Studying Lynx in the North Woods

Deep in the heart of the North Maine Woods, between the Allagash Waterway and the St. John River, lies the small logging community of Clayton Lake. Through the graciousness of the landowners, Maine’s Department of Inland Fisheries and Wildlife (IFW) has based its field operations for the Department’s Canada lynx study at this site. This field station is more than a 60-mile drive from the nearest town in Maine, and more than half the drive is over unpaved, privately owned roads. Why are lynx so important that we travel so far to study them?

Lynx are widely distributed throughout the northern forests of Canada and Alaska, but only three of the lower 48 states are reported to have lynx populations: Washington, Montana, and Maine. The lynx was listed as threatened under the Endangered Species Act in March 2000, following considerable debate over the status of lynx habitat in the northwestern states. However, little is known about the status, habitat requirements, and limiting factors of lynx in Maine and the northeastern United States. Most knowledge of lynx comes from studies that have been conducted in the core range of the species in Canada and Alaska. This lack of knowledge, and the threatened status of lynx, has the potential to affect forest practices and recreational use of forests where lynx are known to exist.

To determine the status of lynx in Maine, and to begin to understand their biology and habitat needs, IFW and the U.S. Fish and Wildlife Service began an intensive research study in January 1999. Many others partners have joined in the study since then, and have helped keep the study going.

There are many aspects and objectives of this study, and it involves year-round field work. While I cannot report on all that is going on, I would like to give you a peek at what we are doing this winter

In northern Maine, the onset of winter guarantees two things: cold temperatures and lots of snow. Despite the harsh conditions, winter is a blessing, as it allows us to collect information that cannot be gathered in other seasons. By finding and following lynx tracks in the snow, we can learn more about their abundance, the types of animals that lynx are preying upon, and the habitat characteristics they prefer.

Our commute from Clayton Lake to the study site is usually between 10 and 20 miles. Leaving the comfort of a warm truck is never easy. The cold air crystallizes breath, freezes eyelashes, and numbs ears. The next step after adjusting to the cold is to unload the snowmobiles, and hope that they will start with only a few pulls. Many times they do not. After a period of warming motors, strapping on snowshoes, daypacks, and other gear, it is time to ride, and ride we do. There are many miles of roads in the North Maine Woods; one of the four towns in the study area contains more than 126 miles of them. The vast majority of these roads do not get plowed, so snowmobile travel is the only option.

Operating snowmobiles along unplowed roads allows us to identify and count animal tracks in the snow. These surveys help us create an index to the relative abundance of lynx, other predators, and prey species such as snowshoe hare. By conducting these surveys over the course of several years, we hope to recognize any changes in local lynx, predator, and prey populations, if they occur.

Tracking the abundance of the snowshoe hare population is important to understanding lynx ecology. The lynx is known as a prey specialist, which means that over 90% of its annual diet is comprised of snowshoe hare. It is quite likely that a lynx will kill and eat one or more hare per day when hare populations are high. But unfortunately for lynx, when hare populations decline, lynx are forced to find alternative food sources. Those individuals that do not find alternative food will succumb to starvation. By routinely and systematically counting the number of snowshoe hare tracks intercepting a segment of road, we essentially are tracking the availability of food for lynx.

Following lynx tracks through the woods, while on snowshoes, is another activity that we do in the winter season. Lynx tracks are unlike the tracks of any other wildlife species in Maine’s woods. The paws of lynx are very big for the size of the animal and act like snowshoes. These large paws keep the lynx from sinking deeply in the snow, and help make it an efficient predator of snowshoe hare. Typically, lynx tracks measure between 3.5 to 5 inches in width and about the same in length. Lynx tracks are easy to identify even though they seldom leave a clear impression in the snow. Because of the size of the paw and the large amount of fur between the toes, the toe pads are often not visible. Lynx have retractable claws, as is characteristic with other cats, so claws almost never register in the snow. The strides (distance between each track) will vary in length depending on the size of the cat and its speed of travel. Generally, a stride will measure between 12 and 18 inches, but occasionally, a lynx will creep along slowly, (commonly on roadways) and the stride is cut in half. A very distinguishable feature of lynx tracks is sinking depth. When the snow becomes deep and powdery, a lynx will only sink 4 inches or less when walking. This feature, coupled with the size of the track, will differentiate lynx tracks from any other track that is likely to be encountered in this part of the state.

While following lynx tracks, we use hand-held GPS units to form a “track-log” of where we, hence the lynx, travel. Points are marked along the way when changes in cover types occur. We also note any unique behavioral signs that we observe. This includes scent-marks, hare chases, hare kills, caches, and rest sites or beds. At the end of each day, we download this information into a computer with mapping software, and actually see the map with our trails and observations. After many days afield with several observers, we gain valuable data on habitat use and behavior.

One behavioral observation we note is how lynx approach a scent-mark (urine). Most wild mammals communicate with one another by their sense of smell. By scent-marking objects as they travel, they leave messages to members of their own species, as well as other species that live around them. Trappers know the value of scent marking, because animals are attracted to the scents of other animals. By placing scents of other animals near their traps, trappers lure target animals to their sets. The techniques used to capture lynx for research purposes employs the same methods used by recreational trappers. We utilize both foothold traps (summer and fall) and cage traps (winter) to capture lynx. In many cases, lures and urines are used to attract lynx to our traps. Observations on how lynx approach a scent-mark help us predict how a lynx will respond to our sets, and where we should place our traps to capitalize on their behavior.

