As we prepare to launch Season 7 (yes! it’s coming soon! stay tuned!), I thought I’d share with you some things we’ve seen in seasons 1-6.
Snapshot Serengeti is over a year old now, but the camera survey itself has been going on since 2010; you guys have helped us process three years of pictures to date!
First, of the >1.2 million capture events you’ve looked through, about two-thirds were empty. That’s a lot of pictures of grass!
But about 330,000 photos are of the wildlife we’re trying to study. A *lot* of those photos are of wildebeest. From all the seasons so far, wildebeest made up just over 100,000 photos! That’s nearly a third of all non-empty images altogether.
We also get a lot of zebra and gazelle – both of which hang out with the wildebeest as they migrate across the study area. We also see a lot of buffalo, hartebeest, and warthog — all of which lions love to eat.
We also get a surprising number of photos of the large carnivores. Nearly 5,000 hyena photos! And over 4,000 lion photos! (Granted, for lions, many of those photos are of them just lyin’ around.)
Curious what else? Check out the full breakdown below…
An unpleasant emotion caused by the belief that someone or something is dangerous, likely to cause pain, or a threat: — Oxford English Dictionary
Fear is an emotion induced by a perceived threat which causes entities to quickly pull far away from it and usually hide. — Wikipedia
To be afraid of (something or someone). To expect or worry about (something bad or unpleasant). To be afraid and worried. — (Not very helpful) Merriam-Webster.com
Both Meredith and I have talked a bit about the meaning and role of “fear” in shaping animal behaviors and population dynamics. The word “fear” is a bit touchy. When ecologists use the word fear, we aren’t talking about the emotion as you and I know it. We are referring to a certain type of situation and response. For example, lions kill and eat wildebeest. This creates “landscape of fear” – meaning that the wildebeest exists in a landscape in which certain physical places have a higher risk of predation. You can envision that this landscape has its own topography — hills and valleys of high and low risk. The differing levels of risk can trigger physiological responses as well as behavioral responses. For example, wildebeest may show higher levels of stress hormone in the “risky” areas, or they may avoid “risky” areas even though that’s where the best food is.
This is what we mean when we talk about fear. We are not talking about whether the wildebeest lies awake at night dreaming bad dreams. We are talking about situations of high and low risk and the physiological and behavioral responses.
That being said, “fear” is an incredibly powerful driving force in the natural world. I’ve touched on this from time to time. The idea that smaller predators are so desperate to avoid being beaten up by the big guys, that they avoid the areas with the best food or den sites, and their populations decline even if they aren’t actively being killed by the big guys. This process still amazes me. Even cooler? Fear doesn’t just matter for big and small predators, it doesn’t just matter for predators and prey. The effects of fear can trickle down from predators to prey to plants, just like the trophic cascades I wrote about last week.
Some of my favorite research on the role of fear in trophic cascades has been done by researchers out of the Schmitz Lab at Yale University.
In 1997, Os Schmitz and his students hypothesized that predators could trigger trophic cascades not just by killing and eating herbivores, but by scaring herbivores and changing their behaviors. Os, in his infinite wisdom, works in systems that are experimentally tractable. So he and his team got a bunch of spiders (their predator) and grasshoppers (their prey) and did an experiment that I will never ever be able to do with lions. They created two treatments: a risk treatment, where the spiders had their pincers glued shut and couldn’t kill the grasshoppers, and a predation treatment, where the spiders got to carry on with all the spidery things they like to do (such as eat grasshoppers). They put the grasshoppers in with one of the two types of spiders, and compared what happened.
So, perhaps unsurprisingly, grasshoppers were afraid of spiders whether or not the spiders had their mouths glued shut. In the presence of any spider, grasshoppers changed their diet to avoid areas that spiders liked to lurk, spent less time eating, and only really came out to eat when the spiders were sleeping. The surprising thing is that these behaviors resulted in lower grasshopper densities irrespective of whether or not the spiders could kill grasshoppers. The presence of spiders with their mouths glued shut changed the behavior of the grasshoppers, which resulted in the grasshoppers acquiring less food, which in turn decreased grasshopper populations. What’s more, these effects trickled down to the plant communities. Grasshoppers eat grass, but mere presence of predatory spiders can reduce the effect of grasshoppers on this grass.
