The hidden danger of stepping outside
I spend significant time outdoors in the pursuit of hobbies like bushwalking, through-hiking, rock climbing, and even for work. Wilderness areas are, naturally, dangerous. Far from humanity's attempts to build a perfectly safe and comfortable environment, you'll likely encounter wildlife that — under the wrong circumstances — may threaten you with a bite, envenomation, or other physical trauma. The earth itself also offers several dangers. One might find themselves spraining an ankle, risking dehydration, or plummeting to their death from a high cliff. Having said that, I wouldn't give up the great outdoors for anything. As with any activity, risks can be managed effectively reducing the chances of injury or death to vanishing odds. One risk I never expected to encounter was losing the ability to eat the meat of mammals.
The lone star tick (Amblyomma americanum). Source: Center for Disease Control and Prevention
I knew it existed, I even came to know a few people afflicted with the condition all of whom work or study in a similar field to myself. Known commonly as red meat allergy or mammalian meat allergy (MMA), the condition is more specifically an allergic reaction to galactose-alpha-1,3-galactose (alpha-gal). Alpha-gal is a sugar found in the muscle tissue of all mammals except old-world monkeys and apes, that includes us and our closest living relatives – the chimpanzee. Oddly enough I developed this condition after I had suffered many tick bites over about a year. Yes, that's right, tick bites are the culprit1. I do not know if it was one unlucky bite or the result of cumulative bites as at the time I was spending a significant amount of time laying in the dirt digging up dung beetles, in addition to hiking as often as I could. That year I got as many as six tick bites, possibly more that I didn’t catch.
An engorged female paralysis tick (Ixodes holocyclus). Source: Australian Museum
It is not just field biologists that need to be concerned, the paralysis tick (Ixodes holocyclus), according to the Australian Department of Health, accounts for 95% of tick bites in eastern Australia. Joining the paralysis tick’s ranks is Ixodes (Endopalpiger) australiensis, recently having been implicated in a case of MMA2. It is not just a risk in Australia either, in America the lone star tick (Amblyomma americanum), in Europe Ixodes ricinus, and in Panama Ixodes cajennense are known to cause MMA. In fact, cases have now been recorded in 17 countries2. Ticks already get a bad rap for being creepy little bloodsuckers who can cause numerous illnesses such as Lyme disease; as if they needed this on top of it all.
In addition to being spread and contracted, MMA is a unique allergy due to the delayed onset of symptoms after exposure. For most food allergies symptoms have an onset of seconds to minutes – think the stereotype of peanut allergy sufferer ballooning up for comedic effect — however for MMA symptoms typically manifest four or more hours after ingestion of mammal meat. Despite the delayed onset, symptoms of MMA are similar to those of other food allergies ranging from gastrointestinal discomfort, rash and hives, to full-blown anaphylactic shock.
The results of self experimentation. Source: me and my body
Because of the delay between exposer and the manifestation of symptoms, it can be rather difficult for those afflicted to make the association between their medium-rare steak and an uncomfortable night on the toilet or worse in the hospital. In my case, I had prior knowledge of the condition so I suspected that the intestinal pain I experienced after eating meat may be due to an allergy. Still, I went ahead and performed an experiment as follows. Several hours after enjoying beef meatballs for dinner I noticed my usual symptoms creeping up, hives where I had previously been bitten by ticks and intestinal pain, so I went ahead and ate the leftovers. Luckily I didn't suffer anaphylaxis, just a painful and sleepless night. Despite this evidence, I still opted to visit an allergy specialist to get blood work confirming my self-diagnosis. Now it should go without saying, I absolutely do not recommend anyone tries the approach I described above. Self-experimentation, especially related to life-threatening medical conditions, should never be attempted – for obvious reasons. Always go see a doctor if you suspect you might have MMA and if you're experiencing symptoms of anaphylaxis get emergency help immediately.
While MMA sounds like a scary consequence of stepping into the bush I do not wish to discourage people from getting outdoors. Many people experience dozens of tick bites and never develop the condition and tick bites can be prevented effectively with the use of repellents and protective clothing. Furthermore, those who do develop MMA can easily manage the risk of exposure by avoiding red meat in their diet. So excuse the overly dramatic title and go out and explore!
Van Nunen SA, O’Connor KS, Clarke LR, Boyle RX, Fernando SL. An association between tick bite reactions and red meat allergy in humans. Med J Aust. 2009.
Kwak M, Somerville C, van Nunen S. A novel Australian tick Ixodes ( Endopalpiger ) australiensis inducing mammalian meat allergy after tick bite . Asia Pac Allergy. 2018. doi:10.5415/apallergy.2018.8.e31
Dung and Diversity
To most people, the idea of digging through piles of dung or spending hours excavating beetle burrows in the dank rain-forest soil sounds like torture at worst and a mundane task at best. For me, it has provided a candid, maybe even arcane, look at a usually hidden pocket of biodiversity. The communities and ecosystems associated with dung are not only expansive but also provide a great service to humans and nature its self.
What is Dung?
Dung – referred to by myriad names such as manure, guano, droppings, feces, poop, crap, shit, and meadow muffins – is the solid or semi-solid excrement or waste product of animals. Although it is indeed a waste product (and smells as such), dung retains lots of nutrients that are easily accessed. That is of course if you’re willing to eat and drink poop!
