About Author: Rachel Chock

Posts by Rachel Chock


Observing Behavior in the Wild


One of our camera traps caught this deer mouse heading for a burrow.

My favorite part of the fieldwork I do (see: A Night with the Pocket Mouse Field Crew)  is watching the pocket mice, kangaroo rats, and other small mammals in the wild. I love releasing them from a trap and watching them take a sand bath, or dig up a cache of seeds they buried previously, or sometimes dive into the closest burrow and get chased right back out by its owner who was already inside.

While the reward (and often the data!) of an animal behavior study is observing your subject do what it does, figuring out how to make the observation can be one of the biggest challenges. You don’t want your presence to affect what the animal is doing—unless you are observing their response to humans.

With big animals that live in fairly open environments, sometimes you just need to be far enough away. As an undergraduate I worked as a field assistant on a pronghorn project in Montana. We hiked up hillsides and watched for females to get their babies out of hiding to nurse. We used binoculars and spotting scopes so we could see well enough to note ear tag colors, yet distant enough to not make the animals feel threatened by our presence.

With the pocket mice, that are so small, quick and nocturnal, getting far away and sitting quietly doesn’t work very well. I spent a dozen or so nights trying, outfitted with a camp chair and night-vision goggles. I set out some seeds on a tray and hoped the pocket mice would come. With one exception, they did not. Those were some of the longest nights I have ever experienced, sitting in the dark, staring at nothing.


Andrea Sork, a field assistant, uses night vision goggles to observe a kangaroo rat. On the right is an infrared camcorder.

What ended up working was trapping them first and then putting the tiny rodents inside a clear arena with the seeds, so I could watch them through the sides. While it isn’t perfect—they spend time exploring the walls and digging to get out—it at least allowed me to see them! And most of the animals decided that the seeds inside the arena were worth taking; even though I was sitting 12 feet away, the mice made multiple trips to the seed pile and back to their burrow. It helped that I sat very still and quiet the whole time. But it was exciting watching the animals come and go!

In addition to physically watching the pocket mice, camera traps can be hugely important. You can set multiple cameras at once and leave them for many nights. Later, as you go through the photos and videos, you can see where the mice were and what they were doing—especially if you leave food trays or set them at burrow entrances or some other specific place. The upside is that you can have a lot more “eyes” out at once, and cameras are less intrusive than a person sitting there. The downside, though, is that you can’t be sure cameras are catching everything, and they often have a pretty narrow view.

If you get a chance to see some animals in the wild, take an extra moment to watch them do their thing. Normal activities like sleeping or eating are a feat to witness, and there is so much to learn just by sitting still and watching!

Rachel Chock is a graduate student and volunteer with San Diego Zoo Institute for Conservation Research’s Pacific pocket mouse project. Read her previous post, Protected Habitat in Southern California.


Protected Habitat in Southern California

A Stephen's kangaroo rat is checked out in the field.

Researchers examine a Stephen’s kangaroo rat in the field.

It’s the middle of November, the holidays are approaching, and 2014 is quickly coming to a close. Normally, I would be done with fieldwork by this time of year, since the Pacific and Los Angeles pocket mice that I study are probably already hibernating (see Where are Pocket Mice during Winter?). Since our Southern California winter hasn’t seemed to hit yet (it is still warm here, even by our standards!), I was able to squeeze in one more week to check out a new potential field site for the spring.

This new site is a California State Wildlife Area, a little piece of land next to a State Park but otherwise surrounded by a freeway, cropland, and cattle farms. Over five nights we caught five species of small mammals, including endangered Stephen’s kangaroo rats, from which we collected genetic samples. My field site this summer was a different State Wildlife Area, and in addition to the small mammals I saw badgers (see Badger and Coyote Caught on Camera), bobcats, foxes, and a spotted skunk.

A spotted skunk is "captured" by a camera trap in a State Wildlife Area.

A spotted skunk is “captured” by a camera trap in a State Wildlife Area.

Prior to starting my fieldwork in Southern California, I hadn’t known much about these 600,000 acres of designated wildlife areas in the state. In addition to our state and national parks, these protected areas make up the primary habitat for many of our local threatened and endangered species. San Diego Zoo Global provides a lot of the conservation research and a great opportunity to view some of these species at the San Diego Zoo and the San Diego Zoo Safari Park, like the Peninsular bighorn sheep (see Bighorn Sheep Roundup Furthers Conservation Research). Only an hour or so from the Safari Park, they are roaming free in Anza-Borrego State Park!

Bighorn sheep lambs frolic.

Bighorn sheep lambs frolic.

