WARNING: This post contains photos and information regarding deceased animals.
179 short-beaked common dolphins stranded on Cape Cod in the past 5 weeks. 108 of these animals were already deceased when they were reported or found on the beach by staff and volunteers. You may be wondering what happens to these animals. Although a necropsy, or post-mortem exam, was performed on some of these animals to try to identify the cause of death, unfortunately a necropsy could not be performed on all carcasses available as live animal's continued to pull all staff and volunteers away from the lab and into the field.
IFAW's Marine Mammal Rescue Program, with the help of their volunteers, collect basic data on each carcass, just like we do when deceased marine mammals wash ashore in our territory. Since so many dolphins were stranding on a daily basis, volunteers and staff would scout particular areas in search for carcasses in order to collect the basic data. This information proved important to collect as it helped IFAW better grasp the magnitude of this unprecedent stranding event. They can also use these data at a later time to better understand factors contributing to the strandings, such as group dynamics.
One location I was assigned to with a team was Lieutenant Island in Wellfleet. Here is what those days consisted of...
The above photo is from standing in the marsh of Lt. Island in Wellfleet. The tidal fluctuations and mud flats make this island a popular location for dolphin strandings. With only a small wooden bridge to access the island by vehicle, which isn't accessible at high tide (perhaps some forshadowing?), my team and I were assigned to spend some time here in search for carcasses as well as monitor the bay for live dolphins.
So what happens when we find a dead dolphin?
When a carcass is found, we collect basic data on the animal such as location (latitude and longitude), gender, total body length, phase of decomposition, and a skin sample is collected. We also examine the animal externally and note nutritional condition and any unusual pathogies. All this information is gathered and will be submitted to NOAA, where a database is utilized to organize this information for future research or monitor stranding trends.
Above, Katie and I collect information on this common dolphin (this was actually a case in Brewster, but similar to the cases we found on Lt. Island). After collecting the data we mark the animal using a paint stick (note the orange 'KP1' on the side) and apply a tag to the dorsal fin. We do this to keep track of which carcasses were already responded to. With over 100 animals to work with, we do not want to repeat our efforts and unfortunately we could not collect every carcass for a full necropsy. We use different color tags for dead animals than we do for live, so the white tag on the dorsal fin, seen in above right photo, indicates a dead animal we responded to. Each organization uses a different color and within the organization different colors are used to differentiate between a live stranding and a dead one. For example, IFAW uses orange dorsal fin tags for live stranded dolphins that are released. This is valuable if it is resighted in the wild as seen in an IFAW case here, or if the live animal restrands.
One of the days on Lt. Island, we split up into teams to look for carcasses when a pod of 100+ live dolphins were swimming toward shore. IFAW's team was able to quickly get in their boat and herd these animals successfully. Some NEAQ volunteers and myself were sent to monitor the herding efforts from Lt. Island while other teams were dispatched to other locations for monitoring or for live animal response. You can read more about IFAW's herding techniques in Connie's blog.
Above, after IFAW successfully herded the dolphins, myself and NEAQ volunteers Maria and Taylor snapped a quick photo before heading off to assist in releasing 2 live animals that stranded in Brewster. See Connie's post here on that release.
The day after the above photo was taken I went back to Lt. Island with another team to finish up the data collection and make sure those live dolphins weren't back in the area. We worked on the other side of the island and found four additional carcasses that were not tagged, indicating they were new animals from the 7+ we found on this island in the previous days. It was getting to be high tide, so we worked quickly to finish data collection and get visuals on the bay in preparation for potential live dolphins in the area. Luckily there were no live animals that we could see.
High tide came and went and we were ready to head back to meet up with the IFAW group for our next assignment when...wait...where did the bridge go?
We ended up being stranded temporarily (photo above), but don't worry, the tide receded quickly (and gave us more time to double check the area) and we eventually made it off the island.
We made it over the bridge when one of the volunteers shouted 'a dolphin!' and sure enough, over to our left in Loagy Bay was a dorsal fin making appearances in the water. (We were so close to getting away!)
The 'dolphin' turned out to be a harbor porpoise. We monitored it for quite some time until we lost sight of it. With the sun starting to set and no sign of the animal, we decided to call it a day. Luckily, I haven't been back to that island since.
The numbers of strandings have dwindled down, but there is still a large amount of data to be organized, necropsies to be performed, and gear to be restocked and cleaned for the IFAW team. They have done amazing work with this mass stranding. We still need to touch on reasons why mass strandings occur (i.e. there have been questions about Navy sonar being a cause but see IFAW's blog here for an explanation) so check back!
~Kerry
