camera trap photos


Learning What We Can Learn From Camera Trap Photos: Part 2


Can an Andean bear’s nose be a way to determine its age?.

I recently wrote about how we’ve determined that, with caution, researchers can identify individual Andean bears in camera trap photos. Researchers should therefore be able to answer some basic questions that have big implications for Andean bear conservation. However, there are many other important questions for which we still don’t have answers. For example, does the population in this watershed have an age structure that will be stable over the long-term?

How do you figure out how old an animal is when it was born in the wild years ago – 2 years ago, 8 years ago, or 14 years ago? Field researchers often use characteristics of mammals’ teeth to estimate their ages, but those methods require capturing the animals and it is definitely not easy to capture Andean bears. It turns out that we can use camera traps.

I might not have seriously considered using camera trap photos to investigate these kinds of questions except for a conversation with a field researcher from our collaborator, the Spectacled Bear Conservation Society. When I showed him a photo of an Andean bear living at the San Diego Zoo, he said “Wow, that’s an old bear!” He was correct, but how did he know that? He couldn’t describe exactly what it was about the photo that suggested that the bear was old, but I remembered that several years earlier some researchers had documented that the nose color of African lions changes as they age. Might the same thing happen in Andean bears?

Using photos of known-age bears from various zoos, we’ve determined that although the changes in nose color aren’t as predictable as we’d like, they’re consistent enough to provide some information about the age of the individual bear. And, using photos of captive- and wild-born cubs, we’ve verified that it’s possible to estimate the ages of young cubs from camera trap photos. Since fewer than a dozen Andean bear birth dens have ever been found in the wild, this could be really helpful in determining when female bears give birth to cubs. That information, in turn, is the first step in determining why females give birth then, and not at other times of the year.


Notice the changes in Tommy’s nose from when he was  (left to right) 2, 17, and 23 years old.

Another set of conservation research questions can only be answered with information on the genetic structure of a population, or information on how individuals are related to one another. Does the population in this mountain range have a functional connection to other populations or is it isolated and inbred? What traits affect the probability that a female, or male, will have surviving offspring? Who knows which cub was sired by which male? Do cubs look like their parents? In other words, do the facial markings of cubs look like the facial markings of their parents? The only Andean bears with known mothers and fathers are the cubs born in captivity, so I worked with collaborators to test whether the markings of related captive-born Andean bears looked more similar than the markings of unrelated captive-bear Andean bears. They don’t. Sometimes bears that are closely related look alike, but sometimes they don’t. On the other hand, sometimes bears that look alike are closely related, but sometimes they’re not related at all. So, although it might be tempting to say that a cub which looks like an adult male is the offspring of that male, that’s a potentially misleading conclusion. We’ll just have to wait for the development of good genetic tools before we can answer questions about the genetics or kinship structure of Andean bear populations.

After thorough review and discussion by other scientists, this work has been published online in PeerJ, where you can read the details and see more photos.

Russ Van Horn is a scientist at the San Diego Zoo Institute for Conservation Research. Read his previous blog, Learning What We Can Learn from Camera Trap Photos: Part 1.


Learning What We Can Learn from Camera Trap Photos: Part 1


Andean bears are sometimes called spectacled bears because of the rings of lighter colored fur around their eyes.

Others have said it before and it’s true: New forms of technology such as camera traps make it possible for field researchers to collect information we could previously only dream about. Technology advances so quickly that we’re still evaluating what we can do with these tools and what questions we can and cannot answer by using them. We have many basic questions that are still unanswered even for species as large as the Andean bear. Here are two of the most basic: How many are there? Are the populations increasing, stable, or decreasing? The answers to these questions and others would help researchers, conservationists, and governments decide how much of their limited resources to invest in research efforts and conservation actions, in the hopes that 100 years from now there will still be bears roaming the forests of South America. Unfortunately, there are still no answers to these questions.

How would you answer these questions? How do you count animals that live in dense forests in rugged habitat, when those animals avoid contact with humans? It’s been said for decades that the markings of individual Andean bears vary so much that you can identify each individual bear just by looking at it. If that’s true, then maybe we could use camera traps to identify individual Andean bears in photographs and then estimate population sizes and densities. However, how do you test whether individual bears can be reliably identified in photographs? In order to test this you’d need photos of a lot of different bears whose identity you definitely knew. That means you can’t just use photos of wild bears from camera traps, because you don’t know how many bears walked in front of the camera traps.


Compare the markings of this bear, Tommy, with the bear above (named Turbo) and notice the differences.

The only way we could think of to test this was to take photos of different bears from captivity, so we’d know the identify of the bears, ask people to compare those photos, and keep score of whether bears were correctly identified, or not. When a group of international collaborators and I did this we were surprised to discover that people were initially not very good at this task. In fact, they would have done just as well if they’d flipped a coin! That’s really not the kind of result we were expecting, or hoping, and it led us to consider whether we were over-confident in our own abilities to identify individual bears. However, it turns out that with a little practice and training, participants became better at identifying bears from their photographs. After thorough review and discussion by other scientists, this work has been published in the journal Wildlife Biology and you can read all the details and see more photos here.

So, the good news is that, if we’re careful, we and other field researchers can use photos from camera traps to identify individual Andean bears, estimate the sizes of their populations, and compare populations densities. Now, we “just” need to get the cameras into the forests where there are bears!

Russ Van Horn is a scientist at the San Diego Zoo Institute for Conservation Research. Read his previous blog, Ambassador Mi Ton Teiow Receives a New Posting.


A Closer Look at Burrowing Owls

Note the difference in coloration (female on left, male on right) with this burrowing owl pair.

Note the difference in coloration (female on left, male on right) with this burrowing owl pair.

For the past two years, our burrowing owl project has been focused on how to effectively relocate California ground squirrels to help re-engineer nonnative grasslands and make them more amenable to burrowing owls (see Burrowing Owls: Closer than You Think and Digging into Burrowing Owl Recovery). But this year, we get to take a closer look at the owls themselves. Don’t get me wrong, I love the squirrels (more than I ever thought I would), but I’m a bird biologist, so I’m really excited to start working directly with the burrowing owls!

Burrowing owls range widely across the western US and make use of a variety of “grassland” habitats, from open prairie to empty suburban lots to airports. But their populations are declining, mostly due to loss of habitat and eradication of the fossorial (digging) mammals that they depend on to build burrows. One solution is the installation of artificial burrows. However, artificial burrows are not self-sustaining like natural squirrel burrows and, although we know the owls use them, we don’t know how they compare to natural burrows.

A male burrowing owl guards his burrow entrance.

A male burrowing owl guards his burrow entrance.

This year, one of our main objectives is to compare reproductive output, food provisioning, and predation at natural versus artificial burrows, using camera traps and banding the birds to accomplish this. The camera traps allow us to see what is going on at the burrow while we aren’t there, and the banding allows us to identify each individual (see Bling with a Purpose).

At this point, the breeding season is in full swing. We are monitoring almost 30 nest burrows (both natural and artificial); this includes placing camera traps at about 20 of the burrows. We check on each burrow about once a week (we don’t want to visit too often and risk disturbing the birds) and do any camera trap maintenance needed, such as changing batteries and switching out the memory cards that contain our priceless data in the form of photographs. We also watch the birds from a distance to figure out what stage of the breeding season they are in—for me, this is the best part!

A camera trap photo shows a burrowing owl pair allopreening at their burrow entrance.

A camera trap photo shows a burrowing owl pair allopreening at their burrow entrance.

Over the last two months, we have been inventorying burrows and following their progression through the breeding season. On any given day, we head out to the field in the morning and work our way through our route for the day checking on each burrow as we go. When we arrive at a burrow, we observe from the truck (which acts as our blind) from a safe distance to see what is going on at the burrow. Early in the breeding season, we might see both parent birds or just the male standing guard at a burrow. In general, the males are lighter in color than the females, because they spend more time outside so the sun bleaches their feathers. As the breeding season progresses, the difference in plumage becomes more marked, as the males get more and more bleached. By the end of the summer, though, it can be hard to tell the males and females apart as both get bleached by the sun.

Two burrowing owl chicks rest at the burrow entrance while Mom stands guard. Camera trap photo.

Two burrowing owl chicks rest at the burrow entrance while Mom stands guard. Camera trap photo.

Once the pair has chosen their nest burrow, we usually only see the male of the pair; he is often standing watch over the burrow from nearby (often at the entrance of a satellite burrow where he spends much of his time—we call it the “man cave”). At this point, the female is spending most of her time in the burrow incubating the eggs. After about a month, the eggs hatch, and two weeks after that, the young start to come out to the burrow entrance. We usually do a quick examination of the photos in the field to help us determine if there are chicks present, but we also get good clues from the female’s behavior. If she is very protective of the burrow or stays very close to the burrow when we approach, it’s a safe bet that there are babies in the burrow.

