iSeal checks in from Monomoy, Cape Cod

On September 15, 2012, a grey seal – named Bronx – was released from West Dennis Beach on Cape Cod with a tag on it’s back. After about 10 days cruising along the shores of Cape Cod, the seal hauled out between Chatham and Monomoy and delivered the first bundles of information about it’s movements and diving behavior back to us. Pretty cool stuff. I’m calling Bronx our ‘iSeal’ (hope Apple doesn’t mind…).

The animal had recovered from a fisheries interaction thanks to the rescue and rehabilitation efforts of folks at the International Fund for Animal Welfare (IFAW) and the Mystic Aquarium. After being nursed back to health the animal was fitted with a new type of telemetry device to assess it’s movements post release. This device, referred to as a ‘GSM tag’ (created by the smart people at Scotlands Sea Mammal Research Unit) combines a Fastloc Global Positioning System (GPS) receiver with a depth sensor and thermistor system to capture details on the seals movements, diving behavior and water temperature on foraging trips away form the beach. However, instead of relying on expensive satellite systems to relay these data back to us, the tag stores the data until the seal returns to the beach. When it does, the tag links into the local cellular phone system and transfers the data across this connection to computers ready to crunch the data. Thanks to Lisa Sette at the Provincetown Center for Coastal Studies (PCCS) for her heroic efforts in mapping out GSM coverage on Cape Cod – that was critical to ensure that we could execute the study successfully!

Anyone out there with an iPhone and the “Find My Friends” feature enabled can relate to this, and our ‘iSeal’ Bronx uses essentially the same technology to give us new insights into what seals do when they leave the beaches and disappear from view. The seal clearly doesn’t have pockets to put the tag in, so we had to attach it securely to the seal before he headed off. The attachment process is benign – the tag is simply glued onto the fur of the seal and the tag will be shed when the seal molts sometime in the next year or so. The tag was expertly fitted by Rob DiGiovanni from the Riverhead Foundation.

[photo size=’medium’ align=’right’ title=’Bronx Tracks Sept 15-25′ link=’http://superpod.ml.duke.edu/johnston/files/2012/09/hg358locationsfirstrip.jpg’ icon=’zoom’ lightbox=’image’]http://superpod.ml.duke.edu/johnston/files/2012/09/hg358locationsfirstrip.jpg[/photo]Bronx is the first ‘iSeal’ on the U.S. east coast, and this initial deployment is part of a larger collaborative project amongst Duke University, IFAW, PCCS and Riverhead that aims to assess the roles that grey seals play in the local marine ecosystem and how their movements overlap with fishing gear and effort. We also hope that these types of devices will help us understand the movements of seals around the Cape Cod region in relation to the growing number of white shark predators found there.

The images in this post provide some details on the data provided by the tag when the seal calls in over the network. The first image at right is the track of the seal over about 10 days. The animal made a series of movements north along the Cape, and then moved around the northern tip into the hook. After a short stint there it moved back offshore the northern end of the Cape and concentrated some foring effort in a localized region. Then is moved back inshore and along the beach south to Monomoy, to join a colony of grey seals for the past two days.

[photo size=’medium’ align=’right’ title=’Bronx Temp Profiles Sept 22′ link=’http://superpod.ml.duke.edu/johnston/files/2012/09/temp_44915004_2012-09-22.dat_.png’ icon=’zoom’ lightbox=’image’]http://superpod.ml.duke.edu/johnston/files/2012/09/temp_44915004_2012-09-22.dat_.png[/photo]The thermistor system on the tag provides us some cool glimpses of how water temperature that the seal encounters varies on dives. Temperature is a key variable for life in the ocean. It likely structures the availability of prey of these animals to some extent, and has implications for the thermoregulatory physiology of the seals themselves. The image at right shows temperature profiles obtain by the tag as the seal swam up to the surface on September 22nd. The vertical access labeled pressure gives details on the depth in meters and the horizontal axis provides water temperature values at that depth.

Using an archival tag coupled with high-bandwidth wireless communications gives us the ability to collect, store and transmit a lot of data. This means that the information on diving behavior of a tagged seal is not decimated and summarized into small amounts of information as done with satellite linked tags. In our case we get everything, the entire dive profile of the animal is sent back to us, providing a the complete story of the animals diving habits. Below is a KML of the movements of Bronx. Some of the tracks are close to shore or on it because the GPS doesn’t sample as frequently as the pressure sensor. But if you are good with Google Maps, you can zoom in on individual locations and really see what the seal was up to.
[divider] [xmlgm {http://www.duke.edu/~dwj2/hg34.kml} maxlat=42.5;minlat=41.4;maxlon=-69.76;minlon=-70.5;maptype=G_SATELLITE_MAP;gpxview=all;width=650;height=650;align=center] [divider] I want to end the post with a cool link into another GPS tagging project that links into this one nicely. Greg Skomal and his colleague Chris Fischer recently tagged a great white shark just off the beach in Chatham. There is a great story about this on the NY Times here. The image below is a screenshot from Chris Fisher’s tagging website that illustrates where Genie the white shark was tagged and where she has gotten to over the past few days. The red line in the center of the image illustrates that the shark was tagged directly offshore of the seal colony at Chatham and then moved south to Nantucket. This track really illustrates the interesting predator/prey relationships amongst the grey seals lounging on the sand beaches of Monomoy and the white sharks waiting offshore for a fresh seal meal.

[photo size=’large’ align=’right’ title=’White shark tagging and tracker’ link=’http://superpod.ml.duke.edu/johnston/files/2012/09/genieshark.png’ icon=’zoom’ lightbox=’image’]http://superpod.ml.duke.edu/johnston/files/2012/09/genieshark.png[/photo] [share_buttons]