A typical cow pat
Nothing goes to waste
Leaving the digestive tract is just the beginning of the excrement expedition. Within moments hundreds of species of insects, having caught the smell in the air, make their way by wing or foot to start feeding, working, and burying the dung. Perhaps the most well-known groups of coprophagous and coprophilic (that's eating dung and attracted to dung respectively) are the flies (Diptera: Muscidae) and the dung beetles (Coleoptera: Scarabaeinae). However, in addition to insects dung is full of Nematodes, Molluscs, Mites, Isopods, Millipedes, Centipedes, worms as well as numerous other orders of insect. Unsurprisingly, a great variety of fungi also call this nutrient-rich sludge home and I would be foolish not to mention the bacteria.
Vicious competition
Onthophagus sagittarius male (left) and female (right). Note the difference in horns. Image from Wattson and Simons (2010)
Dung is an ephemeral resource; it doesn't last long and competition is fierce. Dung beetles will toss and tussle for control of a prime chunk of dung and evidence of this can be seen in the elaborate structures found on the head and pronotum of many Onthophagus dung beetles. These horns are often used as a weapon during competition amongst conspecifics for access to dung or mates. While in almost all cases the males of the species poses horns, and thus engage in aggressive behaviour, in Onthophagus sagittarius both the males and females have horns. Since the females of this species are responsible for obtaining dung, an individual with larger horns is likely to have better access to dung. On the other hand, the male horns may be used to fight off other males or as a signal to females of their quality as a mate.
Evidence of the extreme competition for dung is also seen among the ball-rolling dung beetles. This group of dung beetles are probably the ones that come to mind most often, although, in reality, they are a minority. The African ball-rolling dung beetles are the celebrities of the dung fauna, often getting featured in nature documentaries and for good reason. The persistence and precisions with which they push their prized ball of dung is a spectacular sight. So much so that humans have been enthralled by dung beetle behaviour for thousands of years. Notably, the ancient Egyptians were fascinated enough by the beetle's ability to roll, and subsequently bury, balls of dung that it conceived their solar god, Khepri, whom they believed to roll the sun across the sky each day and burry it each night. As fate would have it, these dung rollers do indeed have a tight connection to the sun and skies above; but more on that in a future post!
Dung down under
An excellent example of the importance of dung and the diversity of organisms within it can be found in the agricultural history of Australia. After the introduction of cattle to Australia in 1788, just three months after the First Fleet made land, Buffalo and Bush flies have had a smorgasbord of big, wet cow dung to breed in. The population of flies eventually became so large it spawned the term ‘Great Aussie Salute’, referring to the constant shooing and swatting to keep flies away from our eyes.
The problem? Dung accumulation, providing more breeding space for flies, because our native Dung beetle fauna isn’t adapted to the large and wet bovine dung. Instead, they prefer the small, dryer pellets left from Kangaroos and Wallabies. The accumulation of dung and density of flies became so bad that in the 1950s a Dr. George Bornemissza - working with the CSIRO - conceived the idea to introduce exotic dung beetles, which are adapted to bovine dung, to reduce the unburied dung and in-turn control the fly population.
Form 1962 to 1984 the CSIRO released a total of 1.73 million dung beetles from 43 different species. As of 2007, there are currently 23 exotic species of dung beetle established in Australia and the dung beetle program has been exceptionally effective in reducing the population of dung breeding flies. In addition to reducing fly numbers, burying dung improves the quality of pastures by returning nutrients to the soil, and assists in sequestering carbon.
Home grown diversity
Photographer: M Bulbert © Australian Museum
In addition to the hand full of introduced dung beetles, Australia also has a plethora of native species. We know of almost 500 different species of native dung beetles and I’d wager that the actual number of species is considerably greater than this.
As well as an incredible diversity of species and forms, our dung beetles also have a wide variety of diets. In addition to dung many species love rotting flesh (yes, from animals), fungi, leaves, and fruit. One group, of the genus Cephalodesmius, even manufacture their own dung out of plant matter such as fruit and leaves. They mince, mash and compost this plant matter, with a little macropod or rodent dung when available, to make a larder of dung like material. This larder is used to progressively add to the egg/ larval ball that the young develop inside.
Tarsal claw of Onthophagus parvus. Image from Matthews (1972)
Cephalodesmius also exemplify an unusual lifestyle amongst dung beetles, they pair for life; the male will forage while the female tends to the nest. We also have parasitic species that, much like cuckoos, will lay their eggs in the nest of another dung beetle to skirt their parental obligations. Finally, we have - in my opinion - the most Australian dung beetles: Macropocopris (this genus is now synonymous with Onthophagus but I like it so I'll use it here). The 7 or so species of this group have evolved a prehensile claw that enables them to cling to the fur of Kangaroos and Wallabies (i.e Macropods). By clinging to the fur around the macropod's anus theses hitchhikers get access to dung directly from the source. Simply let go when your ride takes a toilet break!
Appreciate the dung's diversity
I hope I've provided a little peek inside the cryptic dung fauna, especially the dung beetles. But there is still so much that I didn't cover about dung beetles and dung fauna at large. In the meantime, be thankful that thousands of little workers are there to make sure we don't get buried in poo!
References
Skidmore, P. (1991). Insects of the British cow-dung community. Field Studies Council Occasional Publication.
Australian farming and agriculture – grazing and cropping | australia.gov.au. 2018. Australian farming and agriculture – grazing and cropping | australia.gov.au.
Edwards, P. (2007). Introduced Dung Beetles in Australia 1967-2007.
Monteith, G. (1976). Australian Native Dung Beetles.
Matthews, E. G. (1972). A revision of the Scarabaeine dung beetles of Australia. -I. tribe Onthophaginoi. Australian Journal of Zoology, 19(9), 3–330.
Watson, N. L., & Simmons, L. W. (2010). Mate choice in the dung beetle Onthophagus sagittarius: Are female horns ornaments? Behavioral Ecology, 21(2), 424–430. https://doi.org/10.1093/beheco/arp207