Dr. Nilssen and his colleague Dr. John Anderson of U.C. Berkeley represent the world's leading authorities on the Warble Fly.

These observations occurred between the dates of May 26, 2004 and August 4, 2004.

They all occurred within the region designated as "1002" of the Arctic National Wildlife Refuge. The animals observed and documented represent the Central Arctic Caribou herd.

tolerating the presence of mosquitoes:

leaving the coast proper (area of greatest relief) returning inland to region of higher mosquito concentration:

standing at rest unto a full onslaught of mosquitoes:

driven to and arriving to areas of relief with no mosquito presence, with mosquito presence: no difference in caribou behavior:

extreme and expressive pest avoidance behavior in complete and total absence of mosquitoes:

It became clear that there was no correlation of caribou movement to the either the presence or absence of mosquitoes:

1. While mosquitoes do harass the caribou, they do not drive caribou movements: at least not within the coastal region and not during post calving aggregation.

(response from Dr. Arne Nilssen, Univ. of Norway; Dr. J. R. Anderson, UC Berkeley. Literature and text cited with permission and full support.)

"This is what we also have found out in Northern Scandinavia. No panic when there are only mosquitoes. We have papers on that: Anderson, J.R., and A.C. Nilssen. 1998. Do reindeer aggregate on snow patches to reduce harassment by parasitic flies or to thermoregulate? Rangifer 18:3-17. Anderson, J.R., A.C. Nilssen, and W. Hemmingsen. 2001. Use of host-mimicking trap catches to determine which parasitic flies attack reindeer under different climactic conditions. Canadian-Field Naturalist 115: 274-286."

___________________________

I've witnessed and documented the caribou's extreme and radical behavior of pest avoidance with evidence of only one pest present: Warble Fly. No mosquitoes, no black flies, no deer flies, no nose bot flies. I have documented the gadding of thousands of caribou passing in close proximity to camera, my partner and I subsequently bombarded by Warble Fly attacks.

With random emergence of warble flies at camp, in absence of caribou, we accurately predicted caribou arrival to relief region. Movement and behavior of caribou strongly correlates to Warble Fly activity:

2. The activity of the Warble Fly and related interaction with caribou, does drive caribou, dramatically.

"Yes, that is correct and well known (many publications), the latest is: Hagemoen,R.I.M., and Reimers. 2002. Reindeer summer activity pattern in weather and insect harassment. Journal of Animal Ecology 71: 883-892."

____________________________

In the presence of both mosquito and warble fly pests, patterns and timing issues of caribou activity proved predictable and repetitive:

Caribou would relax at "night time" regardless of mosquito presence:

Morning calm prior to radical avoidance behavior of mid to late day:

Cool days with mosquitoes present while caribou behavior and movements relaxed.

3. Warble Fly activity threshold much more limited than the mosquito's.

"Yes, mosquitoes may be active down to 4-5º C, whereas the warble fly needs at least 12ºC, publication Anderson, J. R., A. C. Nilssen. 1996. Trapping oestrid parasites of reindeer: the response of Cephenemyia trompe and Hypoderma tarandi to baited traps. Medical and Veterinary Entomology 10: 337-346.

4. Warble Fly activity reduced if not absent at "night".

Yes, very reduced. Here in northern Norway with midnight sun warble fly may be active if there is a night with temperatures around 20ºC, which occurs very rarely.

5. Warble Fly will stalk through grass to reach target, will attach without airborne approach.

"Yes, this is observed also in Scandinavia. This mostly happens at moderate levels of warble flies when reindeer are laying down? When the reindeer panic (many warble flies around and warm weather), they will stand and run at short interval. The flies then attack them from the air. Publication: Espmark, Y. 1968. Observations of defence reactions to osterid flies by semi domestic forest reindeer (Rangifer tarandi L.) in Sweden Lapland. Zool. Beitr. 14: 155-167.

________________________

During the Arctic summer season within the 1002 region of the Arctic National Wildlife Refuge there exists a dynamic flow of air and polar influenced temperature currents that flow unobstructed across the Arctic Coastal Plain. The east-west traverse of the Brooks Range, the limiting counter to the southward migration of these polar currents, represents a barrier, the initial transition zone in which the cool polar climate yields to the warmer, intercontinental land mass influences. As temperatures warm, compouding the lack of quality graze, the prevalence of warble flies relegates the near mountains a "hot zone": few caribou, if any, remain in residence.

Across the Arctic Coastal Plain, the transition of cooler air to warmer threshold temperatures creates a thermal barrier, south of which enables the Warble Fly to function. This thermal barrier flows and shifts endlessly across the coastal plain, soley at the whim of air and thermal currents.

The prevalence of cooler temperatures north of this transition zone tend to suppress or completely shut down Warble activity; this ever shifting region of cooler air/insect relief, is sanctuary to the caribou.

It is exactly the free and unimpeded access to this dynamic sanctuary that enable caribou to mitigate stress and parasitic Warble fly infestation.

In addition to the heat induced stress upon the caribou, the warmest summer temperatures of the Arctic Coastal Plain forces a northward migration of this cool-warm transition zone. At these times it is likely that parasite relief is only available at the immediate coastline: the warmth of air temperatures south of the coast, virtually relegating the balance of the region uninhabitable due to excessive Warble fly activity.

While the actual surface area of these regions may be fractional in context of the total land mass of the Arctic National Wildlife Refuge, these regions represent critical habitat for caribou. Within the sanctuary of the 1002, these regions exist as "Super Sanctuary" enabling caribou to mitigate Warble infestation even in face of the most extreme environmental pressures.

It is valid to deduce that if disturbed and denied access to the 1002 and subsequent super-sanctuaries, that caribou would likely face greatly increased levels of warble fly infestation and suffer the consequences thereof: poorer health, lower birth rates, higher mortality.