Seeing animals in the wild, particularly endangered species that scientists have been working so hard to save, is such a treat. The opportunity to visit areas that are set aside and safe from development and to be able to see these animals in their native habitat is definitely something I am thankful for!

Rachel Chock is a graduate student and volunteer with San Diego Zoo Institute for Conservation Research’s Pacific pocket mouse project. Read her previous post, Pocket Mice Powerhouses.


What’s in Your Backyard?

A scorpion is caught under UV light.

A scorpion is caught under UV light. Photo credit: Dr. David Aveline

The school year has started, and I’m back to student life in Los Angeles, where I’m starting the third year of my Ph.D. at UCLA. It really isn’t too far from the costal sage scrub in San Diego County where I’ve spent the last few months in the field studying the Pacific pocket mice (see Up All Night with Pocket Mice), but it feels worlds apart. For starters, I’m back on a normal schedule—I’m awake during the day and get to sleep at night! What a luxury. But being up during the nights, and hiking around outside, is a very different experience than anything I had been used to.

I have always been a little afraid of the dark—and extremely afraid of spiders!—so doing nocturnal fieldwork was never something I envisioned. Actually, it wasn’t something I had ever even thought about existing, let alone doing. But when the opportunity presented itself, I jumped right in and have become fascinated with what is happening when most of us are normally sleeping!

Many mammals are active at night. There are about eight species of rodents I regularly see in the coastal sage scrub along with tons of rabbits. Coyotes are also very busy at night; we hear them yipping and howling so often it has become a normal part of the sound landscape. Other carnivores like bobcats and mountain lions are up during the night. I haven’t spotted any myself, though I have caught a few deer in my headlamp. They have huge eyes that appear to glow bright green when the light hits them. Most nocturnal vertebrates have this eyeshine, which is caused by a reflective layer called the tapetum in their eye behind the retina. This allows light to hit the visual censor twice; once when it passes into the eye and once when it reflects off this extra layer, which lets them take maximum advantage of the available light. Humans do not have the tapetum layer, though cats and dogs do, allowing them to see much better in the dark—and sometimes giving them crazy eyes in photos taken with a flash!

In addition to mammals, owls are around during the night. They hunt rodents, so we often see them in areas where we are working. Owls have unique feathers and a wing structure that allow them to fly silently. I don’t often think of birds making a lot of noise with their wings, but it is very startling when an owl passes close by and there was nothing to warn you it was coming. This stealth tactic helps them hunt unsuspecting prey!

A tarantula hawk carries away its latest catch: a tarantula!

A tarantula hawk carries away its latest catch: a tarantula!

There are also plenty of creepy crawlies out at night. So many scorpions! We quickly discovered that scorpion burrows look a whole lot like pocket mouse burrows. Scorpions fluoresce under a UV light (black light), which we carry around with us to help identify tagged mammals. It’s amazing how much more visible they are when they are glowing bright green! Another fun fact about scorpions is the mothers give live birth to the young (called scorplings!), which then ride around on her back until their first molt, when they gain some protection from predators and can regulate their body moisture.

The most bizarre and (warning!) terrifying creatures I’ve encountered, though, are tarantula hawks. Tarantulas themselves are fairly common at certain times of year, and, while they can have a painful bite, are not particularly dangerous to humans and not at all a problem unless provoked, like being picked up or handled. Tarantula hawks are parasitic wasps that have glossy black bodies, bright orange wings, and a very menacing stinger. The female wasp captures and stings a tarantula, paralyzing but not killing it, and drags it back to her burrow. She lays an egg on the spider’s abdomen, and when the larva hatches, it burrows into the spider and feeds on it, leaving the vital organs so the spider stays alive. After a few weeks, the wasp larva pupates and eventually becomes an adult and emerges from the spider’s abdomen. I actually witnessed a tarantula hawk dragging a paralyzed tarantula toward her burrow!

These are things I imagine in the tropics, in exotic places far away. But this all goes on nightly, right here in southern California! After all these months in the field, I’m much more comfortable being outside at night, but I also appreciate nature for being both more fascinating and horrifying than ever before.

Rachel Chock is a graduate student and volunteer with San Diego Zoo Global’s Pacific pocket mouse project.


Up All Night with Pocket Mice

Rachel holds one of her study subjects, a Pacific pocket mouse.

Rachel holds one of her study subjects, a Pacific pocket mouse.

