The Secret Lives of Shell Dwelling OctopusesLatest update May 23, 2019 Started on May 6, 2019
In the beaches of Balandra, La Paz, Mexico, two species of octopus hide away in shells. In another part of the world, octopuses are using shells as tools, remarkable for an invertebrate, are these Mexican octopuses also tool users?
Finding octopus dens
Octopuses are famous for their camouflage skills; however, they are also very good at hiding in shelters or dens. Apparently, each octopus has several dens to rest and feed in a certain area, within which they move in search of food. According to our experience working with octopuses, we have observed that each octopus has a couple of "main dens" in which they usually rest most of the time and eat quietly after catching various preys. In addition, they have several "auxiliary dens" within its hunting area, which they use to take refuge from predators, hide while hunting or just relax.
All these dens can be found in cracks between or beneath rocks, holes in the sand, abandoned tires, cans or bottles, among others, and are easily recognizable (especially the "main dens") by the empty mollusc shells littering the doorway. The main entrance of these dens is usually surrounded by an accumulation of small stones, shells of dead bivalves and some exoskeletons of arthropods such as crabs or lobsters.
When a den is recent or is inhabited, the remains of shells are completely clean and do not present algae or other epibionts. However, when the shells are visibly accumulated in one place but covered by algae, it can be said that it is an ancient or abandoned lair.
It could be thought that octopuses are somewhat disorganized when leaving the remains of their food right at the entrance of their "houses", or that it is not very intelligent to leave such an obvious signal that the den is occupied by an octopus, however, these remains are actually extremely useful when a predator approaches. We have witnessed that when an octopus feels observed, discovered or threatened inside its den, it hides quickly inside of it and collapses all the shells and rocks in the entrance, creating an immediate barrier against any attacker. This is recycling the "garbage" in a very intelligent and convenient way! This behaviour is especially useful on sandy bottoms where there are not many rocks to use as protection and the shells serve as a rigid and efficient barrier against any threat.
We know that the octopuses we seek in Balandra generally take refuge within bivalve shells, however, when exploring the site, we also found traces of dens under rocks and even in the sand with these characteristic traces. In this case, the shells belonged to very small bivalves (no more than 5 cm in length), so it is likely that they were consumed by the small octopuses that we are looking for.
We still have a lot to document in Balandra and much to discover about these experts in hiding. We hope to find more very soon and share more findings!
Playa de Balandra
As the only non-Mexican on this project, and also the blog writer, I have the scary prospect of describing the uniqueness of the primary field site we will be working at - Playa de Balandra. I hope I can do it justice.
Located on the southern side of the northern tip to the north of La Paz, it is close to Isla Espirito Santo, another well known natural wonder that harbors a huge array of marine life, both above and below the water. Balandra is a coastal bay that includes a spectacular and healthy mangrove forest and beautiful sandy beaches. It is located within one of the main hydrological basins of La Paz.
Both of these amazing places are protected from fishing and sites recognized of outstanding natural beauty and wonder. Frequently recognized as one of the worlds most beautiful beaches, Balandra is visited by hundreds of thousands of tourists each year, it has parking facilities, toilets, and snacks for sale. It even has an emergency health service, something I was extremely grateful for when I ignorantly got stung by a stingray. Dear God that hurt. With tourists so wonderfully catered for how is it so pristine? Why kind of future could it possibly have? How can you conduct field science there?
The answers to these questions come down to a simple but unbreakably strong will of the local people and a great example of the power of social collectivism.
I have just got back from spending two weeks in La Paz and it clear from the outset that people are deeply in love with nature and in particular marine life. Everywhere you go there are incredible murals that mix ancient culture with modern stories of struggle but all feature animals, and nearly always a whale shark, octopus, turtle or other charismatic marina fauna. From seeing this first hand the remarkable story of how the local people have saved, and now 'own' Balandra is not all that surprising.
