Fur seals of Open Bay Islands enjoy a personal service

Press, 8 July 1986, Page 21

Fur seals of Open Bay Islands enjoy a personal service

Off the coast of Haast, the Open Bay Islands are home to a mixture of wildlife. Penguins strut through the low bush, ferhbirds and fantails dart, shags inhabit the sea cliffs, and wekas (introduced birds) roam. There may even be an indigenous gecko — if the wekas have not eaten them all. STAN DARLING visited the small island group last week, with Peter Carey and Craig Franklin, University of Canterbury zoology graduate researchers, to check on the fur seals.

Pieces of pipe lie scattered on the jagged rock reef, wrenched from concrete foundations. They are remnants of a summer experiment that now has to be rebuilt — a series of “seal gazebos” where the fur seals of South Westland’s Open Bay Islands, off the coast of Haast, can find shade. Peter Carey, a University of Canterbury zoology researcher doing his Ph.D. work on the fur seal, looks around for the plywood roofs of his shade shelters. They are nowhere to be seen. In a seawater-filled chasm further up the coast of Taumaka Island, seals still here for the winter cavort with a small section of board, swimming round it and tugging it with their teeth. It might be all that is left of Carey’s attempt to manipulate habitat conditions on the rookeries. This time of year, most of the males that come here for the breeding season are at their bachelor beaches, such as those on the Kaikoura and Otago pen-

insulas. Most of the seals getting about at leisure, with no male territorial boundaries to worry about, are females and pups. Things are different during the summer, when Carey lives on the island for several months to do his site selection mapping. “This is one of the few New Zealand animals that can beat you up if it wants to,” says the researcher, who carries a stout anti-seal device (a stick) in his travels. The stick is used to prod male seals out of the way when they have taken up positions on the track through the scrub, and to ward them off when they are less than persuadable. So far, in two breeding seasons, he has not been bitten, but there have been close calls. Once, he had to leap a 1.2-metre gap in the rocks to avoid a bull seal lunging at his ankles. Another time, he was chased by a large bull and had his forward progress impeded by a sub-adult male running too slowly in front of him down a track bordered by dense undergrowth. There was no place to

sidetrack, and the bull was gaining. Carey finally prodded the young male to hurry it up. Sitting in a hide only a month after his arrival the first season, he had two male seals, one being chased by the other, come within less than a metre of his position. Carey’s growling and howling

were the only things that kept the seals from hitting him. He tore a board off the hide to defend himself if they came closer. With Craig Franklin, a university colleague studying the physiology of salmon, Carey moves down the rocks on one of his study sites. He checks the ends of probes that allow him to check the temperature of sites that seals prefer during certain times of day. They move cautiously, trying to avoid spooking the seals into startled movements that will make them fall off the steep rocks. At the bottom of a steep-sided rock pit, about three metres deep, lies an unmoving pup that seems to have fallen recently (see photographs above). The seal, about six months old, appears to be healthy, if shaken by the fall. There is no way for the pup to get out. Carey returns to the hut on the northern end of the island to get his gloves. He might be able to save the pup without getting bitten. He lowers himself into the hole, then comes up slowly behind the wary pup, which is so fat and healthy-looking that there is no scruff to grab. Carey grasps him firmly behind the neck and lifts him out as he growls, but does not struggle. The pup takes a quick look down at his rescuer before he scurries off towards the sea. Carey hoists himself out and wanders off to look at some rock

pools he has built in a study area by constructing low concrete dams in depressions. The pools help him observe how the seals, males and females, use water in the breeding territories to cool off.

He has closed or reduced the area of some pools by laying plywood and a rock surface over them, creating new pool beaches and successfully encouraging movement of territorial boundaries. Since last season, however, the same winds and waves that destroyed the shade umbrellas have also removed any trace of the pool covering.

Carey’s work on microhabitat selection and sexual preferences is building on foundations laid by two researchers on Open Bay Islands in the 19705. Before that, not much work had been done on the New Zealand fur seal. Carey, an American from Cincinnati, came to New Zealand after getting an undergraduate degree in natural resource management at the University of Alaska. Previous fur seal re,searchers were a Canadian and an American. One reason fur seals distribute themselves the way they do on the exposed rocks seems to be heat. With their thick fur and blubber, they have trouble getting rid of excess heat on land.

Heat can be gained or lost most easily through their flippers. To regulate their temperatures, they swim or enter a land pool, often just a puddle large enough to contain their flippers.

They also go to shaded parts of the rookery. At least females do. Shade is usually found in nooks and crannies where a male’s field of view would be partly blocked, making it harder for him to defend his territory. Also, many shaded areas would be too small for the big bulls. In Carey’s first study season, the part cooling plays in the distribution of seals was clearly seen. In his second season, he set up variables, the shade umbrellas.

When the seals were not being aggressive, he and others built the umbrellas in a barren area, a “cooling void,” to see how they would be used.

During the first season, only one female had been found in the cooling desert. Carey used two shade designs, one a lean-to and the other with a parallel roof. Lean-to >shelters lose shade as the sun moves across the sky. Under the four-legged shelter, shade moves around the area during the day. Carey checks his rookery study sites twice a day, at the coolest and hottest times, to monitor temperatures by his remote sensing techniques — in relative safety, away from the males — and to map seal positions.

Males never used the iean-tos, perhaps because their territorial monitoring would be impaired. Males also preferred the sit-and-spread postures, again perhaps because they give them more chance to keep track of what is happening in and around their territories.

Once in a while, a male with no choice of pool or shade cooling will sprint through other territories, running their gauntlet, to reach the sea. “It is a rare event,” says Carey, “and can be pretty nasty for the sprinter.” In his first two study seasons, he has seen males coming back to the same territories. One question to be answered is whether females are coming ashore and seeking the best pupping sites for themselves, or whether they are selecting the best males, who have already set up their territories.

One problem has been the marking of animals. So far, Carey does not have individuallyrecognisable females to allow comparisons from year to year.

Last year, he and two others tried to tag adult seals for easier identification. They used a deer net in the operation. “It was a real rodeo,” says Carey, and it was not very successful. The net snagged on the sharp rocks. When a seal was finally chased down, two people had to hold it while the third tagged two flippers. It was a rough business. In the end, 10 seals were tagged.

Carey is also experimenting with a paint pellet gun. Some of the marking pellets bounce off the seals’ springy surfaces. Some seals moved off to sea rapidly when they were shot, but Carey thinks that may have been because of the shooter’s highlyvisible approach. ‘ ,T "' ~ n

When they were shot without seeing the shooter first, they only looked around bewildered, and not too concerned. Researchers tried putting a burlap bag over a seal’s head to calm it when it was being tagged, but the procedure only tended to enrage the seal.

Fur coats a

problem