Tag Archive | natural history

Matachia!

One of the coolest spiders I saw in NZ was quite small, and fairly inconspicuous. Matachia is NZ endemic genus of desid spiders which have a characteristic web architecture and retreat. There are several species of Matachia in NZ. Bryce McQuillan helped us find these in Christchurch, along the Avon River (just about here), in low branches above the bank.

Here you can see a Matachia poking out of her retreat, which is in the emergence hole caused by an insect (often the emergence holes of a twig-boring moth, Morovia subfasciata). The webs have radial lines for movement, and zig-zag calamistrated cribellate capture threads. Calamistrated silk is not gluey,

The cutest aspect of Matachia behaviour we saw was that upon returning to their retreat, the spiders invariably enter it butt-first!

The Matachia we saw in Christchurch emerged onto their capture webs quite readily in response to vibrations from an electric toothbrush. Here arachnologist Erin Powell coaxes out a spider, while Bryce photographs it.

Some Matachia webs we saw also had these odd platform-like constructions just near the retreat. I am not sure if the resident spider makes these, or perhaps it is done by a courting male?

A backlit Matachia

I did manage to see a courting male, and the web did have this platform-like construction on it. An interesting thing to note about these males (and males of other calamistrum-bearing species) is that the calamistrum (which brushes out the lacy capture threads from the cribellum) is lost in the adult stage, meaning these males can no longer hunt as adults…

In this image, you can see not only an adult female in her retreat, but also a tiny juvenile, with greenish abdominal markings. In Matachia, the juveniles remain with their mothers until they are 4-5 molts past hatching, which is a remarkably long time!

Symbiosis and inspiration in the jungle

Apr24

A large nest of Polybia liliacea. This is one you probably do not want to disturb!

Compared to my time in French Guiana, I found that travel by river offers a much greater volume of observations than walking in the forest. When I was in French Guiana travelling trails on foot, I was lucky to encounter one example of a particular habitat in a day, but on the boat I could see the same type of habitat many times over. Needless to say, this was a great natural history lesson in the making.

One of the particular habitats we saw a lot of was the meanders of the river, where the river loops and bends around long curves. These bends form spontaneously via the action of vortices along curves in the river, and on the inside of each curve there is high deposition of silt (on the outside is a high level of erosion). This is the process by which oxbow lakes are formed. The result is that the inside curve is an area that was formerly river-scoured, but now has abundant new soil. Within these areas are a sparser forest, dominated by a few fast-growing tree species such as Cecropia and Triplaris (called “Long John” in Guiana). These are habitats that harbor a beautiful example of tropical symbiosis.

Yellow-rumped Caciques (Cacicus cela) bathing together in the early evening. These are highly social birds with colonial nesting.

One of the first things that I noticed about these meander forests is that they more often than not contained a large colony of nesting Icterid birds, either Green Oropendolas, or Red-rumped or Yellow-rumped Caciques, with the latter being the most common. All of these birds are known to preferentially nest in association with large, aggressive wasp species, such as Polybia rejecta and Polybia liliacea. This is thought to benefit the birds in two ways. Number one is that the wasps can help dissuade nest predators, such as monkeys. Number two is that populations of predaceous wasps may reduce the parasite burden (particularly parasitic Philornis flies) that the nestlings endure.

A colony of Cacicus cela nesting in association with Polybia liliacea. We also saw them with Polybia rejecta and Epipona spp. wasps.

In turn, the wasps nest in these particular trees for a reason. They nest in trees that are occupied by Azteca ants, a type of dolichoderine ant that basically owns the tree, with large carton nests containing perhaps millions of moderately small workers and hundreds of queens. The wasps nest here because the Azteca repel one of the wasps’ worst enemies: army ants. Although army ants (Eciton burchellii and Eciton hamatum) vastly outweigh the Azteca individually, the Azteca, by virtue of their overwhelming numbers, can keep army ant columns from advancing quickly up the tree (Servigne 2003). As army ants are all about blitzkrieg, and quickly stripping an area of profitable prey (Kaspari et al. 2011), they have learned to avoid the Azteca trees, which would take a protracted guerilla campaign to overcome. It has been recently shown that the wasps in turn benefit the ants, helping to repel some of their predators, such as woodpeckers (Le Guen et al. 2015)!

Nesting association between Azteca (left), Polybia (centre) and Cacicus (upper right).

In examining again and again the morphology and placement of the nests in these associations, I was struck by a thought: perhaps the birds are also a net benefit to the wasps and the ants as well! I know from my research how formidable Red-throated Caracaras are in destroying wasp nests….What if these large numbers of nesting caciques help protect the wasps from the caracaras? It is not so outlandish a hypothesis, as the large nesting aggregations of caciques have been shown to mob bird nest predators such as monkeys and Black Caracaras and drive them away (Robinson 1985). Perhaps the Red-throated Caracaras may be driven away as well by large numbers of defensive caciques.

Could wasps derive protection from Red-throated Caracaras from cacique or oropendola colonies?

I was amazed by the numbers of large wasp nests we encountered at these sites, in stark contrast to the relatively low numbers I encounter in normal forests. It is not just the presence of ants which is keeping these nests safe, as Azteca occur in large numbers all over the forests. I think something else is going on here to help protect these wasp nests, and I bet it is the birds. Anyway, I would love to go and study this sometime, but this story just reinforces to me the inspiration that I only get by going to the field.

The Black Caracara, a known predator of cacique nests, is sometimes mobbed and driven away by Yellow-rumped Caciques.

References

KASPARI, M., POWELL, S., LATTKE, J., and O’DONNELL, S. 2011. Predation and patchiness in the tropical litter: do swarm-raiding army ants skim the cream or drain the bottle? J. Anim. Ecol. 80:818–23

LE GUEN, R., CORBARA, B., ROSSI, V., AZÉMAR, F., and DEJEAN, A. 2015. Reciprocal protection from natural enemies in an ant-wasp association. C. R. Biol.

MCCANN, S., MOERI, O., JONES, T., O’DONNELL, S., and GRIES, G. 2010. Nesting and Nest-Provisioning of the Red-throated Caracara (Ibycter americanus) in Central French Guiana. J. Raptor Res. 44:236–240.

MCCANN, S., MOERI, O., JONES, T., SCOTT, C., KHASKIN, G., GRIES, R., O’DONNELL, S., and GRIES, G. 2013. Strike fast, strike hard: the Red-throated Caracara exploits absconding behavior of social wasps during nest predation. PLOS One 8:e84114.

ROBINSON, S. S. K. 1985. Coloniality in the Yellow-rumped Cacique as a defense against nest predators. Auk 102:506–519.

SERVIGNE, P. 2003. L’association entre la fourmi Azteca chartifex Forel (Formicidae, Dolichoderinae) et la guepe Polybia rejecta (Fab.) (Vespidae, Polistinae) en Guyane Française. Universite Paris-Nord.

Scenes from a foggy day

Jan7

We have been basking in warm, moist air here on the West Coast, while the rest of the country is freezing in Arctic outflows. This “Pineapple Express” has brought a lot of rain over the past week, but that is now letting up. Yesterday was calm and foggy, and a bit eerie in its warmth. I was in Victoria, so I went walkabout to see what I could see.

Monday night the fog rolled in, smelling of the sea.

On Mt. Tolmie Tuesday morning, the air was still and moist, and collembollans could be found up on the vegetation.

Rock Flipping Day is every day for me, and has been since i was a kid. I found this beautiful spider that looks very much like a Pimoa.

Oddly, I also found 3 colonies of Aphaenogaster occidentalis, under rocks where 2 weeks ago none were evident. The warmth must have penetrated the soil, and the colonies moved themselves and their brood upwards.

These are some of my favourite myrmicines, and appear to be quite common in Garry Oak meadow habitats.

Jackson was along for this outing, and spent some time chewing rocks…You should see his teeth after 9 years of this awful habit!

I even managed to find a beautiful Phidippus!

On the ferry coming back to Vancouver, the waters were calm.

As it was high tide, the seals were hauled up on the rocky shores of Galiano Island.

Here, the ferry comes up on a log with cormorants and gulls.

Which scatter, somewhat comically.

A large volcano, Mt. Baker, which I visited several months back.

Winter lighting in this part of the world means sunset-like conditions at 2:30!

Which make for beautiful backgrounds.

An oasis in Crow City

Dec28

Right in the heart of downtown Victoria, in an abandoned, excavated lot we found this little piece of crow paradise. It was fenced and secure, and had a lovely sunstruck bathing pool.

When we approached, several crows were bathing.

