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Habituation in Harbor Seals

There is a long history of habituation of animals being an interest to humans. Habituation was originally defined by Groves P. M, Thompson R.F, and Spencer W. A., in 1966, but was later revised and the updated functional definition of habituation was published in 2009 (Rankin C. H. et al, 2009). As defined by Rankin C.H. et al, habituation is a behavioral response that decreases due to recurrent stimulation. Habituation is relevant in the understanding of current animal behavior and interactions with humans. As global population continues to rise, animal-human interactions increase and a better understanding of how these interactions effect or potentially change behavior is pivotal to creatinghealthy boundaries between animals and people. Habituation is Harbor seals (Phoca vitulina) has been studiedunder multiple conditions including wild and captive settings and specifically with boaters, noise, and handlers. This paper aims to summarize Harbor seal habituationresearch and suggestwhere there is ability for future work.

When studying Harbor seal habituation to humans in the wild, haul out behaviors were looked in conjunction with boating activity in the area. In a study conducted at the Bair Island Refuge, San Mateo California, it was determined that seals had become habituated to boats passing the haul-out site (Fox K. S, 2008). 70% of seals remained hauled-out during boating events whichsuggest that seals on this haul-out are comfortable with passing watercraft(Fox K. S, 2008). Fox K. S.also notes that in the 13-monthspan of data collection, swimming seals would follow the research watercraft and make eye contact as well as swim parallel towalking researchers. The conclusion that seals can be habituated to disturbances near haul-out sites is supported by Bonner (1982), Johnson et al. (1989) and by personal observation in Chatham, MA. Besides boat disturbances, Harbor seals have been documented to become habituated to soundsunderwater. Therehas been research on Harbor seal habituation to noisescompletedon both wild and captive animals. It has been observed in wild Harbor seals that they can discriminate between the calls of local versus unfamiliar underwater orca calls and react to each accordingly(Deecke et al. 2002). Seals were found to be unresponsive to native fish-eating orca calls buthad highresponsiveness to unfamiliar and mammal-eating orca calls suggestingselectivehabituationto local and nonpredatory orca calls(Deecke et al.2002). The ability to selectively habituate like this is specifically advantageous in predation detection. When captiveHarbor sealswere exposed to underwater broadband pulse sounds, it was determined that Harbor seals easily habituated to the noise and became unresponsive(Kastak D. and Schusterman R.J. 1998). The ability for Harbor seals to both selectively habituate specific whale calls and pulse noises might suggest they can also be habituated to noises coming from boats, planes, and underwater missiles, which continue to encroachon their natural habitat.

Habituation to humans has also been studied in captive situations with Harbor seals. Harbor seals have been found to become easily habituated to their handlers as well as able to identify individuals as familiar and unfamiliar (Taylor et al., 1998). When specifically looking at orientation time, time spent facing a handler, it was found to be significantly (P=0.03) higher towards the unfamiliar human and to decrease over time, suggesting habituation (Taylor et al, 2008). The ability for Harbor seals to become habituated to and familiar with a handler is supported by Morton D.B. (1990) who suggested animals connect handlers with the arrival offood or pain. The habituation of seals in human care has important implication in the field of marine mammal rehabilitation. The data collected by Taylor et al. could suggest that the often-high number of part time volunteers in rehabilitation settings decreases habituation, but could increase vigilance, potentially causing stress. Further research in this area is needed to fully understand the impact of a highly variable versus highly limited number of handlers in rehabilitation settings.

The review above sheds light on the vast amount of research done on Harbor seal habituation and specifically Harbor seal habituation to humans and human actions. The research done on wild animals indicates the importance of giving these wild animals space,while the research completed on captive animals has wider implication in the field of rehabilitation and captive animal management. As mentioned above, further areas of researchcould include habituationto boat sounds underwaterand habituation of wild animals to human caretakers in rehabilitation facilities.

References:

Bonner, W.N. (1982) Seals and man: a study of interactions. Seattle, WA.University of Washington Press.

Deecke, V. B., Slater, P. J., & Ford, J. K. (2002). Selective habituation shapes acoustic predator recognition in harbour seals.Nature,420(6912), 171-173.Fox, K.S. (2008).Harbor seal behavioral response to boaters at Bair Island Refuge[ProQuest Dissertations Publishing]. http://search.proquest.com/docview/304825168/

Johnson, S.R., J.J. Burns, C.I. Malme, and R.A. Davis 1989. Synthesis of information on the effects of noise and disturbance on major haulout concentrations of Bering sea pinnipeds. LGL Alaska Research Associates Report MMS,88-0092.

Kastak, D., & Schusterman, R. J. (1996). Sensitization and habituation to underwater sound by captive pinnipeds.The Journal of the Acoustical Society of America, 99(4), 2577-2603.

Morton D.B. (1990) Adverse effects in animals and their relevance to refining scientific procedures. ATLA 18:29-39.

Rankin, C. H., Abrams, T., Barry, R. J., Bhatnagar, S., Clayton, D. F., Colombo, J., … & McSweeney, F. K. (2009). Habituation revisited: an updated and revised description of the behavioral characteristics of habituation. Neurobiology of learning and memory,92(2), 135-138.

Taylor, A., Davis, H., & Boyle, G. (1998). INCREASED VIGILANCE TOWARD UNFAMILIAR HUMANS BY HARBOR ( PHOCA VITULINA ) AND GRAY ( HALICHOERUS GRYPUS ) SEALS. Marine Mammal Science, 14(3), 575–583.

Research review paper written by summer intern, Morgan Y. Morgan is a student at the Colorado State University studying Zoology.

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