It is a wonderful thing to give a talk to an enthusiastic audience, especially when comes with a chance to travel and meet new people. I was very lucky to have had this opportunity last week when I went to Houston Texas to give a talk on Red-throated Caracaras to the Houston Audubon Society.
Mary-Anne Weber, along with Juanita Perkins arranged for me to travel to Houston to give this talk, and were my most gracious hosts during my trip. I did not have to stay in a hotel, but instead stayed with my friend Cullen Geiselman, a bat researcher who I met at the Nouragues Station.
I am very grateful to have had this wonderful opportunity, and I thank all of the people who came out to hear me talk.
One of the first things I looked for at the Sanctuary was ants, and I was lucky enough to find this Leptogenys elongata colony.
These are members of the subfamily Ponerinae, and are much different in form from the myrmicines and formicines I am used to.
As their name suggests, they are gracile (slender and long limbed) and likely either run fast or climb trees. On this day, they weren’t going anywhere quickly because it was cold and rainy.
On Friday, after my talk, I went out with Mary-Anne Weber and Joe Smith for a birding outing. Here is something we don’t often see in Canada!
This osprey allowed a close approach using the time-tested technique of pretending we didn’t see it!
A couple of local dogs who thought they owned the place!
Several osprey were fishing in the stormwater retention ponds.
A white pelican flies by some construction. This is likely to be another Canadian visitor to Houston.
White pelicans engaged in feeding. They are not spectacular divers like Brown Pelicans, but they sure are majestic. .
This is a juvenile Cooper’s Hawk, which Mary-Anne ID’ed correctly. I was thrown off by the white splotches on the back, which we do not often get on the West Coast.
From the front it looks much like our Cooper’s Hawks.
Everything is bigger in Texas, including the Great Blue Herons! Well, all over the east they are bigger than our West Coast form.
The closest approach of a White Pelican.
Back at the Sanctuary, I found some more ants, this time a very very tiny myrmicine. Any ideas about what this is?
The workers were dimorphic, with this large headed form being present.
I even managed to find a jumping spider, despite the cold wet weather.
And finally, a mystery ground spider, which we will be in a better position to ID after this summer, when Catherine and I will attend a workshop in spider taxonomy in Arizona.
After I left Houston, I took the opportunity to do some aerial photography of the western landscapes we flew over. Here the mountains and deserts look like an alien landscape with the desaturation of distance.
Sometimes the light of a cloudy day is beautiful for photography, making features soft and creamy, eliminating harsh shadows, and enhancing colours. But this is a bright cloudy day we are talking about, not a gloomy, dark and depressing day like we tend to get around Vancouver this time of year. On a day like that, the photographer can only do one thing: eat Cheetos and veg out.
But wait! There is something you can do to get nice defined images of wildlife despite the terrible conditions and your way-too-old, way-too-noisy Canon sensor. Of course! Supplemental light!
I tested out throwing some hard light from trigger-controlled flashguns on a few species at Stanley Park this Saturday, and I am pretty pleased with the results!
This gull gains just a subtle definition from a speedlight placed behind and to the right.
A crow positioned about where the gull was. This time, because the bird is black, the effect is even more subtle, but that rim light on the head and showing up the feathers on the back is all flash.
The light to the back is much more obvious here, and the background branches are also lit. Bokeh is not great.
Again, some nice definition that would not have been present without a flash.
This Song Sparrow benefits from supplemental light, although it is a tad too direct for my taste.
A single shot with the 100 to show how the light was falling. I had the rimlight behind, and a bit of a fill directly in front of the crow (to my right).
Even hard light need not be oppressive. This towhee is still subtle, and I probably gained 3 stops of ISO here, making the image cleaner.
This squirrel gains definition from a single speedlight to the right, and a bit of fill from directly in front. .
This hooded merganser pops a bit more and is crisper overall thanks to speedlights.
Chickadee mid leap. Single speedlight to the right.
Chestnut-backed Chickadee. Again, I am gaining stops and definition.
Overall, I like this method of shooting, but would prefer natural light. For a gloomy day, when all I would get otherwise is a noisy mess, this is a good thing to try. With an actual lighting assistant, I am sure it could be even more fun.
