Largest mammalian predator over most of Australia was island- rather than continent-sized

(writing in progress)

The largest-bodied indigenous mammalian predator over most of Australia, at the time of European arrival, is remarkably small by intercontinental standards.

I refer to the chuditch (Dasyurus geoffroii, https://www.inaturalist.org/taxa/40169-Dasyurus-geoffroii)

This species is remarkably small-bodied, it is mainly insectivorous, and it has remarkably large home ranges.

The body mass of Dasyurus geoffroii is about 1 kilogram in the adult female and 1.5 kilograms in the adult male. This is slightly larger than the meerkat (Suricata suricatta, body mass 0.7 kilograms), similar to the European polecat (Mustela putorius, body mass 0.7-1.5 kilograms), the Indian gray mongoose (Herpestes edwardsii, body mass 0.9-1.7 kilograms) and the Central American cacomistle (Bassariscus sumichrasti, body mass 1-1.5 kilograms), and smaller than the European pine marten (Martes martes, body mass about 1.5 kilograms) and the common genet (Genetta genetta, body mass about 2 kilograms).

The diet of D. geoffroii consists mainly of invertebrates although including vertebrates and fruits.

Furthermore, the chuditch has a surprisingly extensive home-range (about 400 hectares for the female and 900 hectares for the male) for such a small mammal. Reference for dispersal of dasyurus geoffroii, body mass about 1.5 kg, over at least 180 km as crow flies, from cape arid national park to salmon gums town: Morris et al. (2003) re Dasyurus geoffroii: https://books.google.com.au/books?hl=en&lr=&id=5IqhZoTEF10C&oi=fnd&pg=PA435&dq=dasyurus+geoffroii&ots=KNNA8cnXvq&sig=IMcD5Xvhb5b4rc1eE1-zKcRaHVs#v=onepage&q=dasyurus%20geoffroii&f=false

This suggests an extremely limited availability of prey on this nutrient-poor, fire-prone continent.
 
Distribution of Dasyurus geoffroii:
http://www.environment.gov.au/system/files/resources/d6c37be6-42cd-48c4-9cb6-9919457c8898/files/dasyurus-geoffroii-2012.pdf

Dasyurus geoffroii, the largest extant native mammalian predator over most of Australia at the time of European arrival, has body mass ca 1 kg for adult female and ca 1.5 kg for adult male. This makes it smaller than a genet, although larger than a meerkat (suricate).
 
An idea of the body size of D. geoffroii can be got from this video clip: https://twitter.com/hashtag/chuditch
 
The following show the body size of D. geoffroii relative to the human figure for scale.
 
Dasyurus geoffroii with adult male human for scale, southwestern Australia (I think the photo is attributable to Ian Moone):
 
http://i9.photobucket.com/albums/a70/troutylow/ReadyReleaseChuditch.jpg

http://thylacoleo.proboards.com/thread/3010/nannup-tigers 

Dasyurus geoffroii:
http://www.westernwildlife.com.au/Western_Wildlife/Chuditch_files/IMG_1866.jpg

Dasyurus geoffroii:
https://pbs.twimg.com/media/Br6QFQrCIAQFAgb.jpg

Dasyurus geoffroii (body mass about 1 kg), with adult female human for scale:
https://s.yimg.com/ea/img/-/150505/290415genchuditch2_1akgut2-1akgutd.jpg?x=656&sig=.qF3KUEX4HQM7vvLIVyfvA-- 
 
Dasyurus geoffroii with adult male human for scale, southwestern Australia (I think the photo is attributable to Ian Moone):
 
http://i9.photobucket.com/albums/a70/troutylow/ReadyReleaseChuditch.jpg 
 
http://thylacoleo.proboards.com/thread/3010/nannup-tigers 

Dasyurus geoffroii:
http://www.westernwildlife.com.au/Western_Wildlife/Chuditch_files/IMG_1866.jpg 
 
Dasyurus geoffroii:
https://pbs.twimg.com/media/Br6QFQrCIAQFAgb.jpg 

Suricata suricatta with adult male Homo sapiens:
http://i.dailymail.co.uk/i/pix/2012/04/09/article-2127209-1285B792000005DC-407_634x863.jpg

Suricata suricatta with adult male Homo sapiens:
https://i.ytimg.com/vi/_78mkyJCFzw/maxresdefault.jpg
 
Suricata suricatta with adult male Homo sapiens:
http://blog.corbis.com/wp-content/uploads/2014/11/42-63039353.jpg

Two points about Dasyurus geoffroii, the largest extant native mammalian predator found in southwestern Australia:
 
Firstly, this species is not about the same size as a domestic cat, as sometimes claimed. Instead, its body mass is only about 1 kg. That of the domestic cat is at least 3 kg, so in reality this marsupial is only about a quarter of the body mass of the average domestic cat.

