How To Catch A Cat Part III: Setting the trap

This blog post is part of a series that covers how biologists go about catching the wild cats they study.  In the last post I described how to choose a trap site.  Once a trap site is chosen the next step is to actually set the trap.  Different kinds of traps are used for wild cat studies including cage traps and snares.  For use in research, each type of trap offers advantages, and for the purpose of this post, I'll cover how cage traps are set since I exclusively used this type for my bobcat research.

There are a few key tools used when setting cage traps. First, of course, you need the trap itself.  A lot of people ask me exactly what the trap looks like, and in the the pics below (that show the trap setting process) you will get a glimpse, but the traps I almost always use are heavy wire cage traps approximately 2 foot x 3 foot x 4 foot.  They have a single entry point at one end of the cage, and at the back of a cage is a wire treadle plate that when the animal steps on it, the door shuts.  In addition to the cage itself, I always maintained a "tool bag" that I used for setting traps.  In my tool bag I carried a hammer, wire, fishing line, scent lures, a hand shovel, a cloth bag, and a GPS unit.  When trying to trap an animal, it is very important to understand the biology of that animal. Cats, wild or domestic, are very visually-oriented creatures, and so it is important to cater to their visual sensitivity. That's why, among the tools in my tool bag, are always visual lures ones such as a feather pillow, a couple of antlers or bones, and old CDs, big feathers, or old soda cans that can be used as ornaments around the trap to attract the attention of animals.

In my last blog, I described picking a trap site and so once I know where I need to carry and set the trap, I gather all my tools and the cage and head off to the trap site to set the trap.  The cage itself weighs around 35 pounds, so that, along with the tool bag, can make for an interesting walk to the trap site if it is far or through a heavily vegetated area.  For some sites, a 20 min walk can easily double if you are carrying a huge and heavy cage with you.  The benefit though is that it gets you in shape fast if you are setting traps regularly!

When I set the trap that I'll describe below, it was luckily an easy spot not too far off from a human hiking trail The picture below shows a spot I picked out to set a trap. Vegetation in the Santa Monica Mountains can be very dense, so it is hard to tell but it is just on the edge of a natural animal trail, is flat, and is a position that is just between two sage bushes which will be great for disguising the trap. The red arrow in the photo below shows where the trap will be set.

Once I get to my trap site, I set all my tools down, and in the photo below you can see the cage along with my tool bag while I'm getting ready to set the trap.  Here you can see only half the cage, the feather bag inside the cage, and my toolbag on top of the cage.  

 

 Next, I put the cage in position.  I want it sandwiched between vegetation with the door to the cage just about flush with the animal trail.  This way, any bobcat that walks along the trail won't miss the trap.  It can be quite difficult to get a wild cat to go in a cage trap, but a great first step is making sure that the trap is in a position along a trail that increases the odds a bobcat will actually see whatever lure is inside the trap. I always try to have my traps so that the door is not only flush with the animal trail, but that the trap itself is perpendicular to the trail so that no matter which direction a bobcat may be walking along the trail, it will have equal opportunity to see whatever lure is inside the trap.  In the photo below, I have set the trap in the position I want it.

In the pics below, there's a great view inside the trap.  Here we are looking into the cage trap when the door is set open.  In the photo on the left, notice that the bottom of the trap is a hard wire mesh. Because bobcats are ambush predators that like to sneek up on their prey, they can be sensitive and deliberate about where they put their feet.  They are very careful not to make too much noise when hunting since it might alert their prey. Often, the visual lures that are put inside a cage trap to entice a cat inside will resemble potential prey for the bobcat.  In the photo on the right, I've placed a decoy foam rabbit, with the nose of the rabbit facing the back of the cage.  From this view, we see the decoy from behind and it resembles the white tail of a rabbit.  If a bobcat is tricked by this decoy, it may try to stalk and then pounce on it, so I always try to disguise the bottom of the cage with dirt so the bobcat won't feel the hard wire mesh on the bottom.  Putting dirt in the bottom also lends the cage stability, which is another great way to try to eliminate as many "unnatural" things about the trap as possible.  These photos give a great view of the treadle, or the "plate," in the back of the trap where the animal needs to step to trigger the door to shut.  Its hard to see, but the treadle is linked with a chain that controls a bar that keeps the door open.  If the treadle is pressed, the chain pulls the bar, releasing and shutting the door.

