Below is a short article that I wrote for the newsletter of the South African Environmental Observer Network (SAEON) about two seals that were released earlier in the year. HOPE & MINION May 2014 saw two very unusual passengers aboard one of SAEON’s boats. The Honkinii was carrying two young seals that were being taken out to sea for release. And each carried a device that would allow its movements to be monitored while it was at sea. As most of us know, the southern African coastline is home to the Cape fur seal. They are found from southern Angola to Algoa Bay and are familiar to most South Africans. Few people know, however, that another species of seal regularly visits South Africa’s coast. Subantarctic fur seals are found in the waters of the Southern Ocean and haul out to breed on islands such as Marion Island, which is some 2000 km south of South Africa. But this is a wide ranging species and every winter a number of them haul out on South African beaches. While many of these seals are in good condition, others are obviously the worse for their long journey and are starving or suffering injuries. One of SAEON’s partners, the Port Elizabeth Museum at Bayworld is called out in such cases in the Eastern Cape. Our experienced team knows how to capture these animals and rehabilitate them. We have had great success in getting the animals ready for release in the past but we do not know what happens to the seals once they are set free. They are fitted with plastic flipper tags, but these only allow for visual resighting. It is thus an important step forward that a number of individuals and organisations have started a programme to monitor the movements and survival of these animals. These organisations include the Department of Environmental Affairs (DEA), Seaworld in Durban, The East London Aquarium, the Mammal Research Institute at (University of Pretoria) and Bayworld. This programme saw Minion, a young male Subantarctic fur seal fly into Port Elizabeth from Seaworld in Durban at the end of April. A few hours later he was joined by Hope, a young female Cape fur seal that was driven down from the East London Aquarium. The next day both seals were fitted with satellite tags under anaesthetic by veterinarians Alejandra Vargas and Andrew Mackay, and biologists Mike Meyer of the DEA and me. These tags would allow us to follow the seals’ movements at sea and hopefully determine whether they survived and returned home, and therefore whether our efforts to rehabilitate them were valuable. The edge of the continental shelf offshore of Port Elizabeth was chosen as the site for release because it was hoped the southward moving Agulhas Current would act as a conveyer belt to direct Minion back to his home island in the distant waters of the Roaring Forties. All was set for the release except for the boat. The boat normally use by Bayworld had been damaged in an accident and the incipient Tuna Classic had ensured that most others were unavailable. Fortunately Tommy Bornman of SAEON came to our rescue at this moment with the offer of the use of the Honkenii. The next morning both seals were loaded onto this trusty vessel and, under the able skippering of Anthony Opperman, were taken out to sea. Port Elizabeth’s unpredictable weather ensured that we were not able to take the seals out quite as far as we wished but nevertheless they were released quite a distance from the shore. Hope’s turn was first. We did not want to release her too far out since she was a Cape fur seal. She initially splashed around in the water, cleaning herself and then swam circles around the boat before we could head off. Minion was set free further out. We barely saw him after release. He was in a hurry and swam off without a backward glance. The intervening months have brought us very different tales for the two seals, via satellite. Hope chose to visit the shore several times over the next few days. Unfortunately we soon lost her signal. It is very likely that the antenna of her device was damaged by one of these shore visits. Minion on the other hand chose to tell us the tale of his 3700 km swim over the next two months. With little deviation, he headed south west and was soon in the roaring forties. He then curved to take a more westerly track and at the end of seven weeks was south of Gough Island. This site is home to half the world population of Subantarctic fur seals and is likely Minion’s home also. Unfortunately we will never know for certain since his device has stopped transmitting, likely because of battery failure. However, the data has shown, for this seal at least, rehabilitation and release were a success. And from analysis of the data received via satellite for this, and subsequent seals, we will gain insights into their biology. The photo shows Minion (below) and Hope (above). The map shows the track of Minions long swim.
Posted on: Fri, 24 Oct 2014 20:50:16 +0000
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