Wildlife findings

SAVING LIVES WITH PLATYPUS MILK

An Australian breakthrough has introduced an unlikely hero in the global fight against antibiotic resistance: the platypus. Antimicrobial resistance occurs when bacteria build up a resistance to antibiotics and pass it on to the next generation, leading to persistent infections caused by resistant ‘superbugs’. In 2010, scientists discovered that platypus milk contained unique antibacterial properties. Now, a team of CSIRO researchers working with Deakin University has helped explain why platypus milk is so potent. The discovery was made by replicating a special protein contained in platypus milk in a laboratory setting. Platypuses express milk onto their belly for the young to suckle, leaving milk exposed and offspring susceptible to the perils of bacteria. Deakin University’s Dr Julie Sharp believes this is why platypus milk contains a protein with such unusual, antibacterial characteristics. Employing the marvels of molecular biology, the Synchrotron, and CSIRO’s state of the art Collaborative Crystallisation Centre (C3), the team successfully made the protein and then deciphered its structure. They found a never-before-seen 3D fold, which due to its ringlet-like formation, has been dubbed the ‘Shirley Temple’ fold in tribute to the former child-actor’s distinctive curls. Dr Janet Newman, CSIRO scientist and lead author on the research, said finding the new protein fold was pretty special. ‘We’ve identified this highly unusual protein as only existing in monotremes, but this discovery increases our knowledge of protein structures in general and will inform other drug discovery work performed at the Centre,’ she said. CSIRO and Deakin university are seeking collaborators to take the potentially life-saving platypus research to the next stage.

REDBACK SEX: CANNIBALISM BUT NOT ‘COERCION’

It has been known for some time that mature female redback spiders (Latrodectus hasseltii, right) cannibalise male partners during mating, but it has recently been discovered that males also engage in damaging mating tactics. Adult male redbacks mate with immature females (in their final juvenile instar), tearing the exoskeleton that covers the female’s reproductive tract in order to gain access to her newly developed, concealed genitalia. When males mate with mature females, prolonged vibratory courtship is typical, as males that attempt copulation early are killed by females before mating is complete (premature cannibalism). When males approach immature females, they engage in reduced courtship displays but are more likely to copulate twice, thus inseminating the females’ paired sperm-storage organs. The females store the sperm through their final moult and later produce fertilised eggs. At least one-third of immature females are mated this way in the field. Some researchers consider this behaviour coercive, because females do resist these matings (which cause haemolymph bleeding) and respond with elevated deterrent behaviours, such as rapidly raising and lowering their legs, hitting the male or the web near the male, or moving the rear legs and body while the male is mounted. However, coercion is said to occur only if the behaviour reduces overall female fitness. Luciana Baruffaldi and Maydianne Andrade set out to measure whether female fitness was reduced and found that immature-mating in females was either neutral or beneficial, as it meant they did not have to attract a male after moulting. Most immature-mated females did not produce sex pheromones as adults whereas unmated adult females produce sex pheromones that attract mates and trigger courtship. Some 17% of redback females die without mating. Those that do not mate as adults show reduced longevity, dying younger than mated females. Thus, Baruffaldi and Andrade found no reproductive cost for immature-mated females in terms of longevity, fertility or fecundity, and they therefore concluded that this male mating behaviour is not coercive.

Baruffaldi L, et al. 2017. Scientific Reports 7. DOI:10.1038/s41598-017-17524-6

FAIRY-WRENS KNOW THEIR ‘NEIGHBOURS’

Associations between different species (e.g. commensalism or mutualism) are common, but they are generally assumed to be transient and to not involve recognition of individuals. However, long-term interactions between individuals of different species do occur, as is the case between splendid fairy-wrens (Malurus splendens) and variegated fairy-wrens (M. lamberti, right). Allison Johnson and her colleagues
have shown that when both Photo: Jenny Thynne
species of fairy-wren live on
overlapping territories, they defend these territories against intrusion from heterospecific and conspecific individuals from outside the territory. This demonstrates that both splendid and variegated fairy-wrens are able to recognise and discriminate between individuals of the same and other species from within and outside the shared territory. For example, socially dominant males of both species responded more aggressively to songs of neighbouring and foreign heterospecific fairy-wrens than they did to those of their co-resident heterospecifics. While there was no change in the behaviour of splendid fairy-wrens when associating with the variegated fairy-wren, the variegated fairy-wren spent more time foraging, was less vigilant, had greater first-nest fledging success and fewer extra-group young. This suggests that the heterospecific association benefited the variegated fairy-wren.