 

Now that the cage is in place and there's dirt on the bottom of the cage, it is time to start disguising it!  That means gathering a lot of vegetation to put both inside and outside the trap.  On the inside, the treadle needs to be disguised.  On the outside, the trap itself needs disguising so that bobcats that see that trap from the outside don't get suspicous before they even get close enough to see what's inside.  In the photo on the left below, grass goes on the treadle underneath the foam rabbit.  On the right, I've started to put vegetation all around the trap to make it look more natural.

Next, I start putting the finishing touches on!  Vegetation is put on top of the door, and I make sure that all the vegetation on the outside looks natural and is relatively stable.  The vegetation should stay in place even if it gets a little windy at the trap site.  In the photo on the left (below), the red arrow is pointing to the front of the cage trap.  At this point, its hard to even see where the trap is, which is what I'm shooting for!  It looks natural on the landscape.  In the photo on the right, I've put some white feathers just inside the trap and on the trail.  These feathers will help grab the cat's attention when it walks by the trap, hopefully getting the cat to stop and take a look inside the trap and be enticed by the fake rabbit.  The feathers come from the feather pillow that I have prepared with my other cage setting supplies.

At this point, the trap setting is done!  Before I leave the trap, I test the treadle to make sure the trigger action of the trap is just the way I want it, and that if a cat enters the cage and steps on the treadle, the door will shut properly.  When its all done, I'm ready to head out to set another trap, check what traps were already set, or head home for the day.  Now, it can be hard to even see the trap, although the feathers are a dead giveaway!  

 

Heading out, I take one last look at the trapsite (photo below).  Now it really blends in to the landscape (red arrow pointing to trap below).  I'll be back early the next morning to see if I've caught anything.  In total, it usually takes about one hour just to set a trap. Despite the hard work, it's always fun to set a new trap because it really brings on a feeling of total optimisim that you may catch something very exciting in it!

During the next blog post, I'll cover what actually happens when I've caught a bobcat in a trap.  I'm heading out of town next week to visit another urban carnivore study area in South Africa, so it'll take me a few weeks to get the next post up.  Sorry for the delay, but maybe I'll also have a good story to tell from South Africa!  

How To Catch A Cat Part II: Make sure you have a question and a few trapping basics to consider before setting the traps

My first blog entry in this series focused on the very first important step in catching wild cats for research: learning where there may be wild cats to study!  Once you've learned where there are cats to study, you need to also have a good study question that you are going to focus on that requires capturing animals. So this is a good chance to talk a little bit more about my research and why I ended up studying bobcats across the Santa Monica Mountains.   

My study focuses on how urbanization affects the health of bobcats in the urban, fragmented landscape around Los Angeles.  To perform this research, I spent more than two years conducting intensive bobcat trapping so that I could collect samples (blood, urine and fecal material) to measure health indicators in our local bobcats. These health indicators are very similar to what your vet would be interested in if you took your dog or cat to a vet to do a routine check up. Your vet may collect fecal samples to check for internal parasites like tapeworm or roundworms and blood samples to test for viral or bacterial infections.  With blood we can also test whether the animal has a healthy immune system and with both blood and urine samples, we can test whether the animal has normal organ function. So my aim was to evaluate these various factors in wild bobcats in the Santa Monica Mountains since for bobcats living in/near urban areas, they may be exposed to pesticides (like rat poisons), can contract diseases carried by domestic cats, may have reduced genetic health in isolated populations at risk for inbreeding, and generally can have a more stressful life since they are regularly exposed to roads and human activity.

To understand how urbanization affects these health indicators in bobcats, I needed two groups of animals so I could make comparisons between the two groups.  For my first group, I captured "control" group of healthy bobcats, largely unaffected by urban development, so that I could establish baseline values for the tests I was conducting. My second group was bobcats I captured in urban areas.  Luckily, the Santa Monica Mountains offers some areas (like the State Parks- especially Point Mugu State Park) where bobcats are less affected by urban development, and also some areas of habitat fragmented by urbanization but still host to bobcats. So, for my study, I sought samples from bobcats in State Parks (Point Mugu, Malibu Creek, and Topanga State Parks) as well as in urban habitat patches east of the I-405 (Bel Air, Beverly Hills, Hollywood Hills, and Griffith Park) and north of the 101-freeway in Thousand Oaks.

Now that I had a research question and knew where cats were (see previous blog post) in the Santa Monicas, I was ready to start trapping. To start getting your trapline ready, there are a few important things to know about trapping, and about the animal you are trying to trap.  First, once you set a trap, it can take weeks (or months for larger cats like mountain lions) before you get a capture!  A lot of people think that studying these wild cats must be a daily exciting adventure involving seeing wild cats every day at work. But the truth is that biologists studying wild cats actually very rarely see their study animals since they are solitary, territorial, have large homeranges (making it so there are few individuals in a given area) and on top of it all, are very shy and elusive! 

So when you set your traps in a bobcat or mountain lion's territory, you may have to wait for weeks until a cat even walks by the trap.  Of course, setting multiple traps increases your odds, but another important note- we check our traps everyday twice a day- once in the morning and approximately 12 hours later in the late afternoon/early evening! So by time alone, you are limited in how many traps you can get to during the morning before you have to start your afternoon checks.  Another important element biologists must consider is that since wildcats are mostly nocturnal, we are more likely to find cats during the morning trap checks and so you want to make sure it only takes no more than a few hours to check all your traps in the morning so that animals aren't stuck in the traps unnecessarily long.  For bobcats, and sometimes mountain lions, we use large cage traps that, although very safe for the animal caught in them, we always aim to minimize the amount of time animals are in the traps so they aren't unnecessarily stressed. 

Because wild cats do tend to have large homeranges (about 1-3 square miles for bobcats and 60-200+ square miles for mountain lions) you also don't want to have your traps too close together.  Remember that these animals are solitary and territorial, so for bobcats in a 1-3 square mile range, you may only have 2-3 animals roaming around.  So ideally, you want to cover many square miles with your traps, but travelling from trap to trap then increases the time to check your traps, which you are trying to keep to less than 3 hours.   

On average, I had 15-20 traps set at all times during my trapping seasons.  For this number of traps set, I would definitely need two people for every morning trap check to ensure that we covered the ground quick enough.  One of the great things about doing field work like trapping cats is that there can be a LOT of hiking involved!  It is very hard work (I'll cover that in the next blog) as when traps are set, they are open 24/7. Everyday you must check the traps.  We keep traps open 24/7 during trapping season because if a cat only walks by a trap once over a 3-4 week period, you don't want your trap closed the day the cat ends up passing by the trap!  At the end of the day, it's a lot of hard work and requires a LOT of patience. For me, I enjoy being outdoors, hiking around, and doing hard work.  I can be patient to wait for captures to happen, and so when they do, they are very exciting!  

For the next blog I'll cover how the traps themselves are set, and after that, what happens when we get a cat!

How to Catch a Cat, Part I: Finding cats!

I've been studying how urbanization affects the health and disease susceptibility of bobcats in and around the Santa Monica Mountains since 2006.  This work has involved capturing bobcats to collect samples from them.  I've been fortunate to not only maintain my own trapline for this effort, but to collaborate with the National Park Service to get samples from the animals they trap for their own ongoing long-term bobcat research. From 2009-2011, I intensively trapped bobcats for nearly the entire two years (taking breaks only during kitten season when females could have young kittens to tend to).  Because of this work, I've been blessed to have handled at least 100 bobcats, and have myself trapped approximately 60 individuals. In addition to the bobcat work, I've aso been fortunate to collaborate on the National Park Service mountain lion project, also in the Santa Monica Mountains. I've not seen nearly as many mountain lions as bobcats, but working with both species, I've learned important techniques for trapping and handling cats.

 

When describing my work to both scientists and nonscientists alike, most people first ask how we catch the cats to get the samples. So I thought it would be a good blog topic- or topics.  Its a multistep process, so for this entry, I'll focus on the first step- figuring out where the cats are so we know where to put our traps! *(See note at end of entry about trapping ethics)

  

Diving into how to catch a cat...the first step is figuring out where the cats are!  There's a couple ways to do this- when working in a new study area where it is unknown whether your species of interest is present, biologists may set up remote wildlife cameras to determine what species live  in the area. For example, when National Park Service biologists started their mountain lion project in the Santa Monica Mountains in 2002, they had no idea whether there were even mountain lions in the Santa Monicas! Mountain lions are found throughout California but they are very sensitive to urbanization and habitat fragmentation.  So in areas where there is a lot of habitat fragmentation and urban development, there may be areas of "local extinctions" where populations are unable to survive longterm and their populations go "extinct" in a localized region. Given that the Santa Monicas are next to one of the largest cities in the world, its not stretch to imagine that it would be difficult for a healthy mountain lion population to persist in the region! So, to discover if mountain lions were even still present in the Santa Monicas, NPS set up heat-triggered remote wildlife cameras around the Santa Monicas where every time an animal walked by the camera, a photo would be taken. It was using this method they discovered that there were mountain lions in the park!

