Tag Archives: Wolf

Hunting Behavior and Habitat Selection of Wolves in a Low-density Prey System During Winter

This entry details a portion of my thesis work at the University of Alaska Fairbanks, and is intended to communicate the findings of that work in a four-part series. You are reading part three examining wolf movement in the Yukon Flats, Alaska. In order to make the article concise, you  may review the general background of this work in part one. I have truncated the background and methods of this work and focused on a portion of the results.

Wolves are highly studied because they are charismatic, exhibit interesting pack behaviors, and are a key predator in the systems where they exist. Their behaviors including movement speed, movement distances, number of prey killed, and travel distances have been well documented in high prey-density systems, but practically no information exists on these behavior in low or very-low density systems. In an attempt to rectify that, a study was initiated in 2008 to understand the kill rate of moose by wolves in the Yukon Flats, Alaska, where moose are held at low densities (<0.20 per square kilometer) by predation. In an interesting twist, that study found wolves are maintaining kill rates (moose per wolf per day) similar to wolves in high prey density systems. Certainly these results counter what I would predict and lead to a natural question – how are wolves accomplishing such high kill rates in low-prey densities? A known mechanism is that wolves in the Yukon Flats keep small pack sizes to cope with low densities of prey; if you have fewer wolves in a pack, more nutrition is available per wolf during each kill. However, if wolves were traveling further or faster in this low prey-density system was unknown.  I predicted that wolves in a low prey density system were traveling further, but not faster than wolves in a high prey-density system to maintain these kill rates. I also predicted they were selecting for river corridors when traveling. 

Wolf GPS Collar
I captured the image of this wolf outfitted with a GPS collar in Denali National Park in 2014. Collars like this one were used to generate a large dataset for my work.

To understand wolf movement, I used the same dataset from the 2008 kill rate study. It was composed of Global Positioning System (GPS) collars on six packs. Thanks to diligence in the kill rate study, I knew where kills occurred along each of the paths. For each pack, I characterized if the wolves were traveling, resting, at a kill site, or revisiting a kill site. These behaviors gave me enough information to calculate the rate of speed they were traveling, the distance they were traveling, the number of days traveling to make a kill, and how long they spent at kill sites. I also using a Generalized Linear Mixed Model to understand what landscape features were important for traveling wolves.

Wolves study area
The six packs for this study were located around Beaver, Alaska.

I found some interesting results, and put them in context of 16 comparable research papers of movements of wolves in high or medium prey-density systems. I am presenting the most applicable comparisons from the literature review (i.e., systems where moose  are prey and studies where GPS collars were used)  here. I found search time was slightly longer and search distance was 2.4 times greater in my low prey-density study area. Search time and search length are correlated together given that wolves are (almost) always hunting when moving. Due to that relationship, the search time is expected to go up as search days goes up.  I found no evidence that wolves were handling prey longer or traveling faster in the low prey-density system. Those results were not surprising as one researcher found that handling time of moose was not significantly different among packs which varied in size from 2 – 20. Since wolves were not traveling faster in our system, it is probable that regardless of prey density, that on average wolves travel at their maximum comfortable speed that maximizes efficient travel.

Wolf Results
In order to understand these results in the context of other works, I did a broad search of previous studies examining wolf movements in high prey density systems. The results I present here are some of the studies that are most applicable to my results because they were GPS studies of wolf movement in systems with moose.

I also found that wolves were utilizing river corridors and that they were selecting strongly against brushy habitat. In the Yukon Flats, that means they were selecting against thick stands of alder and willow. This was similar to previous studies where they found that wolves were able to travel 2.8 times faster if they used a river corridor rather than moving through a brushy environment. By using rivers, wolves were traveling faster and are likely taking advantage of increased prey density along river corridors.

The results of this work have some useful applications in helping us broadly understand wolf behavior. First, wolf territories are very large within low prey-density wolf systems. The mechanism that creates these large territories was unknown, but long-distance movements by wolves would create large territories by default. Next, back in the mid 1980s a researcher suggested that 0.20 moose per kilometer squared was the lowest density that wolves could persist at. Within the Yukon Flats, they are already persisting at lower densities than that, and since they are able to extend their travel distances to maintain kill rates it seems a minimum prey-density threshold could be much lower. A final implication of this work is that managers should expect wolf territories to increase in size if prey density decreases. In other systems (for instance deer in the mid-west), wolf territories should inflate in size as they move further in search of prey.

I look forward to presenting part four to you soon, which ties together moose hunting by wolves and humans by starting to understand the likelihood of competition.

Biking Touring the Denali Park Road (For Newbies)

First off, Thanks to all who contributed to the new watermark. Your input and voting helped a lot, and I was overwhelmed by the response. It was really great!

If this post had a theme, and I guess it does since I’m suggesting it, the theme would be that there’s always a “silver lining” or “blessings in disguise”.

