Australasian Science: Australia's authority on science since 1938


By Stephen Luntz

A digest of science news.

Equatorial Fish Are Feeling the Heat

The capacity of many warm water fish to respond to climate change has been questioned in Global Change Biology.

Dr Jodie Rummer of the Centre of Excellence for Coral Reef Studies at James Cook University studied the oxygen consumption of six fish species at rest and when swimming hard. The fish were unable to boost their performance in warmer waters, casting doubt on their capacity to evade predators or find food.

“Our studies found that one species could not even survive in water just 3°C warmer than what it lives in now,” said Rummer. “Already we found four species are living at or above the temperatures at which they function best.”

Rummer said that dispersal of fish away from the Equator “will have a substantial impact on the human societies that depend on these fish”.

Lion Population in Decline

West African lions are even more scarce than had previously been recognised, according to a study published in PLOS One.

West African lions are genetically distinct from those in southern and eastern Africa, and are closely related to the extinct Barbary lions of northern Africa. When a survey of the population began it was believed that lions survived in 21 protected locations. However, lead author Dr Phillip Henschel reported: “All but a few of the areas we surveyed were basically paper parks, having neither management budgets nor patrol staff, and had lost all their lions and other iconic large mammals”.

Co-author Dr Lauren Coad of the University of Queensland said the four remaining locations, housing just 250 lions, lacked the capacity to defend against poachers. “Our findings suggest that many of the west African protected areas still supporting lion populations are chronically underfunded and understaffed,” Coad said.

Carnivore Count

A study in Science of 31 carnivores weighing more than 15 kg has found three-quarters in decline, with 17 now eradicated from more than half of their recent range.

“These are some of the world’s iconic predators,” said co-author Dr Arian Wallach of James Cook University’s School of Marine and Tropical Biology. “Because of their position at the top of the food web, they frequently come into conflict with humans.”

Removal of apex predators creates ripples through the ecosystem. One example is the famous case where the hunting of wolves in the American west led to deer overeating vegetation. The good news is that the rare cases of carnivore restoration have been met with rapid recovery.

“Where dingo populations are healthy and stable we see fewer impacts from wild herbivores and smaller predators such as the red fox,” Wallach said. “That allows vegetation and small native animals to recover.”

Why Bikies Ride in Packs

There is a benefit for motorcyclists in sticking together – Attention Perception and Psychophysics reports that they’re less likely to be hit by cars.

“When motorcycles were high frequency, drivers detected them on average 51 metres further away, compared to when they were at low frequency,” said Dr Vanessa Beanland of the Australian National University;s Research School of Psychology. “At a driving speed of 60 km/h, this allowed the driver an extra 3 seconds to respond.”

Two hundred motorbike riders and 50 cyclists are killed in Australia each year, most from collisions with cars. Beanland used a simulator to test the capacity of 40 drivers to respond to vehicles when the number of riders were high and low. “The results suggest that drivers have more difficulty detecting vehicles and hazards that are rare compared to objects they see frequently,” Beanland said.

Multi-drug Resistance in Pets

A study of bacterial samples from Australian pets shows they are free from bacteria resistant to antibiotics of last resort. While this is good news, the discovery of such bacteria in dogs overseas suggests there is no room for complacency.

“Australia now has a limited window of opportunity to implement tight controls to prevent the development of multi-drug resistance in pets,” said Dr Sam Abraham of Adelaide University’s School of Animal and Veterinary Sciences.

Abraham is more than half way through testing 3000 samples of E. coli and staphylococci isolated by veterinary laboratories across Australia in the last year. The university is developing a plan for antimicrobial use and surveillance.

“We need to make better use of currently registered veterinary antibiotics and ensure that carbapenems are administered only as a last resort in companion animals for the very few cases of infection that lack other suitable alternatives,” Abraham said.

Fires Devastate Endangered Birds

Last summer’s bushfires have pushed endangered birds to the edge. The Mallee emu-wren, a tiny bird with tail feathers that resemble those of emus, survived in two conservation parks in South Australia.

“Following the recent fires, the global population of the Mallee emu-wren is now restricted to a single reserve system – one big fire could render the species extinct,” said Dr Rohan Clarke of Monash University’s School of Biological Sciences.

The black-eared miner has been the subject of recovery efforts for more than a decade, with birds released into new colonies. One of three existing colonies was burned entirely, while the loss of 35% of the habitat in a second colony marked a further setback to the program.

“The recent review of Australia’s bird fauna lists 27 bird species as extinct since European colonisation, with a further 20 classified as critically endangered and 60 endangered,” Clarke said.

Sunscreen Safety

Nanoparticles in sunscreen do not represent a risk to the skin, RMIT A/Prof Paul Wright has reported to the International Conference on Nanoscience and Nanotechnology.

Nanoparticles of titanium dioxide and zinc oxide have become popular in sunscreens in recent years as they block ultraviolet (UV) light but are transparent on the skin, rather than milky-white like larger particles.

Wright found that human immune cells exposed to UV-A light experienced a large increase in reactive oxygen molecules, also known as free radicals. When sunscreen nanoparticles were added to the mix, no extra reactive oxygen molecules appeared.

The work confirmed that UV light is far more of a threat to skin than any form of sunscreen. While this was widely reported as confirming the safety of nanoparticles, the study did not investigate the primary fear expressed about their use: that these particles would prove damaging to other organs in the body if they enter through small cuts in the skin.

Mould and Asthma Correlated

The presence of mould in homes is strongly correlated with asthma in middle age, according to a study in Respirology.

“We found that in homes with more rooms affected by mould, there was a stronger trend for asthma, wheezing and night-time chest tightness,” said Dr John Burgess of the University of Melbourne’s School of Population and Global Health.

Burgess noted that asthma studies usually concentrate on children and adolescents, leaving adult triggers poorly understood. Asthma rates have increased dramatically in recent years for adults as well as children.

Second-hand tobacco smoke was also confirmed as a major risk factor for respiratory symptoms.

Sharks Lack Ray of Hope

The first global analysis of 1041 species of sharks and rays by the International Union for the Conservation of Nature has concluded that one-quarter are threatened with extinction, even prior to the Western Australian cull. With only 23% categorised as “least concern”, sharks and their relatives are less likely to be safe than almost any other animal group.

“Surprisingly, we have found that the rays, including sawfish, guitarfish, stingrays and wedgefish, are generally worse off than the sharks, with five out of the seven most threatened families made up of rays,” said James Cook University’s Professor of Environmental Science, Dr Colin Simpfendorfer. “While public, media and government attention to the plight of sharks is growing, the widespread depletion of rays is largely unnoticed. Conservation action for rays is lagging far behind, which only heightens our concern for this species group.”

Shark fin soup is creating demand not only for sharks but rays such as guitarfish, but deep-sea shark livers are also sought.