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Hauling-out is the behaviour associated with pinnipeds (true seals, sea lions, fur seals and walruses) temporarily leaving the water. This occurs between periods of foraging activity. Instead of being in the water, the pinnipeds explore sites on land or ice. Hauling-out is necessary in seals for mating (with the exception of the Baikal seal) and giving birth (though a distinction is generally made between reproductive aggregations, termed "rookeries", and non-reproductive aggregations, termed "haul-outs"). Other benefits of hauling-out may include predator avoidance, thermal regulation, social activity, parasite reduction and rest.
There is much variation in haul-out patterns among different seal species. Haul-out sites may be segregated by age and sex within the same species. Many species of pinniped have only a few localized rookeries where they breed, but periodically occupy hundreds of haul-out sites throughout the range. For example, the Australian fur seals breed on only nine islands in Bass Strait but also occupy up to 50 haul-out sites in south-east Australian waters, and Steller sea lions have around 50 rookeries throughout their range, but several hundred haul-out sites.