LHX tag implantation in harbor seal pups

PAPER IN A NUTSHELL

Intraperitoneal implantation of life-long telemetry transmitters in three rehabilitated harbor seal pups. Markus Horning, Martin Haulena, Justin Rosenberg and Chad Nordstrom. BMC Veterinary Research 2017;13:139.

Does wildlife rehabilitation work, and what is its impact on wild populations?

Ever wonder what happens to rehabilitated seals after they are released from stranding response centers? Well, we certainly do. Depending on the outcome, wild animal release after rehabilitation may arguably alter “natural” selection. That leads to these big questions: how do rehabilitated animals fare after release, can they survive, for how long, and – the most important question: will they breed?

Until recently, there was no effective way to determine post-release survival and reproduction, especially in remote locations. Now however, we have a new high-tech tool, the life history transmitter (LHX tag) that can answer these questions (check out www.sealtag.org).

LHX tags can tell us how long an animal survives, when, where and how it dies, and whether a female seal may have given birth to any pups (see also this previous 60 North blog entry). LHX tags are surgically implanted under gas anesthesia. Since this is a major procedure, the first applications in a new species are done under very controlled conditions, so we can closely monitor the animals after surgery.

In our just published paper, we describe the surgical procedure and report on post-surgical recovery of three female harbor seal pups that each received a single LHX tag at the end of their rehabilitation procedure, at an age of about six weeks. We kept the three pups for about 10 weeks after surgeries at the Vancouver Aquarium Marine Mammal Rescue Center. During this time, the animals were observed, weighed, and had blood samples taken weekly at first and then every other week. Before their release, we attached external satellite tracking devices to them, to monitor their movement.

Here is what we learned:

LHX tag implant surgeries were completed without complications in under one hour. The animals woke up quickly from anesthesia sessions that lasted up to 1 hour and 20 minutes. Appetite, food consumption and weight gain following surgery and until release were within the overall averages for rehab seals of this age. All three animals showed the expected inflammatory response to surgery: blood values changed the way they typically do when a body is dealing with a physical injury. The clearest and most pronounced responses were increased counts of white blood cells, neutrophils and monocytes.

These values returned to ‘normal’ (averages for female rehabilitated seals of comparable age that did not receive implants) after no more than five weeks. We found no signs of infection or immune response to the tags. X-ray images showed the tags moving around in the abdominal cavity. Following release, we tracked the movement of the animals for about nine months. Then the external tags exhausted their batteries or fell off during the molt.

Why is this important?

So far, there is no indication of any unexpected, potentially problematic response to surgeries or tags. That means we now know that we can use these tags in young harbor seals. We do however need to proceed cautiously and continue to monitor for possible effects we may not have detected in our small initial sample size, or effects that only show up after a much longer time. We also know that for any vital rate studies (those that provide survival and reproductive data), we need to confirm survival of any study subject over at least the time frame of the observed inflammatory response (5 weeks). If an implanted, released animal were to die within five weeks of surgery, we could not be sure that its demise might not be related to tags or surgeries. We can now proceed with additional studies using LHX tags in harbor seals, for example to determine the success of rehabilitation programs, or to collect vital rate data from wild animals in remote places.

So, stand by for future papers on LHX tag applications in harbor seals.

The full original paper can be downloaded as a pdf file here.

Written by: Dr. Markus Horning, in collaboration with–

Martin Haulena, DVM is the Head Veterinarian at the Vancouver Aquarium in Vancouver, British Columbia, and has pioneered the implant surgeries described in this paper.

Justin Rosenberg, DVM is a Zoological Medicine Resident in the Department of Small Animal Clinical Science with the University of Florida Gainesville. He did a fellowship in Aquatic and Marine Mammal Medicine at the Vancouver Aquarium at the time of this project.

Chad Nordstrom has been a Research Assistant at the Vancouver Aquarium since 2012. He holds a M.Sc. in Zoology from the University of British Columbia.