By MK Gunn
As I laced up my hiking shoes at my sister’s house in the East Bay area of California, my five-year old niece came running up to me. “MK!” she exclaimed, her dark eyes sparkling and curly hair bouncing. “If you see any animal tracks, will you take a picture for me?!”
I was elated by her interest in nature and told her that I certainly would! Yet I doubted there would be any animal tracks. Then I set off for the trails of Joaquin Miller Park. It was Sunday and, as expected, any critter tracks from the night before had already been covered by tracks from hikers, runners, and mountain bikers. The wild animals around here certainly knew to steer clear of the barrage of weekend recreationists. I barely even heard a few birds on my two hour jaunt.
The interaction with my niece got me thinking about just how different the lives of wild animals are in Colorado compared to areas heavily populated by humans. Since wild animals aren’t often seen, it can be easy to forget about their roles in nature and that their ancestors were here long before most of ours.
Spying wild animal tracks is a daily occurrence in Durango. Many wild animals make their homes on the edge of town and then wander past my house a mere mile from downtown. These include deer, raccoons, skunks, bears, coyotes, gray foxes, kit foxes, squirrels, and the occasional mountain lion. Many birds live right in town such as crows, finches, sparrows, juncos, magpies, and owls.
We are very fortunate in Southwest Colorado to have the state’s largest Wilderness area. (See my column from November 2019 for more about designated Wilderness). The Weminuche Wilderness contains 499,771 acres of roadless area. Joaquin Miller Park and adjacent Redwood Regional Park might seem big when I am on the trails, but their combined area is only 2,330 acres and there are occasional roads running through. Overall, East Bay parks cover a patchwork totaling just 120,000 acres that serves 2.5 million residents! The population in the counties surrounding the Weminuche Wilderness adds up to just 72,490 people – a mere 3% of the East Bay population.
Wild animals do live in areas heavily populated by humans but these animals spend much of their lives sneaking around to avoid humans. Redwood Regional Park is home to surreptitious deer, coyotes, raccoons, rabbits, squirrels and even the rare golden eagle and Alameda striped racer (a type of snake). As humans have encroached further and further on their natural habitats, they have had to adapt in order to survive. Undoubtedly there are far fewer wild animals in these places than there were 100 years ago. Not only have populations dwindled, but diversity of species has also greatly declined.
But there are many places in Colorado where humans are so rare that wild animals don’t even know to be afraid of us. A few years ago, I was on a newly cut section of the Continental Divide Trail. The trail was so new that the pikas were barely cautious when they saw me. As I stood there, they would run up within inches to get a better look at me and then run away. But they didn’t hide. They were so curious and cute! I’ve had similar experiences with pikas in remote corners of the Wind River mountain range in Wyoming. Once, a pika even licked my salty leg while I was taking a rest on a mountainside. Then it tried to nibble on me! There are wild animals living in Colorado that have never even seen a human. They live their entire lives deep in the wilderness.
So, the next time you see a wild animal – even if it’s a common mouse, deer, or magpie – remember how fortunate we are to have such a diversity of wildlife here in Southwest Colorado. But we are all responsible to make sure that wild animals are here for future generations. Please, help us all by doing your part:
- Properly store your trash and toxic chemicals – these can kill wildlife.
- Don’t feed wild animals – they will become habituated to humans and may become subject to starvation or poaching.
- Keep dogs on leash or within sight and under voice control. Don’t let them chase animals.
- Don’t taunt or scare wildlife unless they are clearly threatening you.
- Educate those around you as to what is best for wild animals.
- Remember, the wild is their home. We humans are just visiting!
MK Gunn enjoys sneaking quietly around the nearly 3 million acres of public land in southwest Colorado hoping that only pikas try to nibble on her. Contact her at MK@sjma.org.
By MK Gunn
’Tis the season where most of us take time for year-end reflection and are getting excited about the upcoming year.
For me, this exercise reminds me of how grateful I am for this community and how we all work together to care for our public lands. Even though I have been known to disappear for days with no one else but me, I understand the importance of community and having so many people working toward the same conservation goals as me. Even the most introverted of introverts can’t get much accomplished without occasionally enlisting help from other people.
Think about it: What would you be able to accomplish without your community members? If you live on a farm, maybe you can produce your own food, but where did you get that tractor? You can claim self-sufficiency and commute everywhere by bike swearing that you don’t need the local gas stations, but you still need bike tires, chain lube and brake pads. You can collect all the firewood you need to heat your house, but what’s fueling your water heater? And what if you just need someone to listen and give you a hug? I’m sure every one of you has an arsenal of local supporters that help make your life easier and more enjoyable.
Our local public lands also have a huge family of support. In 2019, the San Juan Mountains Association collaborated with a number of local partners. Some have been with us since the beginning (like the San Juan National Forest), and others are new (Durango Outdoor Exchange), but every one brings something important to the table as we work toward a common goal – empowering the public to explore, learn about and protect our local wilderness areas and public lands.
I wish I could list all of our community partners, but then this article would take up pages. Our supporters at The Durango Herald and Cortez Journal graciously offer us a column each month, not pages. Here are just a few highlights of SJMA’s collaborations with local partners in 2019:
- Encouraged more than 4,000 trail users to “Leave No Trace” at the Ice Lakes trailhead thanks to the Outdoor Research Tiny Home, Backcountry Experience and our tireless volunteers
- Co-hosted the seventh annual Forests to Faucets teacher workshop with Mountain Studies Institute, Water Information Program and the Fort Lewis College teacher education department. Sponsors also included the Southwest Water Conservation District, Colorado Water Conservation Board, Durango Education Foundation, Colorado Alliance for Environmental Education and Trout Unlimited 5 Rivers Chapter
- Co-hosted the Hermosa Resilience Project with Trails 2000, Durango Nature Studies, MSI and the San Juan National Forest
- Educated more than 300 locals and tourists about the flora, fauna and geology of the San Juan National Forest thanks to Purgatory Resort
- Raised money for the Weminuche Wilderness and conservation education at our Christmas tree lot thanks to Alpine Bank, San Juan National Forest, Southwest Ag and a long list of individual volunteers. Special thanks to Alpine Bank for its longstanding support of SJMA programming and for being our 2019-2020 corporate partner
- Assisted locals and tourists with selecting a wild Christmas tree as part of the Christmas tree train – a collaboration with Durango & Silverton Narrow Gauge Railroad, Wildfire Adapted Partnership and San Juan National Forest
- Provided hunter information to more than 100 hunters at our hunting booth at the Colorado Parks and Wildlife Durango office
- Hosted a “Share the Trails” poker run with stellar assistance from the BLM Tres Rios Field Office, Creeper Jeepers, Mesa Verde Backcountry Horsemen, Mancos Trails Group and Hoofbeats 4H
- Raised money for the Weminuche Wilderness with a 10k trail run and a chili cook-off thanks to Backcountry Experience, Ska Brewing, Durango Running Club, the city of Durango and a variety of local chili cooks from local nonprofit and for-profit businesses
- Provided visitor information to thousands of locals and tourists at our 14 bookstore locations thanks to support from district and supervisors’ offices throughout the San Juan National Forest and Rio Grande National Forest as well as the Mancos and Silverton visitor centers
- Created a greater awareness of recreation and conservation opportunities on public lands by connecting with young people in Montezuma County thanks to the Montezuma Inspire Coalition and Great Outdoors Colorado
- Raised a glass to wilderness and supporting local businesses on Noel Night at Pine Needle Mountaineering
To find a more complete list and contact information for these wonderful supporters, visit shorturl.at/btvGU.
Last but certainly not least is the community of individuals and families who support public land stewardship through memberships, donations and copious volunteer hours! Thousands of people from all over the country devote their time to caring for the public lands of Southwest Colorado. Best wishes to all of you this holiday season and on through 2020. What an amazing community we have.
MK Gunn is volunteer and education specialist for San Juan Mountains Association. She will be joyously celebrating the season thanks to her favorite community members. Contact her at MK@sjma.org.
By Gabi Morey, Education Outreach Director, San Jun Mountains Association
Sometimes winter in the forest can seem like there isn’t much going on – especially if, like me, you might be out there with a group of 60 excited school children. Wildlife often make themselves scarce when that school bus pulls up. However, even if I don’t see them, I always know that an animal I love to teach and learn more about, the Abert’s squirrel, is around from the evidence they leave behind. Curious? Read on to find out more.
If you’re lucky enough see an Abert’s squirrel, you’ll recognize it most likely from its signature ear tufts, or tassels. These can be longer in the winter, and may almost seem to disappear in the summer. These squirrels typically have a grey back with reddish color on the sides, with a white belly. They weigh about 2 pounds and their head and body are about 12 inches long, and tail is about 9 inches long. They mate in the spring and have a litter of 2 to 5 pups about 40 days later.
Abert’s squirrels are found in Colorado, southeast Utah, and south into New Mexico, Arizona, and even Mexico. There are 9 subspecies of Abert’s squirrels that are associated with different areas, but one commonality among almost all the geographic areas (Mexico excepted) is the presence of ponderosa pine trees. Abert’s squirrels have a mutualistic, symbiotic relationship with these trees, which provide them with just about everything they need in terms of food and shelter. They eat seeds from the pine cones, inner bark, buds, and pollen cones. They will pluck a mature pine cone from a tree, remove the scales, then eat the protein-packed seeds. They also eat pine needles and the ‘inner bark’, or phloem, of twigs from the trees. One of my favorite ‘nature finds’ in the winter are the ends of ponderosa pine twigs on the ground. Abert’s squirrels gnaw off the ends of the branches, letting the pine needle ends fall to the ground. They retain the remainder of the branch, removing the outer bark, and eating the inner bark. The dropped twigs can coincidentally provide food for mule deer. In the summer the squirrels will collect mushrooms, and hang them all over trees to dry. These become winter meals for the squirrels. For shelter, the squirrels build nests out of small branches of the ponderosa pine that they can weave into a safe place to raise young. They also often use mistletoe found in the trees as a great place to build a nest.
Some researchers have found that Abert’s squirrels return to the same ponderosa pine trees year after year. It appears that trees the squirrels prefer have more sugary sap, as well as more carbohydrates, nitrogen and sodium, and less iron, and mercury. Other researchers have found that the preferred trees may simply have bark that is easier to remove.
Interestingly, the squirrels actually help the ponderosa pine trees, in addition to using them. Ponderosa pine trees have a mutualistic relationship with mycorrhizal fungi, found in the soil. The fungi extend the reach of the tree’s roots, helping it get to more water, phosphate, nitrogen and other nutrients, while the tree provides the fungi with carbohydrates. From late spring to early fall, the squirrels eat the ‘fruiting body’ of the ectomycorrhizal fungi – the part that shows up above ground for part of the year. This mushroom has spores throughout it, which the fungi use to reproduce. When eaten, the spores survive through the digestive tract of the squirrel, coming out in its scat, and get spread throughout the ponderosa pine forest, especially those trees where the squirrels like to hang out. This is an amazing trifecta of a mutualistic relationship – among the Abert’s squirrels, ponderosa pine trees, and ectomycorrhizal fungi.
Of course, the squirrels are a continuing part of the food chain. Goshawks, a type of forest raptor, are the main predator of Abert’s squirrels. Other predators may include bobcats, mountain lions, and coyotes.
This winter when you are out exploring our beautiful ponderosa forests, take a quiet moment to look around – chances are you’ll find evidence of some of our tree-dwelling, and tree-helping, friends around.
There is a lot of negative talk these days about human planted non-native species. Burmese pythons that were once household pets are wiping out the small animal population in parts of Florida in part because they have no predators to control their population. The tamarisk bush is decimating the native cottonwood and willow populations of the Southwest U.S. by adding alkalinity to the soils. In the Northeast and other parts of the U.S., purple loosestrife, a pretty flower that holds together river banks, is taking the place of cattails – a popular bird food and habitat. The list goes on and on.
With all these stories of humans inadvertently wreaking havoc on the natural environment, how about a story of hope? Once in a while, a non-native species can actually have a positive effect on the environment. Read on for a success story right here in Southwest Colorado.
Lodgepole pines are native in Colorado and are mostly found on the Front Range in areas such as Rocky Mountain National Park and Summit County. (Lodgepoles are a type of pine widely decimated by pine beetles.) However, lodgepole pines are not native to Southwest Colorado. There is a large area of these pines between Coal Bank and Molas passes along US highway 550and the story about how they got there is interesting.
Back in 1879, there was a major forest fire in that area. It was named the Lime Creek burn because of its vicinity to Lime Creek. It was assumed that the area would regenerate naturally as do many forests after a fire. It did not. To this day, burned out stumps from this fire can be seen along the Colorado Trail heading west from Little Molas Lake. Some stand like sentinels in the high open meadows along the trail.
In the early 1900’s there was some concern about the lack of regrowth. Many trees were replanted including lodgepole pines. Some thought that the non-native pines would give way to native subalpine fur and Engelmann spruce, but that never happened. The pines thrived and multiplied.
Fortunately, lodgepole pines do not have some of the mechanisms to take over other plants the way tamarisk or purple loosestrife do. In fact these lodgepole pines have helped an animal on the U.S. Fish and Wildlife Service’s threatened species list – the Canada lynx.
Canada Lynx are wild cats that thrive in the snow. Their range covers much of Alaska and Canada as well as parts of the Northern U.S. Lynx can often be confused with bobcats although there are subtle differences. Lynx are usually larger than bobcats and are not as spotted. Their tails generally have a solid black tip and their ear tufts can be as large as the ears themselves. Lynx have large feet that act as snowshoes and are specially adapted to keep them somewhat on top of the snow. The favorite food of the lynx is the snowshoe hare although it will also eat carrion, ground-dwelling birds such as grouse and ptarmigan, and small mammals like mice and voles. A lynx can spot a mouse 250 feet away!
The lynx, much like other beautifully furred mammals of Colorado, were hunted nearly to extinction in the state. It is thought that the lynx may have disappeared from Colorado around 1973 mostly due to being trapped for their fur as well as habitat destruction. However, in 1999 a reintroduction program started to get a population going in the San Juan Mountains. By 2005, 200 lynx had been released, and kittens were even being born! It is only through reintroduction, careful monitoring and a chance lodgepole pine replanting that lynx are beginning to thrive again in Southwest Colorado.
Snowshoe Hares – the Links to Survival
At this point you may be wondering what the connection is between lynx and lodgepole pines. The links (no pun intended) are snowshoe hares.
Snowshoe hares are a major food source for the lynx. Lynx will eat other small mammals, but the hares are preferred. Interestingly, lynx populations are so dependent on snowshoe hares that when the hare population decreases, so does the lynx’s. This cycle occurs about every 10 years. The evidence is astounding for this relationship.
Snowshoe hares love to feed on lodgepole pine needles in the winter. They prefer this food source over other available conifers. There are a number of statements to support the snowshoe hare’s love of lodgepole pines as a food source in a report published by the US Forest Service. (Click here: http://www.fs.fed.us/database/feis/animals/mammal/leam/all.html ) Mainly,” Winter snowshoe hare pellet counts were highest in 20-year-old lodgepole pine stands, lower in older lodgepole stands, and lowest in spruce-dominated stands” and “In British Columbia overstocked juvenile lodgepole pine (Pinus contorta) stands formed optimal snowshoe hare habitat”.
So, back in the aftermath of the Lime Creek Burn, who would have ever suspected this result? Lynx were not even endangered at the time of the replanting. Also, it was expected that the lodgepole pines would be taken over by the other trees. It was really just a happy accident. In winter 2012, retired National Park Service employee Steve Chaney, photographed two lynx from the window of his car on Molas Pass in the San Juan National Forest. So, be on the lookout for these fine and resilient felines the next time you are driving, hiking, or otherwise recreating in the Coal Bank and Molas Pass area. If nothing else, you may see a snowshoe hare!
Field and Classroom Activities
Field Trip: Visit the Lime Creek Burn Area:
Get the kids outside to see the lodgepole pines in the Lime Creek Burn Area.
– The Coal Creek Trail ascends through the lodgepole pines. Although it is a generally steep trail, the lower portion is not too bad.
– An informational sign about the fire is located along the east side of the highway.
– Be on the lookout for lynx and snowshoe hare!
Outdoor Activity: Oh Deer!
Taken From: http://www.projectwild.org/documents/ohdeer.pdf)
Grade Level: 5–8
Subject Areas: Science, Environmental Education, Mathematics, Expressive Arts
Duration: one 30- to 45-minute session
Group Size: 15 and larger recommended
Setting: indoors or outdoors; large area for running needed
Key Terms: habitat, limiting factors, predator, prey, population, balance of nature, ecosystem
Objectives: Students will (1) identify and describe food, water, and shelter as three essential components of habitat; (2) describe factors that influence carrying capacity; (3) define “limiting factors” and give examples; and (4) recognize that some fluctuations in wildlife populations are natural as ecological systems undergo constant change.
Method: Students portray deer and habitat components in a physical activity.
Materials: An area—either indoors or outdoors—large enough for students to run (e.g., playing field), chalkboard or flip chart, writing materials
Carrying capacity refers to the dynamic balance between the availability of habitat components and the number of animals the habitat can support. A variety of factors related to carrying capacity affect the ability of wildlife species to successfully reproduce and to maintain their populations over time. The most fundamental of life’s necessities for any animal are food, water, shelter, and space in a suitable arrangement. Without these essential components, animals cannot survive.
However, some naturally caused and culturally induced limiting factors serve to prevent wildlife populations from reproducing in numbers greater than their habitat can support. Disease, predator and prey relationships, varying impacts of weather conditions from season to season
(e.g., early freezing, heavy snows, flooding, drought), accidents, environmental pollution, and habitat destruction and degradation are among these factors. An excess of such limiting factors leads to threatening, endangering, and eliminating whole species of animals.
This activity illustrates that:
• good habitat is the key to wildlife survival,
- a population will continue to increase in size until some limiting factors are imposed,
- limiting factors contribute to fluctuations in wildlife populations, and
- nature is never in “balance,” but is constantly is changing. Wildlife populations are not static. They continuously fluctuate in response to a variety of stimulating and limiting factors. We tend to speak of limiting factors as applying to a single species, although one factor may affect many species. Carrying capacity limitations can result in competition among domestic animals, wildlife, and humans. Natural limiting factors, or those modeled after factors in natural systems, tend to maintain populations of species at levels within predictable ranges. This kind of “balance in nature” is not static but is more like a teeter-totter than a balance. Some species fluctuate or cycle annually. Quail, for example, may start with a population of 100 pairs in early spring, grow to a population of 1,200 birds by late spring, and decline
slowly to a winter population of 100 pairs again. This cycle appears to be almost totally controlled by the habitat components of food, water, shelter, and space, which are also limiting factors. Habitat components are the most fundamental and the most critical of limiting factors in most natural settings. This activity is a simple but powerful way for students to grasp some basic concepts: first, that everything in natural systems is interrelated; second, that populations of organisms are continuously affected by elements of their environment; and third that populations of animals are continually changing in a process of maintaining dynamic equilibrium in natural systems.
- Tell students they will be participating in an activity that emphasizes the most essential things animals need in order to survive. Review the essential components of habitat with the students: food, water, shelter, and space in a suitable arrangement. This activity emphasizes three of those habitat components—food, water, and shelter—but the students should not forget the importance of the animals having sufficient space in which to live, and that all the components must be in a suitable arrangement for wildlife populations to reach their maximum size.
- Ask the students to count off in fours. Have all the ones go to one area; all twos, threes, and fours go together to another area. Mark two parallel lines on the ground or floor 10 to 20 yards apart. Have the ones line up behind one line; the rest of the students line up behind the other line, facing the ones.
- The ones become “deer.” All deer need good habitat to survive. Again ask the students what the essential components of habitat are
(food, water, shelter and space in a suitable arrangement). For this activity, assume that the deer have enough space in which to live.
The deer (the ones) need to find food, water, and shelter to survive. When a deer is looking for food, it should clamp its “hooves” over its
stomach. When it is looking for water, it puts its “hooves” over its mouth. When it is looking for shelter, it holds its “hooves” together over its head. A deer can choose to look for any one of its needs during each around or segment of the activity;
the deer cannot, however, change what it is looking for (e.g., when it sees what is available during that round). It can change what it is looking for in the next round,
if it survives.
- The twos, threes, and fours are food, water, and shelter—components of habitat.
Each student is allowed to choose at the beginning of each round which component he or she will be during that round. The students depict which component they are in the same way the deer show what they are looking for (i.e., hands on stomach for food, and so on).
- The activity starts with all players lined up behind their respective lines (deer on one side, habitat components on the other side)—and with their backs facing the students along the other line.
6. Begin the first round by asking all of the students to make their signs—each deer
deciding what it is looking for, each habitat component deciding what it is. Give the students a few moments to put their hands in place—over stomachs, over mouths, or over their heads. (The two lines of students normally will display a lot of variety—with some students portraying water, some food, and some shelter. As the activity proceeds, sometimes the students confer with each other and all make the same sign. That’s okay.
- When the students are ready, say, “Oh Deer!” Each deer and each habitat component turn to face the opposite group, continuing to hold their signs clearly.
- When deer see the habitat component they need, they should run to it. Each deer must hold the sign of what it is looking for until getting to the habitat component student with the same sign. Each deer that reaches its necessary habitat component takes the “food,” “water,” or “shelter” back to the deer
side of the line. “Capturing” a component represents the deer successfully meeting
its needs and successfully reproducing as a result. Any deer that fails to find its food, water, or shelter dies and becomes part of the habitat. That is, any deer that died will be a habitat component in the next round and so is available as food, water, or shelter to the deer that are still alive. NOTE: When more than one deer reaches a habitat component, the student who arrives there first survives. Habitat components stay in place until a deer chooses them. If no deer needs a particular habitat component during a round, the habitat component just stays where it is in the habitat. The habitat component can, however, change which component it is from round to round.
- Record the number of deer at the beginning of the activity and at the end of each round. Continue the activity for approximately 15 rounds. 10. At the end of the 15 rounds, bring the students together to discuss the activity.
Encourage them to talk about what they experienced and saw. For example, they saw a small herd of deer (7 students in a class size of 28) begin by finding more than enough of its habitat needs. However, because the population of deer expanded over two to three rounds of the activity until it exceeded the carrying capacity of the habitat, there was not sufficient food, water, and shelter for all
members of the herd. At that point, deer starved or died of thirst or lack of shelter,
and they returned as part of the habitat. Such things happen in nature also. NOTE: In real life, large mammal populations might also experience higher infant mortality and lower reproductive rates.
11.Using a flip chart pad or chalkboard, post the data recorded during the activity. The number of deer at the beginning of the activity and at the end of each round represents the number of deer in a series of years. That is, the beginning of the activity is year one; each round is an additional year. Deer can be posted by fives for convenience. For example, the students will see this visual reminder of what they experienced during the activity: the deer population fluctuated over a period
of years. This process is natural as long as the factors that limit the population do not become excessive to the point where the animals cannot successfully reproduce. The wildlife populations will tend to peak, decline, and rebuild; peak, decline, and rebuild—as long as there is good habitat and sufficient numbers of animals to reproduce successfully, although do not encourage it. For example, all the students in habitat might decide to be shelter. That could represent a drought year with no available food or water.) NOTE: Switching symbols in the middle of
a round can be avoided by having stacks of three different tokens—or pieces of colored paper—to represent food, water, and shelter at both the habitat and deer ends of the field. At the start of each round, players choose one of the symbols before turning around to face the other group.
12.What is realistic and unrealistic about this simulation? (Deer that do not survive
Do become recycled as nutrients but it is not instantaneous. Deer need all habitat components to survive. Poor habitat usually results in a weakened individual that succumbs to disease, not instant death.)
- In discussion, ask the students to summarize some of the things they learned from this activity. What do animals need to survive? How do these components influence carrying capacity? What are some “limiting factors” that affect the survival of animals? How do factors that limit carrying capacity affect the health, numbers, and distribution of animals? How do these factors affect competition within a species? Why is good habitat important for animals? Are wildlife populations static
, or do they tend to fluctuate as part of an overall “balance” of nature? Is nature ever really in “balance” or are ecological systems involved in a process of constant change?
Indoor Activity: Predator-Prey Models: Canadian Lynx and Snowshoe Hares
(Taken from https://www.math.duke.edu//education/ccp/materials/diffeq/predprey/pred1.html)
In the study of the dynamics of a single population, we typically take into consideration such factors as the “natural” growth rate and the “carrying capacity” of the environment. Mathematical ecology requires the study of populations that interact, thereby affecting each other’s growth rates. In this module we study a very special case of such an interaction, in which there are exactly two species, one of which — the predators — eats the other — the prey. Such pairs exist throughout nature:
- lions and gazelles,
- birds and insects,
- pandas and eucalyptus trees,
- Venus fly traps and flies.
To keep our model simple, we will make some assumptions that would be unrealistic in most of these predator-prey situations. Specifically, we will assume that
- the predator species is totally dependent on a single prey species as its only food supply,
- the prey species has an unlimited food supply, and
- there is no threat to the prey other than the specific predator.
Very few such “pure” predator-prey interactions have been observed in nature, but there is a classical set of data on a pair of interacting populations that come close: the Canadian lynx and snowshoe hare pelt-trading records of the Hudson Bay Company over almost a century. The following figure (adapted from Odum, Fundamentals of Ecology, Saunders, 1953) shows a plot of that data.
To a first approximation, there was apparently nothing keeping the hare population in check other than predation by lynx, and the lynx depended entirely on hares for food. To be sure, trapping for pelts removed large numbers of both species from the populations — otherwise we would have no data — but these numbers were quite small in comparison to the total populations, so trapping was not a significant factor in determining the size of either population. On the other hand, it is reasonable to assume that the success of trapping each species was roughly proportional to the numbers of that species in the wild at any given time. Thus, the Hudson Bay data give us a reasonable picture of predator-prey interaction over an extended period of time. The dominant feature of this picture is the oscillating behavior of both populations.
- On average, what was the period of oscillation of the lynx population?
- On average, what was the period of oscillation of the hare population?
- On average, do the peaks of the predator population match or slightly precede or slightly lag those of the prey population? If they don’t match, by how much do they differ? (Measure the difference, if any, as a fraction of the average period.)
To be candid, things are never as simple in nature as we would like to assume in our models. In areas of Canada where lynx died out completely, there is evidence that the snowshoe hare population continued to oscillate — which suggests that lynx were not the only effective predator for hares. However, we will ignore that in our subsequent development.
One of the neat things about living in Colorado is the ability to see all kinds of lizards in their natural habitat. Lizards are a type of reptile – reptiles also include snakes, crocodiles and alligators, and turtles. Lizards are classified in the phylum Chordata, subphylum Vertebrata, class Reptilia, order Squamata, suborder Sauria. Lizards typically have dry, scaly skin, four feet, claws and a long tail. They can be found in various habitats, including trees (arboreal), underground (fossorial), on the ground (terrestrial), and even sometimes in water (aquatic). Most female lizards lay eggs, although some bear live young. It used to be thought that there were only 2 venomous species of lizard – the Gila monster and the Mexican beaded lizard. Both are found in the Sonoran desert. However, not that long ago scientists discovered that monitor lizards (including Komodo dragons) and some in the Suborder iguania (including some iguanas) have mouth glands that secrete venom.
There are over 3,000 species of lizard in the world, and they are found everywhere except the arctic and Antarctic. Lizards are often fast runners, and some can run up to 15 miles per hour!
Colorado has 19 species of lizards, and most are generally found under 8,000 feet of elevation. This is due to the fact that they are cold-blooded (also called ectothermic), meaning that their body temperature is typically the same as the temperature of their immediate environment. For this reason, you will often find them sunning themselves on a warm rock when the air temperature is cool, and conversely hiding in a cool hole when the air temperature is hot.
Lizards use their tongue to find odors, as snakes do. They are closely related to snakes, but lizards generally have legs, ear openings and eyelids. Lizards have small teeth to bite their prey. Most lizard bites in Colorado will feel like a pinch, although the bite of the Eastern collared lizard may cause some bleeding. Lizard prey usually includes insects and spiders, and lizards can often help in controlling pest species. They may also sometimes eat mice, and smaller lizards.
One interesting adaptation of lizards is that they will lose their tail when it is grabbed by a predator. The predator is left with a squirming tail (the muscles in the tail continue to contract for a while), while the lizard runs and hides. A new tail will grow back, but it may take several months, and a lot of the lizard’s energy. For that reason, we should never try to make a lizard lose its tail on purpose!
Although lizards may all look the same to some people, they often have distinct features that help to identify them. Lizards in Colorado range from the Eastern collared lizard to the diploid checkered whiptail, to the Roundtail horned lizard, to the Many-lined skink. Skinks generally look like a ‘true’ lizard, but have almost no neck, and shortened limbs. Horned lizards are often incorrectly called horned toads because of the shape of their short, squat bodies. Their ‘horns’ are actually spines found on the back of the head. Some whiptail species are one of the few species of animal that can reproduce asexually – females lay eggs that develop without fertilization. Essentially, the whiptail lizard clones itself. The checkered whiptail in Colorado can be either diploid (having two sets of chromosomes) or triploid (having 3 sets of chromosomes).
A couple of Colorado Lizards…
In our part of the state, the Eastern collared lizard is one of the most common, and easily identified lizards, especially during mating season. During this time, males change to bright colors of yellow, blue and green. They can also be brown, and have various patterns of spots and dark bands. During mating season the males especially may be easy to spot, as they display themselves on top of a rock or log. The collared lizard gets its name from the 2 black bands on its neck that are usually separated at the nape of the neck. Collared lizards may eat anything from grasshoppers and spiders, to smaller lizards and snakes. They are preyed upon by hawks and large snakes. When trying to escape a predator, they have been seen to run away on only their hind feet!
Longnose Leopard Lizard
If you haven’t heard of the longnose leopard lizard before, you are probably not alone. Although they can be very common in the Great Basin of Nevada and Utah, the longnose leopard lizard is only found in a few distinct places in western Colorado, one of which happens to be Canyons of the Ancients National Monument (CANM), west of Cortez. In fact, this species is considered to be a sensitive species by the Bureau of Land Management (BLM), meaning that it is a species that could have some risk of becoming endangered.
Not much is known about the longnose leopard lizard in Colorado. Geoffrey Hammerson, author of Amphibians and Reptiles in Colorado, states in his book that longnose leopard lizards only appear above ground for a short period during the year – from late May to early August, and are most active from 2-6 hours after sunrise. Otherwise they are either hibernating while it is cold, or aestivating, staying underground while it is extremely hot. One thing getting them above ground is the opportunity to mate, and females will usually produce between 6-10 eggs every year. Longnose leopard lizards probably used to be more widely distributed in Colorado, but with the expansion of development and agriculture, not to mention cheatgrass, their populations have declined.
MYTH: The tail of a skink is “poisonous” and can sting you.
No, their tail is not a stinger and is not venomous.
MYTH: If a lizard bites you, it will hold on until it thunders.
No, they have no reason to hold on that long.
In Egypt, they say that in spring lizards climb an east-facing wall and look to the east. When the Sun rises, the lizards sight have the ability to restore the sight of a blind person.
In Australia, the aborigines believe that the sky will fall if you kill a lizard.
In ancient Egypt and Greek symbolism the lizard represented divine wisdom and good fortune. In Roman mythology, lizards symbolize both death and resurrection because it was thought that they slept through the winter, and woke up at the end of it. Early Christianity associated the lizard with evil. On the Pacific islands of Polynesia and Maoris lizards are revered as a “heaven god.”
Dinosaurs weren’t lizards! Current scientific theory is that dinosaurs were reptiles, but were not lizards. The main difference is the way their legs attach to their bodies. Dinosaurs’ legs go down, as our legs do. Lizard legs go out in a squatting position. It is also possible that dinosaurs were warm-blooded animals, unlike cold-blooded lizards.
Lizards in Colorado
Roundtail horned lizard
Greater short-horned lizard
Texas horned lizard*
Great plains skink
Prairie lizard/Plateau lizard
Desert spiny lizard*
Ornate tree lizard
Longnose leopard lizard*
Eastern collared lizard
Plateau striped whiptail
Lesser earless lizard
Diploid checkered whiptail
Triploid checkered whiptail
(* denotes sensitive species as designated by the BLM)
Found a lizard in Colorado you can’t identify? Colorado Parks and Wildlife has a handy Lizards of Colorado key found here: http://cpw.state.co.us/documents/education/studentactivities/coherpquickkey.pdf
If you find a lizard in the wild, observe it from a distance so it doesn’t run away. Do not try to capture it, as it may lose its tail, or become very stressed. Lizards in Colorado are lucky to live here, so please leave them in the wild, where you found them!
The summer rains have arrived. Yippee! These rains are helpful in so many ways. Perhaps mostly noticeably they provide enough water for the mountain wildflowers to bloom. These flowers coat the hillsides is a glorious canvas of color. The flowers also produce delicious nectar that is enjoyed by many of nature’s creatures. Look carefully and you will see hummingbirds, ants, bees, flies and others feeding on the nectar. When the sun is shining, butterflies are often seen drinking from these fantastic flowers.
What is a Butterfly?
Butterflies are a member of the insect family, and together with moths makeup the order known as ‘Lepidoptera’. The dividing line between butterflies and moths is fairly fuzzy and some creatures could seem to fall into either category. However, the main difference between them is butterflies are generally active in the day and moths are active at night. Also, in a resting position, moths lay their wings down over their bodies, while butterflies stand their wings up so that their undersides may be seen.
Fairly large colorful wings grace the butterfly and give the ability to fly. The large number of yellow winged varieties is probably responsible for the name. The wings seem uniquely designed to help avoid predators, but at the same time to attract mates. Eye patterns in some wings will ward off discerning birds and colorful displays sometimes serve as a warning of bitter flavors to keep away the epicureans. Meanwhile these patterns are recognized by other butterflies of the same species as a call to mate.
Butterflies have a large proboscis, which is actually a mouthpart, and is used to suck nectar and fluids from flowers. While feeding themselves butterflies also serve the function of helping to pollinate flowers.Adult females lay the eggs on a leaf that will become a food source for the new caterpillars. The caterpillars grow bigger and bigger as they eat the leaves. Eventually something is triggered in the caterpillar and it finds aquiet spot to go into its chrysalis phase. The caterpillar does not “build” a chrysalis around itself. Instead, the caterpillar sheds its skin and the chrysalis is underneath.
Their antennae are generally “clubbed” and covered with tiny hairs that also may be found on much of the rest of the body. These hairs tell the butterfly about wind currents, water, vibrations and nearby objects. Butterflies have two compound eyes that see a broad spectrum of light including ultraviolet.
The time lines for (adult) butterflies vary widely, from a few weeks to a couple of years. Some, such as the monarch butterfly actually migrate for various stages and activities. Butterflies also vary widely in size, color and activity.
A butterfly has four stages in its life cycle: egg, larva (caterpillar), pupa (chrysalis) and adult (butterfly). It is a repetitive cycle, but the butterfly does not turn back into an egg!
Like most animals, the male and female adults work together to produce new fertilized eggs.
Adult females lay the eggs on a leaf that will become a food source for the new caterpillars. The caterpillars grow bigger and bigger as they eat the leaves. Eventually something is triggered in the caterpillar and it finds a quiet spot to go into its chrysalis phase. The caterpillar does not “build” a chrysalis around itself. Instead, the caterpillar sheds its skin and the chrysalis is underneath. When the butterfly emerges from its chrysalis, its new wings are fragile. It waits patiently for the wings to dry out and strengthen. Then it flutters away! Many other insects go through similar life cycles.
Colorado Mountain Butterflies and Flowers
There are over 60 species of butterflies in Colorado. Here are some of the more common ones seen in the summer above 8,500 feet and the flowers on which they feed. They vary greatly in size, color and plant food. Read on to learn more about these winged wonders!
