About Vultures and Australia... (1 Viewer)

[JessB]

Hello!

I'm helping someone put together a talk about vultures, and there was one question that came up while we were doing research that has both of us scratching our heads:

Throughout the world, vultures play a very important role as scavengers, but their act of consuming carrion also removes various harmful viruses and bacteria from the environment (including anthrax, botulism and rabies) -- their extremely acidic stomach fluids kill these pathogens, and in places where vulture populations have dropped severely, the diseases they would normally keep under control have spiked dramatically.

However, there are no vultures in Australia. Unsurprisingly, there are various scavengers there that fill a similar niche, but it's not clear to me if any of them have the same sort of pathogen-destroying prowess that vultures have that would curb the spread of the aforementioned diseases.

Could anyone possibly shed some light on this little quandary?

Thanks in advance!

 

[stoop]

Hello!

I'm helping someone put together a talk about vultures, and there was one question that came up while we were doing research that has both of us scratching our heads:

Throughout the world, vultures play a very important role as scavengers, but their act of consuming carrion also removes various harmful viruses and bacteria from the environment (including anthrax, botulism and rabies) -- their extremely acidic stomach fluids kill these pathogens, and in places where vulture populations have dropped severely, the diseases they would normally keep under control have spiked dramatically.

However, there are no vultures in Australia. Unsurprisingly, there are various scavengers there that fill a similar niche, but it's not clear to me if any of them have the same sort of pathogen-destroying prowess that vultures have that would curb the spread of the aforementioned diseases.

Could anyone possibly shed some light on this little quandary?

Thanks in advance!

This is a great question. It kept me awake many a night when I was young. I will keep an eye on this thread. My guess as for the behavioural side of things is that Wedge-tailed Eagles are large, very aggressive and can gather in groups thus warding off competing scavengers. That said, also, a lot of native wildlife in Australia is not so large. Even the biggest kangaroos aren't so big compared to larger animals on other continents. Camels and buffalo have been introduced in the last couple of hundred years, but before that smaller dead animals would have been cleaned up quickly by even smaller kites etc. I think any scavenger would prevent the spread of pathogens but I'm not a scientist.

 

[Chosun Juan]

I'd also be interested to know more about this side of things.

I know that many species of raptors will supplement their diet with carrion at times (even the mighty Golden Eagle overseas).

This is often linked to lifestages (immature dispersing often do this during lean seasons), as well as seasonal times (prey scarcity, adverse weather, altered landscapes). Many breeding raptors will exclusively? take live prey as they prepare the nest and incubate and fledge young.

Raptor size according to latitude distribution is also a factor - I can't imagine Tasmanian Wedge-tailed Eagles feeding too much on carrion when they are big enough to take down anything on the island, and the Tasmanian Devil somewhat fills that niche.

The other big elephant in the room is altered landscapes, water theft etc wrecking the web of life and altering prey availability.

I have never ever seen Nankeen Kestrels, or Black-shouldered Kites, Square-tailed Kites, or Australian Hobbies, or Peregrine Falcons take carrion. At times I have seen Whistling Kites, and Spotted Harriers take fresh carrion - stranded fish, fresh killed rabbits etc. .... and in certain areas (like outback highways) juvenile Wedge-tails seem to factor roadkill heavily into the diet.

Having only ever seen a Black-breasted Buzzard twice, I can't comment - but would they take more carrion ? or is the 'Buzzard' name a misnomer like so much in this country .....



Chosun 👧

 

[Sangahyando]

This is a great question. It kept me awake many a night when I was young. I will keep an eye on this thread. My guess as for the behavioural side of things is that Wedge-tailed Eagles are large, very aggressive and can gather in groups thus warding off competing scavengers. That said, also, a lot of native wildlife in Australia is not so large. Even the biggest kangaroos aren't so big compared to larger animals on other continents. Camels and buffalo have been introduced in the last couple of hundred years, but before that smaller dead animals would have been cleaned up quickly by even smaller kites etc. I think any scavenger would prevent the spread of pathogens but I'm not a scientist.