Photography brings me a great deal of pleasure, and I indulge in it whenever I can. A few years ago, I was with my dad, driving north from Victoria to my brother’s wedding. Along the way is Goldstream Park, a real gem where the Golstream River empties into Saanich Inlet. We had some time to kill, so we went out for a short stroll with our cameras. It was a beautiful fall day, although the early morning forest was still dark. After photographing some salamanders in the forest, I decided to check out the highway bridge over Niagara Creek for overwintering mosquitoes.
A western red-backed salamander we found under a log.
Many overintering arthropods can be found in man-made structures. Here are three harvestmen and three Triphosa haesitata under the abutment of the Niagara Creek trestle. I have also found bats, camel crickets and five species of mosquito under similar structures.
During my undergrad, I did an Honours thesis on overwintering mosquitoes, and one of my field sites was just upstream, at the railroad trestle above the creek. Here I found several species of mosquito, including Anopheles punctipennis, Culex tarsalis, Culex territans and Culiseta incidens. So when I checked out the highway bridge, I took a few shots of of the mosquitoes. Most of these were the large and very common Culiseta incidens, but I saw a smaller and browner one that I knew was a Culex. Not having many good shots of Culex tarsalis, I strained to reach the camera over my head to shoot the insect. Like many overwintering mosquitoes, this one was still able to fly, so I only got the one shot. Upon reviewing it however, I saw that it was not Culex tarsalis, as I expected, but rather Culex restuans! This species looks much like the common house mosquito, but is distinguished by the two light scale patches on the scutum. I had never encountered this species during my thesis research, as it had not been reported for BC. In talking with Dr. Peter Belton, he urged me to write up the sighting for the Journal of the Entomological Society of BC as a new species record for the province.
Several years passed, where I was busy with tropical field research, and I had put the Culex record on the back burner. When Dr. Belton presented me with a draft of the report, I knew I had to do my part. I added some detail to the manuscript and sent it off. Click here to see the paper!
Not bad for a quick snapshot. Here are some other pictures I took that day:
On top of the bridge I found this jumper with a droplet for a hat.
“Ants, particularly army ants, exert such strong predation pressure that they are considered to be the main driving force in the evolution of Neotropical social wasps, to the point of influencing their nest architecture.” -Corbara et al. 2009
It is not too surprising that many tropical ecologists consider ants to be such superior predators. Come across an army ant swarm, and you are likely to witness many hundreds of acts of predation playing out before your eyes on the jungle floor. An army ant swarm is like a blitzkreig, and it would seem that nothing can stand in its path. Even social wasps, normally so aggressive in nest defence, will abandon their nest immediately rather than risk the entire colony in a vain attempt to repel the tens of thousands of army ant raiders.
But is it really accurate to infer from these types of observations that the risk of predation by ants on nests of social wasps surpasses that of all other predators? This never really sat right with me, particularly considering how an army ant predation event on social wasps is a random, and probably relatively rare event. Army ants cannot see, and they do not target wasp nests in particular. Even those species which prefer preying on social insects are much more likely to be raiding other species of ants rather than wasps.
How would army ants stack up against a true specialist wasp predator, such as the Red-throated Caracara? Luckily, I had some data to work with to answer these questions. I have written this up in a paper in Insectes Sociaux, which unfortunately is not open access, but you can email me for a copy!
A Polybia nest brought via an overhead branch.
From our nest camera study in 2008 and 2009, we had footage which showed adult provisioning of single caracara chicks (McCann et al. 2010). In order to calculate the number of wasp nests per day consumed by the chicks, we lumped all events of provisioning with nest fragments of the same genus being brought within 30 min of each other.
Each of these events was then termed a “unique nest delivery”. By summing the unique nest deliveries daily for the two sampling periods, we found that a single caracara chick eats between 7.8 and 12.4 nests per day. If we assume that the adults are eating just as many wasp nests, a group of 6 adults would consume 46-74 nests per day (not counting the chick). On a per-hectare basis, caracaras could possibly be consuming 0.117-0.186 nests/ha/day.
Wasp-eating machine! Is the Red-throated Caracara a major source of colony failure in Neotropical social wasps?