Favorite flowers: milkweeds, thistles, dogbane, vetch,red clover, cow parsnip
Appropriately named, this butterfly is identified by thespots within its checkered pattern. There are at least 8 species of checkerspots in Colorado and pattern varies within each species.
Favorite flowers: asters, paintbrushes
One of the largest butterflies you will see, these are also some of the most common butterflies during June and July.
Favorite flowers: many flowers, including red clover,dandelion and thistles
These little beauties are so small, you might miss them…until you startle them and they flutter away. Look for them in muddy, wet areas. They love moisture.Arrowhead blues are one of many species of blues in Colorado. It is differentiated by a tiny orange arrowhead on the outside bottom of each hind wing.
Favorite flowers: anything in the pea family, especially lupines
Easily mistaken for the larger Tortoiseshell, the Comma has a small comma in the center underside of its hind wing. This butterfly hibernates in winter.
Favorite flowers: varies, includes currants
This butterfly is not as common in this area as the name would imply. Look carefully and you may be fortunate enough to spot one.
Favorite flowers: grasses, cow parsnip, bittercress
All photos copyright MK Gunn 2007 – 2012 unless otherwise noted.
Save the Date!
Want to learn more about butterflies and flowers? MK Gunn is leading a Butterflies and Blooms hike up Cascade Creek on Saturday, July 30th, 9:30am – noon. Details can be found here.
Why do Birds Migrate?
Although many people may associate the timing of bird migration with cold weather, it’s not exactly the cold that makes birds want to move to a different part of the world. Many theories are around trying to explain this phenomenon, from the shortening of the days to hormonal changes. Some scientists have found that changes in the length of daylight affects a gland in some birds’ bodies that produces a hormone that allows their bodies to start storing more fat under their skin, preparing for their long journeys. In the end, though, most birds migrate so that they’ll be able to find food. This is especially true for insectivores, whose food supply of insects either greatly diminishes or completely disappears in the winter. Whatever the reason, something in their bodies triggers the need to migrate, and they must then prepare for the long journey ahead.
Migration – Physical Changes in their bodies
The shape of birds’ bodies assists them in their migration treks across continents. With their streamlined body, hollow bones and well-developed pectoral muscles, not to mention their extremely efficient heart, most birds are literally built to fly long distances. As you can imagine, birds must consume A LOT of food before embarking on their twice a year journey. Small birds will actually double their body weight, while larger birds will increase their weight, but not as much. Building up these fat reserves in small birds allows them to travel for extremely long distances before needing to stop to ‘re-fuel’ – some birds may travel 90 hours before stopping even once! Other birds may migrate for one night, then rest for two or three in an area called a ‘stopover’. These birds may travel as far as 2,000 miles in one night, especially if they have a tail wind. Even tiny hummingbirds migrate. Ruby-throated hummingbirds travel across the ocean from Texas to the Yucatan peninsula, a trip of about 500 miles, without stopping for about 24 hours. Arctic terns fly 22,000 miles roundtrip from the arctic to the Antarctic and back every year!
To help reserve some of their energy, many birds will soar and glide, rather than constantly flapping their wings while migrating. This is especially true for larger birds who can’t store as much energy as the smaller birds. Examples of these birds include eagles, buzzards, and even storks. When hawks migrate together, they are called a ‘kettle’, and you may see them gliding on thermals of air. Thermals are updrafts of air caused by solar heating. One drawback to this method of gliding, however, is that the journey takes longer than if they flapped their wings the entire time.
How do they find their way?
Almost no migrating birds bring their young along to show them their migration route for their first time (although the sandhill crane is one exception). So, at least part of the reason birds migrate, and their knowledge of their migration routes, is instinctual. However, there are still many environmental cues that birds do use to find their way.
Birds often fly along migratory pathways called ‘flyways’. This isn’t necessarily because they like to hang out together, but because they’re all following the same basic clues to get them from point A to point B. The North American flyways include the Pacific, Central, Mississippi, and Atlantic. You can probably guess what they’re following – the Pacific and Atlantic coastlines, the Mississippi river, and the Rocky Mountains (Central flyway). Interestingly, some birds do not take the same route south as they take going north. One possible reason for this may be food availability, although it may also be due to winds at different times of the year.
Many smaller birds migrate at night rather than during the day. This may be because the air masses are more stable, there are fewer predators, and the air is cooler so they have less of a risk of dehydration and overheating. When they are traveling at night, it is speculated that birds may use the stars to navigate, as well as the setting sun. Experiments have been done to demonstrate that birds even use the earth’s magnetic field to set their internal compass and help them find their way north or south. This would be useful especially on overcast days or nights when visibility is low.
It has been estimated that half of all migrants that head south in the winter won’t return in the spring. Bird migration has even more challenges than just having enough energy and being able to find their way. They may encounter predation and bad weather along the way. Birds must also deal with the effects that humans have had on the environment. Sometimes the stopovers that birds have typically used may become strip malls, or their fall/winter grounds in the tropical rainforest may have been clear-cut. Many birds also fly into windows during their migration, especially windows on skyscrapers, killing or seriously injuring themselves. To help prevent this, we can break up the reflection of the sky in the windows with awnings or window screens, or by planting trees close to windows or putting bird feeders within a few feet of windows. Our natural areas and public lands, such as those in the San Juan National Forest, and the Tres Rios Resource Area (BLM), provide important habitat for many migratory species.
• At what heights do most birds migrate? Songbirds travel at less than 5,000 feet, and most of them even stay lower than 2,500 feet. Waterfowl and shorebirds, however, might fly as high as 10,000 to 20,000 feet!
• Songbirds travel about 20 miles/hour, while waterfowl and shorebirds may travel 40 miles/hour or more.
• Birds may migrate together in flocks of the same, or mixed, species, or they may go it alone. Loners might include herons, hummingbirds, kingfishers and woodpeckers, while “flockers” can include ducks, geese, cranes, gulls, doves, crows, jays and blackbirds.
Websites on Bird Migration:
- Bird Sleuth program – students in elementary and middle school use scientific methods to become citizen scientists and study birds: birds.cornell.edu/birdsleuth
- Activity ideas and support materials to help students learn about birds: birds.cornell.edu/schoolyard
- North American flyways: http://www.birdnature.com/flyways.html
- A science education program that uses the internet to track migration – Journey North: www.learner.org/jnorth/
What an amazing mid-winter thaw! All this warm weather makes it hard to remember the preceding cold and snowy months of January and December and even early February. The deep snow and bitter cold have made this winter extra tough and stressful for local wildlife.
While some animals are hibernating and others have migrated to warmer latitudes, those that have adapted to tolerate the winter have to work harder to stay alive.
Tolerating wildlife have a variety of techniques for surviving the winter. One technique is to yard up. Deer often do this in the deep snow. They create a small network of trails and sleeping areas. They do not stray out of this area into the deep snow, even if they see other food nearby. To do this would risk too much energy. In a particularly harsh winter, animals may run out of food in the yarded area.
As a result of the harsh winter, there will be more winter kill among local wildlife this year. Although this is all part of nature, one can’t help but feel a little sad about starving and frozen critters. The Durango Herald reported back in January that Durango locals have spotted many carcasses near town and even seen mountain lions feeding.
But it doesn’t have to be all doom and gloom. There are measures you can take to help wildlife make it through the winter.
Respect wildlife closure areas. Both the Bureau of Land Management and Colorado Parks and Wildlife manage seasonal closures of public lands. These closures prohibit public access in order to create a less stressful environment for wintering animals, or in some cases, nesting raptors. Starving animals conserve calories by moving as little as possible. Human encroachment from foot travel, biking, motor vehicle use and dogs – even on a leash – can startle wildlife and cause animals to run, therefore using valuable energy stores.
For more information about winter closure areas in Southwest Colorado, including maps, contact the BLM Tres Rios Field Office in Dolores at 882-7296 or Durango at 247-4874, and the CPW Durango office at 247-0855.
Minimize Impact Elsewhere. Animals that live near paved roads, populated areas and ski areas are habituated to noisy humans and are not as stressed by startling sounds. However, winter recreationists – skiers, snowshoers, fat bikers, snowmobilers and even ice climbers – who venture miles away from civilization pose a threat to the survival of wintering animals.
There are a number of studies out there that weigh the effects of noise from different types of human travel in winter. One study showed that deer are more startled by people on foot than snowmobiles. However, snowmobiles do have a greater impact in one way – the weight of snowmobiles causes the snow to collapse, destroying the subnivean underlayers needed by small mammals to survive winter – subnivian meaning “under the snow.” These subnivian creatures create a network of tunnels in the snow and create food caches. It is often much warmer under the snow than out in the open.
Owls are also suffering during this harsh winter. A study on the northern spotted owl showed that a visual disturbance from as far away as 100 meters can disturb the owls.
If you read the Feb. 14 Herald article about the tough winter for wildlife near Glenwood Springs, you are familiar with the fact that there has been an unusual number of dead owls this winter.
This was attributed in part to a lack of small animals above the snow, but human encroachment can also play a part.
So when going into the winter backcountry, think about the creatures that live out there and tolerate the weather all winter long. We humans can choose a warm bed at night, whether we tolerate by heating our house or migrate to southern Arizona and camp out where it is warm.
By MK Gunn
Winter in southwest Colorado is finally here! In this weather our local animals have many survival strategies – they may migrate, hibernate, or adapt their lives to the new surroundings. However, some of the most fascinating animals are those that manage to survive while remaining underneath large amounts of snow throughout the winter. Their environment is called the subnivian zone, meaning “under snow”.
When the temperatures get frigid outside, a deep layer of snow – about 10 inches or so – can act as an insulating layer to animals beneath it. The warmth here actually comes from the Earth’s core. The snow at the bottom of this layer changes form, and becomes ‘sugar snow’, or depth hoar, where the flakes don’t stick together very well. This is a benefit to small animals who can then move through it easily. Some of the most common animals that can be found under the snow are mice, voles and shrews. They burrow under the snow, finding seeds, stems and even beetles and larvae to eat. Some of the plants they find to eat even manage to stay green and growing during the winter. The small mammals living here make an amazing network of snow tunnels, and even create air shafts to get oxygen. However, it is typically very dark under the snow, making eyesight a secondary sense to these animals. Whiskers help profusely to help them find their way through the network of tunnels.
Despite these small mammals seeming to be well hidden under the snow, predators such as ermine, owls, foxes and coyotes are aware of their presence. Ermine, or long-tailed weasels, are small and thin enough to actually enter the tunnels, while larger predators appear from above, diving snout first (such as with coyotes and foxes) or feet first (such as with owls and other raptors) to grasp their prey. When you’re out this winter, look for the beautiful wing prints that owls and other raptors leave in the snow when capturing their prey.
Animals even smaller than mice manage to live under the snow as well. This includes mites, springtails and spiders. Springtails, which are small insects that can spring themselves into the air can actually be seen above the snow as well on warmer winter days, and are a great food source for the spiders under the snow. In order to survive under the snow some spiders and insects produce a sort of antifreeze in their bodies which prevents ice crystals from forming.
Things also change for animals and plants beneath the ice in the winter. Water beneath the ice doesn’t freeze, but it still remains extremely cold – usually in the mid-‘30s. Actually, the main problem for animals down there is not the cold, but the lack of oxygen in the water. During the rest of the year oxygen is added to the water through air and water currents, waves, and plants photosynthesizing. In the winter, none of this happens. Animals that live beneath the ice are cold blooded, meaning their body temperature is the same as their environment. Thus their metabolism slows down, as do their movements – some even become dormant. In this way they need less oxygen and food through the winter.
When outside this winter, you can experiment with your own ‘subnivean zone’ by creating a snow shelter, sometimes called a quinzee. These need to have quite thick walls (1 – 2 feet) to work best, but once you’ve built it you can even sleep in it at night! Or, if sleeping in the snow isn’t your thing, enjoy having a hot chocolate in front of the fire and give a thought to the animals and plants surviving the season outside in the cold.
By Gabrielle Morey, SJMA Education Outreach Director