When Aaron and I began our bike tour on the Denali Park Road our eagerness was tangible. Even the first big hill after Savage River could not dampen it. However, the next few long climbs put out some of our internal fires. While we are talking about hills, if you do go to Denali National Park remember, it is known for it’s mountains and one of them, who’s name literally means “The Great One”, is the tallest in North America. Gradients are often 5-9% and can extend for 2 or 3 miles. Getting over or around these stone giants is the name of the game.

The video here does a great job of capturing the incredible wildlife (bears, sheep, ptarmigan, wolves) as well as the joy of riding down a big hill and some of the scenery. For context on the video make sure to read the rest of the post 😉

The first night we peddled into the Sanctuary River Campground which was is located at mile twenty-three. We got a a late start, so when we arrived at camp around 8:30 PM it was time for bed. The next morning’s sky looked promising. Blue sky overhead was allowing the rising sun to illuminate the fall colors. Autumn in Denali NP was in full bloom. White-barked aspens were fluorescent yellow and stubby, dwarf shrubs were dark red. Willows along the banks were a mellow yellow and the bowl of mountains provided a stark, snow-covered backdrop.

As we pushed our gear up the road to Igloo Campground the curtains were pulled and the sky when flat gray. It stayed that way for the grueling climb over Sable Pass where we encountered a few inches of snow on the ground, but a clear road. The sky remained gray for our joyride down the back of Sable Pass. By the time we had reached the Polychrome Mountain Overlook rain seemed imminent. The Polychrome Mountains are known for their red-streaked banding which resulted from old volcanic activity. However, on Saturday we could barely make them out, and shifty fog was hanging in the valley and around the toes of the mountains.

P9062131
The Denali Park Road as it heads up Polychrome Pass. The reds in the rock are a result of volcanic activity and were sculpted by glaciers.

At the bottom of Polychrome pass, approximately 43 miles into the park disaster hit. The bike that Aaron was using broke down when the spokes in the rear wheel loosened up. We knew we could grab a bus at anytime, but before hanging our hat on that fate pushed our bikes the 2 miles to the top of Sable Pass. We reached the top and a few minutes later a bus trundled up. The bus driver opened up the door and told us the great news – there were two wolves headed up the pass and would be there in just 90 seconds!! I grabbed my gear, set up, and just a few seconds later encountered my first wolves of Alaska when they popped up 50 yards away. One was a collared animal which I assume is female and was traveling with one of her offspring. Both of the wolves seemed a bit thin. Lately wolf numbers in the park have been way down for unknown reasons, so since approximately 25% of visitors see wolves I was ecstatic to be so close! The encounter lasted for less than 45 seconds before they moved on and were never seen again. It is amazing to think that if Aaron’s bike had not broken down and if we chose to take the bus right away that we never would have had this incredible encounter. What an experience! That’s my silver lining story!

A collared Denali Wolf at the top of Sable Pass. What a treat!!
A collared Denali Wolf at the top of Sable Pass. What a treat!!
This juvenile wolf was traveling with the collared wolf. Who knows how many were still in the brush. This wolf seems a bit thin, hopefully he bulks up before winter for his sake!
This juvenile wolf was traveling with the collared wolf. Who knows how many were still in the brush. This wolf seems a bit thin, hopefully he bulks up before winter for his sake!

After the wolf Aaron caught a bus back to Igloo campground and I biked through the snow and rain to the bottom. As night fell the sun broke through the clouds and lit the mountains up in coral pink. We were optimistic for great weather on Sunday!

Just as the sun set it lit the sky up in an ever-intensifying pink. The snow capped mountains and sky all the incredible shade of color.
Just as the sun set it lit the sky up in an ever-intensifying pink. The snow capped mountains and sky all the incredible shade of color.

The next morning Aaron got an adrenaline rush right-off-the-bat when he encountered a mature brown bear at the food lockers. The bear did not hang around long, but since Aaron was carrying food to the locker when he came up to it, the experience was pretty electrifying! Without bikes we decided to hike up one of the snow clear summit of Igloo Mountain. We climbed from about 1200 feet and were greeted by sheep, snow covered peaks, a piping arctic ground squirrel and blue skies. Our journey was almost done as we pushed our bikes to Teklanika River where a bear came to the rivers edge to strip berries and flip rocks for insects. We exited the rest of the park on motorized wheels. Trip accomplished with a final count of three grizzly bears, two wolves, loads of sheep, and buckets of memories!

I guess this is Bear Ass picture. This big brown bear appeared in camp on Sunday morning. After very briefly checking the food lockers he forded Igloo Creek and headed to the bridge and down the road.
I guess this is Bear Ass picture. This big brown bear appeared in camp on Sunday morning. After very briefly checking the food lockers he forded Igloo Creek and headed to the bridge and down the road.
Teklanika River Grizzly
This grizzly came out and stripped berries and flipped rocks along the river.

 

Igloo Mountain Summit
Near the summit of Igloo Mountain. What a day!

Thanks for checking in!