Telemetry on Wild Sea Lions: Impacts of Our Research
By Markus Horning
As scientists, we do not want our research activities to change the very information we are collecting. For example, when studying the survival of sea lions, we have to be absolutely certain that we are not affecting their survival with our surgeries or implants. More than that, from our respect for the animals we study, we have concerns for the well-being of the individual sea lions we work with. These are the main reasons why we kept the first few implanted sea lions under close observation at the Alaska Sea Life Center for two months after surgery.
How painful are the surgeries for the sea lions?
The surgeries are done under full gas anesthesia so that the animals do not feel any pain during the procedure. Just before waking up after the surgeries, the sea lions receive an injection of a drug that reduces inflammation and also acts as a painkiller. This type of drug is called an ‘analgesic’ and lasts for about three days. From our observations at the Alaska Sea Life Center, we learned that the sea lions have exactly the type of response to a fairly substantial surgery that one would expect. The animals show some pain and discomfort for the first few days after surgery. However, just like with our pets at home it is very hard to find out just how much the surgery is troubling the animals. After all, we can’t just ask them like a doctor would ask a human patient. Instead, we studied their behavior for any changes in movement, posture or activity after surgeries that could be related to pain. Using results from that study, we are able to select pain management drugs that lead to smaller changes in behavior after surgery.
How long does it take for the surgical incision to heal?
To study this, we collect small blood samples from the sea lions about once per week. Just like in a hospital, we check the blood for various indicators of stress and wound healing. We can measure the levels of specific hormones that our bodies release when we get ‘stressed out’. These so-called ‘corticosteroids’ showed us that the surgeries are actually less stressful than capture and transport to our facility. We can also measure the levels of certain white blood cells (called ‘lymphocytes’) and proteins (in this case the so-called ‘haptoglobins’) involved in the healing process. When our own medical doctors want to see if our bodies are fighting off a problem from a wound, they check for the number of lymphocytes in our blood. If our body is sending in the immune system troops to deal with intruders, it produces more lymphocytes and their count in our blood goes up. Our sea lions showed an increase in lymphocytes in the week following surgery, but by two weeks after the surgery things were already back to normal. However, it takes longer than that for a wound to completely heal over: the sea lions produced the most haptoglobin proteins that aid in the healing process during the third week after surgery. Their levels were back to normal about 45 days after surgery. That is how long it takes for the surgical incision to fully heal, though the animals are already moving around, swimming and diving well before then.
If it takes 45 days for the wound to completely heal, why are we now releasing animals after only 1-2 weeks?
Though it does take 6 weeks for all healing to be complete, the animals move and dive well much sooner, and the tissue is strong enough to withstand the abuses everyday life throws at a young sea lion. Since captivity is stressful on its own and the frozen herring we feed the animals may not be as tasty as fresh wild salmon, it is in the best interest of the animals to be released as soon as possible. However, if something were to happen to our animals in the first six weeks after surgery, we could not be sure whether this might have something to do with our surgery. Only after six weeks do we feel confident that the animals no longer show any signs of the healing process. This is why we track the animals after we release them as early as one week after surgery, using external satellite tracking devices that we glue to the fur on the back. These devices only allow us to track the animals for about one to six months since they fall off when the sea lions shed their fur once a year. This is called the ‘molt’ and is the main reason why we need LHX tags to get data from animals beyond one year. From the data sent by these external satellite transmitters, we have learned that all 32 animals we released between 2005 and 2010 have survived beyond the 45 days needed to no longer feel any effects from surgery. In fact, we have seen many of our study animals well after their external tags fell off. On our most recent capture cruise in Prince William Sound in June of 2011, we saw the very first female that was released with LHX tags in November of 2005 – she is still doing well and looking healthy more than five years later.
Do the animals behave normally after their release from extended captivity?
The external devices told us not only that all 32 animals survived past the first 45 days following surgery, these devices also transmitted data on the sea lions behavior: how deep they dive, how long their dives are, where they go and how active they are. From this we learned that these 32 sea lions with LHX implants behaved pretty much exactly as 23 of their buddies that also stayed at the Alaska Sea Life Center for up to eight weeks but were released without any LHX implants (what scientists call the ‘control group’). And all of these animals behaved like another ‘control group’ of animals that were captured and received external satellite transmitters, but were released immediately after capture and never took up temporary residence at the Alaska Sea Life Center.
Is the survival of LHX-implanted sea lions different from wild Steller sea lions in the region?
No, it is not. We have compared the survival rate that we can calculate from LHX tag data returns to the survival rate that the National Marine Mammal Laboratory of the National Marine Fisheries Service has estimated using resightings of individually marked sea lions. So far, there appear to be no differences in survival rates.
If the Fisheries Service can estimate survival from markings, why then do we need to use LHX tags?
There are many good reasons, but the foremost is that searching for marked animals does not tell us when, where and why they die if we never see them again. LHX tags give us just that crucial information.
You can find more information on our impacts studies in the following scientific publications that are also accessible through our published papers page: