Excerpt: 'Tails of the City: Urban Animals Beating the System', by Rhianna Boyle

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A Julodimorpha bakewelli specimen. Altered from a photograph by Hectonichus. Reproduced from the Wikimedia Commons under the Creative Commons Attribution-ShareAlike 3.0 Unported licence.

 

Human technological innovations can be disastrous for animals, especially those with which we share our habitat. Ever since we invented the first candle, and the first moth incinerated itself in a blaze of confusion, our technology has been an unfortunate source of false advertising to other species.

This is demonstrated in spectacular fashion by the plight of Julodimorpha bakewelli, a species of Australian Jewel Beetle. Before European settlement, a large body size and a shiny orange shell were reliable indications that a female Jewel Beetle was fecund and had good genes. But since people have built roads through the beetles’ habitat, and started leaving rubbish along these roads, these signals can mean something very different: that the ‘female’ in question is not an attractive mate, as she might appear to be, but is actually a shiny, amber beer bottle.

In the early 1980s, scientists observed that male Jewel Beetles along roadsides in Western Australia were mounting beer bottles and fruitlessly attempting to mate with them. Despite the setbacks, the males would persist with their attempts, ignoring the many available—though considerably smaller—females of their species. The number of eggs a female insect can lay is proportional to her size, which might explain why the males were so persistent in following the bigger-is-better rule of thumb that had served their forebears so well. The males would often die of exposure or would be eaten by ants, all the while still clinging to the bottles.

It’s not only beer bottles that pose a threat to some insects. Midges and mayflies are small, mosquito-like insects that lay their eggs on the surface of water. Unfortunately, the reflection of light off the surface of a wet bitumen road looks very similar to the reflection produced by the surface of a pond. Consequently, these insects sometimes descend en masse to lay their eggs on wet roads, with predictably dismal outcomes for their offspring. There are also reports of midges laying eggs on the roofs of dark-coloured cars in sale yards. When the sun comes out, the drying gelatinous egg masses destroy the paintwork.

Insects aren’t widely regarded for their smarts, but more adaptable animals like birds are also easily led astray. In Iceland, puffin fledglings – or pufflings, as they are called – use the moon to navigate away from the burrows in which they are raised and towards to open ocean. When their burrows are near human habitat, it’s common for confused pufflings to mistake town streetlights for the moon, and be found wandering town streets.

These dramatic examples of signal breakdown, where previously reliable environmental cues have been scrambled by technology, are unusual. Human alterations to the landscape more commonly cause the demise of other species through more expected impacts, such as loss of habitat, or competition and predation from introduced species. But a select group of species is learning to overcome the hazards of urban development, or, in some cases, even use the altered environment to their advantage. Most obvious are the ubiquitous rats and pigeons that have long fed off our refuse. But it’s not only food that is discarded in cities.

Cigarette butts are another common urban waste product. A recent study found that most house finch and house sparrow nests in Mexico City incorporated shredded cigarette butts – up to 48 butts in a single nest. While the butts are a readily available structural component of nests, it’s possible that their presence has other benefits for young birds: tobacco leaves contain nicotine, which is as an insect repellent. Nests with higher numbers of cigarette butts had lower numbers of parasites, apparently as a result of these natural insecticides. Some bird species in rural environments have long lined their nests with aromatic plants, also in order to repel insects, so it may be that the urban butt-collectors are adapting an evolved behaviour to a newly available material. For human beings, smoking harms your baby, but on the bright side, it could be doing wonders for a baby house finch.

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This is an excerpt from ‘Tails of the City: Urban Animals Beating the System’, Rhianna Boyle’s Nature column in The Lifted Brow #22. Get your copy now.