The Little Penguin (Eudyptula minor) breeds in colonies on the mainland and offshore islands of southern Australia and New Zealand. The distribution of colonies is irregular throughout this area and colony size varies from a few breeding pairs to tens of thousands. Little Penguins forage at sea during the day and return to their nesting colonies at dusk. They are philopatric, returning to their natal (birth) colony to molt every year and to breed (typically producing 2 eggs) at 2 or 3 years of age. However, banding and genetic studies show that dispersal does occur, although infrequently, at least in southeastern Australia. During their first year, juveniles may travel distances of several hundred kilometers and fledglings have been observed migrating to breed at non-natal colonies. Although some pair bonds are maintained across seasons, competition for mates and nest burrows is intense and extra-pair copulations and mate switching occur. Breeding birds live to an average age of 7 years, but several individuals have been known to exceed 20 years in the wild. (Billing et al. 2007 and references therein; Peucker et. al. 2009 and references therein)
Giling et al. (2008) reported on a population of Little Penguins that has nested for many years between boulders on the St, Kilda breakwater in Melbourne, Australia, a city with a population of around 3.5 million humans. Penguins at this site are presumably well protected from predators and have good access to prey, factors that apparently outweigh the detrimental effects of close proximity to humans (although the birds do tend to avoid portions of the site subject to greater human disturbance).
Like most penguins, Little Penguins are small enough that their expected heat loss in cold water would be too rapid for survival without some method of actively reducing this loss. In fact, anatomical studies of the wings and feet of penguins provide evidence of one such adaptation in the form of a countercurrent heat exchange system in which heat from arterial blood is transferred to colder venous blood (similar systems have evolved in other animals, e.g., to regulate heat or gas exchange, and are used by human engineers as well). By having warmer blood running adjacent to cooler blood but in an opposite direction, as the warmer blood cools along its path, it continues to encounter even cooler blood flowing past it in the opposite direction, to which it transfers heat. Thus, warmth is returned to the body instead of being lost to the environment. Thomas and Fordyce (2007) studied the vascular anatomy of the Little Penguin and its inferred (although not directly measured) impact on heat retention.
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