Since this 1997 experiment, Os’s lab has gone on to produce some of my favorite research on the role of fear in driving ecological systems. Now if only I could figure out how do such enlightening experiments in the Serengeti…
Reference: Schmitz, O.J., Beckerman, A.P. & O’Brien, K.M. (1997) BEHAVIORALLY MEDIATED TROPHIC CASCADES: EFFECTS OF PREDATION RISK ON FOOD WEB INTERACTIONS. Ecology, 78, 1388–1399.
Weather.com says it’s a whopping 6 degrees outside right now, but that it feels like -14. I am really wishing I were back at the conference in California right now…
By now, both Meredith and I have gushed about all the “bio-celebrities” at the Gordon Research Conference on Predator Prey Interactions. How we got to come face to face with the scientists whose work we’ve read, memorized, admired for years. But what I think has been an even more exciting outcome of this research conference than getting to hang out with our scientific heros and listen awe-struck about everything they’ve done in the past that has led to their fame today, was a chance to sit down with them over a beer or glass of overpriced red, and talk about the future. Not just where our various and varied subfields have been, and not even just where they are going, but where they need to go. Where the holes are in our knowledge, and what we need to do to fill them.
Much of ecology is about developing “predictive capacity.” The ability to not just describe the patterns we see in the world about us, but the ability to predict what will happen when things change. Understanding how climate change affects annual bird migrations, for example, or what losing species means for the spread of disease. We develop conceptual frameworks to tie together outcomes from different experiments and scattered observations drawn from ecosystems around the world, and these frameworks give us a way to articulate our expectations about 1) what underlying processes we think are driving the dynamics of a system and 2) a way to test those hypotheses: do the outcomes match what we predicted would happen? Or is something else going on that we need to investigate further?
One of the things I slowly worked up the courage to articulate at the conference was that I think that science surrounding predator-predator dynamics really lacks this sort of integrated, synthetic, predictive framework. We draw on a whole bunch of different sets of theories to understand the patterns of suppression and coexistence apparent in apex-mesopredator (top- and middle- predator) systems. There’s a ton of theory out there on how species coexist when they eat the same thing, or how they coexist when they eat the same thing and also eat each other. There’s a lot of theory on how predators coexist with the things they eat. There are predictions for when we expect to see species able to coexist, when we don’t, and how these different outcomes change from, say, low productivity tundra to high productivity rainforests.
But around the world, top predators suppress populations of smaller predators (called mesopredator suppression). It’s not because the top predators are eating up all the food, and it’s not because the top predators are eating the mesopredators. It seems to happen because the bigger guys chase, harass, and kill the smaller guys. This is bad enough, but it also creates a “landscape of fear” in which that the smaller guys change their behaviors to try and avoid these aggressive encounters. There are lots and lots of ways in which mesopredator suppression can happen…but we (as a community of ecologists) don’t have a good, integrated framework for making predictions about when we expect to see mesopredator suppression vs. when we don’t. We don’t have a set of expectations about how these patterns change with different behaviors or different types of environments. We don’t have a solid understanding of what mesopredator suppression means for other small predators, prey animals, and the plants that the prey animals eat. We have lots and lots of examples of all sorts of complex things happening…but we don’t yet have the ability to predict how these things play out in new systems.
And that, to me, is one of the most exciting “holes” that needs filling. How do we tie together our knowledge from all of these disparate studies, where lions suppress wild dogs but not cheetahs, or coyotes kill foxes left and right but aren’t actually the reason that fox populations are low. I guess my PhD is trying to fill a tiny, tiny bit of that hole. But it’s a damn big hole and sometimes it’s hard to see how one PhD will cover a whole lot of ground. I guess what was so exciting at the GRC is just how many other people are also trying to fill those holes…and with all of us working together, we just might actually be able to understand the world around us that much better.