For decades rumors of outside investment in the region brought warnings of mass development to the area - think mega hotels, golf courses and worse. In 2007 the Colectivo Balandra (see here: http://balandraesnuestra.org/)) was formed to give a voice to local people, a voice of at least 18,000 citizens, of all ages and social groups, to request the authorities to protect Balandra. This social movement generated many great achievements, not least the publication of a state law that allows municipal governments to protect key terrestrial habitats within their territory; the creation of the first municipal protected natural area in this area that protects the hydrological basins that surround the wetland from urban development; the inclusion of Balandra in the Ramsar List of wetlands of international importance; and the beginning of the process to create a complementary natural area of federal protection in the waters surrounding the municipal protected area. What is really striking is not that the movement was formed, many people around the world would want to protect their natural beauty, but that they succeeded to such a high degree!
This has resulted not only in an area of outstanding beauty being protected from urban development AND fishing, but it has created an immensely powerful feedback loop. Despite the very busy day, I was there, there was little or no rubbish of any kind lying around, even though plastic wrapping was being sold everywhere. It was much cleaner than many areas of 'beauty' I have visited around the world. It seemed to me that once you establish something and work hard to own it, it gives you a reason to take care of it. I was so impressed, but that is the wrong word, patronising even: I am in awe of what has been achieved here. At a time when my own country (the UK) is in political disarray, it is rejuvenating to see the people put aside differences to unite against overdevelopment.
So that is why we are working there, to start with. Such ideal conditions, without fisheries interference, allows us to test behavioural ecology hypotheses on animals that are not unduly influenced by 'artificial' selection for those who can avoid being caught or disturbed by human fishing. Of the two shelling dwelling octopuses we know reside there, one seems to be a lot bolder (sassy even!). In 'equal' times perhaps they coexist by dividing the shell occupancy niche, who knows (yet!) but when we have a natural baseline we can then see how these species with different 'behavioural syndromes' (not individual personality, but species-wide temperament) manage within areas without the same level of protection. This knowledge may then be used all around the world where the 'sassy-ness', or otherwise, of a species might influence how animals may coexist with humans. Just another testable hypothesis brought about by this expedition.
Must read: http://balandraesnuestra.org
Dr Gavan Cooke
The disappearance of the Humbolt Squid (Dosidicus gigas)
Another important and incredibly valuable use of the Trident ROV will be to work in much deeper waters. The Gulf of California (more properly Baja California) once held seemingly unlimited numbers of one of the largest cephalopods, a squid, known as Humbolt's squid (Dosidicus gigas). Humbolt was a famous 17th-century polymath (basically good at everything!) who explored central and Latin American extensively (https://en.wikipedia.org/wiki/AlexandervonHumboldt). Amongst other pioneering work he discovered and described one of the largest squids to be found anywhere in the world.
This squid is a ferocious predator (https://en.wikipedia.org/wiki/Humboldtsquid) that can easily get to 2m in length - see picture - and has a very nasty beak, so nasty that divers have had to wear chain mail diving suits to dive with them, as our friend Luke Inman is doing in the photograph. They used to be superabundant in Baja California but due to over-fishing they have seemingly all but disappeared.
It may be that they have gotten smaller (known as fihseries induced evolution) so no longer caught, or they have changed their behavior, or actually gone altogether. It is striking that every scientist I spoke to on my visit to La Paz a few weeks ago asked me what I thought had happened to them. So, with so many people keen to find out, we will use the ROV, and less fancy light trapping kit, to investigate whether these amazing animals have gone forever.
Image courtesy of Luke Inman featuring himself and a large Humbolt squid (Dosidicus gigas)
As these beaches and shallow waters have so much to offer, we are not missing the opportunity to investigate as much as we can. The areas are also home to hundreds of other species that might only come out at night. These species include squids, another favourite cephalopod of ours. We have bought a special green underwater LED lighting system, perfectly powered by a very small motorcycle battery.
This colour of light is known to attract squid, it is used by fishermen around the world. We hope to attract the squid and conduct a biodiversity survey, seeing which species are in the waters at various times of the year.
We also have another trick up our sleeves. We can modify a water container to house a light which will attract the larvae or babies of many different species. A small LED light is inserted, whilst the bottom is cut away and replaced with a plankton mesh (~5-10 micrometers): this allows mixing of water which prevents all the little trapped animals missing out on Oxygen. We can lower this to different depths and catch things that inhabit the waters horizontally. As many species have way many more individual offspring than fully grown adults, we be more likely to come across rare or unusual things.
