Book Review: Penguins: The Ultimate Guide

Reviewed by Ephraim Nissan (London, England)

De Roy, T., M. Jones, and J. Cornthwaite, eds. 2022. Penguins: The Ultimate Guide. Second edition. Princeton University Press, Princeton, NJ, 240 pp. ($28.00 cloth, $19.60 e-book with 20% PS discount.)

This lavishly illustrated, large-format book provides a full-rounded treatment of all extant penguin species, but it also is an eye-opener on fossil and subfossil penguin species. Part 1 is by Tui de Roy, and covers their life cycle, the “jackass” group of braying penguins, Antarctica’s three long-tailed species (the Adélie, chinstrap, and Gentoo penguins), the crested penguins, the rockhoppers, the Little penguin of Oceania, and finally the King and Emperor penguins of Antarctica.

Julie Cornthwaite authored Part 3, surveying all species one by one, in profiles sharing their structure. Part 2 instead, “Science and Conservation”, is edited by Mark Jones, and comprises 17 chapters (all but the first, of just two pages) by different scholars. For example, “March of the Fossil Penguins” by Daniel Ksepka (pp. 158–159), and Matthew Shawkey’s “Penguin Colours and Pigments” (pp. 162–163), which also discusses their evolution (a glitch chopped off its last line): “melanosomes from [the 36-million-year-old] Inkayacu [giant penguin found mummified (p. 159)] were smaller than those from modern penguins, and more similar in size and shape to those of other birds” (p. 162): perhaps larger melanosomes make feathers stiffer. “Second, Inkayacu’s plumage lacked countershading. Instead it had a brown underside and grey back” (162). Seals were diversifying, and countershading may have evolved as a response to increasing predation pressure.

There is a chapter by Sanne Boessenkool (pp. 164–165) about the Waitaha penguin of New Zealand, extinct and whose place was taken by the larger, closely related Yellow-eyed penguin. In “The Crested Penguin Egg-size Conundrum”, Kyle Morrison discusses why all crested penguins’ first-laid eggs are much smaller than the second-laid ones, and are neglected by parents (pp. 174–175). “Would you invest in something with next to no hope of receiving a return?” (p. 174). The B‑chick is the one more likely to survive. “Even when both eggs hatch, the A‑chick usually starves to death within a week, non-aggressively out-competed for food by the larger B‑chick. The B‑chick is bigger not only because it emerges from a larger egg, but also because, surprisingly, it usually hatches a day before the A‑chick — despite the B‑egg being laid 4–5 days after the A‑egg!” (p. 174). So probably the ancestral crested penguin already both laid dimorphic eggs, and made long-distance foraging trips offshore while breeding (p. 175), whereas laying two eggs “is likely the ancestral trait of all penguins” (p. 175): only King and Emperor penguins only lay one egg. This is a course of evolution crested penguins did not take, as their “B‑egg had a better chance than the A‑egg of producing a viable offspring. If so, this higher fitness of the B‑egg would select against elimination of the second ovulation that produces it” (p. 175). Or then, the two-egg clutch is not maladaptive but adaptive, e.g., “acting as insurance against failure of the B‑egg/chick, and allowing the potential to raise two chicks under particularly favourable conditions” (p. 175). Morrison points out that these explanations are problematic. One solution is that as these and some other penguins delay full incubation until the second egg is laid, this gave a better chance to the B‑egg, but risk of predation was lesser for the more solitary Yellow-eyed penguin (175), so the two eggs are more similar.

Ksepka, one of whose research goals has been to reconstruct an evolutionary tree for penguins—archaic taxa include eight from the Palaeocene, and ten from the Eocene—situates in the Miocene the transition to features that can be considered modern: “the oldest fossils of modern penguins (those that shared the most recent common ancestor of all living species) are only 11 to 13 million years old, suggesting that turnover between archaic species and modern species happened quite recently from a geological perspective” (p. 158), and “the distribution of fossil penguin lineages strongly suggests that early species originated in temperate latitudes” (p. 158). “During the Eocene Epoch, penguins were living close to the Equator in Peru—at a time when the global temperature was on average 5º to 8º hotter than today (p. 159). And “penguins appear to have colonized permanently glaciated environments very late in their history” (p. 158). Yet, penguin thermoregulatory features started evolving already in the archaic stage. “Such features can be thought of as exaptations, structures that evolved for one purpose and were later co‑opted for another” (p. 158). The early purpose was long underwater foraging, but such body heat conservation is now “one key for surviving the icy Antarctic season in the modern world” (p. 158).

The oldest ‘proto-penguins’ known (Waimanu, Muriwaimanu, and Sesuiwaimanu) are from around sixty million years ago, were flightless but still able to “fold their wings to a certain extent” (159), and were from New Zealand, which “was home to many different fossil penguin species, including the gigantic 35 million-year-old Pachydyptes ponderosus,” but an “even larger species”, the 57 million-year-old Kumimanu biceae tilted the scales at ~120 kg (265 lb). Some unusually svelte penguins also plied the ancient seas of New Zealand” (p. 159), such as the “over 1.2 m (4 ft) tall” Kairuku waitaki. The crested penguin Eudyptes warhami, from the Chatham Islands, “was driven to extinction 700 years ago” (p. 159).

This is a book neontologists will treasure, while paleontologists, too, stand to benefit, both because their interests are directly catered to, and because here is a trove of detailed information conducive to ideas arising that may turn useful in paleontology, in understanding processes of diversification.

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