Whose head is that? The case of the missing penguin bodies

Whose head is that? The case of the missing penguin bodies

How does a penguin head end up in the stomach of a deep-sea Antarctic toothfish? This mystery is one that our researcher Lara Shepherd, vertebrate curators Alan Tennyson and Colin Miskelly, and French marine expert Yves Cherel recently examined.

Um, thanks? A grisly donation

Te Papa receives many donations of dead birds every year. Recently one of the most intriguing was the remains of several penguins. These had been recovered from the stomachs of Antarctic toothfish caught by fishing boats near Antarctica.

A large dead fish on a yellow counter with a white wall behind it.
Antarctic toothfish (Dissostichus mawsoni) from the South Shetland Islands. Photo by Valerie Loeb / Southwest Fisheries Science Center, NOAA Fisheries Service. Public Domain via Wikimedia

These large fish typically eat other fish and squid and live at depths of around 1 to 1.5 km under the ocean. Penguins can’t dive to this depth so our specimens can’t have been killed by an Antarctic toothfish.

To further add to the mystery only penguin heads and flippers were found in the stomachs. What happened to the rest of the penguins?

A penguin head lying on a white card. There's also a measuring key that says 5cm on the bottom left-hand corner.
Head of a royal penguin found within an Antarctic toothfish stomach. Photo by Jean-Claude Stahl, Te Papa

Who bit the royal head off?

We think there are two possible suspects for who killed and partially consumed these penguins: killer whales or leopard seals.

Both of these species occur in the area and have been observed to eat only selected parts of birds, leaving behind the less tasty parts, such as the feet and head.

These remains might then sink to a depth where they could be scavenged by Antarctic toothfish.

Parts of a penguin laid out on a white card. The main body is missing.
Remains of a royal penguin found within an Antarctic toothfish stomach. Photo by Jean-Claude Stahl, Te Papa

What species are the penguin remains?

Features of the heads indicated that they were either royal or macaroni penguins. But the birds were immature, making their identification to species difficult.

Our DNA sequencing showed that they were royal penguins, a species that breeds at Macquarie Island.

This is also the closest breeding colony of either macaroni or royal penguins to where the toothfish were caught.

Penguins with yellow eyebrows in the wild. There are two in the foreground.
Royal penguin (front) with macaroni penguin behind, Iles Kerguelen. Photo by Colin Miskelly

A penguin OE to Antarctica?

We also reviewed museum specimens and other records of royal and macaroni penguins that turned up in Antarctica. We found that most of these were royal penguins and the majority were also immature birds.

It seems that young birds are the age group most likely to travel large distances (up to 4000 km) from their breeding colonies. Perhaps they like to see a bit of the world before settling down to embrace family life.

Reference

Shepherd LD, Miskelly CM, Cherel Y, Tennyson AJD (2021) Genetic identification informs on the distributions of vagrant Royal (Eudyptes schlegeli) and Macaroni (Eudyptes chrysolophus) Penguins. Polar Biology

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