The Challenge of Observing Behavior in the Deep Green

Observing animal behavior underwater presents several challenges not faced by those in the terrestrial world.  For bird-watchers, all you really need is patience and a good set of binoculars. Any decent sized sea cliff in the UK will attract a horde of twitchers, cameras and lenses at the ready, who can blissfully watch birds taking off, landing, feeding their chicks, and arguing over nesting spots.  Similarly, back-garden bird watchers may have to contend with shyer species more likely to take off when noticed, but a diversity of feeders and nest sites (and an absence of cats) can reliably guarantee that some bird behavior will be seen.

Underwater, the biggest challenge is time... depending upon your equipment and depth you may have anything between ten minutes and two hours to observe as much as you can.  Finding fish or other sea life that are doing anything interesting (e.g., not simply swimming or resting) becomes a race against time with your air supply the limiting factor.  Diving a wreck, or a site known for a given species can up the odds significantly, but for some of the more interesting animals, it all comes down to luck.

Unless you are using a rebreather, you are also noisy as hell under water and likely to disturb or scare off the animals you are trying to observe.  Take a look at the octopus and the seal in the prior two videos... both animals are well aware of me, and neither is particularly happy that I'm around.  The octopus is fleeing from me and sees me as a predator.  The seal is taking a more wait-and-see attitude, but is clearly not comfortable being cornered by two divers.  There is no sound on either video, but if I had left the sound in, you would hear the very loud sound of my breathing and exhaling through my respirator. Rebreather divers have an advantage here, as they are virtually soundless, and they are the equipment of choice for professional underwater photographers for this reason... ...but with a cost of roughly £5,000 for the kit and training, this presents a substanial barrier to entry.

Finally, its gets dark underwater, particularly in the UK, and its easy to miss a lot of what is going on around you.  The seal and octopus videos were taken off the NE coast of England at around 10 meters... visibility is still good.  This below is more typical:




Note how much darker everything is outside of the beam of the torch... (also the noise I'm making!)  That means that a school of fish can be 10 meters away from you, just at the edge of your visibility, and deliberately avoiding this noisy invader of the deep!  Quite a few times I have seen interesting shadows swimming at the edge of my vision, or just glimpsed something disappearing into a crevice, meters away from me but too far to see clearly in the murk.

A Seal Encounter at the Farnes

The Farnes Islands just off the coast of NE England are famous for their seal colonies, and for how friendly the seals are with divers.  In this clip, my dive partner and I came across a seal at approx. 10 meters that was having a rest.... I guess it felt a bit cornered, as after a few minutes it swam off.

Color in the depths

The Spiny Squat Lobster (Galathea strigosa) is one of the more striking denizens of the depths in UK waters. This specimen I photographed at the Farnes was not to keen to pose, but I was able to capture some of the brilliant blue patterning that characterizes this species.

Its interesting to speculate what the purpose is of the bright blue lines, considering that without the benefit of a camera flash, the murk and darkness soaks up much of the color and that these crustaceans are most active at night. The key, I suspect, is that the color blue is one of the last colors to fade out as you go deeper, and would be one of the few still visible at depth (the orange, in contrast, would be indistinguishable from other nearby colors). Some crabs have been shown to make use of coloration patterns to distinguish conspecifics and to evaluate potential rivals, while the lines (appearing as dark streaks on a light background) could help confuse predators by breaking up the body pattern.  Other than some speculative observations on the related Galathea intermedia I haven't come across any studies that try to test this, however.

Wheres Waldo underwater

Can you find the Painted Gobies (Pomatoschistus pictus) in this picture? (Taken at the Farnes, Sept 17, approx 20m depth).

(hint - click on the photograph to enlarge)