To compare this rate of predation with that of army ants, we needed an estimate of army ant density. Unfortunately, only one method for assessing Eciton density has been developed, for Eciton burchellii.
This method was developed by Nigel Franks, and relies on the predictable behaviour of swarms of this species (Franks 1982). These ants raid in a roughly linear column from their bivouac site, extending the raid 7 m per hour. The landscape at any given time is thus like a plane with many lines of ants of similar length scattered about it at random. The probability of encountering a swarm is thus proportional to the density of colonies in the area, and by repeated walks of suitable length, an estimate of the total density can be made. Mathematically-inclined readers may realize this is an extension of the problem of Buffon’s Needle*, and relies on similar calculations Incidentally, Buffon also published the first species description of the Red-throated Caracara. You can read about that here.
Catherine Scott and I went to the Nouragues station in 2012 to perform an estimate of the Eciton burchellii density in order to calculate the potential impact of army ant predation on social wasps.
Here are the three trails we surveyed. We walked each trail 5 times, for a total of 72 km. Each encounter with an Eciton swarm is marked with an X. We encountered Eciton burchellii only 5 times, translating to a density of only 0.021 swarms/ha.
Our estimate for Eciton burchellii density was a moderate 0.021 swarms/ha, pretty well comparable to other lowland rainforest sites. But how many wasp nests could each swarm take? Well, there is no easy answer for this, but there was only one study that documented rates of army ant predation on social wasps. Ruth Chadab published an estimate of 1-3 nests per day taken by Eciton hamatum, a related species with a greater predilection for social insect nest plundering (Chadab, 1979). Because we had no estimate for daily wasp nest predation for E. burchellii, we used Ruth Chadab’s estimate of 3 nests per day as a rough approximation. This translates into 0.06 nests/ha/day, or 24 nests per day in a 400 ha caracara territory.
We conclude that Red-throated Caracaras, as specialist wasp predators, are comparable to army ants in their predatory impact on social wasps. Taken together with other species, such as monkeys, antshrikes (McCann et al. 2014) and woodpeckers (Sazima 2014), social wasps are at considerable risk from vertebrates.
So what about vertebrate predators and the adaptations of social wasps against them? If we look carefully at social wasp behaviour, it is easy to see how much vertebrate predation has influenced both behaviour and nest architecture. For one, massed stinging attacks are ineffective against ants, and are definitely a feature that protects wasp colonies from vertebrate attack. Audible warnings, such as those produce by Synoeca, would not be effective against ants, nor would visual camouflage (ants hunt by scent, and army ants cannot see anyway).
Visual crypsis of Leipomeles dorsata nest.The envelope of this nest is fitted carefully to the underside of the leaf, and made to resemble it in colour. Photo by Alex Popovkin, used under a Creative Commons 2.0 licence.
Likewise, armouring of a nest, such as is seen in some Epipona and Chartergus wasps (Richards 1978), would have limited effect on ants, as they can enter and take prey through any opening a wasp can. Analogous armouring consisting of a mud envelope is evident in this Polybia singularis nest. In 5 seasons I worked at the Nouragues camp, this nest never fell prey to the caracaras. What is notable about the nests of most wasps with armoured envelopes is that they are often located high up in trees, easily visible on distal branches. The wasps may gain some protection from ants by nesting so high, which they can afford because they are (by virtue of the strength of their nest) already relatively safe from vertebrate attack.
Nest of Polybia singularis, with an envelope of hardened mud. Such nests can weigh up to 5 kg! This nest was never taken by caracaras in all the years I studied at the Nouragues station.
As more and more naturalists describe and publish their observations of Neotropical biology, we are continually discovering new things. I hope that this study, gained in a few short months of research adds to the understanding of the role of vertebrates as predators of social wasps, especially the important role of the Red-throated Caracara. In a future post I will take up the issue of the diversity of wasps taken by caracaras, and what some of the numbers might mean for tropical wasp biologists.
Please do go and read the paper, and if you do not have access to it email me for a copy!
CHADAB, R. 1979. Army ant predation on social wasps. PhD Thesis. University of Connecticut, Storrs, CT.
