Where evolution is concerned, the city is a cauldron exerting its own unique mix of selection pressures on the organisms living here. The metronome beating at the heart of this process is sex. For this book, retired physician Kenneth D. Frank has explored his hometown of Philadelphia in the Eastern US state of Pennsylvania and documented the astonishing variety of sex lives playing out right under our noses. Many of these organisms can be found in cities around the world. Remarkably well-researched and richly illustrated with photos, this collection of 106 one-page vignettes shows what avocational naturalists can contribute both in terms of observations and in terms of highlighting the many basic questions that are still unanswered.

Sex in City Plants, Animals, Fungi, and More: A Guide to Reproductive Diversity, written by Kenneth D. Frank, published by Columbia University Press in May 2022 (paperback, 175 pages)

That animals get up to all sorts of reproductive shenanigans is something I would know. I spent five years for my PhD degree looking at the sex life of a small fish, the three-spined stickleback, and especially how males have different options when it comes to siring offspring, known as alternative reproductive tactics. Frank, however, opens the book with some 30-odd vignettes on plants, reminding me that I really do not appreciate plants enough.

Take purple cliffbrake fern (Pellaea atropurpurea) that does not need to be fertilized by sperm and whose embryos emerge from somatic (i.e. body) cells. Jewelweed (Impatiens capensis) can form big showy flowers that are cross-fertilized (i.e. the regular bees-and-flowers story) or it can form smaller flowers that fertilize themselves under conditions of drought and shade. St. John’s Wort (Hypericum perforatum) can do it all: self-fertilization, cross-fertilization, double fertilization^[1], single fertilization, or no fertilization. All these species are well adapted for variable conditions in city environments. Meanwhile, a tree such as Norway maple (Acer platanoides) can change its sex over the course of days, producing male flowers followed by female flowers, or vice versa. This prevents self-fertilization, which is a measure of last resort from an evolutionary point of view as it produces offspring that are less genetically diverse.

“[…] this collection of 106 one-page vignettes shows what avocational naturalists can contribute both in terms of observations and in terms of highlighting the many basic questions that are still unanswered.”

The next major group Frank covers are insects and other invertebrates whose sex lives are just wicked. Male European paper wasps (Polistes dominula) are a lekking species, which means they congregate in a small area, the lek, to collectively advertise their presence in the hope of picking up a female. (One could theoretically argue that nightclubs fulfil a similar function in humans.) Male blue dasher dragonflies (Pachydiplax longipennis) are territorial and defend areas preferred by egg-laying females. The females can mimic the male in appearance and it seems these mimics avoid harassment by males. A problem for both sexes is light reflected by metal and glass, which is polarized—the light waves vibrate predominantly in one direction—and resembles light reflected by water. Some dragonflies end up defending the shiny surface of a car bonnet rather than a pond. Milkweed aphids (Aphis nerrii) are such pests as they reproduce through parthenogenesis: eggs develop into embryos without requiring fertilization, and all grow into females that will never mate. The bridge spider (Larinioides sclopetarius) thrives around outdoor lights, which form hubs where spiders “eat, meet, and mate” (p. 76). Males have secondary genitalia and first transfer their sperm to two so-called pedipalps: pom-pom-like appendages in front of their head that they use to inseminate females with.

In comparison, vertebrates seem tame. As in many other reptiles, sex in red-eared slider turtles (Trachemys scripta elegans) is temperature-dependent. What I did not know is they simply have no sex chromosomes! Male bluegill fish (Lepomis macrochirus) build nesting areas to which they attract females. Afterwards, they nurse the broods on their own. Some males, sneaker males, forego all this effort and simply intrude on an ongoing mating, releasing their own cloud of sperm in the water (the sticklebacks I studied do the same). Male eastern gray squirrels (Sciurus carolinensis) leave a mating plug in the female’s genital tract which is hypothesized to have one or more functions (including a sperm blocker to other males, a hormone booster, or maybe an anti-aphrodisiac pheromone releaser). European starlings (Sturnus vulgaris) are a fine example of a species that is socially but not sexually monogamous, as paternity tests have shown. Notably missing from the book are mammalian predators such as and coyotes that also thrive in city environments.

“Frank highlights where we know or suspect that certain strategies result in organisms either thriving or struggling in urban environments; not every organism can radically reorganise its sex life to take advantage of the city.”