Another aspect of a lynx’s life that snow tracking gives us clues to, is the animal’s foraging behavior. By noting and marking the locations of prey chases and kills, we learn about the frequency of foraging, as well as how successful they are at securing food. The species composition of their diet may help predict changes in prey densities. When snowshoe hare populations decline, lynx are forced to find alternative prey items. As previously discussed, hare are the most common prey item that we observe; however, we have observed where lynx have killed and consumed two ruffed grouse and a blue jay. These observations provide useful information about the dietary

requirements of lynx, and the types of habitat used by lynx and their prey. Lynx are known to be very efficient predators, which we can attest to. On many occasions, we have observed where a lynx has killed a snowshoe hare. Witnessing where a lynx has chased a hare through fir thickets is an amazing sight. Lynx are capable of leaping 15 to 20 feet at a time, even through thick cover, and this is all accomplished without injuring themselves!

Once a hare has been captured, a lynx usually eats the hare at the capture site. It is not uncommon to find where an entire hare has been consumed, at least all but the inedible feet and a few scraps of fur. Other times we have seen where a lynx has only eaten part of the hare. On these occasions, the remains of the hare are buried, or “cached” in the snow. Cats typically cache leftover food with the intention of returning to consume it at a later time, especially if they are unsuccessful at catching additional prey. Finding a hare cached by a lynx is a good indication that hare are abundant, and that the lynx is adept at catching them.

After making a kill, and consuming its catch, a lynx will often lay down to rest. Although it is difficult to know exactly how long they stay at one bed, many times the amount of melting in the snow will give a reasonable clue. We estimate from our observations that lynx will rest between one and six hours at a time.

Tracking a family group of lynx is an especially difficult task that will test a tracker’s abilities. A family group of lynx consists of the adult female and her offspring of the previous spring, usually one to four kittens. In winter, the kittens are approximately one-half the size of an adult, but they are capable of capturing their own food. Family groups appear to hunt cooperatively, perhaps attempting to flush hare to one another. When following the trails of family groups, we have noticed that lynx will sometimes follow directly in one another’s footsteps, or they will spread out and cross each other’s tracks routinely. Trying to remain on the track of a specific individual is often a futile effort.

Snow-tracking lynx through thick, regenerating stands of conifers is oftentimes easier said than done. One quickly recognizes that lynx can easily enter and travel through areas that a person would have great difficulty walking. We seem to spend the majority of our time tracking in 15-25 year old clearcuts. In these areas, down woody material is quite plentiful. Walking with snowshoes over these debris and through thick regeneration is similar to shoveling snow in a snowstorm – you just do not get too far too fast. Lynx seem to enjoy traveling on top of young, thick stands of regenerating trees that have been bent over by several feet of snow. This allows them to get up high and see greater distances, which is how they typically hunt. In contrast to members of the dog family (coyotes and foxes), cats generally hunt with their eyes rather than their nose. Their light body weight allows them to travel on top of these areas, but a tracker’s weight usually causes the snow to collapse, creating “snow caves”. Getting out of these sinkholes can be an arduous task. After a full day of tracking a lynx in northern Maine, you can be assured that you will sleep well.

As mentioned previously, part of our work entails capturing lynx during the winter. Our primary purpose for catching lynx is to attach a radiocollar, which enables us to track their movements. Tracking by radio, or radiotelemetry, can provide much more information to biologists than relying solely on tracking lynx in the snow. By having transmitters on lynx, we are able to identify individuals. When radiocollars are used in conjunction with snow tracking, we know the relative age and sex of the cat we follow. Radiocollars also allow researchers to determine the home range sizes and dispersal characteristics of lynx by tracking them throughout the year, not just during the winter. A home range is the area that is used by an animal that provides the animal with resources such as food, water, and shelter. Dispersal is the term used when young animals move away from the area where they were born. We also are able to identify causes of death, characteristics of habitats used throughout the year, and reproductive rates of lynx that are equipped with radiocollars — all are essential parameters that biologists must understand to effectively manage a species. Because we knew very little about lynx in Maine when we began this research, we have focused on attaining the most information for our investment, and this is best accomplished through a radio telemetry study.

When a lynx is captured, we do much more than attach radio transmitters. Uniquely numbered ear tags are placed in each ear, body measurements are taken, a blood sample is collected for genetic analysis, and the age is estimated. These procedures allow us to learn all we can about each animal by only having to handle them one time. When the samples are collected and the measurements taken, we release the animal at the same place it was captured.

Since the study began in 1999, we have captured and radiocollared 27 different lynx (15 females, 12 males); documented the production of 8 litters (1 litter in 1999, 3 litters in 2000, and 4 litters in 2001); and investigated the deaths of 1 kitten (female) and 9 radio-collared adults (3 males, 6 females). Three lynx died from starvation, 3 from predation, one was illegally killed, and 3 died of unknown causes.

We plan to continue the study for at least another year so that ultimately we can make lynx management recommendations for Maine and the Northeast that are based on solid scientific data, including recommendations for land-use practices and recreational use.

-Adam Vashon, Wildlife Biologist, Mammal Group, Department of Inland Fisheries and Wildlife

Tags: Lynx

Posted on Thursday, July 23rd, 2009
Filed under Guide Articles.