, and the ones of the mimic by me with some crayons.
  • Arm patterns II: Mimic octopus have a continuous white outline along the border of each arm. The wunderpus does not have this, instead the band-pattern continues across the border.
  • Head: Mimics have a “U-“-shape on the back of their head, where wunderpus have a white patch.
  • Colour: Wunderpus usually have more of a red/brown colour shade to them than mimics, which are almost always black and white. Careful though, they can both change colour so this is not the best way of telling them apart.
  • Behaviour: The hunting behaviour I described earlier is a hint, though not always consistent. From my experience, wunderpus live in areas where the sand is more coarse (gravelly) than mimic octopus, which could also explain why they have slightly different hunting methods.

Finally, because you made it this far, here is a video I took of mating mimic octopus in Indonesia:

New publication: Flash photography impacts on fish – To flash or not to flash?

The final paper of my PhD thesis has just been published online in the journal Scientific Reports. The paper, titled “Behavioural and pathomorphological impacts of flash photography on benthic fishes” explains the effects of typical diver behaviour while photographing small critters such as seahorses or frogfishes.

The paper itself can be a tad technical, so with the help of two co-authors (Dr. Ben Saunders and Tanika Shalders), I wrote this summary of the research, which was published first at The Conversation (original article here).


We all enjoy watching animals, whether they’re our own pets, birds in the garden, or elephants on a safari during our holidays. People take pictures during many of these wildlife encounters, but not all of these photographic episodes are harmless.

There is no shortage of stories where the quest for the perfect animal picture results in wildlife harassment. Just taking photos is believed to cause harm in some cases – flash photography is banned in many aquariums as a result.

But it’s not always clear how bright camera flashes affect eyes that are so different from our own. Our latest research, published in Nature Scientific Reports, shows that flash photography does not damage the eyes of seahorses, but touching seahorses and other fish can alter their behaviour.

Look but don’t touch

In the ocean it is often easier to get close to your subject than on land. Slow-moving species such as seahorses rely on camouflage rather than flight responses. This makes it very easy for divers to approach within touching distance of the animals.

Previous research has shown that many divers cannot resist touching animals to encourage them to move so as to get a better shot. Additionally, the high-powered strobes used by keen underwater photographers frequently raise questions about the welfare of the animal being photographed. Do they cause eye damage or even blindness?

_MG_6706

Does flash harm fishes? Photo: Luke Gordon

Aquariums all around the world have taken well-meaning precautionary action. Most of us will have seen the signs that prohibit the use of flash photography.

Similarly, a variety of guidelines and laws exist in the scuba-diving community. In the United Kingdom, flash photography is prohibited around seahorses. Dive centres around the world have guidelines that include prohibiting flash or limiting the number of flashes per fish.

While all these guidelines are well-intended, none are based on scientific research. Proof of any damage is lacking. Our research investigated the effects of flash photography on slow-moving fish using three different experiments.

What our research found

During the first experiment we tested how different fish react to the typical behaviour of scuba-diving photographers. The results showed very clearly that touching has a very strong effect on seahorses, frogfishes and ghost pipefishes. The fish moved much more, either by turning away from the diver, or by swimming away to escape the poorly behaving divers. Flash photography, on the other hand, had no more effect than the presence of a diver simply watching the fishes.

For slow-moving fishes, every extra movement they make means a huge expense of energy. In the wild, seahorses need to hunt almost non-stop due to their primitive digestive system, so frequent interruptions by divers could lead to chronic stress or malnutrition.

The goal of the second experiment was to test how seahorses react to flash without humans present. To do this we kept 36 West Australian seahorses (Hippocampus subelongatus) in the aquarium facility at Curtin University. During the experiment we fed the seahorses with artemia (“sea monkeys”) and tested for changes in their behaviour, including how successful seahorses were at catching their prey while being flashed with underwater camera strobes.

img_8812

The aquaria were the seahorses were housed during the experiment

An important caveat to this experiment: the underwater strobes we used were much stronger than the flashes of normal cameras or phones. The strobes were used at maximum strength, which is not usually done while photographing small animals at close range. So our results represent a worst-case scenario that is unlikely to happen in the real world.