Here a crow ducks down in the water, splashing furiously.

Ah, that’s better!

Victoria, much like Vancouver is a city of crows. Although there are some ravens in both cities now, the predominant corvids are crows.

On Boxing Day, right next door from my mother’s house, A huge gathering of crows came down to feed of the subterranean larvae of European chafer, a type of scarab beetle.

Perched up on a power line, the crows wait for a dog to pass.

Many of the crows in Victoria communally roost on Discovery and Chatham Island, like the Vancouver crows nest in Burnaby. Here is one fresh off the morning flight from the islands.

I really enjoy watching crows, and despite their ubiquity, find them a challenge photographically.

Capturing their behaviour accurately remains one of my photographic goals. How cool would it be to get good photos at a nest? Close up views of their prey? Mating? I think I will keep watching and shooting crows for a good long while before I am satisfied!

White Woodpecker preying on wasp nests!

Oct21

Melanerpes candidus approaching the nest of social paper wasps. Photo by Miguel Rangel Jr. used under terms of a CC-BY-SA licence.

In the latest issue of Revista Brasileira de Ornithologia, I found a paper on a topic near and dear to my heart: birds preying on wasp nests. In this case, it is an account of the White Woodpecker, Melanerpes candidus preying on the nests of Polybia paulista. In this paper, Ivan Sazima describes the predation tactics used by this woodpecker when attacking a large, well-defended nest. Ivan conducted this research at Parque Ecológico Prof. Hermógenes de Freitas Leitão, in the state of São Paulo, Brazil.

Like the Red-throated Caracaras I studied, the White Woodpecker appears to exploit the absconding response of these swarm-founding wasps in order to secure its meal of wasp brood. Rather than inflicting rapid, catastrophic damage, however, the woodpecker takes its time, approaching the nest gradually and tapping the branch to which the nest is attached. During this approach, some of the wasps come out to sting, and if this gets too fierce, the woodpecker will retreat. Sazima attempted this tactic himself with a similar nest of P. paulista, and got stung severely for his efforts. Sazima suspects that the continuous nature of the woodpecker’s disturbance is what is required to induce the wasps to abandon their nest. Also, the agility of the birds at evading attacking wasps also means they can keep this harassment up longer than an unprotected human.

This paper is a valuable contribution to the study of wasp and bird behaviour, as it highlights that certain anti-predator strategies of social wasps (stinging, alarm recruitment) can be defeated by exploiting the evacuation swarming (absconding) behaviour of these wasps. Bearing this in mind, it is no wonder that so many species of swarm founding wasps have cryptic nests to escape the detection of diurnal vertebrate predators.

I especially love one of the concluding sentences:

The foraging behaviour of the White Woodpecker reported herein results from so-called anecdotic, natural history oriented observations, often disregarded by theory-trained biologists. Nevertheless, this kind of observation draws attention to phenomena that later may prove more widespread or commoner that previously thought.

I could not agree more. Please head over to read the paper yourself, as the photos of the behaviour are great, and the text well worth the read.

Update: See another wasp predator in action here.

Photo by Márcio Vinícius Pinheiro, shared under the terms of a CC BY-NC-ND 2.0 licence.

Spider rappelling! A great way to get around.

Sep11

When a spider wants to make a long distance traverse between two objects, or just wants a quick way to ascend an obstacle, what can he do? Lets find out by watching a male crab spider.

Well, as in ballooning, the spider can jet out a thread of silk, letting it be carried by the wind.

The spider then turns and checks the tension on the web to see if it has snagged a target. In this case, there is no tension, so the spider reels in the thread. I am not sure if crab spiders consume the spent silk.

Another try, in another direction.

This time the tension is right, and the spider quickly disappears from the frame.

And arrives safely at another, more lively flower.

Keeping my naturalist cred!

Mar14

Ogden Point is a great place to see otters, as there is abundant food, as well as crevices between the big stone blocks forming the breakwater where they have dens. My brother got an even better shot!

Yesterday’s great post by Chris Buddle over at Expiscor highlighted the importance of natural history and the people who practice it. I have generally considered myself a naturalist, but the last few weeks have not been very active for me, as I have been engaged in a lot of writing. Luckily, I scheduled a few hours yesterday morning to go out to Ogden Point and Beacon Hill Park to do some nature photography and keep my naturalist cred!