To put this into a South African perspective, D. geoffroii is larger than a suricate but about half the mass of a genet. Both of the species of genets found in the vicinity of Cape Town are about double the body mass of D. geoffroii, because both have body mass about 2 kg (about half of the average domestic cat in Cape Town). In fact, the closest similarity in body mass can be found with the zorilla (Ictonyx striatus), often seen as road-kill in South Africa.

Yes, that small carnivore represents the largest extant native mammalian predator in the whole of southwestern Australia, an area larger than the whole of South Africa. I exclude the dingo because it seems that this canid was introduced only about five thousand years ago.
  
It is thoroughly remarkable what a limited capacity the natural ecosystem in southwestern Australia had to support mammalian carnivores. Extinct in the area (before European arrival) are Sarcophilus harrisii and Thylacinus cynocephalus, but even those carnivorous marsupials are only about jackal-size, not wolf-size.
 
What I learned during a talk by Dr Peter Mawson, who leads the captive breeding programme for D. geoffroii at Perth Zoo, is how vast the home ranges of this species are. The home range of males is about 1000 ha! A captive-bred individual released in Cape Arid National Park (just west of the Nullarbor) next turned up (healthy) in a chicken pen in Salmon Gums, which means that even if he moved in a straight line he walked at least 150 km! (probably closer to 200 km).

I would not have suspected that this rather dumpy little marsupial has such a wandering nature, and is so mobile. The species is largely terrestrial (less arboreal than, say, genets) although it can climb. But it does not have what I would call a cursorial body-form; in its limb proportions I find nothing to suggest particular adaptation to long-distance movement. So my interpretation of these enormous home-ranges is that the species is adapted to extreme sparsity of prey.
 
Please pause to think about this. It seems that the southwestern Australian environment had such a poor supply of prey that the largest fully indigenous mammalian predator is merely the size of a zorilla (a species so tiny that it manages to survive in the intensively farmed Swartland), and only about a quarter of the body mass of the average domestic cat. And even so, this marsupial has to range over vast areas to find enough food.
 
South African naturalists, can you imagine releasing a zorilla in Cape Town and finding it next in the Cederberg? I cannot find any information on home ranges in the zorilla, but it would not surprise me to find that this species usually spends its whole life on one farm.
 
Now comes an even more interesting aspect. Dasyurids have a tendency to live short lives and some species are downright semelparous. This syndrome is not particularly marked in D. geoffroii, but even this species has a lifespan of only about five years. It has a surprisingly short life, i.e. a remarkably limited longevity, for its body size. Even the domestic cat, which belongs to a short-lived group (Felidae) can live about 15 years. This short lifespan is unexpected for marsupials otherwise adapted to sparse food-supplies and an overall limited rate of reproduction and growth. To be clear: Dasyurus, although living such a short time, does NOT break the general marsupial rule of having limited rates of reproduction and growth relative to comparable placentals; it’s just that it uses a different life-history strategy to achieve these limited rates.
 
But my overall point is:
Although D. geoffroii is rather unremarkable in body form and dentition, coming over as a generalised animal compared to the more specialised-looking zorilla, genets, and mongooses of southern Africa, it is anything but generalised in its behaviour. It has the ability and proclivity to wander over an amazingly large area, and its lifespan is surprisingly short. I suspect that, among non-volant mammals, it has one of the greatest ratios of home range to lifespan ever recorded. I wonder if we could quantify that further?
  
For footage of a genet, showing body size relative to human size, see https://www.youtube.com/watch?v=nqowT5swY_A .
 