As Meredith mentioned last week, she, Craig, and I are counting down the days until we head out to sunny California for an academic conference. I am really looking forward to above-zero temperatures. I am rather less enthused about the prospect of presenting a poster. Yes, it is good networking. Yes, I get to personally advertise results from a study that are currently in review at a journal (and hopefully will be published “soon”). Yes, I get to engage with brilliant minds whose research I have read forward, backwards, and sideways. Despite all of that, I’m still not excited.
Poster-ing is perhaps the most awkward component of an academic conference. Academics are not known for their mingling skills. Add to that the inherent awkwardness of having to lurk like an ambush predator by your poster while fellow ever-so-socially-savvy scientists trudge through the narrow aisle ways, trying to sneak non-committal glances at figures and headings without pausing long enough for the poster-presenter to pounce with their “poster spiel.” For the browsers who do stop and study your poster, you have stand there pretending that you aren’t just standing there breathing down their necks while they try to read your poster until they decide that a) this is really interesting and they want to talk to you, or b) phew that was close, they almost got roped into having to talk to you about something they know/care nothing about. Most conferences have figure out that poster sessions are a lot less painful if beer is served.
Working with big, fuzzy animals means that I usually get a pretty decent sized crowd at my posters. About half of those people want to ask me about job opportunities or to tell me about the time that they worked in a wildlife sanctuary and got to hug a lion and do I get to hug lions when I’m working? I once had a pleistocene re-wilding advocate approach me for advice on – no joke – introducing African lions into suburban America. But they aren’t all bad. I’ve met a number of people in poster sessions who have gone on to become respected colleagues and casual friends. I’ve met faculty members whose labs I am now applying to for post-doctoral research positions. And I’ve learned how to condense a 20-page paper into a 2 minute monologue — which is a remarkably handy skill to have.
As much as I gripe and grumble about poster sessions, I know they’re good for me. At least with this one, I’ll be close to the beach!!
Below is a copy of my (draft) poster for the upcoming Gordon Research Conference that a chunk of the Snapshot Serengeti team will be at. It’s mostly on data outside of Snapshot Serengeti, but you might find it interesting nonetheless! (Minor suggestions and typo corrections welcome! I know I still have to add a legend or two…)
I have successfully survived the trials and tribulations of my first semester of graduate school! Huzzah! That being said, a student’s work is never done – you can still find me sitting in my office, plugging away at data and up to my eyeballs in pdfs and textbooks. Although it certainly helps when I know that, in a few short weeks, I’ll be showing off my preliminary data on a nice warm beach in California. Well, the Gordon Research Conference that Ali and I will both be attending will probably not be held directly ON the beach, but it’s a nice fantasy to have when your fingers are freezing off in Minnesota.
The theme of the conference is predator-prey interactions, but approached from a very interdisciplinary standpoint. Topics range from genes and the causes of childhood anxiety up through ecosystems, evolution, and Craig’s presentation on man-eating lions. It’s been over a year since I last attended a conference, and it’s going to be intimidating and inspiring to meet the Who’s Who in our field. All the papers piled up around my desk, underlined and annotated and thoroughly mulled over? Hopefully I’ll have a chance to chat with their authors in person and get these scientists’ input on the direction of my current research ideas.
My particular focus, predator intimidation (“fear”), is delightfully billed in the conference descriptions as “the persistent threat of immediate violent death.” The blurb continues on to state that “most wild animals are in peril every moment of every day of being torn limb from limb by any number of predators.” Language far more colorful that I can get away with in most of my proposals, but certainly right on point! There will be talks on fear’s impacts on evolutionary ecology and population- and ecosystem-level processes as well as about the effect of predators as stressors that I’m am particularly keen to attend.