The above is a small sample from the wide range of reproductive diversity on display in urban environments. Frank highlights where we know or suspect that certain strategies result in organisms either thriving or struggling in urban environments; not every organism can radically reorganise its sex life to take advantage of the city. Obviously, Frank has not observed all these phenomena first-hand, and the amount of research that has gone into this book is impressive. The reference section spans 32 pages, which is a lot considering the vignettes take up only 106 pages. Many include facts and data from five to ten different papers. He also uses this opportunity to highlight how many basic biological questions remain unanswered. For example, does nocturnal light pollution interfere with moths fertilizing flowers of white campion (Silene latifolia)? How do female dragonflies mimicking males mate and could this be a post-fertilization adaptation? Does artificial crowding in city parks cause male squirrels to become less aggressive over time? What Frank has done is track down nearly all the species discussed here: the book is richly illustrated with his (macro)photography, with some contributions by others.

As much as Sex in City Plants, Animals, Fungi, and More is a nicely curated collection of interesting nuggets, it lacks an overall narrative. In particular, the bigger picture of how reproduction translates into longer-term evolutionary changes is only occasionally hinted at. Menno Schilthuizen wrote a very entertaining account in Darwin Comes to Town, but it has become a serious subfield of evolutionary biology. As such, this is a popular science book that is great for dipping into (whether it would make for suitable bedtime reading depends entirely on what you are into…). And if you are looking for inspiration for student or PhD projects, the book provides numerous ideas of biological mysteries at your doorstep.

1. ↑ double fertilization is the default in flowering plants. One fertilized cell forms the embryo, and the other forms endosperm that offers nutritional support to the developing embryo.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

Sex in City Plants, Animals, Fungi, and More

Other recommended books mentioned in this review:

__________________________________________________________________

This has to be a story worthy of the name “scoop of the century”. Penguin biologist Lloyd Spencer Davis has been studying mating behaviour in Adelie penguins since 1977, carefully documenting how penguins are far from the paragons of monogamy that they were long held to be. That is until 2012 when an unpublished manuscript comes to light showing that somebody beat him to the punch… by more than six decades! A certain George Murray Levick carefully documented the same penguin antics that Davis would later build his career on. But who was this Levick? And why did he never publish his observations? Join Davis for a most unlikely story of polar exploration, penguins, and perversion.

A Polar Affair: Antarctica’s Forgotten Hero and the Secret Love Lives of Penguins, written by Lloyd Spencer Davis, published by Pegasus Books in October 2019 (hardback, 382 pages)

George Murray Levick was part of Captain Robert Falcon Scott’s doomed 1910-1913 expedition to reach the South Pole. While Scott’s team was racing the Norwegian explorer Roald Amundsen to be the first to plant a flag at the bottom of the world, Levick was part of a team that stayed behind at their base camp at the edge of Antarctica. To while away the long, cold days he started observing the Adelie penguins with whom they shared the spit of ice-free land, quite by accident becoming the world’s first penguin biologist. Much like Davis would do decades later, he observed that especially males are far from monogamous; they engage in homosexual behaviour, hump dead bodies, and molest females. But females are no angels either, dumping males when they do not return from sea in a timely fashion to feed their chick, or trading sex for stones to build their nests with. As Davis explains, given the short breeding season these are all behaviours for which there are sensible biological explanations.

Levick would write up his findings in the 1914 book Antarctic Penguin: A Study of Their Social Habits with which Davis is intimately familiar. What Davis did not know is that Levick left out his most salacious observations, which were instead written down in a short unpublished manuscript that was considered too offensive to Victorian morals. A small print run of 100 copies, labelled “not for publication”, was printed for internal circulation at the British Museum of Natural History but quickly forgotten. Until, that is, 2012 when a librarian at the museum finds a copy and publishes it with a commentary in the journal Polar Record.

This unlikely chain of events forms the starting point of A Polar Affair where we accompany Davis as he tries to learn all he can about Levick and his observations, leading him to Levick’s original notebook containing passages furtively written in secret code. But the book is about much more than just Levick and horny penguins – we do not actually get to these until page 160. Davis describes at length all the other people who are part of the grand adventure in which Levick took part: the infamous race for the South Pole between Scott and Amundsen and the people who in turn inspired them, including explorers such as Ernest Shackleton, Fridtjof Nansen, and Robert Peary.

“Much like Davis would do decades later, [Levick] observes that especially males are far from monogamous; they engage in homosexual behaviour, hump dead bodies, and molest females. But females are no angels either […]”

I was already familiar with some of these people; Shackleton’s expeditions came up in my review of Erebus while the recently reviewed The Ice at the End of the World introduced me to Nansen, Peary and other Greenland explorers. Ironically, I was less familiar with the better-publicised stories of Scott and Amundsen. Since the 2011-2012 centenary of the race to the South Pole you could fill a small library with books about these two: see e.g. Scott of the Antarctic and The Last Viking for biographies, while the London Natural History Museum published two entry-level books with Scott’s Last Expedition and Race to the End. More in-depth are The Last Place on Earth and Race for the South Pole that, uniquely, contains Scott’s and Amundsen’s expedition diaries side by side. An Empire of Ice, meanwhile, places this era in a wider context. And this is on top of all the books that the various people participating in these expeditions wrote upon their return.