14808071_10154728145537608_910910029_o

West Australian seahorses (Hippocampus subelongatus) in their aquarium at Curtin University

The conclusive, yet somewhat surprising, result of this experiment was that even the highest flash treatment did not affect the feeding success of the seahorses. “Unflashed” seahorses spent just as much time hunting and catching prey as the flashed seahorses. These results are important, as they show that flashing a seahorse is not likely to change the short-term hunting success (or food intake) of seahorses.

We only observed a difference in the highest flash treatment (four flashes per minute, for ten minutes). Seahorses in this group spent less time resting and sometimes showed “startled” reactions. These reactions looked like the start of an escape reaction, but since the seahorses were in an aquarium, escape was impossible. In the ocean or a large aquarium seahorses would simply move away, which would end the disturbance.

Our last experiment tested if seahorses indeed “go blind” by being exposed to strong flashes. In scientific lingo: we tested if flash photography caused any “pathomorphological” impacts. To do this we euthanised (following strict ethical protocols) some of the unflashed and highly flashed seahorses from the previous experiments. The eyes of the seahorses were then investigated to look for any potential damage.

The results? We found no effects in any of the variables we tested. After more than 4,600 flashes, we can confidently say that the seahorses in our experiments suffered no negative consequences to their visual system.

What this means for scuba divers

A potential explanation as to why flash has no negative impact is the ripple effect caused by sunlight focusing through waves or wavelets on a sunny day. These bands of light are of a very short duration, but very high intensity (up to 100 times stronger than without the ripple effect). Fish living in such conditions would have evolved to deal with such rapidly changing light conditions.

This of course raises the question: would our results be the same for deep-water species? That’s a question for another study, perhaps.

So what does this mean for aquariums and scuba diving? We really should focus on not touching animals, rather than worrying about the flash.

Flash photography does not make seahorses blind or stop them from catching their prey. The strobes we used had a higher intensity than those usually used by aquarium visitors or divers, so it is highly unlikely that normal flashes will cause any damage. Touching, on the other hand, has a big effect on the well-being of marine life, so scuba divers should always keep their hands to themselves.

Luke_Snoot_Black Hairy

Look, take pictures, but don’t touch!


NOTE: I realise that this is a controversial topic in underwater photography. If you have relevant questions, comments, or thoughts you want to share, feel free to add them in the comment section below. If you are interested, I would highly advise you to read the original research paper via this link. The paper is open access, so anyone can read and download it. If you have specific questions about the paper, you can always contact me via email here.

Chasing the seadragon

dragon sign_mirrorOne month ago I realised one of my absolute critter dreams. I got to see Leafy Seadragons (Phycodurus eques) in the wild!  We had to travel to southern West Australia to find them. An area which is absolutely stunning and worth checking out, even if it didn’t have dragons. Since it was so much fun, I decided to share some of the highlights of the trip with you. Get ready for lots of pictures and start checking your calendar when you can go dragon hunting yourself!

dragons

Dragon hunting in Bremer Bay and Cape Le Grand (Western Australia)

We started in Bremer Bay, a sleepy little town that only really gets busy in summer tourist season. Since we got there well before high season, we practically had the town (and more importantly the ocean) to ourselves. Before we even got to hunt for dragons, we explored some of the many beaches and oh my, was that worth it!

Beach view

Banky Beach

Tanika clifwalk

Climbing down to Banky Beach

Surfing native dog beach

Surfers at Native Dog Beach

Obviously our main goal was to find seadragons, preferably Leafy Seadragons. So we decided to go for a dive with Craig from Bremer Bay Dive. Craig is known as the expert to find dragons and knows the area like the back of his hand. Weather conditions were not ideal and unfortunately we only had one chance for a boat dive, so the stakes were high when we set out on a blustery morning.

Bremer Bay faces the Southern Ocean (the one around Antarctica) so the water tends to be on the chilly side. On the bright side, the water is a LOT clearer than what I have gotten used to in Perth. An average day will often have more than 20m visibility and I have been told it gets much better than this. Just dropping in and enjoying the views of the rocky reefs covered in kelp and schooling fish is worth diving here.