As excited as I am, I’m honestly a bit frantic trying to synthesize our Snapshot data to produce distribution graphs and other basic preliminary results. A few months ago, I couldn’t have programmed my own name into “R” – the bread and butter statistical program of beloved (well, it’s a bittersweet relationship) by biologists. With long evenings in front of the computer and by the generous grace and goodwill of Ali, I’ve been making progress. Ideally, I would like to show up to this conference with not only an outline of my research to be picked apart by the aforementioned greatest minds in the field, but also with maps of the monthly distributions of several herbivore species in relation the changing vegetative landscape and predator movements. No breakthroughs so far; I foresee a great deal of coffee in my future between now and January…
P.S. Congrats to Margaret for defending her PhD!!!
I’ve got to echo Margaret’s apology for our sporadic blog posts lately. Things have been a bit hectic for all of us — Dr (!!!) Margaret Kosmala is finishing up her dissertation revisions and moving on to an exciting post-doctoral position at Harvard, our latest addition, Meredith, is finishing up her first semester (finals! ah!), and I’m knee deep in analyses (and snow!).
So,\ please bear with us through the craziness and rest assured that we’ll pick up the blog posts again after the holidays. In the meanwhile, I’ll show you something that got me really excited last week. (Warning: this involves graphs, not cute pictures.)
Last week, I was summarizing some of the Snapshot Serengeti data to present to my committee members. (My committee is the group of faculty members that eventually decide whether my research warrants a PhD, so holding these meetings is always a little nerve-wracking.) As a quick summary, I made this graph of the total number of photographs of the top carnivores. Note that I’m currently only working with data from Seasons 1-3, since we’re having trouble with the timestamps from Seasons 4-6, so the numbers below are about half of what I’ll eventually be able to analyze.
The height of each bar represents the total number of pictures for each species. The color of the bar reflects whether or not a sighting is “unique” or “repeat.” Repeated sightings happen when an animal plops down in front of the camera for a period of time, and we get lots and lots of photos of it. This most likely happens when animals seek out shade to lie in. Notice that lions have wayyyy more repeated sightings percentage-wise than other species. This makes sense — while we do occasionally see cheetahs and hyenas conked out in front of a well-shaded camera, this is a much bigger issue for lions.
I also dived a little deeper into the temporal patterns of activity for each species. The next graph shows the number of unique camera trap captures of each species for every hour of the day. See the huge spike in lion photos from 10am-2pm? It’s weird, right? Lions, like the other carnivores, are mostly nocturnal….so why are there so many photos of them at midday? Well, these photos are almost always lions who have wandered over for a well-shaded naptime snoozing spot. While there are a fair number of cheetahs who seem to do this too, it doesn’t seem to be as big of a deal for hyenas or leopards.
Why is this so exciting? Well, recall how I’ve repeatedly lamented about the way shade biases camera trap captures of lions? Because lions are so drawn to nice, shady trees, we get these camera trap hotspots that don’t match up with our lion radio-collar data. The map below shows lion densities, with highest densities in green, and camera traps in circles. The bigger the circle, the more lions were seen there.
The “lion hotspots” in relatively low density lion areas have been driving me mad all year. These are nice, shady trees that lions are drawn to from up to several kilometers away, and I’ve been struggling to reconcile the lion radio-collar data with the camera trapping data.
What the graphs above suggest, though, is that there likely to be much less bias for hyenas and leopards. Lions are drawn to shade, because they are big and bulky and easily overheated. We see this in the data in the form of many repeated sightings (indicating that lions like to lie down in one spot for hours) and in the “naptime spike” in the timing of camera trap captures that suggest lions seeking out shade trees to go to. Although this remains a bit of an issue for cheetahs, what the graphs above suggest is that using camera traps to understand hyena and leopard activity will be much less biased and much more straightforward — ultimately, much easier than it is for lions. And this is really good news for me.
Last week I posted an animated GIF of hourly carnivore sightings. To clarify, the map showed patterns of temporal activity across all days over the last 3 years — so the map at 9am shows sites where lions, leopards, cheetahs, and hyenas like to be in general at that time of day (not on any one specific day).
These maps here actually show where the carnivores are on consecutive days and months (the dates are printed across the top). [For whatever reason, the embedded .GIFs hate me; click on the map to open in a new tab and see the animation!]
