Nature Blog



The Feral Cat
bobcat
Spring 2011
By Jeff Horn, JDCF Land Stewardship Specialist

In my previous post, bobcats (Lynx rufus) were highlighted and their importance in the ecosystem established. They have adapted to the changing landscape over time, as have the other plants and animals native to the area. In this post, we’ll discuss the feral cat (Felis catus) and its impact on those native species.

The domestic cat was brought over mainly by European settlers on their ships and then became part of American farms. Their numbers have increased dramatically in recent years, and over 100 million cats are now estimated to live in the United States, with between 10-50 million of those being “feral” or free-ranging. The feral cat is a solitary species that mainly eats mice, birds, and reptiles. An average adult cat weighs 8-11 pounds with an average total length of 30 inches. They can have multiple litters per year and average three kittens/litter. Research indicates that the survival rate of feral cats is under 20%, so about one of every five cats born outside is surviving to adulthood. Male cats in Illinois can have home ranges of over 500 acres in size. Females have ranges of about half that size or less.

The impact of feral cats on the environment is difficult to quantify, but their role as a vector of diseases has been well documented. Cats are the definitive host for Toxoplasmosis gondii, a protozoan that causes illness and death in many different wildlife species and humans. They can also transmit several other diseases to wildlife, livestock, pets, and humans.

Another documented role of cats is that of predator. Cats impact wildlife by reducing prey and making it harder for native predators to find food. Many cats receive food from humans, thus maintaining higher densities than native predators and dramatically influencing wildlife populations. Cats have decimated entire populations of animals on islands. Patches of forest and prairie fragments in Illinois are similar to islands, and the impact of cats on these fragmented populations could also be severe.

Pet owners can take steps to prevent their cat from impacting its environment. First, limit or prevent cats from going outside. The Audubon Society has launched a Keep Cats Indoors program which educates the public on the importance of keeping cats indoors. Second, provide proper veterinary care for your pets. The disease-related impact can be limited if all cat owners keep their cats vaccinated. Third, place bird feeders or other wildlife attractants out of the reach of cats. Studies show that cats will capture prey if they are well fed.

As conservationists we should not only be mindful of the impact we have on our environment, but also the impact our pets have. I would also caution our readers that there is a great deal of information is available regarding cats, but much of it is not peer- reviewed, unbiased, or scientific in nature. For further reading I recommend the following peer-reviewed scientific articles:
  • Warner, R. E. 1985. Demography and movements of free-ranging domestic cats in rural Illinois. Journal of Wildlife Management 49:340-346.
  • Gutilla, D. C., and P. Stapp.2010. Effects of sterilization on movements of feral cats at the wildlife-urban interface. Journal of Mammalogy 91:482-489.

The Bobcat — Making a Recovery in Illinois
bobcat
Winter 2011
By Jeff Horn, JDCF Land Stewardship Specialist

With the onset of winter, I thought it would be a good time to write about the elusive bobcat. It is difficult to see this animal in the wild but easier to find signs of them in the snow.

The bobcat has a short tail, hence the name. They stand about two feet high at the shoulders and average three feet in length. Males weigh around 22 pounds, with females being 25% smaller. Their fur is brownish or grayish with black spots. They also have distinctive black-tipped pointed ears and white spots on their backs.

As a biologist, I have always been amazed by the skill and agility of cats as hunters. They will often stalk their prey, but can also sit and wait for hours for prey to go by and will then pounce. The bobcat is a strict carnivore; its diet consists mainly of rabbits, voles, and squirrels. They are also known to eat mice, woodchucks, chipmunks, opossums, muskrats, shrews, and deer. Bobcats will attack a deer as it sleeps and suffocate it by biting its throat. They will then cover the carcass with snow or leaves to eat later.

Bobcats occupy a variety of habitats across their range. Here in Illinois they use mainly forested lands with immature trees, thick underbrush, clearings, cliffs and timbered swamps. Common homes include fallen trees, hollow logs or trees, thickets, caves and rock piles. Some bobcats make their dens in abandoned or little-used barns and buildings.

Like most felids, bobcats are solitary animals. The male and the female interact during the mating season, but interactions between the same sex are very rare. Bobcats have home ranges of several square kilometers and sometimes cross the entire area in one night. Male home ranges will overlap with female ranges, but not with ranges of other males.

Bobcats were once common in Illinois but declined due to trapping, hunting, and habitat destruction. They were listed as a threatened species in Illinois from 1977-1999, but have increased in recent years. They are now seen more frequently, especially in southern Illinois.

A study conducted in southern Illinois found that 61% of the core areas used by bobcats are forested, therefore destruction or loss of that habitat is detrimental to the species. Free-ranging domestic (Felis catus) cats may also cause problems. They compete for many of the same prey species and can spread several diseases — such as Toxoplasmosis gondii — to bobcats as well as other wildlife, pets, and humans. This disease is spread through oocytes shed in the feces; these oocytes can remain viable for months in the soil. It is important to keep your cats inside to prevent these interactions. More to come on feral cats in a future post.


The King of Butterflies — The Monarch Butterfly
monarch butterfly
Fall 2010
By Jeff Horn, JDCF Land Stewardship Specialist

The monarch butterfly is perhaps the best known of all North American butterflies. Its wings feature an easily recognizable orange and black pattern, with a wingspan of 3.5 to 4 inches. The monarch is famous for its southward migration and northward return in the summer in the Americas, the only butterfly to migrate this way and this far, some 2,500 miles. However, no single individual makes the entire round trip.

Monarch butterflies go through four stages during one life cycle and through four generations in one year. The four stages are the egg, the larvae, the pupa (chrysalis), and the adult butterfly. The four generations are actually four different butterflies going through these four stages during one year until it is time to start over again with stage one and generation one. In February and March, the final generation of hibernating monarchs comes out of hibernation to mate. They then migrate north and east in order to find a place to lay their eggs. This starts stage one and generation one of the new year for the butterfly.

In March and April the eggs are laid on milkweed plants. In about four days they hatch into baby caterpillars, also called the larvae. The young caterpillars don’t do much more than eat the milkweed in order to grow. After about two week, the caterpillar will be fully grown and find a place to attach itself so that it can start the process of metamorphosis. It will attach itself to a stem or a leaf using silk and transform into a chrysalis. Although, from the outside, the 10 days of the chrysalis phase appears to be a time of little action, it is really a time of rapid change. Within the chrysalis, the old parts of the caterpillar are undergoing a remarkable transformation, called metamorphosis, to become the beautiful parts that make up the butterfly that will emerge. When the adult butterfly emerges, it will fly away, feeding on flowers for only two to six weeks. This first generation monarch will then die after laying eggs for generation number two.

The second generation of monarch butterflies is born in May and June, and then the third will be born in July and August. These monarchs will go through exactly the same four stage life cycles as the first generation did, dying two to six weeks after becoming a butterfly.

The fourth generation is a bit different than the first three. It is born in September and October and goes through the same process as the first three with the exception that it does not die after two to six weeks. Instead, this generation of Monarchs migrates to warmer climates in parts of California and Mexico and live for six to eight months until it is time to start the entire process over again.

Monarchs cannot survive in the cold winters across most of the United States, so they migrate south and west each autumn to escape the weather. If the monarch lives in the eastern part of the country (east of the Rockies) it will migrate to Mexico and hibernate in oyamel fir trees. If the butterfly lives west of the Rockies, it will generally hibernate in central coastal and southern California, notably in eucalyptus trees in Pacific Grove and Santa Cruz. Despite the fact that these are the new forth generation monarchs, they use the exact same trees as their predecessors year after year. How the species manages to return to the same over wintering spots over a gap of several generations is still a subject of research.

Given the large population of monarchs, that gather to migrate each season, estimated at up to 100 million by the organization, Monarch Watch, it is hard to imagine that the species could face any threat of extinction. The reality is, however, that monarchs and their migration are seriously threatened by human activities in both their summer and overwintering sites. In the north, monarchs face direct habitat destruction cause by new roads, housing developments, and agricultural expansion, all of which alter the natural landscapes the monarchs call home. They also face the loss of their Milkweed host plant which is considered noxious by many people and therefore destroyed. In their southern range, logging and population pressures threaten the monarchs overwintering sites. Conservation groups such as Monarch Watch are responding with efforts such as the Monarch Project, which works to protect these sites in California most often through conservation easements on lands that are prime monarch habitats.