NatureWatch: Animals putting on a show

Startling discovery about the praying mantis

The praying mantis is not unique in using the “startle display” as a form of defence against would-be predators, but its performance repertoire is among the more elaborate.

A full show can include striking displays of colour, wild movements of arms and wings, impressive sound production and even a wide-open mouth.

Now researchers from Australia, Canada and the US have discovered that the displays seem to be more complex in groups of closely related mantises.

“Even within a species, an individual praying mantis can choose to vary their displays by mixing up different types of behaviours or deploying different elements of their display in different circumstances,” says Kate Umbers from Western Sydney University, co-author of a paper in the journal Proceedings of the Royal Society B.

“This is possibly because being different to the relatives with which they may share predators prevents those predators from learning what to expect and increases the protective value of the startle.”

The researchers reviewed the behaviours and colours associated with the startle displays of 58 species of praying mantis and also examined 294 specimens from 49 species held in museums.

Umbers says the variations in the complexity of displays are significant because behavioural traits are easily changed, and this flexibility seems to be an important step in the evolutionary process.

“Next we need to figure out why exactly predators are so put off by these quirky performances. They have evolved so many times in different groups of animals – there could be some universal feature of predators that is being exploited.”

Skinks really care for their kids

Researchers have shed new light on the way reptiles care for their offspring after capturing rare footage of skinks fighting off Eastern Brown snakes and chasing magpies.

Husband and wife team Greg and Jolanta Watson, from Australia’s University of the Sunshine Coast, studied Cunningham’s skinks (Egernia cunninghami) in the Snowy Mountains for three years and were surprised to find they actively defend their young against predators.

“Among reptiles, evidence of parental protection in their natural environment has been typically anecdotal,” Greg Watson says. “A few studies of members of the crocodile family and an egg laying lizard have been previously documented.”

“Our observations of aggressive biting and pursuits by adult skinks may shed new light in relation to parental behaviour and offspring survival mechanisms in live-bearing lizards.”

Writing in the Australian Journal of Zoology, the Watsons say the initial aim of the study was to use thermal imaging to record how organisms that live in a range of habitats, such as skinks, would cope with climate change, but it evolved into an opportunity to study the social bonds and interactions between offspring and parents in lizards.

Available data suggests infanticide occur among the genus of skinks, but they “evidenced no such behaviour among the Cunningham’s skink”.

“[B]oth sub-adult and adult skinks demonstrated no aggression towards each other or towards young or newborns,” Jolanta Watson says.

Congratulations, it’s a starfish

Australian marine researchers have used the same technology as in-home pregnancy tests to develop a dipstick test that can detect crown-of-thorns starfish (CoTS) on coral reefs.

Designed to measure specific DNA that the destructive pests release into seawater, it can locate them in very low numbers and in hard-to-reach areas for ordinary survey methods.

“Organisms leave a genetic shadow wherever they go, so we use the genetic shadow of CoTS in seawater to flag the presence of both adults and babies,” says Jason Doyle from the Australian Institute of Marine Science, lead author of a paper in the journal Environmental DNA.

That works in the lab. The trick was to provide a way for scientists, citizen scientists and tourism operators to do it in the field.

Doyle and colleague Sven Uthicke adapted an off-the-shelf dipstick and a technology called Lateral Flow Assay (LFA), which has been used for many years in home blood sugar and pregnancy tests, and more recently for COVID-19 tests.

The new test can measure very small amounts of CoTS DNA – down to 0.1 picograms – and reveals a positive response via the appearance of a stripe. In tests off north Queensland, it found DNA where traditional survey methods did not.

It’s not a replacement for surveys, the researchers say, but it could complement them nicely.

Follow the (older) leader

Far from being loners, older male elephants may play important roles as experienced leaders for younger males when navigating unknown or risky environments, according to a study published in Scientific Reports.

It is known that in long-lived species older individuals often respond better to changing environments, which may benefit younger animals, but research in this area has tended to focus on females.

When researchers led by Connie Allen, from the University of Exeter, UK, investigated 1264 male savannah elephants travelling on pathways to and from the Boteti River in Botswana’s Makgadikgadi Pans National Park, 20% of sightings were of lone elephants.

However, adolescent males travelled alone significantly less often than expected, which may suggest that lone travel is riskier for newly independent and less experienced individuals. Older adults were significantly more likely to travel at the front of groups of males, suggesting that mature adult bulls may be leaders during collective movement.