They don’t howl, they don’t race each other to the sound of an easy meal and we rarely even see them, no matter how hard we try. Some predator hunters go years without seeing a bobcat. In many places, however, they are far more abundant than we realize.
How do we know? Biologists have been studying the animals for decades, but recent advances in technology have allowed scientists to get more detailed information than ever on the animals.
A little hair of the dog … errr, cat
DNA analysis, which can be gathered from everything from hair and saliva to scat and blood, is arguably the most important tool for assessing populations of secretive animals like bobcats. A study in West Virginia, for example, used homemade traps to snag hair from animals that walk into them. According to West Virginia University graduate student Stephanie Landry, the homemade traps were nothing more than two boards attached to form a semi-V. Each board had a series of bristles that grabbed hairs from the animals as they walked into the traps.
“We used castor oil, skunk essence and a mix of meat to attract bobcats,” she said.
The baits attracted a variety of other animals, which made identification more difficult. Landry and fellow researchers were able to eliminate hair from such animals as bears and dogs through visual inspection, but anything that looked like a cat, whether a bobcat or house cat, was sent to a lab for DNA analysis.
The study covered the entire state and multiple traps were set in all 55 counties. Landry said there were several hundred traps out, including in remote areas of national forest and within the city limits of Charleston.
Researchers certainly didn’t expect to gather a hair sample from every bobcat in the state. They don’t need to. Instead, they use DNA data to determine home range size and sex. Males tend to have larger home ranges.
“If we get the same animal in different traps, we can determine its home range size and then extrapolate that to the rest of the state,” explained Landry. “That will allow us to estimate the statewide population. The most recent population estimate was between 10,000 and 12,000, but that was from the 1970s or even earlier.”
Cats caught on camera
Remote cameras, a common tool among deer hunters, have also allowed scientists to gather valuable data without actually handling or otherwise disturbing animals. They were used on a study to determine bobcat numbers near Fort Hood in central Texas and during a study conducted in western and eastern Colorado, where researchers set out 80 remote cameras on four grids. Two were on the eastern slope of the Rocky Mountains and two on the Uncompahgre Plateau on the state’s Western Slope. Cameras took 335 photos of bobcats on 70 sites over the course of 113 days. Some of the photos were of the same cats. Lead author Dr. Jesse Lewis, a graduate student at Colorado State University at the time of the study, also cage-trapped 36 bobcats and attached GPS collars and ear tags to them.
“We used different color combinations on the collars and ear tags so we could identify animals caught on cameras. Some camera surveys have relied on pelt patterns to identify individual animals, but that’s not always reliable,” explained Lewis.
By determining specific animals at specific locations, he was able to determine home ranges along with population density much the same way Landry did, through extrapolation. Not all of the marked bobcats were photographed. However, by using some simple formulas, Lewis was able to estimate populations and densities with the data he had.
Bobcat numbers
As with any wild animal, bobcat numbers are highest where the habitat is best. Of course, “highest” and “best” are relative terms. Generally, though, they are found in all 48 contiguous states, the southern regions of five Canadian provinces and parts of Mexico, but population densities tend to be higher overall in the southern and southwestern United States.
According to a report published by the International Union of Conservation of Nature, bobcat populations are either stable or rising throughout much of their range. That’s due largely to conservation measures that limit mortality from hunting and trapping. Only a few states have bans on killing bobcats, but nearly all have season limits.
Only populations in Florida appear to be decreasing, according to the report. That could be a result of continued habitat loss. Florida’s human population is one of the fastest growing in the nation. However, one study suggested that non-native pythons are playing a considerable role in the decline of mammals where the snakes are present.
Overall, the total US bobcat population is estimated at as many as 3½ million in 2010, according to the IUCN report.
Population densities
Even in what might be considered good habitat overall, cat numbers are relatively low, which might explain why we see so few when we hunt. Of course, coyotes typically show up first, and most hunters won’t pass up a coyote to wait for a bobcat that may never appear.
A study on Ft. Hood in central Texas found an average population density of just one animal per three square miles. That figure counted all of the landscape, including areas like agricultural fields, developed areas and other places cats normally don’t go. Not surprisingly, researchers noted that densities were lowest “in the most heavily modified landscape.”
The IUCN report referred to various population estimates based on studies in different states, noting that Virginia had about one cat for every 4 square miles, while Arizona had about one per 1,000 acres. A 1990 study showed Idaho has one bobcat per 2,700 acres.
California has a somewhat higher density, thanks in part to high-quality habitat and low hunting pressure, along with a statewide bobcat trapping ban. Some estimates suggest there are as many as two per square mile in the best habitat.
The area with the highest bobcat population in the Colorado study was the wildland area on the Western Slope. There was about one bobcat for every 1½ square miles. The other Western Slope study area consisted of a mix wildland and home sites randomly scattered throughout the landscape. A bobcat occupied about every 2 square miles.
The Front Range study areas included land on the fringes of the city of Boulder and what is known as wildland-urban interface, the transition zone between the urban area and the wildlands. Generally, bobcat densities were about the same as they were on the Western Slope.
The human factor
“They did tend to avoid areas with higher human density, which is what you might expect, but some most certainly did use urban areas. Each animal is an individual, so one may be more comfortable around cars and dogs and lights than another,” said Lewis.
Bobcats don’t seem to adapt to the presence of humans as well as coyotes. In some places, coyote densities are actually higher in urban areas than they are in the surrounding rural landscape. They are generally successful at evading cars, which means they have relatively low mortality rates. Urban coyotes also enjoy an abundance of food, including discarded human food, road-killed animals, and live prey like rabbits, mice and squirrels. Bobcats are also pretty good at avoiding cars, but that’s likely because they don’t cross busy roads much. A study in California found that two major freeways prevented the animals from moving distances similar to those traveled by bobcats in rural landscapes.
Although home ranges vary from one region to another, Lewis found that bobcats in his study area had home ranges of anywhere from 3,700 acres to upwards of 10,000 acres.
“Studies in Texas and California have found much smaller home ranges, anywhere from 500 to 1,200 acres,” noted Lewis. “Bobcats in some urban and suburban areas around Los Angeles likely have much smaller home ranges than that and higher populations than in the wildland areas because the bobcats are essentially trapped by roads.”
What kills cats?
Cars likely take the heaviest toll on urban and suburban populations, but hunting and trapping in particular result in the highest mortality rate for most bobcat populations.
“Our study took place before hunting and trapping season started, but most were killed over several years by hunters and trappers. Trapping accounted for the most deaths,” said Lewis.
Even with high human-specific mortality, there will always be bobcats on the landscape thanks to the scientists who study them and the wildlife agencies who use those studies to manage them. You may not see them, but you can be sure they can see you.
Featured image: iStock