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.
Catherine and I got the new year off to a good start with an early-morning trip to Boundary Bay, in the hopes of seeing some owls. We did not manage to see any except for a solitary Short-eared Owl from a distance, but we made up for it with some other great birds!
We weren’t the only ones out there, several other bird-spotters had already arrived.
Harriers were the most common raptors we saw flying over the beach and grasslands.
We saw a couple of dives for voles, but no captures.
I like the light tones of the frosty ground in this one.
In between feeding, this female flicker was investigating this hole. Perhaps she nested in it previously, or is planning to!
This gorgeous pup was having a great outing!
A House Finch male was a bright splash of colour on the dead branches.
An odd posture as the finch changes positions.
This female was a bit more shy.
A harrier doing a close flyby.
There were a bunch of Kildeers on the icy fields, but seemed to disappear when they stood still.
Our final cool bird was the European Starling, which was posing nicely for us on a sunny branch.
Here is a great shot my brother got using his iphone of Catherine posing with a male widow.
This weekend, our last for winter break in Victoria, Catherine, my brother and I headed up to Island View Beach to see what we could see. After the hectic holiday family-related chores (presents and cooking) it was great to get outdoors on a non-rainy day.
First up was a Tegenaria, which like most of the spiders we found was dewy under the frozen boards and logs we turned.
This doesn’t really count as a natural pose, but I was taking advantage of the dawn sky.
Centipedes are much much more cooperative when cold!
I think that winter centipede photography will be my go-to technique from now on.
We actually have no real idea what this spider is… Possibly a gnaphosid, but we did not get a great look at it.
The winter sky at dawn is often quite beautiful, provided there is not an impenetrable cloud bank to the east.
Again, a centipede, looking elegant and not thrashing about wildly!
We found some winter male widows, which are almost always big and black and female-like.
Catherine found an overwintering queen Vespula pensylvanica. She was totally quiescent and could not be woken up for a photo shoot.
More obligatory widow shots! We were quite happy to see the widows doing so well.
Some kind of tiny Lentinellus-like fungi.
This is a recently-metamorphosed ground beetle of sorts. So nice to see these not scurrying around rapidly! The non-black colour is also really helpful for making a good exposure.
This one is definitely a gnaphosid. we saw the prominent spinnerets!
Catherine provokes a penultimate male widow into defensive silk-throwing.
Just after this, he was docile and cooperative for some photos showing his beautiful palps.
On the way out, we saw a number of Golden-crowned Sparrows.
Winter time can be a great time for photography, even of insects and spiders!
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!
This morning, Dec. 26 is Boxing Day (in Canada). The presents are opened, the turkey consumed, and I was having an early morning coffee by the fire with my mom. Suddenly, she screamed. There was a spider crawling on her neck! She flicked it off, and I captured it, seeing that it was an immature giant house spider, Eratigena atrica. It was a Christmas miracle!
Christmas spider in a field of moles.
Anyway, after some boring shots on my skin, I decided to take advantage of the beautiful Christmas tree lights for a nice background. These LED Christmas tree lights are not what they used to be! I had to drag the shutter at 1/30th to get even a modicum of background illumination.
Anyway, that is my Christmas spider story from this morning. Now I am heading out to see if I can get some more otter or bird shots at sunrise. Happy Holidays!
Christmas spider posing in front of the tree.
This Christmas spider is pretty dusty, so I will not show a real close-up.
This post is about a paper recently published in PLOS-ONE, on the chemical ecology of elderberry longhorn beetles. If you want to read it in its entirety, click here. Below is the story of my end of the collaboration leading to this publication.
In 2011, I attended the annual meeting of the International Society for Chemical Ecology (ISCE). This was one of my easiest conferences ever, as it was being held at Simon Fraser University, where I was doing my PhD. I had the great pleasure of meeting with Dr. Annie Ray, who was then researching chemical ecology of lepturine longhorn beetles, commonly known as flower longhorns.
She gave a great talk about her research topic, which was at the time a fairly neglected area of research, as there are few lepturine pests, and hence little interest in researching their sex pheromones.