Dasyurus geoffroii (body mass about 1 kg and about the size of the road-killed zorilla you see while driving to the Cederberg):
http://nnimg-a.akamaihd.net/silverstone-feed-data/d1c3e942-0a20-48c3-acfd-efa24cc66791.jpg

Dasyurus geoffroii (body mass about 1 kg):
http://www.australianwildlife.org/media/59030/Chuditch-Ali-D.jpg
 
Salmon Gums is a town inside the pink area in the following map. An individual of D. geoffroii, released in Cape Arid National Park to the southeast (see it just west of Israelite Bay in the map below) walked all the way to Salmon Gums with no problem. This is about the distance from Cape Town to the Cederberg.
  
Dasyurus geoffroii (body mass about 1 kg), with adult female human for scale:
https://s.yimg.com/ea/img/-/150505/290415genchuditch2_1akgut2-1akgutd.jpg?x=656&sig=.qF3KUEX4HQM7vvLIVyfvA--

The largest extant native mammalian predator in an area as big as South Africa in southwestern Australia, pictured above, is only half the body mass shown below for genets.
 
Genetta sp., body mass about 2 kg:
https://www.youtube.com/watch?v=nqowT5swY_A 
 
Genetta genetta in Zululand:
http://smithsonianscience.si.edu/wordpress/wp-content/uploads/2014/09/Genet-rhino_3_watermark-e1411439284371.jpg

http://voices.nationalgeographic.com/files/2014/09/Genet-rhino_7_watermark-1024x789.jpg

http://smithsonianscience.si.edu/wordpress/wp-content/uploads/2014/09/Hluhluwe-Buffalo-and-Genet-1_edited_watermark-Wildlife-Act-630x451.jpg

https://bonnie8878.files.wordpress.com/2014/09/nature-genet-buffalo_1_watermark-1024x790.jpg?w=940&h=400&crop=1

https://i.ytimg.com/vi/YOrhmA1oUkQ/maxresdefault.jpg

(writing in progress)

Publicado el 29 de junio de 2022 por milewski milewski

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@ludwig_muller @jeremygilmore

Australian and southern African naturalists have opposite psychological  challenges in terms of an appreciation of their biogeographical situations.

Whereas in Australia and New Guinea the lack of large mammals is so extreme that it is tempting to 'invent' animals to fill the void (e.g. by pointing out that larger animals existed in the Pleistocene), in southern Africa the fauna is so replete that some large-bodied mammals get routinely overlooked.

I gave the example of the Cape warthog (Phacochoerus aethiopicus aethiopicus) in an earlier Post.

Here is another example: the occurrence of the aardvark on the Cape Peninsula.

Even near Cape Town, which is in some ways more like Europe or California than like Africa, naturalists are ‘spoiled for choice’. Even the southwestern Cape of South Africa is so richly endowed with large-bodied that it does not seem to have occurred to anyone that the aardvark is indigenous locally (https://www.sanparks.org/parks/table_mountain/conservation/fauna.php#:~:text=Other%20mammals%20include%3A%20Cape%20Mountain,Clawless%20Otter%20(Aonyx%20capensis)%2C). 
 
The aardvark is/was recently widespread from the Cape to Cairo. I have seen evidence of it myself at Cape Agulhas, the southernmost point in Africa (where the local farmers confirmed the presence of the species unambiguously). The species is certainly present in the Fynbos Biome. Yet how many people have ever asked themselves ‘did the aardvark formerly occur on the Cape Peninusula?’
 
I suspect that, when Jan Van Riebeeck arrived in 1652, the aardvark was indeed present where Cape Town now stands. And it might even have lived in what is now the Cape Point section of Table Mountain National Park (although everyone would agree that, if so, the population there would have been minimal, perhaps only dispersing subadults). So, I do not think anyone – if they really investigated the matter – would deny that the aardvark is an indigenous species to Table Mountain National Park.
 
This is an animal about the same size as the human species (i.e. ca 60 kg), and the most massive specialised insectivore on Earth. It is about the same size as the Cape warthog, and would be larger than any extant mammal indigenous to many cities of the world, such as the capital cities of islands such as Jamaica, Cuba, Fiji, New Guinea, etc. etc.

In Perth, Western Australia, the lack of large mammals is so incredible that few acknowledge that the largest mammalian predator was merely an insectivore.

Meanwhile, a 'mirror city', Cape Town, not particularly rich in large indigenous mammals by African standards, is still so rich that everyone has ‘lost track’ of the faunal list - overwhelmed by the sheer number of spectacular large mammals in the modern fauna.

Publicado por milewski hace más de 1 año

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