What happens next is an insect version of the famous blues song about the philandering Back Door Man<\/em>. While the horned male diligently protects his turf, a smaller, horn-less male \u2014 possessing big testes full of sperm \u2014 sneaks in through a side tunnel and meets up with the female.<\/p>\n\n\n\n \u201cBecause of climate change, we have species expansion, but there\u2019s still a lot to learn about why some species are expanding, and why some species are not.\u201d<\/p><\/blockquote><\/figure>\n\n\n\n For evolutionary biologist Erin McCullough, the mating rituals of dung beetles are not only fascinating, they also can provide a window into understanding how climate change might affect biodiversity.<\/p>\n\n\n\n Native to the Mediterranean but accidentally introduced to Florida in the 1970s, the range of Onthophagus taurus<\/em> has expanded steadily northward across the U.S. All the way to Massachusetts.<\/p>\n\n\n\n \u201cBecause of climate change, we have species expansion,\u201d says McCullough, assistant professor of biology. \u201cBut there\u2019s still a lot to learn about why some species are expanding, and why some species are not. Understanding how sexual selection plays a role in all of this is not well documented.\u201d<\/p>\n\n\n\n McCullough first began researching\u00a0Onthophagus taurus<\/em>\u00a0during her postdoctoral research at the University of Western Australia. The dung beetle is not only the world\u2019s strongest insect but also the strongest animal; a male\u00a0Onthophagus taurus<\/em>\u00a0\u201ccan pull 1,141 times their own body weight: the equivalent of an average person pulling six double-decker buses full of people,\u201d according to a British study.<\/p>\n\n\n\n \u201cWhy in some populations is the introduced species the most abundant? And why in other populations is it not? I think that maybe patterns of sexual selection may help explain some of these differences.\u201d<\/p><\/blockquote><\/figure>\n\n\n\n Part of the Scarabaeidae<\/em> family, whose members are commonly known as scarabs, dung beetles have been celebrated as \u201cnature\u2019s pooper scoopers.\u201d Depending on the species, they eat manure as adults or larvae. Many \u2014 like the Onthophagus taurus<\/em> and tuberculifrons<\/em> that McCullough captured at farms in Massachusetts and Connecticut \u2014 favor dung from herbivores like cows and horses. But some \u2014 like Onthophagus hecate, orpheus<\/em>, and striatulus<\/em>, all of which she collected from traps set in Clark\u2019s Hadwen Arboretum \u2014 dine on dog feces.<\/p>\n\n\n\n Dung beetles fall into three categories \u2014 rollers, which form dung into balls; dwellers, which live in manure; and tunnelers, which dig underneath a dung pad to lay their eggs. The genus Onthophagus<\/em> is a large and diverse group of tunnelers, with more than 2,400 described species, the most of any genus in the animal kingdom.<\/p>\n\n\n\n \u201cThey bring balls of dung down into their tunnels and construct what we call a brood ball,\u201d McCullough explains. \u201cThe baby beetle feeds on the brood ball and then emerges from the tunnel as an adult.\u201d<\/p>\n\n\n\n In Australia, native dung beetles could not be relied upon to eat cattle manure \u2014 they preferred marsupial feces instead \u2014 so farmers introduced the tunneling Onthophagus taurus<\/em> to attack the cow pies and curb flies.<\/p>\n\n\n\n Farmers across the world value dung beetles like Onthophagus taurus<\/em> because they degrade manure and aerate and transfer nutrients into the soil. In the United States alone, researchers estimate that dung beetle activity is worth nearly $6 billion a year to the country\u2019s economy.<\/p>\n\n\n\n \u201cIn Australia, there can be a thousand beetles per dung pad,\u201d McCullough says, \u201cand they\u2019ll shred the dung pad in an hour.\u201d<\/p>\n\n\n\n The downside to Onthophagus taurus\u2019<\/em> success in Australia is that \u201cthis introduced species is outcompeting native species, and it\u2019s disrupting the ecological balance,\u201d she points out.<\/p>\n\n\n\n McCullough is studying whether that\u2019s the case in Massachusetts. She is examining how Onthophagus taurus\u2019<\/em> expansion has affected native dung beetles. And she also wonders whether taurus has changed its sexual selection traits and tactics as it has expanded.