This post belongs to a series written by students in the Conservation Biology course BSC4052 at the University of South Florida. This course provides an overview of major themes in conservation practice and related applied problems in biology, including: population ecology in the context of conservation, patterns of diversity, valuing diversity, threats to diversity, management actions and strategies for preserving diversity.
Article Reference: Salazar-Casals A, Arriba-Garcia A, Mignucci-Giannoni A, O’Connor J, Rubio-Garcia A. 2019. Hematology and serum biochemistry of harbor seal (Phoca vitulina) pups after rehabilitation in The Netherlands. Journal of Zoo and Wildlife Medicine (Washington D.C.) 50:1021-1025. https://doi.org/10.1638/2018-0098
Caroline Reges just graduated from the University of South Florida with concurrent degrees in Animal Biology and German, and will be starting her Masters in Biology at Miami University this fall. She is interested in researching how animals physiology is impacted by the changing climate.
For many animal lovers, working as a seal rehabilitator seems like a dream job. You spend all day taking care of baby seals and release them when they’re strong enough to live on their own. But have these types of rehabilitation centers done enough research on what makes a seal ready for release? Could the time spent in rehabilitation cause the seals future problems or make it harder for them to survive in the wild? If so, should we stop seal rehabilitation all together?
Why rehabilitate seals?
Marine mammal populations are declining due to pollution, prey depletion, and incidental catch in fishing equipment. These factors lead to many injured and malnourished seals which could benefit from rehabilitation. Rehabilitation involves taking in injured or weak seals washed up on shore, giving them food and medical attention so they become stronger, and then releasing them back into the wild. Rehabilitation can help support population size when population numbers are low and is especially crucial for threatened or endangered populations.
Sealcentre Pieterburen in Pieterburen, the Netherlands, takes in mostly young, weak and/or injured harbor (Phoca vitulina) and gray seals (Halichoerus grypus) and cares for them until they are strong enough to be released. Birthing season for gray seals is winter, and summer for harbor seals, so those seasons bring a high volume of seals to the center, while spring and fall have few seals. Currently, a seal is considered ready for release if they have reached a healthy weight. However, to understand how the rehabilitation process could be improved, a recent study investigated normal blood values for harbor seal pups to develop a baseline for blood and biochemistry ranges after rehabilitation.
What can we learn from seals in rehabilitation?
When seals first enter the center, they are usually very young. Newborns usually have a very immature immune system, which is built up during the first few months of their lives. Seals receiving care at Sealcentre Pieterburen gain weight before being released, but because of their age their blood ranges can be lower than wild adult harbor seals. When these seals have reached a healthy weight, they get released back into the seal population in the Wadden Sea. Anna Salazar-Casals and colleagues from Sealcentre Pieterburen showed that seals leaving the Sealcentre Pieterburen had lower overall white blood cell, lymphocyte, and granulocyte levels than wild adult harbor seals. How this impacts seals after being released into the wild is not known. Nor do we know how the blood values of rehabilitated seals compare to seals in the wild of the same age. Normal diving and sea water exposure is necessary to stimulate certain reactions within the body to produce red blood cells which seals at the center can’t get.
What should seal rehabilitation centers do?
Seal centers need to continue research efforts to get a better understanding of the best way to rehabilitate seals, perhaps by comparing rehabilitated seals to wild seals of the same age in order, to produce more specific standards of what qualifies a seal as “ready for release”. This would allow rehabilitation centers to improve their rehabilitation methods and the success of seals released in the wild. Currently, in this region a healthy seal pup weighing about 27-30kg is ready for release. Continued monitoring of wild seal population sizes will also help us understand how many seals should be rehabilitated to maintain a healthy population. Injury by humans causes a majority of the seals to be brought into the center of the first place, which is caused partially by a lack of information. Seal rehabilitation centers play an important role in educating the public about seal populations, so these discoveries must spread to promote scientists to initiate more studies.
How can you help the seals?
You don’t need to work as a seal rehabilitator to benefit seal populations. Advocacy with local governments to limit the human activities that affect seal populations means that fewer seals end up in rehabilitation in the first place. All seal advocates should know that if you see a lone baby seal crying out, to leave it alone, and call a seal rescue center so they can check on it. Too many perfectly healthy baby seals get mistakenly brought into rehabilitation because people don’t know what a seal in need of care looks like. The public can educate themselves on issues relating to seals, which allows the community to begin taking more measures to protect them, including advocacy, volunteering, and donations.