Keep in mind that in the early days (June-Sept 2010) we didn’t have a whole lot of cameras on the ground, and that the cameras were taken down from Nov 2010-Feb 2011 (so that’s why those maps are empty).
The day-by-day map is pretty sparse, and in fact looks pretty random. The take-home message for this is that lions, hyenas, cheetahs, and leopards are all *around*, but the chances of them walking past a camera on any given day are kinda low. I’m still trying to find a pattern in the monthly distributions below.
So this is what I’ve been staring at in my turkey-induced post-Thanksgiving coma. Could be worse!
Truth be told, I *have* been working on data analysis from the start. It’s actually one of my favorite parts of research — piecing together the story from all the different puzzle pieces that have been collected over the years.
But right now I am knee-deep in taking a closer look at the camera trap data. Since we have *so* many cameras taking pictures every day I want to look at where the animals are not just overall, but from day to day, hour to hour. I’m not 100% sure what analytical approaches are out there, but my first step is to simply visualize the data. What does it look like?
So I’ve started making animations within the statistical programming software R. Here’s one of my first ones (stay tuned over the holidays for more). Each frame represents a different hour on the 24 hour clock: 0 is midnight, 12 is noon, 23 is 11pm, etc. Each dot is sized proportionally to the number of captures of that species at that site at that time of day. The dots are set to be a little transparent so you can see when sites are hotspots for multiple species. [*note: if the .gif isn't animating for you in the blog, try clicking on it so it opens in a new tab.]
Maybe from time to time you’ve wondered: Who are these scientists running Snapshot Serengeti? How did they get where they are? (And why am I sitting here instead of traipsing across the Serengeti myself?)
Ali and I are both graduate students at the University of Minnesota. What that means is that a while ago (seven years for me!) we filled out an application and wrote some essays for admission to the University of Minnesota’s graduate school — just like you would do for college admissions. The difference is that for graduate school, you also need to identify an advisor — a faculty member who will become both your mentor and your judge — and an area of research that you want to pursue. And while the admissions materials matter, it’s very important that your future advisor want to take you on as a student and that your area of research interest meshes well with hers or his.
In the U.S., you can apply for a Masters program or a Ph.D. program. In some places you can get a Masters on the way to a Ph.D., but that’s not the case at Minnesota. So I applied for the Ph.D., got admitted and started as a Ph.D. student in the fall of 2007. I’m pretty much only going to talk about Ph.D.s from here on out. And I should point out that graduate school systems vary from country to country. I’m just going to talk about how it works in the U.S. because I’m not terribly familiar with what happens in other countries.
For the first 2-3 years in our program, students spend much of their time taking classes. These are mostly higher level classes that assume you already took college-level classes in basic biology, math, etc. I came in with an college degree in computer science, and so a bunch of the classes I took were actually more fundamental ecology and evolution classes so I could get caught up. But many classes are reserved for just graduate students or for grad students plus motivated seniors.
At the same time as taking these classes, students are expected to come up with a research plan to pursue. The first couple years are filled with a lot of anxiety about what exactly to do, and there are plenty of missteps. My first attempt at a research project involved tracking the movement of wildebeest in the Serengeti using satellites and airplane surveys. (Yes, you can see individual wildebeest in Google Earth if you hunt around!) But it turned out not to be a logically or financially feasible project, so I discarded it — after a lot of time and energy investment.
Around the end of the second year and beginning of the third year, grad students in the U.S. take what are called “preliminary” or “comprehensive” exams. These vary from school to school and from department to department. But they usually consist of both a written and oral component. In some places the goal of these exams to to assess whether you know enough about the broad discipline to be allowed to proceed. In other places, the goal is to judge whether or not you’ve put together a reasonable research plan. The program Ali and I are in leans more toward the latter. It requires a written proposal about what you plan to do for research. This proposal is reviewed by several faculty who decide whether it passes or not.