Schooling fish

Good conditions for dragon searching

Blue Devil

A Western Blue Devil (Paraplesiops sinclairi)

Now this might be obvious, especially for someone who studies cryptic critters for a living, but seadragons have some pretty damn good camouflage! 30 minutes into the dive we still hadn’t caught as much as a glimpse of one. I was still enjoying myself and I know better than most that the ocean is not a zoo. But I also realised that with the bad weather coming in, this was likely to be our only chance of seeing a Leafy Seadragon.

Leafy seadragon profile

The beautiful Leafy Seadragon (Phycodurus eques)

So when a few minutes later Craig enthusiastically pointed out a dragon, I was more than a little bit excited. It’s hard to describe just how amazing these animals are, or how I overwhelmed I felt to actually get to see one. But I’m getting goosebumps just writing this and thinking about the dive. Leafy Seadragons are without a doubt one of the most outlandish, beautiful and downright weird fish that roam the seas, and I count my lucky stars that I got to see them underwater.

Having fulfilled our Leafy Seadragon mission, we relaxed a few more days in Bremer Bay, hoping for the weather to clear before driving to Cape Le Grand National Park in Esperance. The area is known for it’s stunning beaches, great hikes, and outstanding marine life.

lucky bay

Lucky Bay, Cape Le Grand National Park

We camped in Lucky Bay, while we were not very lucky with the weather (thunderstorms and tents are not the best combination), the bay itself is gorgeous. If you’ve ever seen a picture of kangaroo lounging on a white sand beach with turquoise waters, chances are very high it was taking in Lucky Bay (see below). More interesting for us is that you can also dive right off the beach, and that dragons are rumored to roam the waters.

Despite the less than ideal conditions, we decided to give it a go and hope for the best. The rocky dive site is surrounded by vast seagrass meadows, which make an ideal habitat for the Leafy Seadragon’s cousin; the Weedy Seadragon (Phyllopteryx taeniolatus). Weedies have less frills, and are a bit more colourful than Leafies. They also seem to be more common, and are found higher up the Australian coast than Leafies. We don’t know much more about them, but their preferred habitats are disappearing, which is cause for concern.

Weedy seadragon Tanika

Tanika watching a Weedy Seadragon (Phyllopteryx taeniolatus)

Initially we started looking for Leafies (which are sometimes present at the site) near the rocks covered with kelp, but the swelly conditions really weren’t helping. Once we changed our focus to the seagrass instead, it did not take us very long before we found two beautiful Weedy Seadragons. It was interesting to see that these Weedies were much more green in colour compared to the ones I’d seen before in Perth and Sydney. Perhaps an adaption to the high seagrass cover in the area? Food for thought!

The day after, it was already time to head back to Perth, although I would have loved to stay around much longer (even with the crappy weather). I definitely hope I’ll make it back there soon, not just to chase more dragons. There is more to do in the areas than just diving and snorkeling. Next time I’m definitely bringing a surfboard and my hiking shoes. Most of all, I’ll make sure to have more than just a week to do both spots.

Tanika beach 3

Beach walks, not a bad way to spend your time between dives

If you’ve made it this far in this blog, well done! As a reward I can offer you some more pictures of the trip, enjoy! 🙂

Leafy seadragon Craig

Craig the dragon-chaser and a male Leafy Seadragon (Phycodurus eques)

 

Coastal flowers

Bremer Bay flora

Tanika bushwalk

Heading to a hidden beach

Tanika beach

Wandering the beach in Bremer Bay

Dragon gate

Fancy seadragon gate

 

 

 

 

 

New publication: How well do divers, cameras, and critters play together on the sand?

A new paper from my PhD research was published two weeks ago. This paper is the first of two papers that investigate the impacts of scuba divers. The title of this one is: “Time to stop mucking around? Impacts of underwater photography on cryptobenthic fauna found in soft sediment habitats” and was published in the Journal of Environmental Management. In the paper I describe how divers behaved while interacting with critters on muck dive sites and coral reefs.

