The Secret Lives of Carnivorous Marsupials: biology with bite
Predators come in all shapes and sizes, and Australia’s carnivorous marsupials are no exception. From miniscule marsupials weighing just a few grams, to Tasmanian Devils, which reach dog-sized proportions, most lead lives shrouded in mystery.
So what does it take to reveal the secrets of these unique and wonderful mammals – well a modern-day mammal hunter and collector of course (with just a little help from her Mum!)
Dr Marissa Parrott is a Reproductive Biologist who has worked in the field with many a marsupial. She is also a contributing author to Secret Lives of Carnivorous Marsupials, and in this edited extract from the book she shares some of her insights and adventures with the Agile Antechinus.
I first met the amazing Agile Antechinus (Antechinus agilis) during my honours year at the University of Melbourne. At the time, I was studying another small marsupial, the Feathertail Glider (Acrobates pygmaeus) – a gentle little creature that shared their nest box homes with antechinus, often with dire consequences. I occasionally found empty skins of feathertails and little else. The antechinus eat with surgical precision and can readily kill creatures their own size or larger! When I met my first antechinus, it promptly sunk its canines through the top of my fingernail; a pain I would become familiar with. Yet I fell in love with these voracious predatory marsupials and their big, brave personalities. I began a four year PhD studying female mate choice and breeding success in the species, both in captivity and the wild.
The Agile Antechinus inhabits the forests and woodlands of south-eastern Australia, hunting for invertebrates and small vertebrates. They are excellent climbers and have been caught on remote cameras raiding bird nests for eggs and even small adults, which they can dispatch with a lethal bite to the head and neck. In captivity and the wild, I have had large males run at me and try to bite me in an effort to scare me off – an impressive feat given that the ‘large’ males were less than 40 grams! I often said if antechinus were any larger, humans would never have survived in Australia.
Antechinuses are also highly intelligent. I was amazed by their deductive powers and how quickly they learned while working with them in captivity. The females build the most wonderful ball-shaped woven nests for their young – magnificent constructions. In the wild, I had many trap-happy animals that enjoyed my bait (the universal rolled oats, peanut butter and syrup mix) very much. I fondly remember one male who I would catch in multiple traps every day. He would race me to new traps to devour the food (gaining weight at each weighing) before finally leaving with a full bait ball in his mouth to enjoy later!
One of the most fascinating aspects of antechinus biology is their reproductive system. They have a highly synchronised annual two week breeding season during which males will attempt to secure as many matings as possible and females may mate with up to seven different males. After this brief, but vigorous, mating season, all males promptly die from stress. The female antechinus live on to produce and raise their litters, with 98 per cent of litters sired by more than one father. Females can store sperm from different males in specially designed isthmic crypts in their oviducts for up to two weeks. This means they can give birth after the male die-off, so for a period, there may be no males in the population. I found that female mate choice is important in antechinus, with females choosing males genetically dissimilar to themselves based on scent. Although females do not choose males based on size in captive experiments, in the wild, larger males will sire a higher proportion of young than small males. Females can have eight or ten young depending on the number of teats in their pouch and they often produce an excess number of young higher than the number of teats – this means most teats are generally occupied and it is survival of the fittest from the start! This is an amazingly complex reproductive system, with many more secrets to unravel.
My work with antechinus in the wild took place in the occasionally well-named Mt Disappointment State Forest. Although it is a beautiful tree fern-filled wet sclerophyll forest, it did frequently conspire to kill both myself and my volunteers (most regularly my long-suffering Mum who luckily is as stubborn and wildlife-loving as I am!) The temperatures ranged from boiling hot to below freezing which meant that large stressed trees frequently pulled out of the ground and could be heard crashing around us. The summer heat also brought the threat of bushfire (most owing to a serial arsonist, who thankfully was caught) – in fact, 15 separate fires occurred during my study period. Due to my field site’s proximity to Melbourne, there were many people who also used the forest, from nature-loving campers and legal deer hunters, to illegal hunters. Also present were illegal drug cultivators – I was quite surprised to find one of my field sites trip-wired with plastic explosives to protect an old drug site.
It was all worth it, however, to work with the beautiful wildlife in the area – the Agile and Mainland Dusky Antechinuses, and Bush Rats, which filled my traps. The magnificent parrots and cockatoos flying overhead, and dancing and singing lyrebirds on the forest floor. Biologists do suffer for their work, but discovering the secrets of the carnivorous marsupials and the wild lives of the agile antechinus is a life-long passion that continues today.
Dr Marissa Parrott is the Reproductive Biologist in the Wildlife Conservation and Science Department at Zoos Victoria, and an Honorary Research Associate in the School of Biosciences at the University of Melbourne. This is an edited extract from the Secret Lives of Carnivorous Marsupials. Marissa is also a contributing author to Saving the Tasmanian Devil: Recovery through Science-based Management.