Davis intertwines all these storylines, chronicling the extraordinary hardships on the ice, the triumph of Amundsen’s party arriving first, the tragedy of Scott’s party arriving second and then succumbing to cold and hunger on their return journey, and the astonishing feat of survival when a side-quest by Levick and five others goes awry and results in them having to overwinter on the Antarctic ice sheet for nine months with virtually no food reserves or suitable gear. He furthermore mixes in anecdotes of his own penguin research over the decades with the story of Levick’s observations, which make for fascinating reading.

“The book is about much more than just Levick and horny penguins […] Davis describes at length all the other people who are part of the grand adventure in which Levick took part: the infamous race for the South Pole”

The resulting patchwork becomes a bit chaotic in places, as Davis keeps switching between storylines and time periods within each chapter. Some memory aids in the form of a map with all the locations and routes, a timeline, or short biographies of the main actors would have been helpful. Nevertheless, the story is so darn fascinating and unlikely that I could not stop reading.

Davis is outspoken, explicit in his description of penguin sexual behaviour, and does not avoid strong language. I personally do not mind and thought he was hilariously crass in places, especially when talking penguin biology. Starting right on page 3: “Survival of the fittest is really a euphemism for survival of those who fuck the most“, or later: “males will bonk anything that comes within a flipper’s length“. But he similarly gleefully draws parallels between the penguins and the explorers, showing that the latter were not necessarily upstanding characters either, many having affairs at every turn. His description of Amundsen and Sigrid Castberg’s first tryst (“she kisses him and the last piece of the ice shelf that has kept this man so stiff and removed from feminine involvement melts away […] for a moment [he] becomes a bowing, immensely grateful male penguin in her hands“) more than reeks of a bit of artistic license but, again, cracked me up.

I was more shocked by his frustration with Levick post-expedition. Levick never looked back on his time in Antarctica, and Davis admits that he so badly wanted him to be more of an inspiration that he judges Levick rather harshly for his choices, at one point even admonishing him for his lack of empathy when writing a stiff, formal note to go on a funerary wreath with a brusque: “for fuck’s sake Levick, is that the best you can do?“

“[Davis is] hilariously crass in places, especially when talking penguin biology”

I am sure that some biologists will cringe at Davis’s liberal use of anthropomorphising terms such as “divorce”, “rape”, and “prostitution”, though he lampoons the multisyllabic alternatives biologists use. With everything else going on, the book is also rather thin on factual information on penguins. Readers might want to turn to Davis’s book Professor Penguin for more on his research (or to Strycker’s similar book Among Penguins), an introductory book such as Penguins: The Animal Answer Guide, the more serious Poyser monograph The Penguins that Davis co-authored, or the recent Penguins: Natural History and Conservation.

Despite the above, A Polar Affair is an engrossing book. The details of the race for the pole are extraordinary by themselves, but the penguin subplot gives it a further twist, even if Davis can never quite work out whether Levick was muzzled upon return or chose to censor himself. An unusual and colourful page-turner that is recommended if you enjoyed provocative books such as The Myth of Monogamy or Sex at Dawn. It had me in stitches more than once.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

A Polar Affair paperback, hardback, ebook, audiobook or audio CD

Other recommended books mentioned in this review:

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

Having just reviewed The Mosquito, I am continuing the theme of small things running the world. Here is another overlooked insect that literally moves mountains, doing the dirty job that nobody wants to do: the dung beetle. Entomologist Marcus Byrne has teamed up with popular science writer Helen Lunn for Dance of the Dung Beetles, a captivating and charming introduction to their cultural history, their role in the history of biology as a discipline, and some really funky contemporary research.

Dance of the Dung Beetles: Their Role in Our Changing World, written by Marcus Byrne and Helen Lunn, published by Wits University Press in April 2019 (paperback, 252 pages)

Dance of the Dung Beetles is really a book in three parts. Any book that wants to give a complete introduction to the cultural and biological history of dung beetles – or scarabs – has to begin in Ancient Egypt. With its habit of moulding excrement into neat little balls being interpreted as an act of creation, and the rolling of the ball as the daily passage of the sun, dung beetles entered the Egyptian pantheon as the scarab-faced deity Khepri.