_MG_6706

Underwater photography is fun, but what are the impacts? (Photo: Luke Gordon)

First a bit of context to this particular piece of research. It is well known that divers can cause serious damage to coral reefs, for example by accidentally kicking down coral with their fins, dragging equipment over the fragile bottom, or even breaking off bits of coral as a souvenir. We also know that wildlife photographers (under water and at the surface) can sometimes get carried away in their quest for the perfect picture, and show some very unethical behaviour while doing so. I have written about this before on this blog, but the recent story of yet another wildlife photography winner that was disqualified shows just how common this problem can be.

The goal of my research was to investigate how diver behaviour changes when divers are close to critters, if there is a difference between photographers / non-photographers, and how this changes on the sand versus coral reefs. Importantly, my goal was NOT to investigate if muck diving is a bad thing, or if photography should be banned. Ultimately, what this paper aims to achieve, is to help improve the sustainability of dive tourism.

I had some good fun observing divers in Indonesia and the Philippines during the fieldwork for this research. Divers were not told what research I was doing, to make sure they did not change their behaviour. Instead I explained that I was investigating the habitat requirements of little critters. This meant I had to pretend to be very interested in the bottom, while cheekily observing what divers were up to. To the point where all my notes had to be coded, so divers could not accidentally read what I was doing either.

So I was basically doing university-approved spying on people…the kind of things you end up doing for science 😉 In case  you were worried, all divers were informed of the real purpose of the research afterwards, and were asked for permission to use the (anonymous) data I collected.

The results of the research mostly confirmed what I expected and won’t come as a surprise to people who often go muck diving. When divers were close to critters (either just watching or taking pictures), they caused more impacts than when diving around normally.  During these “critter interactions”, divers touched the bottom three times as much than when they were not close to critters. During these interactions, divers that were taking pictures touched the bottom much more than the divers that were just watching marine life, or showing it to their buddies.

 

Luke1

Luke photographing like a pro: great buoyancy control, no equipment dragging over the bottom, and touching nothing except his camera

Divers on coral reefs had much less contact with the bottom than divers on muck dive sites, until they started observing or photographing critters. Once divers were near small marine life, they touched the bottom just as much on corals as on sand. Basically, divers pay attention not to damage coral reefs, until they get distracted by an interesting little critter.

Using a camera underwater caused some clear impacts. Compact camera users caused more damage than divers without a camera, or those with a dSLR camera. All camera users touched the bottom more often than non-camera users. Finally, divers with a camera spent much more time interacting with critters than divers without a camera.

Picture1Finally, throughout this study, I very frequently  observed divers touching marine life. Despite the fact that every dive training organisation teaches people not to touch anything underwater, touching animals seems to be a common thing while observing and photographing critters. Sometimes this touching is limited to a minor “prod”, but at its worst, divers can rip of arms of feather stars, smack fish around (you read that correctly!) or crush frogfish under big cameras. It is clear that this cannot be the goal of muck diving.

How can we use these results to improve the sustainability of dive tourism? These three guidelines could already make a big difference:

  1. Better education for divers and dive guides on how unethical behaviour impacts marine life. At the very least during briefings, but ideally using programs such as Green Fins or by incorporating it in diver training.
  2. Developing a (region-specific) code of conduct that is supported by all local stakeholders. This would include: dive centre operators, dive professionals, local government, training agencies, NGOs, etc.
  3. Increasing awareness of the impacts of wildlife photography on a global scale. This can only be achieved when the big players get involved. By this I mean not only organising committees of photography competitions, but also dive magazines, dive expos, wildlife magazines like National Geographic,… If all these organisations would send a clear signal to no longer publish pictures that were clearly the result of wildlife manipulation, keen divers would be far less likely to try and do it themselves.

In conclusion: muck diving and underwater critter-interactions have clear impacts, but it is possible to do something about it. The most important thing to start with is changing the mentality of quite a few divers who seem to think that their pictures are worth more than the damage they might cause to marine life.

PS: The paper is behind a paywall, but if you want to read it, please contact me via email or in a personal message on any social media (instagram, twitter, researchgate)