Ant Volcanoes

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Pat Miller
Posts: 215
Joined: Tue Sep 04, 2012 9:36 am

Ant Volcanoes

Postby Pat Miller » Wed Aug 11, 2021 5:35 pm

download/file.php?mode=view&id=10534https://www.birdingnz.net/forum/download/file.php?mode=view&id=10535
Hi Folks,
The bottom photo is an "ant volcano" photographed in Western Australia in August 2019. The story we were told at the time is that the ants that build these walls around their holes can predict a day or two in advance when it is going to rain and build these to prevent their holes being flooded. This seems to be true, because we found freshly built ones at Kalbarri National Park one day and then a day or two later it rained.

The top photo is of a structure photographed on the track to Uretiti Beach, Northland on 10 June this year. I'm picking this is also an ant construction, although I didn't dig it up to find out. I didn't know we had ants in NZ that built these constructions, so what I am wondering is, does anybody know what species might have built it? And, is it only ants that build these little volcanoes, or do other ground dwelling insects?

The Australian ones were about 15 - 20 cm in diameter, the NZ ones only about 40mm in diameter.
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David Riddell
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Re: Ant Volcanoes

Postby David Riddell » Thu Aug 12, 2021 12:34 pm

I wonder if it could be a sandhopper (Talorchestia sp.)?
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Steps
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Re: Ant Volcanoes

Postby Steps » Fri Aug 13, 2021 8:25 am

Could it just be the medium they are digging in?
As kids we had/ made sand ant farms with couple bit glass each side. The surface level of sand increased each side of the entrance(s) as they constructed their tunnels. Ants being very efficient in what they do, I dont see carrying tunnel material far or the effort to spreading it out.
Also a loose cone has the potential of trapping other insects for food.

Also where I laid cobble stones over sand, and joins in cement paths, the ants only took their excavation material to around the hole.. forming a cone.
In soils insects prefer ,often need uncompacted soil...no need to carry to the surface, simply walls compact has go.

A loose sand cone would be of very little defense against rain. Even moderate drops of rain will soon flatten it out before 'flood' waters reach the volcano ridge.
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Pat Miller
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Joined: Tue Sep 04, 2012 9:36 am

Re: Ant Volcanoes

Postby Pat Miller » Sat Aug 14, 2021 6:47 pm

Hi David, yes maybe, but sandhoppers in my experience are usually on the beach and this was behind the dunes. If I find more of them I'll dig one up next time.

Thanks for your comments Steps. I agree with your last paragraph for the size that the NZ one was, but the Aussie ones actually stood up to the rain quite well. They eroded a bit, but were still intact after rain - much bigger than the Uretiti one though.
Pat Miller
Posts: 215
Joined: Tue Sep 04, 2012 9:36 am

Re: Ant Volcanoes

Postby Pat Miller » Mon Sep 27, 2021 11:11 am

Hi Folks,
I found some more of these ant volcanoes recently in two areas of sand dunes on vegetated vehicle tracks. The first lot were at Kauri Mountain Beach dunes on a grassy area of an access track and the second lot in dunes south of Uretiti Tip Road access (about 5km south of he earlier posting site). This time the sand was dryer and the ants were active at both sites carrying sand out of the tunnel and dropping it on the top of the volcano or on the outside edge - one grain at a time per ant. The volcanos at these more recent sites were flatter - about 10mm high and 60 - 70 mm in diameter.

Yeah, Steps, I have been wondering since these two more recent finds, whether they are a particular species of "sand ant" or whether the reason I haven't seen these volcanoes in other substrates is that other substrates don't collapse the ants burrows as readily as sand does.
The ants were small dark brown ones about 4 mm long. Inlight of my recent finds, they appear to be quite common locally in sand dunes anyway. I'll try and attach some photos.
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Kauri Mountain Beach Dunes ant volcano
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Kauri Mountain Beach dunes ant volcanos
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Kauri Mountain Beach dunes ant volcano
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