Currently, we have nests in all different stages of breeding—some have pretty large chicks, some still have eggs, and some still seem to be deciding if they are even going to breed. In the coming weeks, we will band all of the owls from burrows that have camera traps, and over the next several months, we will pour over the hundreds of thousands of camera trap photos to catalogue how often prey was delivered to the burrow, what type of prey was brought, what types of predators come to the burrow, and other pertinent information. This is a huge undertaking, since we have almost 40 camera traps set up that can take over 30,000 pictures in one week alone! Any volunteers? Seriously, if you’re interested in helping, visit our volunteer page and sign up! Who wouldn’t want to spend their time looking at pictures of these adorable and comical little birds?!

Colleen Wisinski is a senior research technician for the San Diego Zoo Institute for Conservation Research.


Peru: Conservation Science at Local Level

The SBC field team Isaí Sanchez, Javier Vallejo, and José Vallejo) practices the collection of behavioral observations on domestic sheep.

“Se ha producido el error ‘2176’ en tiempo de ejucución; el valor para esta propiedad es demasiado largo.”
Okay, that’s not good. Let’s try it again. Go ahead and click on the “save” icon.
“No se ha encontrado la ruto de acceso.”
Well, that’s just great.
Isn’t it about time for a coffee break?

In other words, we had some unexpected troubleshooting to do. The plan was that I would work with the team from the Spectacled Bear Conservation – Peru (SBC) and a Peruvian university student (Álvaro Garcia) to create a database for the management and analysis of the photos from the camera traps in the dry forest. The programming to create databases like this was written by Mathias Tobler, a large-mammal ecologist now with the San Diego Zoo Institute for Conservation Research. I’d successfully tested this programming, called Camera Base, with photos from camera traps in southern Peru. Unfortunately, we couldn’t get it to work right with the dry forest photos. Eventually, Mathias was able to help me identify the problems, which is a big relief since the database will make it much easier and faster to conduct analyses on the data from the camera trap photos.

One of the goals of the Andean (spectacled) bear program, and much of the work of the Institute for Conservation Research, is to train people from wherever we work to conduct conservation science. So, I’m excited that more Peruvians are now getting involved in the program and learning new techniques. The SBC field team members also continue to expand and hone their skill set. For example, we’ve developed protocols by which they’ll be able to collect data by observing the behavior of wild Andean bears in the dry forest. These methods are derived from standard practices in the fields of behavioral ecology, and they’ve been used to study the behavior of captive bears of several species, including those at the San Diego Zoo.

However, the practice of behavioral ecology is not common in Peru, so we’re breaking new ground, and it’s a challenge for me to convey to the field team the underlying concepts and technical issues involved in collecting behavioral data. So, to ensure we’ve got it right, we practice our technique. Sometimes this appears a bit strange to the neighbors. How do you explain to the guy next door why four people are intently watching his flock of sheep, not saying a word, and making notes on clipboards every minute? Ah, this is conservation science!

Russ Van Horn is a scientist in the Applied Animal Ecology Division of the San Diego Zoo Institute for Conservation Research. Read his previous post, Dry Forest Rain.


Camera Trap: Puma (Mountain Lion)

A puma triggers the camera trap's eye.

I’ve just had the opportunity to quickly review the photos that our remote cameras have taken in the cloud forest of southeastern Peru over the last few months. As usual, in spite of our best efforts, the frequent strong rains and constant high humidity affected some of the cameras. However, most cameras functioned well, and we continue to collect photos of interesting animal behavior that we could not have predicted.

Our remote cameras are currently programmed to take 10 photos in rapid succession whenever they detect motion. One set of photographs, taken at around dawn on March 9, 2011, shows a puma (also known as a mountain lion or cougar) rubbing its chin and the side of its face against a small sapling growing beside the trail. This is a scent-marking behavior, and you may have seen domestic house cats rub their chin and face on objects, and perhaps even on you.

A second set of remote camera photographs, taken very early on March 18, 2011, shows a puma returning up the trail and performing the same behavior on the same sapling. I suspect it was the same puma as photographed on March 9, but to be honest, although some researchers can identify individual pumas from remote camera photos, I don’t think I can do so. If I’m correct, and it was the same puma, then this cat was renewing its scent on the sampling, advertising that it was still in the area. When we placed that remote camera in the forest, we knew that wild animal trails crossed that spot, but we did not know that pumas were using that sapling as a scent post. If we had the same sense of smell as a house cat, I suspect that would have been obvious to us!

Russ Van Horn is a scientist with the San Diego Zoo Institute for Conservation Research, leading our Andean bear conservation program. Read his previous post, Vegetarian Bears?