Australia used to have a megafauna - for example, the creatures known as Megalania (a giant monitor lizard), Quinkana (a large terrestrial crocodile), Diprotodon (a rhino-sized wombat relative), Thylacoleo carnifex (the "Marsupial Lion"), the Thylacine (which you've probably heard about, as it lingered on in Tasmania), and there were larger Kangaroos and flightless birds around, too. Their extinction, broadly speaking, coincides with the arrival of humans, as in other parts of the world.
I don't know if there were vultures or vulture analogues around back then, maybe a paleontologist can enlighten us.

Having only ever seen a Black-breasted Buzzard twice, I can't comment - but would they take more carrion ? or is the 'Buzzard' name a misnomer like so much in this country .....

Buzzard originally refers to members of the genus Buteo, which take both live prey and carrion (mostly roadkill these days).

 

[Chosun Juan]

Their extinction, broadly speaking, coincides with the arrival of humans, as in other parts of the world.

That's debatable !
There is evidence that humans and mega fauna coexisted for 10's of 1000's of years ....
As for 'arriving' in Australia - again, evidence says that humans were here 10's, 100's? of thousands of years before any convenient land bridges arose .....
I'm seem to recall posting some references in the now locked (apparently a post about love and peace was too much for some) , "Terra nullius" thread .....
I'm sure more bones will surface to tell the story when they are good and ready (or is that when everyone else is 'good' and ready 😉 )



Chosun 🙅

 

[Sangahyando]

That goes against the scientific consensus, and thus would require extraordinary quality of proof. All the evidence points to humanity originating in Africa, and co-evolving with the local fauna there. Which is why the African megafauna (until very recently) was less negatively impacted by humans than its counterparts elsewhere, particularly in Australia, the Americas, and remote islands.

 

[stoop]

I emailed a learned friend who got out all his books and emailed me back. He said there were a lot of contradictions on the matter. However, he pointed out that Australia has a lot of monitor lizards that fill the role of scavengers. Also, I just realised that Australia still maintains strict biosecurity laws and that many diseases, such as anthrax and rabies were absent. (Is rabies a disease?). My mate also said that old world and new vultures evolved parallel to each other after megafauna in Australia is believe to have disappeared and that the largest Australian mainland animal would hav e been Red Kangaroos which are much smaller than the herd animals in vulture environments. I will leave it at that but because there are many contradictions, I can see we could go on with endless hypotheses. I hope some of this helps.

 

[stoop]

I am still interested in seeing more about the discussion. As I said earlier, I was mad about raptors when I was a kid and my raptor books had pictures of amazing Gryphons and Condors and I was jealous why I didn't have any floating around my house in Australia. I need answers.

 

[jurek]

To my knowledge, there is no known sub-fossil extinct bird of prey or large stork in Australia, which could be scavengers which went extinct together with giant marsupials. Which is interesting that in Pleistocene, there was a species of white-headed vulture in Java and adjutant stork in Flores, so geographically relatively close.

I think wedge-tailed eagles, buzzards and kites fill this niche. And this shows that ecological rules are very broad considerations, not exact ones.

 

[Sangahyando]

I emailed a learned friend who got out all his books and emailed me back. He said there were a lot of contradictions on the matter. However, he pointed out that Australia has a lot of monitor lizards that fill the role of scavengers. Also, I just realised that Australia still maintains strict biosecurity laws and that many diseases, such as anthrax and rabies were absent. (Is rabies a disease?).

It's true that Australia has a large number of squamates; IIRC it has the largest number of extant native reptile species of any country. So monitor lizards playing a bigger role than elsewhere makes sense.

My mate also said that old world and new vultures evolved parallel to each other after megafauna in Australia is believe to have disappeared and that the largest Australian mainland animal would hav e been Red Kangaroos which are much smaller than the herd animals in vulture environments. I will leave it at that but because there are many contradictions, I can see we could go on with endless hypotheses. I hope some of this helps.

I don't quite follow that line of argument; the extinction of the Australian megafauna was relatively recent in evolutionary terms (even though it was a long time ago by human standards). IIRC Old World and New World Vultures only occurring in their respective hemispheres is also a new phenomenon; I remember reading somewhere that in prehistoric times, there were some species of New World Vultures in Eurasia/Africa, and vice versa.

I think wedge-tailed eagles, buzzards and kites fill this niche. And this shows that ecological rules are very broad considerations, not exact ones.

Well, theoretically it's also possible that some of the extinct mammals were more or less specialized carrion eaters.

