Re-imagining focal follows

On our third day in Shetland we headed to the south for more exploring and watches. Quite different landscapes here with long sandy beaches and marshlands. We found another town hall community-run campsite in Levenwick, and headed to Sumburgh head to join the National Whale and Dolphin Watch. There we met Karen Hall, marine mammal advisor to the Scottish Natural Heritage and regional coordinator for Sea Watch Foundation. She collates reports of marine mammal sightings, nowadays made mostly in social media, into sightings data for Sea Watch and also shares it with the Shetland’s Biological Records Centre.

Karen recounted some of her numerous observations of orca predation events and whale tracking around the islands, which often don’t have roads going all the way around the coastline. With the dramatic shores and dizzying cliffs, land-based views to the whales can often be obstructed. This presents an obvious challenge to conducting ‘focal follow’ sightings of the whales.

Focal follow sampling is an age-old method used by researchers to track individual animal behaviour over time. It has been to used to measure activity time budgets of primates and cetaceans especially (Mann 1999, Karniski et Al 2014), although visual observations are increasingly being replaced with animal-attached data loggers and transmitters. With species that are challenging to tag however, such as killer whales, focal follows can provide a low-impact method to understand their behaviour.

One of the assumptions of focal follow sampling is continuous observations. Typically, behaviour data are recorded at set time intervals following an individual, or a group of individuals. But what if the observer cannot follow the individuals continuously, and is having to run to the car and drive around a headland to catch a glimpse of the whales again? An example of such follow was documented in Emily’s blog ‘On the Killer Whale Trail‘.

On the upside, there is at least one advantage to studying killer whales in Scotland: most of the time, there will be just one group in a given area, and so the pod can be tracked with relatively sparse sightings. To see for yourself, check out the detailed tracks that Andrew Scullion managed to put together on this google map using social media sightings from 2018.

Perhaps one way to go about a fragmented follow such as this would be to record the visible segments with start/end time and coordinates – then join the dots for invisible segments until the whales are re-sighted again. That way their travel speed, and some movement/foraging effort during the visible segment could be quantified (and some uncertainty estimated for the invisible segments?). I look forward to hearing everyone’s thoughts on this, and crossing my fingers again for some whales to put the theory into practice..