Subsequent religions held no such fascination for the dung beetle, so the authors pick up the historical thread in the Middle Ages. Here, the first naturalists started noticing them again, in particular the Italian scholar Ulisse Aldrovandi, whose 1602 book De Animalibus Insectis (for short) described their nesting behaviour. Colonialism and trade brought vast quantities of unknown flora and fauna back to Europe, feeding a craze for curiosity cabinets to display these. A knowledge vacuum became apparent and naturalists mostly busied themselves describing and cataloguing all this diversity. It was Linneaus who would ultimately stamp his mark on this era with his binomial naming system introduced in his book Systema Naturae. Byrne & Lunn discuss how dung beetles pop up in this period in books and paintings, showing a renewed awareness and interest in them.

“studies […] on dung beetles and dung producers (elephants) moved research from single species towards ecosystems”

This cultural history spans a good 40% of the book before the authors turn to the dung beetle’s role in the history of biological disciplines. The boom of agriculture in North America after the American Civil War in the 1860s saw a surging interest in biological pest control and the birth of the discipline of economic entomology. Although dung beetles do not attack insect pests directly, they do limit their breeding grounds by rapidly burying animal dung. Dung beetles were subsequently imported into Hawai’i and later Australia, and scientists learned important lessons on the particular habitat and food requirements of each beetle species when introductions failed. Not all dung is created equally, it seems. But where they were successful, the positive effect of dung beetles on soil health has not gone unnoticed, as witnessed by the ongoing work of, for example, Dung Beetle Solutions Australia (see also Dung Down Under: Dung Beetles for Australia).

This leads into a very interesting if slightly off-topic chapter on elephants. Byrne & Lunn provide a short but pointed introduction to the trade in ivory (initially indigenous, then boosted by the desires of colonial powers) and the establishment of game parks. Especially on the latter, they have some interesting and outspoken opinions. A rinderpest pandemic sweeping through Africa at the end of the 19th century emptied many areas of livestock, leading to a spike in tsetse flies and accompanying sleeping sickness. Colonial governments responded by relocating whole populations, often turning the abandoned areas into game reserves, without ever considering if these areas were fit for animal populations. Byrne & Lunn highlight the clashes between newly minted and haughty conservation ecologists who had limited knowledge of, for example, elephants lording over these reserves, and the game wardens and naturalists on the ground. It is an interesting aside before they get to the link with dung beetles. It was studies in Tsavo National Park, Kenya, on dung beetles and dung producers (elephants) that moved research from single species towards ecosystems, made famous by further work by the late Ilkka Hanski.

“some [dung beetles] orient themselves at night by the light of the Milky Way. This involved delightful experiments observing dung beetles rolling balls in planetariums”

Not until the last two chapters do the authors finally talk about the topics I really came here for: the fantastic contemporary research on beetle behaviour. There is the huge variety in dung processing, for not all dung beetles roll balls. There is the wild divergence in mating tactics, which is what the dung ball rolling is all about: brood provisioning. Males roll balls which are gifted to females who will lay an egg in it, providing a safe and nutritious cradle for their offspring. Some males have horns with which they defend their dung balls, others do not and engage in sneaky copulations (the topic of my own PhD research). This allows Byrne and Lunn to talk about sexual selection, evolution, and genetics and casually give some of the best concise explanations of epigenetics and gene translation and regulation I have read in a popular science book.

And then there are the experiments that catapulted dung beetles into fame in 2013 when it turned out that some species orient themselves at night by the light of the Milky Way. This involved delightful experiments observing dung beetles rolling balls in planetariums, using polarised light filters in the field, and fitting beetles with mini-hats to prevent them from seeing the sky. I would have loved to read more about these and other experiments, and this part of the book felt too short – there must be more unusual research that could have been covered. Rather than reducing the interesting sections on cultural history, I would not have minded had the authors expanded the book as a whole, adding a few more chapters on specific biology topics.

As far as I can tell, the only similar popular book with which Dance of the Dung Beetles competes for your attention at the moment is Call of Nature, which delights in dung more generally. That book has line drawings of many of the insect species discussed, something which this book could have profited from, though there is an extended colour plate section with excellent photos here to make up for that. For readers such as myself who want to dig deeper into the biology, there are always the edited collections Ecology and Evolution of Dung Beetles and Evolutionary Biology and Conservation of Dung Beetles. For general readers, though, this book offers a wide-ranging introduction to the fascinating dung beetle that is very hard to put down.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

Dance of the Dung Beetles paperback

Other recommended books mentioned in this review:

__________________________________________________________________