So not only is the title a reference for the ‘How I met your Mother’ fans out there and a nod to the amazing American holiday that is fast approaching, but it is an appropriate title for the topic of today’s blog:
When two male seals face off, the interaction usually consists of each opening their mouth in an aptly named ‘open mouth threat’, a few shuffles, and then each rolling back to the spot where they began. Once in a while the interaction escalates into a full fight with tooth and claw and muddy wrestling, but to say a typical interaction is low-key is a bit of an understatement.
However, I’ve lucked out with my study site in that it is one of the few known locations where males do something more: they Body Slap (also called ‘belly-flopping’ at a nearby colony). Since starting my PhD, this behaviour has intrigued me. First off, it is a fairly eye-catching display consisting of a male doing a press-up (that’s a push up for the American readers) and then letting his entire, enormous bulk SLAP back down onto the ground. As imagined it creates a distinctly loud sound but also a tangible shudder through the ground. More intriguing though, is that although the behaviour has been noted by wildlife enthusiasts and reserve wardens since the mid-1990s no one ever bothered to look into the behaviour—especially since as far as we know it is only performed along the Eastern and Southern Coast of England and has not been seen in Scotland or Canada.
Since my PhD is investigating the Behavioural, Social and Environmental roles in male conflict and conflict reduction, as well as Individual variations or strategies, looking into what exactly the body slap communicates and how it shapes decisions during aggressive contests immediately struck my interest. We recently published our first analysis of the behaviour in Marine Mammal Science (Bishop et al. 2013). We found the Body Slap is not a submissive display and likely has something to do with signaling dominance or size, and that males seemed to perform it more on the sandy substrate than the grassy dunes…but what information the display contains, and how that information is conveyed was still a mystery.
This is where the cryptic prior posts where I’ve mentioned keeping guard on my ‘kit’ come in. You see when our lab group were tossing around ideas about the behavior, two years ago now, we thought the acoustic component was probably a given—the noise is loud when the sand is wet—but we also wondered if the seals were using the vibrations caused by the slap to judge each others’ size. A study back in 1991 demonstrated that Elephant seals do generate seismic signals and that they can sense the vibrations and react to them, but no one has ever shown this in other pinnipeds or tested to see what the signals are communicating. Only one thing to do….call up our Geology department and attempt to get our hands on some seismometers to answer that question!
Well it wasn’t that easy. Our Department didn’t have the kit available so we applied for a loan through Seis-UK, a branch of NERC that supplies equipment for research projects. Along with our collaborator at the British Geological Survey, we successfully deployed two seismometers this year and the data is rolling in!! (Literally. The devices record 24/7 and at 1000 data points per second….so…much…data!). As with most fieldwork, the process hasn’t always run smoothly but I am learning more about ground waves, electronics and just how many D-cell batteries the local Morrison’s has in stock (exactly 48…I bought them all) and the results are well worth it!
The goal is to see if the magnitude of the seismic signal the males create can be measured, if it is related to their size, and how the environmental and anthropogenic factors impact this pathway of communication! I’ll be presenting our preliminary results at the Society for Marine Mammalogy Biennial Conference in NZ in just a few weeks so stay tuned for more updates from there!