Another method is to get out in the field and look for animal tracks and sign. Every species of animal has a distinctive track and many have distinctive fecal material (also known as "scat"). Some animals (like bobcats or mountain lions) mark their territory with distinctive scrapes on the ground.  The scrapes for bobcats and mountain lions look very similar, but mountain lion scrapes are much larger than bobcats!  So, as a local carnivore biologist, I've learned some distinctive signs (scat, tracks or scrapes) for fox, mountain lion, coyote, skunk, and raccoon.  Using both this method of looking for animal sign, along with the remote cameras, is useful to not only identify what animals live in an area, but also learn what are common paths that animals use.  Knowing the best paths is the next step to knowing how to catch a cat!  My next entry will focus on choosing a trap site, so keep posted for that! 

*An important note- we (myself along with my National Park Service collaborators) do not take trapping and handling animals lightly.  When trapping and handling animals, it induces stress in the captured animals and there's always a risk that something can go wrong for the animal or the biologist.  For projects that involve this invasive techniques, we must have our protocols reviewed by animal ethics committees and weigh the cost of stressing an animal with the benefit of the research where the benefit must outweigh the cost.

  

Not So Urban Carnivores

In September, the UCLA lab I work in took a trip to Yellowstone National Park.  Our lab, the Robert Wayne lab, is a conservation genetics lab, specializing in dog and especially wolf genetics.  Most of the lab members study domestic dog or wild dog species, such as grey wolves and Channel Island foxes.  But just because people in our lab study these animals, it doesn't mean we are always around these animals!

So, in order to see some wolves in action, we decided to take a trip to Yellowstone.  Given the expense of flying to the Yellowstone area, many of us drove the long 17-19 hours to the park.  Once we got to Yellowstone, everyone in my car was excited to see some wildlife and take a nice long hike!

Watching wolves in Yellowstone mostly involves a lot of driving around.  In order to see them, you generally have to go to the open valley areas where, with binoculars or spotting scopes, you can observe them from a distance. To find them, you have to drive around to see if you can spot them- or spot the people that have already found them and are standing with binoculars and spotting scopes looking off in the distance.  In the open valley areas, you don't have vegetation blocking the view.  Wolves and other wild dogs are quite different than most wild cat species in that you can actually observe them!  With wild cats, because they are elusive and solitary, it makes it difficult to find them, let alone observe them for an extended period of time.

What's particularly amazing to me about the wolves in Yellowstone is that when they make a kill, it is sometimes possible to see them feeding on their kills.  And their kills also attract other scavenging animals like grizzly bears, coyotes, and ravens to name a few.  So if you are lucky to find a fresh kill close enough to the road, you may have the chance to see multiple species feeding and potentially interacting with each other.

Unfortunately for us, we didn't see bears feeding on any kills, but we did see wolves, including wolf pups, feeding on a fresh kill they made.  We also observed a coyote scavenging an older kill. The coyote we had the chance to see seemed almost nervous to scavenge the old wolf kill! Perhaps it was nervous to encounter any wolves potentially still on the kill.  

Beyond wolves and their kills, we did see other amazing things.  We observed a coyote hunting for what appeared to be gophers (see photos in slideshow below). One thing that's interesting about the Yellowstone coyotes is they look vastly different from coyotes in the Santa Monica mountains!  Their coats are a lighter grayish brown, rather than reddish brown. They are also larger and a little bulkier.  This isn't surprising given the colder climate the coyotes face in Yellowstone vs. in the Santa Monica Mountains. The bulkiness of Yellowstone coyotes helps them survive the winters, and their coat color helps them blend in better with the Yellowstone environment.  

