Welcome to our first blog post! We are excited to start sharing marine mammal news with you through periodic blog postings, keeping you up to date with PacMam and the wider world of marine mammal research.
If you follow us on social media you may have already seen that we just published our first paper on our harbor porpoise photo-ID work, so I wanted to use this first post to share some of the most interesting findings from that paper.
We have spent many, many hours in the cold, warm, windy and sunny days collecting data and taking pictures of the harbor porpoises that use Burrows Pass, off Fidalgo Island. One of the comments we frequently hear is “getting pictures of harbor porpoises is difficult”…and you’d be right! But it is possible (thanks to those many, many hours of field work) and many of those photos can be used to identify individual animals! Using various markings including pigmentation patterns, scars and dorsal fin characteristics, we have identified more than 55 individual harbor porpoises with over 35% of these returning to the area. As we know very little about this species’ home range and movement patterns, this information is extremely important because it shows some level of residency, or “site fidelity”, to this particular area. Knowing where porpoises go on a regular basis will be crucial to understanding and protecting them.
We also looked at their grouping patterns; what influences their group size and composition? Group sizes were typically small (which is usual for harbor porpoises) but were significantly larger when porpoises were feeding, suggesting this may be a useful strategy when foraging in Burrows Pass. One of the most interesting results was that the tidal cycle influenced group composition. Calves were most likely to be seen during slack tides when water movement was slower. The rip tides in Burrows Pass are very strong and swimming in strong currents would be more difficult for a small calf than for adults, so it makes sense that mothers and calves would avoid the Pass during those times.
Harbor porpoises are found year-round in Burrows Pass, but there was a striking seasonal difference in their presence. Harbor porpoises were less likely to be seen in the summer months (June-August) and were found in smaller groups. Thankfully for us being in the field is fun even when porpoises aren’t around!
So those are some of the highlights from the paper, I hope you enjoyed learning more about this fascinating, little-understood species! We look forward to discovering more about their lives and sharing the information with you, along with other topics such as harbor seals, birds, the Salish Sea, and cool stories from around the world, so stay tuned for more blogs in the New Year!
To check out the full article, go here: http://onlinelibrary.wiley.com/doi/10.1111/mms.12459/abstract; or email email@example.com.
Dr. Cindy Elliser
Pacific Mammal Research