It is summer again, which means it is time to be up all night with Pacific pocket mice! I started studying them about two years ago, when I began my PhD program at the University of California, Los Angeles (see Getting Started with Pacific Pocket Mice). Last summer, I met my first Pacific pocket mice (PPM) as I worked with Maryke Swartz and Debra Shier, trapping in the three remaining areas where the species are found to bring individuals into the captive breeding program (see Bringing in the Pacific Pocket Mouse). It was a great experience, and I learned how to look for Pacific pocket mouse burrows, the routine of setting and checking the traps (usually at midnight and 4 a.m.!), and how to handle pocket mice. I had experience working with other small mammals and rodents, but pocket mice are SO TINY; it feels really different to handle an animal that is smaller than my thumb!

This summer, I’m using all those skills and beginning my own research on how these mice interact with other rodent species in their community. Behavioral observations come with their own set of challenges. Pocket mice, like many rodents, are nocturnal. Combined with their very small size, it is almost impossible to see them! Technology helps: we get to use night vision goggles and an infrared camcorder. One thing I am studying is the mice’s caching behavior: how they store food, usually in their burrows, and specifically which other species pilfer, or steal, from these caches.

A Pacific pocket mouse (PPM) as seen through night vision goggles: she is sitting next to my backpack, and you can see how she is smaller than the buckle!

A Pacific pocket mouse (PPM) as seen through night vision goggles: she is sitting next to my backpack, and you can see how she is smaller than the buckle!

To do this, I have to get a pocket mouse to take seeds I have dyed with a non-toxic powder so I can track where these seeds end up—literally—by checking the feces of any animals I trap in the area for traces of color. I set out a seed tray by a pocket mouse burrow and sit and watch and wait for one to come out and fill its cheek pouches and take the seeds away to cache them. There have been a lot of nights where there is no activity whatsoever or when another species comes to the seed tray, and I need to make a noise or toss sand toward it to scare it off.

The nights can feel really long, but when a pocket mouse does come to the seed tray—wow! My heart feels like it stops for a second when I first spot it and when I am frantically (silently and motionlessly) determining whether it really is a Pacific pocket mouse. The next 20 or so minutes are thrilling as I get to watch it make multiple trips from the seed tray to its burrow. Often times they are quite furtive at first, taking long pauses in the shrub cover, spending only a few seconds at the tray before disappearing again. After a couple of trips, they seem to become a little less hesitant and spend up to a minute at the seed tray, filling their cheek pouches and running directly back to their burrow. After taking all the seeds from the tray, one little female decided to investigate us! She took a few minutes to approach us as we sat in chairs and watched silently. She came up to where my backpack was sitting on the ground right next to me and even touched my shoe. Moments like this make all the waiting worth it, and it is such a privilege to see these tiny, fascinating animals in action!

If you are interested in learning more about the research I am doing, you can check out this short video I made!

Rachel Chock is a doctoral student at the University of California, Los Angeles, and is working with Debra Shier, Ph.D., from the San Diego Zoo Institute for Conservation Research.


Getting Started with Pacific Pocket Mice

What is it like to start a research project? Hopefully, you can find out along with me as I begin my doctorate studies at UCLA and learn about the endangered Pacific pocket mouse here in Southern California. I haven’t even met a Pacific pocket mouse yet (PPM) but have been reading a lot of scientific articles written by people who have studied them. I will start fieldwork this coming summer. It would be hard to see any PPMs right now anyway, because they hibernate in their burrows during the winter, so it is a good time for me to do a lot of background reading!

There are only three known populations of PPMs left, and San Diego Zoo Global is starting a managed-care breeding program in 2012 to raise enough individuals for a reintroduction the following year. A reintroduction moves captive-bred animals to areas of habitat they have historically lived in, while a translocation moves wild-caught animals to other areas of their historic range. Usually translocations are more successful, but there just aren’t enough PPMs to move!

There are a lot of factors that have to be considered in either a translocation or a reintroduction. A suitable habitat must provide food, water, and shelter, and predator control can result in higher survival rates and reproductive success (see post Mountain Lions Help Kangaroo Rats?). I am going to be looking at things from a slightly different angle: what effects competitors have on a reintroduction. Pacific pocket mice share their habitat with three other small rodents, and I am going to be studying competition between PPMs and these other species to see how they make it work when they all live in the same area.

The flip side of this is looking at habitat where PPMs could live (but don’t) and studying competitors in these environments to figure out how we can make it easier for PPMs to move in. This will help when we are designing the reintroduction plans for PPMs, and we should learn a lot along the way! Stay tuned for lots more on PPMs and what it is like to be starting a career in conservation research!

Rachel Chock is a doctoral student at the University of California, Los Angeles, and is working with Debra Shier, Ph.D., from the San Diego Zoo Institute for Conservation Research.