<\/p>\n\n\n\n \u201cA lot of biology is about sex and death. That\u2019s really what\u00a0matters.\u201d<\/p><\/blockquote><\/figure>\n\n\n\n \u201cWhy in some populations is the introduced species the most abundant? And why in other populations is it not?\u201d she asks. \u201cI think that maybe patterns of sexual selection may help explain some of these differences.\u201d<\/p>\n\n\n\n In cases where taurus<\/em> does not dominate, the female may mate only once and then die. In cases where taurus<\/em> succeeds, the female may mate multiple times with different males before dying, McCullough suggests. And even within the female\u2019s reproductive tract, the sperm of different males compete to reproduce.<\/p>\n\n\n\n \u201cA lot of biology is about sex and death,\u201d she says. \u201cThat\u2019s really what matters.\u201d<\/p>\n\n\n\n When McCullough arrived at Clark in 2022, she began setting traps at various sites and collecting varieties of Onthophagus<\/em>. This summer, she was accompanied by Syd Kochensparger \u201925, an environmental science major who works in McCullough\u2019s lab and received funding through Clark\u2019s Penn Family Research Award. Kochensparger already is familiar with Onthophagus taurus<\/em>, the same dung beetle they had observed eating through piles of manure on their family\u2019s horse farm in St. Cloud, Florida.<\/p>\n\n\n\n Another student, Bea Altopp \u201925, a double major in biology and global environmental studies, has joined the lab this fall. McCullough and her two students are now studying the species collected at the Arboretum \u2014\u00a0orpheus<\/em> (found to be the most abundant), hecate,<\/em>\u00a0and\u00a0striatulus<\/em>.<\/p>\n\n\n\n \u201cOver the course of my career at Clark, in real time, I can observe how these populations are changing.\u201d<\/p><\/blockquote><\/figure>\n\n\n\n \u201cThese are all native species, and we know very little about them,\u201d she says. \u201cMy students and I are raising them in the lab so we can figure out if and how they court and fight.\u201d<\/p>\n\n\n\n McCullough enjoys researching the tunnelers \u201cbecause they have interesting mating tactics,\u201d she says. \u201cSometimes they fight, sometimes they court, sometimes they sneak.\u201d<\/p>\n\n\n\n During her postdoc, she explored the role that male-to-male fighting plays in the female Onthophagus taurus\u2019<\/em>\u00a0sexual selection.<\/p>\n\n\n\n \u201cWe found that physical strength, horn length, and body mass were significant predictors of male fighting success, but males that won fights were not more attractive to females,\u201d she and her co-authors concluded in a 2016 article published in Behavioral Ecology. \u201cRather, females preferred males that delivered a high courtship rate, which was not correlated with strength, horn length, or body mass, but previously has been shown to be genetically correlated with body condition.\u201d<\/p>\n\n\n\n Before dung beetles, McCullough studied the sexual behaviors of rhinoceros beetles, whose males sport elaborate horns in the shape of pitchforks, hammers, or crowbars to fight for females. Later, she examined the molecular interactions that occur between sperm and eggs in the reproductive tracts of fruit flies before fertilization.<\/p>\n\n\n\n![\"Evolutionary](\"https:\/\/www.clarku.edu\/news\/wp-content\/uploads\/sites\/37\/Dung-Beetle-Research-1-1.jpg\")
![\"Left](\"https:\/\/www.clarku.edu\/news\/wp-content\/uploads\/sites\/37\/Dung-Beetle-Research-10-1.jpg\")
\u2018Nature\u2019s pooper scoopers\u2019<\/h2>\n\n\n\n
![\"Close](\"https:\/\/www.clarku.edu\/news\/wp-content\/uploads\/sites\/37\/Dung-Beetle-Research-142-1.jpg\")
![\"Evolutionary](\"https:\/\/www.clarku.edu\/news\/wp-content\/uploads\/sites\/37\/Dung-Beetle-Research-52-1-1.jpg\")
Dung beetles at work: a $6 billion \u2018industry\u2019<\/h2>\n\n\n\n
![\"Onthophagus](\"https:\/\/www.clarku.edu\/news\/wp-content\/uploads\/sites\/37\/Onthophagus-taurus-female-1.jpg\")
![\"Side](\"https:\/\/www.clarku.edu\/news\/wp-content\/uploads\/sites\/37\/Orpheus-side-1.jpg\")
Fight club, dung beetle-style<\/h2>\n\n\n\n