 

[stoop]

I don't quite follow that line of argument; the extinction of the Australian megafauna was relatively recent in evolutionary terms (even though it was a long time ago by human standards). IIRC Old World and New World Vultures only occurring in their respective hemispheres is also a new phenomenon; I remember reading somewhere that in prehistoric times, there were some species of New World Vultures in Eurasia/Africa, and vice versa.

I was just suggesting that maybe existing vultures evolved after the extinction of Australian megafauna, and that vultures exist where large herd animals roamed. I think you restated what I was suggesting. I cannot back it up, and would need to do much more research. I'm told there are already contradictory arguments on the matter so whatever I suggested could be argued with. I am interested in the subject but I don't have the time to study it all or write about it.
I also wondered if biohazards associated with large herd animals once existed in Australia but died out with larger animals and I wonder if it is relevent or not, whether any of the megafauna once existing in Australia were herd animals? I admit I am too ignorant to make any conclusions. I think each region has its causes and conditions for evolution. We could ask now, why large marsupials are only found outside Australia? Have marsupials ever coexisted with vultures anywhere?

 

[MikeMules]

I was just suggesting that maybe existing vultures evolved after the extinction of Australian megafauna, and that vultures exist where large herd animals roamed.

That won't have happened. The main extinction period for Australian megafauna (excluding those that are still around today of course) was between approx. 60,000 and 10,000 years ago, and fossil Old World Vultures have been found dating back to between 10-15 million years ago (see https://www.researchgate.net/figure/Fossil-records-of-extinct-Old-World-vultures_tbl1_233301973)

 

[stoop]

That won't have happened. The main extinction period for Australian megafauna (excluding those that are still around today of course) was between approx. 60,000 and 10,000 years ago, and fossil Old World Vultures have been found dating back to between 10-15 million years ago (see https://www.researchgate.net/figure/Fossil-records-of-extinct-Old-World-vultures_tbl1_233301973)

Nice to learn, Mike. Thank you.

 

[jurek]

Well, theoretically it's also possible that some of the extinct mammals were more or less specialized carrion eaters.

Extinct giant monitor lizard could be a very good scavenger, too. But it does not explain absence of vultures. Hyenas are specialized scavengers, but birds are able to bypass scavenging mammals. Soaring and gliding flight is so efficient and fast that vultures locate and eat the carrion before scavenging terrestrial animal can walk there.

 

[THE_FERN]

and that the largest Australian mainland animal would hav e been Red Kangaroos which are much smaller than the herd animals in vulture environments.

Red kangaroo roughly same weight as an impala (so not true). However, Australia is a much less productive land (generally speaking of course) than Africa.

On the point about coexistence of new and old world vultures: does anyone have a ref for this?

 

[stoop]

Sorry, I was thinking Buffalo, elephant sized animals.

 

[THE_FERN]

Red kangaroo roughly same weight as an impala (so not true). However, Australia is a much less productive land (generally speaking of course) than Africa.

On the point about coexistence of new and old world vultures: does anyone have a ref for this?

Fred replied on the palaeontology thread. Yes, a "new world" vulture is known from France [I didn't check to see if "old world" vultures were around there then too but probably]

 

[THE_FERN]

Sorry, I was thinking Buffalo, elephant sized animals.

Those things are "relatively" rare and neither is likely to be very common prey item compared with smaller species. In the distant past, until c 44k years ago, there was a huge wombat thing in Oz, Diprotodon:

Diprotodon - Wikipedia

...at 2m tall and a couple of tonnes that would do the job.

 

[lgonz1008]

Probably well-known, but another cause for the lack of vultures (and other bird groups like woodpeckers, hornbills, etc.) in Australia is due to the Wallace Line, very few groups of unique animals from Australasia and the Sundas actually go beyond this line on either way. So while we did have records in the past of vultures in Java, the fact that they never made it to the Australasian region is not that surprising if you consider what other common (if not more widespread) groups of birds and wildlife did not cross the invisible line in the region.

 

[THE_FERN]

Hmm not 1000% sure I agree with Wallace line arguments either. It seems much more permeable than generally assumed (even in your example, Blyth's hornbill is widespread in New Guinea [=Australasia]).

Vultures are very unlikely to be constrained by Wallace's line. Other large gliders like Sarus crane, black-necked stork, brahminy kite made it to Oz ok...