Caught in the act: Echidnas found sucking on endangered turtle eggs
Endangered freshwater turtle eggs are now on the menu for the short-beaked echidna (Tachyglossus aculeatus) which had previously been thought to only eat insects, according to a study by a CQUniversity researcher just published in the Australian Journal of Zoology.
The ‘cracking’ discovery by researcher Kymberly Robinson from Rockhampton in Central Queensland has busted the theory that echidnas are solely insectivorous and has unearthed the reality that some endangered turtle species are now under threat from a previously unknown predator.
The published report is the result of a five-year study of three river catchments in Queensland – the Fitzroy, Burnett and Mary – which revealed echidnas (once referred to as spiny anteaters) had been helping themselves to four different species of freshwater turtle eggs.
But it’s the two threatened bum-breathing species whose eggs have been dipped into – potentially spurring on their extinction – which have concerned researchers.
Ms Robinson said the white-throated snapping turtle (Elseya albagula) and the Fitzroy River turtle (Rheodytes leukops) are both facing grave futures due to high depredation levels and now the echidna has been added to the list of predators.
Her study revealed that the white-throated snapping turtle clutches had lower depredation compared to the Fitzroy River turtle clutches that have been hit the hardest by the spiny predator.
She said the vulnerability of the Fitzroy River turtle eggs may be due to their egg chambers being shallower. From the substrate surface to the first egg is just 14.2cm – a similar length to the beak of an echidna.
The short-beaked echidna is a monotreme (one of only a few species of extant egg-laying mammals) found in Australia and parts of New Guinea.
The species features fur and spines, a distinctive snout and a tongue previously thought to only catch its insect prey.
“Other predators like foxes, water rats or even wild pigs dig up the eggs and chew them, but the echidnas poke their beak through the egg and lick out the contents, leaving very minimal disturbance on the surface of the nests.”
Ms Robinson’s Fitzroy River turtle nest monitoring shows dramatic increase in echidna activity of nest depredation from 2.8% in 2018 to 47.4% in 2022.
“The depredation is significant for the Fitzroy River turtle increasing by 44.4 per cent within the five-year study.”
“With such a jump in echidnas destroying nests, you start to ask yourself: is this a natural thing, or is it other human interference elsewhere that has caused it?” Ms Robinson said.
“Or it could simply be a couple of echidnas have developed a taste of the eggs now.”
The findings have shocked many experts in echidna behaviour, however the way in which the echidnas have consumed the eggs via sucking could be the reason why scientists have not found eggshell remnants in their scat.
Ms Robinson said she hoped that by understanding more about the threatened freshwater turtles she could help tailor future management practices and strategies.
“The most important thing to me is to learn more about the species and how we can better protect them.
“Our focus should be on getting more hatchlings into the rivers systems.”
Studying turtle nesting ecology is not for the faint hearted. It requires a person who doesn’t mind getting their hands dirty at all times of the day and night and who has a deep respect for the dangers that lurk in Australian tropical waterways.
“Studying nesting ecology means I'm out monitoring riverbanks only accessible by boat during the nesting season – rain, hail or shine,” she explained.
The Fitzroy River system is home to another modern ‘dinosaur’ Australia’s saltwater crocodile – definitely a species to watch out for when monitoring the nesting banks.
However, Ms Robinson is no stranger to the Fitzroy River system – it’s been her ‘backyard’ since she was a child.
“I started out volunteering for a monitoring program when I was 16, helping protect nests from predators and seeing many hatchlings make it into the water.”
Seventeen years on, she’s just as passionate about the turtles and their habitat, but now as a published researcher she has the knowledge and platform to make a real difference.
“Previous studies of the Fitzroy River turtle have focused on the cloacal respiration, but there is so much we don't know about this threatened species,” explained Ms Robinson.
“The Fitzroy River turtle is currently listed as vulnerable with their status under review to change to endangered.”
“I hope that the findings of my study can help with future management decisions that affect the species directly including the river and riparian management that can impact the nesting ecology.”
Transcript
Meet Australia's short beaked echidna. Until recently this monotreme or egg laying mammal was only thought to eat insects. That was until a CQUniversity researcher confirmed the sneaky predator had been dipping his beak quite literally into the eggs of some of Australia's endangered freshwater turtles. The cracking discovery by CQUniversity researcher Kymberly Robinson revealed two threatened bum-breathing species, the white-throated snapping turtle and the Fitzroy River turtle, were facing grave futures due to high nest depredation. But it's the Fitzroy River turtle who has been hit the hardest by the predator. One of the interesting discoveries we've made is that echidnas are actually depredating on not just the Fitzroy River turtle eggs but the white throated snapping turtle eggs as well which are both threatened species so yeah very interesting. So the echidna has always been I guess thought of being insectivorous so only praying on things like ants and termites so this is the first time it's actually been I guess recorded and published that they eat something different to to that. In the zoological industry they actually feed echidnas egg in a slurry so to some people it hasn't really been a surprise but some of the other people that have been studying echidnas for a long time it was yeah very unsuspecting um predator. Kymberly says the vulnerability of the Fitzroy River turtle eggs may be due to their egg chambers being shallower than other species. So we found that um interestingly enough the echidna's beak probing in the substrate was a similar depth to the top egg of the Fitzroy River turtle um we also found the echidnas were more active during the springtime when the Fitzroy River turtle is nesting rather than the winter time when the white throated snapping turtle was nesting so um we're unsure if the depredation is higher for that species because of the actual beak depth and the top egg measurement we're unsure but um yes very similar very interesting. Most predators are easy to identify so if you have a fox a pig or anything like that they tend to dig the chamber out and chew on the eggs and and leave the eggshell sort of scattered on the ground um whereas the echidna we were coming across these nests that were depredated but all the eggs were sort of contained in the chamber and they just had one single puncher hole in them so it was quite unusual um in the beginning cause I was just like you know what animal is able to actually eat the contents of the eggs without removing them. Kymberly's monitoring of Fitzroy River turtle nests has shown a dramatic increase in echidna activity of nest depredation from 2.8% in 2018 to 47.4% % in 2022. With such a jump in destroyed nests you may wonder if this is natural occurrence or is it human interference at play or could it simply be that the echidnas have developed a taste of the eggs. Researchers may not have the answers quite yet but one thing is for sure the Fitzroy River turtle is worth protecting. So the Fitzroy River turtle is listed um as vulnerable both federally and state um so it means they're in a little bit of trouble or a little bit concerned that into the future the the species may totally disappear um so they're pretty special turtle they're only found in the Fitzroy catchment so that's the only place they're found in the whole entire world and um they're the only living species of their genus. So yeah very special little guys. Studying turtle nesting ecology is not for the faint-hearted it requires a person who doesn't mind getting their hands dirty at all times of the day and night and who has a deep respect for the dangers that lurk in Australian tropical waterways and Kymberly is no stranger to the turtles and the Fitzroy River system after all it's been her backyard since she was a child. Yeah sort of um fell into I guess working with freshwater turtles I've always been a big animal lover and when I was 16 I was given the opportunity to go and join um a group that was going out doing nest protection for the Fitzroy River turtle and um I guess I was sort of hooked after I went out on my first time so I've now been doing that kind of work for 17 years and it sort of led me to become pretty passionate about the species and and now I'm studying them. Kymberly hopes her study findings will help get more turtles back into the water.
