Though Adelie penguins (Pygoscelis adeliae) are monogamous, the couple does not spend the winter together. In fact, the pair migrates separately and will only return to the rookery where they last mate during the breeding season (from November to February). The males will arrive at the breeding site prior to the females to build the nesting sites. Unless one of the partners fails to return, the couple will reunite every breeding season. The penguins are able to recognise its mate’s call or even, physical features.
For first time breeders, there are generally three distinct types of visual/auditory courtship displays. (Watch this – courtship of penguins)
- Ecstatic. The male penguins will swing their head, and flap their flippers. These actions show possession of a breeding site, to attract females, and to keep other male intruders away.
- Mutual. Once paired, both the male and female penguins will stretch their head and neck upward.
- Bowing (Figure 1). Bowing displays reduce aggression; strengthen bonds and recognition between partners.
Are Adelie penguins truly monogamous?
Research has found that both male and female Adelie penguins may have more than one breeding partner in its life (F. M. Hunter, G. D. Miller and L.S. Davis, 1995). In fact, about 21-30% of the female penguins were involved in mating with more than one male in a single breeding season, either through extra pair copulations (EPC’s) or mate-switching (Harshaw, 2005).
A female may copulate with multiple partners to enhance genetic quality or diversity of her offspring. The female penguin may also mate with numerous males to (1) ensure that her eggs are fertilised in the event of her partner being infertile, (2) gain potential partners in the future years should her partner leave her (F. M. Hunter, G. D. Miller and L.S. Davis, 1995).
In addition, it seems that the females engage in EPC’s so as to collect more stones or nesting materials to build a better nest. This will benefit the males in terms of living conditions as well. Furthermore, after the eggs have been laid, the males have the responsibility to incubate them. As such, the male is unable to leave the nest to protect its mate from engaging in EPC’s since an unguarded nest will invite predation.
While we decide whether the Adelie penguins are indeed monogamous, it is important to note that the survival of all species of penguins is greatly challenged by weather conditions and food availability. According to Dee Boersma, a University of Washington biology professor, the population of penguins in the Punta Tombo colony has reduced by more than 20% in the last 22 years (Science Daily, 2009). Some possible reasons for the decline are human activities such as oil pollution and overfishing. As such, it is crucial human amend their ways to save our declining ecosystem.
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