A few more bits about the octopuses and our research
O. fitchi and P. digueti inhabit the tidal and subtidal waters off the coast of La Paz, Mexico, and surrounding area. The two species are small benthic octopods (Cephalopoda) that have life histories that may be relatively unique in this branch of Cephalopoda. Octopus’s are thought to be nearly exclusively asocial but as they are both shell dwellers, meaning they seek refuge in dead clams, this resource may be under intense competition and encourages social interactions rarely seen in octopuses. This life history trait may be somewhat similar to that seen in hermit crabs which also use abandoned mollusk shells as refuges, which could be constantly fought over and would provide an interesting comparative approach to intraspecific resource competition, a fundamental area of behavioural ecology.
These octopuses have short lifespans (~12 months) and are therefore potentially ideal laboratory models, many generations can be reared and experimentally investigated in a relatively short amount of time. Cephalopods are notoriously difficult to track in the wild, due to the difficulty of inserting and maintain physical tags in and or on their very soft bodies. Using the refuge bivalve shell as a proxy to marking the animal provides a unique opportunity to follow the octopuses over the month we are out there.
Nefer, and her colleagues at CICIMAR (http://www.cicimar.ipn.mx/Paginas/Inicio.aspx), had knowledge about the shell dwelling octopuses presence in the region for a long time and had worked with them from an environmental toxicology standpoint. When they told me about their shell dwelling existence, as a behavioral ecologist, I wondered just what they were up to...so Nefer and I went out and had a look for ourselves...
We set out into the field on a very typical blue-skied beautiful La Paz day, wading into the warm (for an Englishman!) waters that were crystal clear and less than 1m deep (at a low tide).
We managed to survey a small area, looking specifically for shells that might contain octopuses. Within a reasonably short time, I found one - success! I must have got lucky...we had a look inside the candidate shell and there one was...a rather large looking Paroctopus digueti (https://en.wikipedia.org/wiki/Paroctopus). This was very exciting, it was the first time I had encountered them and luckily for me, the photograph does not contain the sounds of me squealing like a little boy.
After the small survey area, the red square on the map provided, we waded around the area and summarised, with tides taken into account, the likely area where more would reside (within the green area). And this is just in Balandra...other sites close by are also known for their presence.
One last amazing discovery of the reconnaissance mission was the finding of a small but energetic fiddler crab population. These guys wave their claws around to attract females and are an important model in sexual selection (a part of evolutionary biology) studies. I love watching these guys do their thing (wait 13 seconds in the video) . A great end to a great day.
The team in this project also run a citizen science project for cephalopod observations (https://www.facebook.com/groups/554841448361864/) and amazingly the amazing citizens and students of La Paz are providing us with field observations of these wonderful animals
Octopuses are well known for their incredible abilities, they can change their appearance instantaneously, hunt with other species and incredibly, use tools!
A species of octopus in Indonesia uses clam and coconut shells to hide from predators. Instead of simply hiding in them and then abandoning them when the coast is clear, they actually have the foresight to pick them and take them on their journeys. As this inhibits there normal rate of progress scientists have determined that they pass the test for the scientific definition of tool use.
We have discovered two species of octopuses in La Paz, Mexico, that are frequently seen hiding in clams, just like their Indonesian counterparts. These octopuses reside in the beautiful, pristine and protected beaches of Balandra.
Our mission is to investigate just what these secretly smart cephalopods are up to - are they using the clam shells as tools? If so, to what extent? We intend to use the full range of behavioral ecology and field techniques to answer defined scientific questions. We have a team of amazingly talented local undergraduates and postgraduates, some assistance from the local marine research institute and permissions from local authorities.
So far we in the process of gathering habitat ecology data via field surveys carried out by student volunteers. The ROV will be used to watch the wild behavior of these secretive yet amazing animals. This equipment is vital as disturbing via snorkeling causes them to hide away
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