|Cam’s Top 10
Biodiversity highlights from Field Biology, Aug. 21-27, 2011
1. Zombie ants
The behaviour of Dicrocoelium-infected ants is surely a biological marvel. We observed ‘clinging’ ants on clover, American vetch and goldenrod at various sites in CHP. The ‘clingers’ are common in CHP, but probably nowhere else in North America. This pathogen of domestic grazers and wildlife is an invader from Europe, infecting high proportions of deer, elk, and cattle in CHP. Recall that the first intermediate host is the terrestrial snail, Oreohelix, common within aspen-dominated forests in CHP. In it’s snail host, which is permanently castrated by infection, asexually-produced cercariae are housed within host-derived slime balls. The slime balls, containing about 100 cercariae, are favored prey of formica ants. Details are in Goater and Colwell (2007).
2. Forest of death
We observed countless numbers of dead yellow dung flies attached to certain types of understory vegetation throughout CHP. These flies are infected with the fungus, Entomophthora muscae. The fungus produces hyphae from the legs of flies, which attaches them to plants. This is an ‘enslaver parasite’ that manipulates it’s host’s orientation on the plant (see arrow) to increase the rate of transmission of spores to new hosts. On hot days, male flies prefer to feed on nectar from shaded flowering plants. This is the likely mechanism behind our observation that dead flies were observed only on understory plants (such as bull thistle) near Camp McCoy. Details are in Maitland (1994).
3. Harvestman Hay-day
We observed high densities of Harvestmen throughout CHP, especially in the pitfall traps on the grazing plots. We often find small numbers of Harvestmen in the traps (from 0-5), but this year there were often 100’s. There are 8 species of Harvestmen in Aberta; we likely had Phalangium opilio, an introduced species from Europe. This is a classically ‘eruptive’ group of arthropods, whereby certain environmental conditions lead to enormous increases in population size. Their voracious apetites, especially of noctural males, makes them suitable as biocontrol agents of agricultural pests. Demographic characteristics of harvestmen have not been studied in Alberta (nor have their mites!). Details are in Allard and Yeargan (2005) and Newton and Yeargan (2002).
Perhaps fortunately, we did not see cougars. But we did observe the cougar kill site near Camp McCoy, and the fresh tracks along Beaver creek were unmistakable. An ongoing study based out of U of A estimates that there are 8-12 resident adults in CHP, with about 33 animals in total. Data from one radio-collared male and a female show that over 90% of their diet over two years consisted of elk, deer, and moose. CHP is an important location for the re-establishment of this key predator, representing the most eastern confirmed location for breeding cougars in Canada. Details are in Bacon and Boyce (2009).
5. Banded horntail
This large, distinctive insect (Urocerus gigas), known as the giant wood wasp, was found in one of Dara and Brayden’s pitfall traps within the recently logged pine and spruce forests. This primitive sawfly can make you jump, but the ‘stinger’ is actually the female’s ovipositer that she uses to penetrate recently dead spruce and pine trees to deposit eggs. Larvae bore tunnels as they feed. This is a cosmopolitan species that is often found in recently logged or burned habitats. Check the video footage of an ovipositing female at http://www.youtube.com/watch?v=MCSQ9zI-3lc.
6. Bedstraw hawkmoth and parasitoid fly
We found two of these large hawkmoth (Hyles gallii) catipillars on the upper plateau. Recall that the larvae in the right-most petri dish once looked like the one on the left, until it exploded to release about 12 larvae of a tachinid fly parasitoid. This hawkmoth is cosmopolitan within boreal forests, found wherever it’s main food source, northern bedstraw and fireweed, is common. The identity of the parasitoid is unknown.
7. Blackspot in minnows
Virtually all of the 1000’s of fathead minnows (Pimephales promelas) in the small pond adjacent to Reesor Lake were infected with the encysting stage of this fluke. This minnow has two distinctive larvae just behind the eyes. The first host is the pond snail, Helisoma, the second are minnows. The final hosts are pelicans. Studies have shown that the black cyst increases the conspicuousness of infected fish, leading to higher predation rates by avian final hosts. Oddly, fatheads in adjacent Reesor lake were very lightly infected. Details are in Tobler and Schlupp (2008).
8. American Redstart
This was one of several passerine birds that arrived in the array of mist nets during the week. Recall that the sophisticated banding operation that has been running for the past two years is producing fantastic results from a conservation perspective. Most importantly, CHP is now regarded as a critical staging region for an astonishing number and diversity of birds that breed within Canada’s boreal and arctic habitats. This redstart, Setaphaga ruticilla, one of the wood warblers, is a classical boreal and aspen parkland breeder. It is well known for its acrobatic fly-catching behaviour and its distinctive flash patterns in flight. This individual had been caught and banded 6 days earlier. Over that interval, it had increased its mass by about 20%, an adaptation linked to its requirement to migrate 1000’s of kilometers to its wintering sites in the tropics. See Bonter et al. (2006) for important ideas regarding migration behaviour, stopover locations, and remote sensing.
9. Long-eared owls
This is a medium-sized, woodland owl. It is known to occur in CHP, but it is very rarely sighted. Students that were lucky enough to visit the roosting site with Jeremiah will recall a low, silent flier. They feed mostly on voles and mice, but will also take birds and even amphibians. These owls tend to use abandoned crow and magpie nests for nesting and roosting. Nests are almost always found in heavily wooded edges adjacent to clearings or grassland – exactly the type of habitat where we observed this owl.
10. Parasitoid of Oreohelix
This is the largest and most distinctive of the approximate 12 species of terrestrial snails in CHP. It is one of only a few viviparous snails in Alberta. This is a favored prey of some birds and also mice. It is the first intermediate host of Dicrocoelium in CHP. While Becky and Steven were evaluating crushed Oreohelix for the presence of Dicrocoelium, they found a small number of snails infected with the larvae or pupae of an enormous parasitoid fly. We observed several parasitoid/host interactions over the week (recall the complex system involving the Solidago ball gall). But a parasitoid fly of snails is a bizarre twist indeed. Details are nowhere to be found!