We also saw bald eagles, golden eagles, a big grizzly, tons of elk, and pronghorn antelope. Pronghorn are really cool animals- they aren't true antelope, though the fill a similar ecological role as antelope in Africa. They are actually unique in that they are the only surviving members of the family (a type of classification for organisms) Antilocapridae.  One cool thing about them though is that they are the fastest land mammal in North America and can run up to 65 miles per hour.  They evolved their speed due to pressure from the now extinct North American cheetah that once roamed the plains of North America.  The cheetah went extinct thousands of years ago, but the pronghorn remains.  

One other cool thing we observed was that we heard elk bugling- something the males do to attract the females. Since it the elk were in rut (the mating season), there were large harems of female cow elk, with males watching over and claiming them as his own!

see the youtube video to hear and see it : http://www.youtube.com/watch?v=pYzWmKlZtrU)

 

Overall, the Yellowstone trip was quite a success!

An unusual scene

Over the weekend, I went out with a couple friends, Tanner* and Johanna, to investigate what appeared to be a lion kill that Johanna stumbled upon the day before.  Johanna and Tanner are citizen scientists, meaning that although not trained in biology, they have a keen interest in biology and desire to contribute to scientific research locally in southern California.  Because of their passion for local wildlife and learning what they can about wildlife in their natural habitat, they spend most of their free-time hiking around various open spaces honing skills such as wildlife tracking and the use of remote cameras to study carnivore behavior.  Their skills in tracking and remote camera use exceed those of many biologists I know, and every time I go out with them, I learn something new!  So when Johanna stumbled upon a dead deer but was unsure how it died, I was only too eager to go check it out.  The deer appeared have died at some point earlier in the week, but had no overt signs that something was feeding on it. One possibility, of course, was that it was killed by a mountain lion earlier in the week (though the there were not signs it was still eating the deer if that's what happened), and if so, this provided a potentially opportunity to gather mountain lion DNA (swab any bite marks or look for mountain lion scat that they sometimes leave at their kills).  It is unusual for a lion to kill something and not feed on it, but not impossible for that to occur.  I should clarify before continuing with the story- we did not expect to encounter a mountain lion, and if we believed there was a reasonable risk of encountering one, we wouldn't have revisited the dead deer.  So, although we should all acknowledge that mountain lions live in our local State Parks and we should all act accordingly, we weren't out there to chase down a mountain lion. 

So, we headed out to the Santa Monicas where Johanna found the deer, and where Tanner also happened to also have wildlife cameras as part of his volunteer work with the National Park Service.  By time we got there, the deer's head was covered with maggots, and no bite wounds were visible either on the head or neck, so it remained unclear if a mountain lion was responsible for the death (although Johanna did get the pics below when she first discovered it, and no maggots were present).

 However, Tanner happened to have a remote camera within 10 feet of the dead deer, but where the deer died was just out of the visual field of the camera.  The camera still picked up some very interesting footage that provide some clues as to what may have happened.  In the video, we see two deer startled by something out of view of the camera.  The deer seem to be attempting to run from whatever startled them.  Then, out of view of the camera, we hear loud breathing and a few grunts, presumably by the deer, or perhaps whatever startled it.  The startled running combined with the sounds do lead me, at least, to believe that the deer was killed by a mountain lion.  There was a patch of missing fur that seemed perhaps licked off by whatever killed it just under the left elbow of the deer (see photo).  I did swab that region, so perhaps if the fur was licked off by a mountain lion, I will get DNA off the swab.  If no DNA is present, perhaps this will remain a mystery forever!  But check out the video footage and see what you think!     

*Please note: Tanner is a volunteer with the National Park Service, and so the work he does with cameras in State Parks within the Santa Monica Mountains National Recreation Area falls under research permits conducted by wildlife biologists with the National Park Service.  

Update on Tuesday, October 16, 2012 at 6:07PM by Laurel Serieys

In the previous blog entry, I was planning to conduct genetic analysis on the swab I took on the bare spot of the deer's hide.  I wanted to know if a mountain lion had at least licked off the spot of fur- which could also suggest that a mountain lion killed the deer to begin with.  Well, the results are in and indeed, it was a mountain lion that licked the bare spot of fur off.  Not only that, it was a female mountain lion!  There generally seem to be less evidence female mountain lions in the Santa Monica Mountains than males (although the documented ratio of males to females born in SAMO so far is about 50/50).  So, finding evidence of a female mountain lion is very exciting, as well as getting a genetic sample!