Behavioural responses of Cape fur seals (Arctocephalus pusillus) to swim-with-seal tourism activities in the Robberg Marine Protected Area in South Africa

Abstract

Marine mammal tourism is growing, and experiences that provide close-up encounters are becoming more popular. One of such activity is the swim-with-seal (SWS) activity, which occurs within two marine protected areas (MPAs) in the Western Cape Province of South Africa, namely at the Robberg MPA in Plettenberg Bay and at sites in the Table Mountain National Park MPA. Information regarding SWS activities and their impacts on Cape fur seal Arctocephalus pusillus pusillus colonies is limited. This study aimed to assess the impacts of swim-with-seal (SWS) tourism on the behaviour of seals at the seal colony in the Robberg MPA. This was conducted through a modified Before-After-Control-Impact (BACI) behavioural study designed for simultaneous observations of Impact and Control areas (site factor) Before, During and After SWS activities (phase factor). Observations were carried out from an elevation at distances from the experimental sites that precluded observer impacts, with sequential photography of the colony providing the basis for enumerating seals in different behavioural categories and comparing these between sites and between phases, as well as interactive effects of site and phase. Behavioural categories included “primary” behavioural categories (lying down, sitting, moving) and “secondary” behavioural categories (grooming, nourishing, interacting, alertness) that seals within one of the primary categories could be secondarily engaged with. Between November 2020 and October 2021, 54 SWS trips were observed. Concerning the primary behaviour categories, seals in the colony were mostly observed to be lying down (74%) in relation to sitting (23%) or moving in the colony (3%). While most seals were at rest during the tourist activity, it was clear that SWS activity and associated boat approaches brought about certain behavioural responses in the colony, as shown by changes in some behavioural categories. However, even where there were significant differences in behaviour between sites and/or phases that could be attributed to tourist activity, it was only a small proportion of animals in the study area that were affected. For example, whereas the proportion of animals sitting relative to the numbers lying down in the Impact site increased as SWS activities commenced, the numbers of animals showing a switch in this behavioural posture were only approximately 2% of the numbers of animals at the site, on average. Furthermore, although the proportion of animals in the Impact site that showed alert behaviour (a secondary behavioural category) in response to activity increased statistically compared with the earlier phases or versus the Control Site, it still represented only about half a percent of the animals at the Impact Site, on average. No extreme reactions by seals, such as stampedes, were observed throughout the study. Modelled responses of seals to the distances of the boat or swimmers to the colony, indicate that some responses (certain behavioural categories) decline with distance to the colony, suggesting that the seals respond mostly to the activity when they first become aware of the tourist presence but decline as they become used to it. Overall, the reactions of seals point to the habituation of the seals to the tourist activity. The results also attest to the efficacy of the modus operandi adopted by the tourist operator during the study period, which is informed by legislation and a voluntary Code of Conduct, with the aims of avoiding disturbance to the colony and ensuring human safety.