Abstract
We developed a tracking unit that uses the Japanese mobile phone network to transmit data from Kuril harbor seals (Phoca vitulina stejnegeri), which are difficult to recapture. The unit senses location by GPS, hauling-out status, depth and temperature. Six wild Kuril harbor seal pups were tracked at Cape Erimo, Japan, in summer. GPS data indicated that the seals hauled out only on insular rocks in a known haul-out site at Cape Erimo. Although the data of hauling-out status were limited in accuracy, they at least indicated the seals often hauled out both at daytime and at nighttime. The depth logs of four of the seals were analyzed. The greatest depth recorded was 131m. Of the depth logs >1m, 98% were <50m. The seals may tend to use deep water when nearshore water is rough. Three of four seals tended to have depth logs distributed at about 30m. The seals tended to spend more time at shallow depths at night than at other times.
