In November 2016, a short clip from Nat Geo Wild's series Animal Fight Night became one of the most shared animal videos of the year. Its story: a male Magellanic penguin returns to his nest, finds his partner with another male, and a bloody fight follows.
The "homewrecker penguin" video
National Geographic reported on 5 November 2016 that the clip had gone viral, drawing hundreds of thousands of viewers within days. The footage shows two violent clashes between the males at the nest, and both birds come out of it bloodied. By the end, the female is with the other male. The clip contains real injuries, so it may upset some viewers.
The narration frames the scene as a husband discovering an unfaithful wife. Biologists who were asked about it offered a more interesting reading. Michael Polito of Louisiana State University told Inverse that the footage could equally show an intruder trying to displace a resident male from his nest.
Magellanic penguins at a glance
According to the University of Michigan's Animal Diversity Web, Magellanic penguins breed along the southern coasts of South America, in Chile and Argentina, and on the Falkland Islands.
- Size: males average about 4.7 kg and females about 4.0 kg.
- Breeding season: adults arrive in early September, eggs are laid in late October and chicks fledge between January and early March.
- Nests: usually close to shore under a bush, or in burrows dug in soft soil. Colonies are dense, with nests often little more than a metre or two apart.
- Eggs: two per clutch; the second chick often starves unless food is plentiful.
- Lifespan: around 25 to 30 years in the wild.
- Status: Near Threatened, with oil spills, fishing nets and declining small-fish stocks among the threats.
Punta Tombo in Argentina is the best-known colony, visited by more than 100,000 people a year.
Pair bonds and penguin "breakups"
Magellanic penguins are socially monogamous, and pairs often stay together for many seasons, reinforcing their bond with mutual preening. Inverse cited a figure of 72 percent of Magellanic penguins pairing with the same mate each year, which means a sizeable minority do not.
Polito listed the usual reasons a pair bond breaks: one partner arriving at the colony at the wrong time, the death of a mate, a failed breeding season or the chance of a better mate. Aviculturist Laura Dray told National Geographic that "there are penguin breakups, but the reasons are often strictly logistical."
Why male penguins fight over nests
A nest site is a valuable resource in a crowded colony, and males fight for nests and mates. Animal Diversity Web notes a detail that fits the video well: before eggs are laid, the larger male usually wins, while after laying the nest owner usually wins regardless of size.
Researchers have studied nest intrusions more closely in the related Humboldt penguin. Sabrina Taylor of LSU described intruder males trying to take over occupied nests and mates, and in one observed Humboldt fight the battle lasted more than two hours. A 1999 study of the same species found about 20 percent of males and 30 percent of females nesting with a bird other than their mate.
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