If you pass your written component, you then give a public talk on your proposed research followed by a grueling two to three hour interview with your committee. In our program, students choose their committee members, following a few sets of rules about who can be on it. My committee had five people, including my two advisors. They took turns asking me questions about my proposed research, how I would collect data, analyze it, how I would deal with adversity. The committee then met without me to decide whether I passed or not. (spoiler: I passed)
So, assuming a student passes the preliminary exams, she or he is then considered a “Ph.D. Candidate,” which basically means that all requirements except the actual dissertation itself have been fulfilled. If you’ve ever heard the term “A.B.D.” or “All But Dissertation,” that is what this means. The student got through the first hurdles, but never got a dissertation done (or accepted).
Now it’s time for the research. With luck, persistence, motivation, and lack of confounding factors, a student can do the research and write the dissertation in about three years. Doing research at first is slow because, like learning anything new, you make mistakes. I spent a lot of time gathering data that I’m not going to end up using. Now that I’ve been doing research for a few years, I can better estimate which data is worth collecting and which is not. And so I’m more efficient. While doing research, the student is also reading other people’s related research, and often picking up a side-project or two.
Eventually, the student, together with the advisor(s) and committee members, decides that she or he has done enough research to prove that she or he is a capable professional scientist. All the research gets written up into a massive tome called the dissertation. These days, it’s not uncommon for graduate students in the sciences to write up their dissertation chapters as formal papers that then get published in scientific journals. Sometimes one or more chapters is already published by the time the dissertation is submitted.
When the writing of the dissertation is finished, it gets sent to the committee to read. The student then gives a formal, public talk on the results of the dissertation research, followed by another two to three hour interview with the committee. This time it’s called the “Dissertation Defense,” and the committee asks questions about the research results (and possibly asks the student to fight a snake). The committee then meets without the student and comes up with a decision of whether the student passes or not. There is also often a conditional part of this decision that requires some portion of the dissertation to be revised or added to. So, a decision of “pass, conditional on the following revisions:” is pretty common.
I should mention that while being a grad student has been mostly quite fun, you may not want to drop your day job and run off to academia just yet. There’s the issue of funding. On the plus side, you can acquire funding in the sciences so that you don’t have to take on debt to do your degree (which is not so true in the humanities). Ali and I have both applied for and received fellowships that have allowed us to do most of our graduate program without having to work. But many — maybe most — grad students in the sciences work essentially part-time jobs (20 hours/week) as teaching assistants for faculty. This can really slow down research progress, as well as making some types of research impossible (for example, those that require lengthy trips to the Serengeti). Whether working or on fellowship, students typically gross no more than $30,000 annually, and often less than $25,000, which can be quite reasonable (single person living in a low-cost-of-living area) or prohibitive (person supporting a family living in a high-cost-of-living area). Benefits are pretty much non-existent, with the exception of health coverage, which can range from great (thanks, Minnesota!) to really bad to non-existent.
I mention all this this because I am about to defend my dissertation! In a little less than two weeks I will give a talk, sit down with my committee, and try to convince them I’m a decent scientist. Wish me luck.
Crazy week this week, so I just wanted to post a link to this fascinating and hilarious blog post about plant communication. Yup, you heard right. Animals aren’t the only things that communicate: plants do too! But instead of using sound, plants communicate via chemicals.
First, some plants respond to hungry predators (e.g. bugs, mammalian herbivores) by producing bad-tasting or toxic chemicals that stops would-be-munchers in their tracks — this is called and “induced response” or “induced defense” and is pretty well documented in terrestrial plants. But what’s even cooler is that attacked plants might also release chemical signals to “talk” to neighbors — allowing un-munched-on plants to trigger pre-emptive defenses. Originally known as the “talking trees hypothesis,” this interplant communication was first described in the 1980′s — though more recent research suggests that “eavesdropping” might better capture the true nature of the interaction.
More recently and perhaps even cooler is that plants not only “talk” to each other, but to other animals! The blog post linked above describes an intertidal plant that basically calls in the predators of its predators. When the plant gets munched on, by, say, a snail, it releases a chemical signal that attracts things that eat snails, like crabs.
Crazy, and awesome. Even though I think I’ll stick with studying big furry things, plants are pretty cool.