Jonnson AE, et al. 2018. Behavioral Ecology. DOI:10.1093/beheco/ary071

NAIVE BILBIES SNIFF OUT CANINE FOE

The evolutionary timeframe necessary for naïve prey species to recognise and respond to novel predators is difficult to ascertain. For instance, does it scale to
how long a species has coevolved with a predator (known as the ‘ghost of predators past’ hypothesis), is it based upon ontogenetic experience (altered behaviour based on plasticity or learning), or is it a generalised response triggered by shared characteristics of predators (known as the ‘predator archetype’ hypothesis)? The ‘ghosts of predators past’ hypothesis posits that prey species possess hard-wired antipredator responses to predators they have coevolved with over long timeframes. A December 2017 paper by Lisa Steindler and colleagues suggests support for that hypothesis in research conducted on predator-naïve greater bilbies (Macrotis lagotis, above) within a 60 km2 predator-free enclosure at Arid Recovery Reserve, South Australia, where bilbies have been isolated from predators for 16 years. Since the dingo (Canis lupis dingo) arrived in Australia some 4000 years ago, greater bilbies have coevolved with dogs on the continent for many centuries longer than the two centuries in which they have encountered cats (Felis
catus). Bilbys’ burrow-emergence behaviour was found to differ accordingly when presented with olfactory stimuli (faeces) from introduced domestic dogs versus domestic cats. When dog faeces, which are chemically indistinguishable from dingo scats, were present, the bilbies spent more time with only their head and shoulders out of the burrow than they did when cat, rabbit, or unscented control faeces were present (in which case they emerged entirely). The findings support the ‘ghost of predators past’ hypothesis, as bilbies have retained antipredator responses to dogs/dingo scent while remaining oblivious to the danger of cats. In 2012, Carthey and Banks suggested that naturalisation of a predator should be deemed to have occurred once a prey species is no longer naïve towards it. Steindler et al. propose that this clear discrimination, even when these bilbies had no lifetime exposure to mammalian predators, supports the notion that dingoes should be considered a naturalised species in Australia.

Steindler LA, et al. 2018. Animal Behaviour. DOI: 10.1016/j.anbehav.2018.01.013

NEW VENOMOUS BANDY-BANDY FOUND

Analysis of genetic and morphological data collected from specimens of bandy-bandy discovered in northern Queensland by Dr Bryan Fry and Dr Freek Vonk in 2014 have confirmed the snake is a new, mildly venomous species – the Weipa bandy-bandy (Vermicella parscauda, below). This 80–100 cm black-and-white banded snake, while part of the venomous elapidae family, is not considered harmful to humans. In fact, its venom may contain medicinal properties, suggests Dr Kevin Arbuckle of Swansea University, who led the
molecular data analysis. The species’ distribution
is limited and threatened by bauxite mining, so formal evaluation will likely result in it being classified as endangered or critically endangered.
Derez CM, et al. 2018. Zootaxa. DOI: 10.11646/
zootaxa.4446.1.1

WEEDS DISPLACE KELP WHEN CO2 IS HIGH

New research by Prof. Sean Connell and an international team from Europe, Canada, the USA, and Hong Kong has found that the higher carbon dioxide levels predicted for our oceans will favour subordinate weedy plants over formerly dominant, more ecologically valuable kelp forests. Disturbances to ecosystems, such as increasing ocean acidification from higher CO2 levels, often create opportunities for particular organisms to thrive at the expense of others. As weedy species are better able to exploit carbon as a nutrient, they will grow faster than their natural predators (sea urchins) can consume them, displacing more biodiverse kelp forests and potentially resulting in conservation implications for species such as the leafy seadragon (Phycodurus eques) and common seadragon (Phyllopteryx taeniolatus, below), which inhabit kelp-covered rocky habitats in Australia’s southern waters. Led by the University of Adelaide, the researchers used natural volcanic CO2 seeps to compare today’s growth of weeds and kelps with levels of CO2 forecast for the turn of the century. ‘Under the level of acidification we will find in oceans in a few decades, marine life is likely to be dominated by fast-growing, opportunistic species at the expense of longer-lived species with specialist lifestyles,’ co-author Prof. Ivan Nagelkerken states. ‘We need to consider how natural enemies might be managed so that those weedy species are kept under control.’

Connell S, et al. 2018. Ecology. DOI:10.1002/ecy.2209

BIRD-EATING ROOS MIGHT TAKE THE BAIT

Western grey kangaroos
(Macropus fuliginosus, left) are common in woodland, open forest, mallee, and coastal heath habitats of southern Western Australia and are known to frequent the beach at Lucky Bay in Cape Le Grand National Park. Like all living kangaroo species, they are considered herbivorous browsers; however, a 2017 sighting of M. fuliginosus consuming the carcass of a silver gull at Lucky Bay led Michael Hughes and Valériane Bérengier to examine the conservation implications of this behaviour, particularly the risk of poisoning from 1080 baits. They found that a western grey kangaroo was earlier observed eating the body of a shearwater at Lucky Bay in 2013. Newspaper articles from 2003 also report western grey kangaroos consuming fish and seabirds and suggest that low-nutrient soils may lead these coastal macropods to seek calcium through bone-gnawing (known behaviour that facilitates calcium and phosphorous uptake in many species of wild and domesticated herbivores). An earlier 2014 study by Dundas et al. in Western Australia revealed that 99% of dried 1080 baits were taken by non-target species, the majority of them macropods (some 48% by quokkas and 10% by western grey kangaroos). Some Western Australian species have evolved a natural tolerance for fluoroacetate – contained in 1080 as the active toxin sodium fluoroacetate but also a naturally occuring organofluorine in species of endemic Gastrolobium, Gompholobium, Oxylobium, Nemcia and Acacia. Adult tolerance aside, pouch young may be susceptible to 1080 poisoning if M. fuliginosus ingests baited meat. The authors recommend more research to determine the extent of meat-eating/bone-gnawing in this species and whether 1080 bait poisoning presents a realistic threat to joeys.

Hughes M & Bérengier V. 2018. Pacific Conservation Biology. DOI:10.1071/PC17038