When cold is not cold enough.

Winter can be tough on invertebrates. Even endotherms can find winters a bit grim if it’s extremely cold. Harsh freezing conditions are unforgiving, especially to those who cannot regulate their own body temperature. Parasites that have life stages involving intermediate hosts fare somewhat better than those free-living in the environment. But  there is still risk to their survival, especially if the intermediate host is an invertebrate. In this way, the cold winter temperatures regulate the populations of parasites by increasing their mortality.

Muskox (via Wikimedia commons)

The effects of warmer winters on parasite abundance, and as a consequence, host health, have been known for some time. A neat example of this comes from the Canadian arctic, in the relationship between the nematode Umingmakstrongylus pallikuukensis and its definitive host is the muskox (Ovibos moschatus). The nematode has an intermediate host, usually a slug, where larvae develop to infective stages. When the infective stage nematodes are consumed by a muskox, they take up residence in its lungs. Heavy infections can accumulate as the host gets older, causing serious pathology and can even kill muskox (Kutz et al. 2009). The accumulation was key, because under ‘normal’ (i.e., cold) winter conditions, it takes two years for the nematodes to reach maturity in their intermediate hosts. But if it warms up, they can be ready to infect muskox in only one year, without having their development arrested during a winter (Kutz, et al. 2002). This is bad news for the muskox, because it means that far more nematodes will be around at any one time.

It’s a tick-infested ghost moose. If this makes you a bit sad, please don’t google ‘ghost moose’ images.

Another effect of warmer winters is increased survival of ticks. While not yet present in the Arctic, the winter tick, Dermacentor albipictus, feeds on moose (Alces alces) in parts of southern Canada and the northern United States. Cold winters play a large part in regulating the populations of the ticks, as many larvae perish during winter as they wait for a moose to walk past. The time it takes for females to reach maturity is also thought to be regulated by a combination of time and temperature (Hueffer et al. 2011), meaning that warmer weather will go some way to speeding up the development of the ticks. The ticks stay on their moose hosts for their whole life, feeding and moulting. This means that moose can be subject to thousands of ticks feeding on them continuously from winter to the start of summer. Moose that suffer heavy infestations are called ‘ghost moose’. With up to 400,000 individual ticks feeding on a single individual (Kutz, et al. 2009), the ghost moose suffer hair loss, anemia, emaciation and secondary infections, and can die. Increased mortality of moose populations in northern US have been linked to increased abundance of ticks (ref Washington Post), which will affect trophic cascades in the boreal forests the moose live.

These are just two examples of how parasites interact with their hosts. By adding environmental perturbation (be it climate, urbanisation, habitat loss etc.), the dynamics of these interactions will change. Distribution changes, host switches, alteration to phenology and emerging pathogens are all on the cards as we hurtle through the 21st century.


Hueffer et al. (2011) Acta Veterinaria Scandinavica 53, doi: 10.1186/1751-0147-53-17

Kutz et al. (2002) Canadian Journal of Zoology 80, 1977-1985.

Kutz et al. (2009) Veterinary Parasitology 163, 217-228.

Show us your spots! Quoll trapping in northern Queensland.

Recently, I went on a little data-collecting trip. The scenery was pretty cool and I was collecting parasites from some rather cute marsupials, so I thought it might be nice to share it with you.


One of our rockier sites – a creek running through a gorge.

The field sites were on the Atherton Tableland, northern Queensland. Sites were in hilly, rocky areas, because we were trapping northern quolls (Dasyurus hallucatus), and they live in hilly, rocky habitats. Northern quolls are classified as ‘endangered’ by the federal government, which was one reason why this fieldwork was done – a colleague was collecting samples for population genetics analysis. Live mammal trapping involves getting up before sunrise to check traps nice and early (so the animals don’t get caught in the sun!), even though all our traps were covered with a thick layer of vegetation for protection. Walking around in the dawn light for the purposes of handling little marsupials is definitely one of those “I love my job” moments.

being at work at sunrise is not all bad.

Being at work at sunrise is not all bad.

It turns out that northern quolls are pretty easy to catch. Using collapsible cage traps baited with chicken frames from the butcher, we caught ourselves many quolls. The traps were treadle-operated, meaning that there was a little flap on the floor attached to the door of the trap by a metal rod. As an animal steps on the flap on its way in to eat the bait, it dislodges the rod and the door swings down, trapping the animal.

Northern quoll, Dasyurus hallucatus, in a bag.

Northern quoll, Dasyurus hallucatus, in a bag.

Once caught, the quolls get transferred to a handling bag where they had their measurements taken, and were examined for ectoparasites. Generally, they do not get checked for parasites, but because I was there, I collected any ectoparasites I found on each animal.

Me, collecting parasites from a quoll.

Me, collecting parasites from a quoll.

Paydirt! Ticks on the back of a quoll's ear.

Paydirt! Ticks on the back of a quoll’s ear.

After I’d finished picking at their ears and combing their fur (for fleas!), they got their photo taken – in a kitchen garbage bin, no less. It was the best thing to show up their spots, and they couldn’t jump out of it. Usually. We did have a couple of escape attempts. The purpose of the photography was as an identification method for upcoming remote camera trapping, as quolls have individual spot patterns. Then, they were done, and released at the site of capture. We caught several quolls again and again. Seems they didn’t mind the indignity of a night in a trap as long as they could have a chicken dinner!

Quoll showing us its good side.

Quoll showing us its good side.

Getting released - going...

Getting released – going…



Back at the lab, I have a collection of ticks, mites, fleas and lice from the quolls that were captured. I sorted them into separate vials and am now going through the process of identifying them. Some are easier than others! Very little is known about the parasites of northern quolls, so my work will shed a bit more light on the ecology of parasites on an increasingly rare marsupial.

It's like Christmas came early in the parasite lab!

Christmas came early in the parasite lab!

Scicomm win: explanatory videos for papers.

Some people I know at ANU have published a review called ‘Conceptual domain of the matrix in fragmented landscapes’ (Driscoll et al. TREE in press, look at it here). They sought to identify how the matrix works in terms of animals moving around in fragmented landscapes (i.e., between patches of remnant vegetation). The authors have also released a short animated video to describe the main findings from their work. This is the cool bit. They’ve managed to condense their research into 4 mins – which is a hard task in itself. Observe:


Some journals now include a graphical abstract for works published (e.g., International Journal for Parasitology), where authors of papers provide a picture to represent their work. Making a video takes it a step further, and allows research to be more accessible, particularly for busy people, and interested people across all levels of scientific understanding. For example, reading the paper is probably beyond the comprehension of most school kids. But the video could make an important contribution to an environmental science class and help kids understand sophisticated concepts. Stop-motion animation may be beyond some people’s AV capabilities (me included!), but a video narrated in plain English is a brilliant way to communicate science, and to get your science to reach more people.