Nonetheless, there are definitely applications for this knowledge, especially to better study the endangered valley elderberry longhorn beetle (Desmocerus californicusdimorphus, hereafter VELB), which has been of major conservation concern in California’s Central Valley for decades.
Dr. Ray, along with Dr. Jocelyn Millar and others had recently identified the VELB pheromone as (R)-desmolactone, and had showed that it was effective in trapping male VELB in the field.
We got to talking after her presentation, and Dr. Ray mentioned that we had a species of Desmocerus in BC. I told her that if she ever needed any help trapping these beetles, she should look me up. I did not think it was likely that anything would come of it, as our local Desmocerus aureipennis is not endangered, but sure enough, the next season, a bunch of traps and some chemicals arrived at the lab. Dr. Ray and Dr. Jocelyn Millar wanted to test out their synthetic candidate pheromone for VELB on its relatives!
I quickly racked my brain for areas to test these compounds. We had extensive elderberry as understory vegetation on Burnaby Mountain, so I set up some replicates just outside the Biology Department in the woods. These traps caught nothing, so doing some reading on VELB, I realized that the California species likes “elderberry savannah” habitat. The only place I could think of that fit that description close by was Colony Farm Regional Park, a location where I had done some volunteer bird banding.
After applying for and receiving permits, the flight season for the beetles was almost over. Nonetheless, the traps caught many beetles. This was a promising start.
Banding birds at Colony Farm. The bushes in the background are Red Elderberry.
The next season, we were ready. We had new traps, plus two enatiomers of the candidate pheromone, in order to determine which of the two, or perhaps both were active. We prepared traps with a mixture of the two chemicals (called a racemic mixture or racemate), in order to determine whether one would inhibit the effectiveness of the other. This is important in chemical ecology of insects, as preparation of a racemic mixture is vastly cheaper than production of an enantiomerically pure chemical, and if the racemate is attractive, there is no need to go to the trouble of producing the pure substance.
With the traps out, we waited a week. When we came back, the traps with the racemate and the (R)-desmolactone had caught many many beetles, whereas the control and the traps containing S-desmolactone only had only caught a single beetle each (one trap almost caught a bear, but that is another story). Therefore, the (R)-desmolactone appears to be the sex pheromone of Desmocerus auriepennis, as it was for D. californicus.
I had never seen these beetles in the field until I did the trapping experiment, so I took the opportunity to do some photography of a few males we had caught.
When the results started coming in from other trapping sites in the experiment, we quickly saw that this pattern held true for a number of Desmocerus species and subspecies. Desmocerus palliatus, D. auriepennis auriepennis, and D. lacustris all responded well to the (R)-enatiomer and somewhat less strongly to the racemic mixture.
FIGURE 1: Photos of the species and subspecies of Desmocerus included in the present manuscript. A: D. a. aureipennis; B: D. a cribripennis; C: D. a. lacustris; D. D. c. dimorphus (VELB); E. D. palliatus. (Photo of D. palliatus by Paul Bedell). doi:10.1371/journal.pone.0115498.g001
When Dr. Ray sent me the first draft of the paper, I thought it might be good to have some photos of the species under study, so I prepared Figure 1 above. Since we did not have any pictures of Desmocerus palliatus, I reached out to Paul Beddell, and asked if we could publish his great photo in the paper. I was also interested to learn that my Colony Farm traps were by far the most effective, catching many times more individuals than other sites.
Desmocerus auriepennis cribripennis shot on some Red Elderberry. Their flight season at Colony Farm seems to coincide with the flowering of this shrub, and ends when the fruits are formed.
Using the results from these studies, areas can be more effectively surveyed for the endangered VELB, making this kind of surveillance cheaper and more effective. The pheromone catches only male beetles, so risk to females is low, and using a live trap design, males can usually be released unharmed.
In addition, now that we know that the pheromone is effective for VELB’s congeners, any studies of these beetles have got a great head start. I for one would be interested to survey the distribution and abundance of the beetles in BC, as Red Elderberry is a common shrub in forested habitats. Why are they so abundant at Colony Farm? Are there some populations to be found in other habitat types? Are there any differences in the pheromone mixtures produced by the various Desmocerus species?