Archive | February 2014

Big Cat Wars

I’m in the process of writing up some *really* cool camera trap results from Seasons 1-6, and plan to share them here next week (as soon as I make them pretty). It would never have been possible without your guys’ help.  But in the meanwhile, this just aired again on TV, and thought you might enjoy a bit of a break! They talk about the camera traps a bit ~33 minutes in.

 

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Pholidota is in the air…

I hope you kids didn’t get too crazy celebrating the holiday last weekend. It’s so easy to go overboard with the flowers and the chocolates and the small armored African mammals…

Because you all were celebrating WORLD PANGOLIN DAY last Saturday, right? Of course you were. Pangolins! Now, if you don’t know what a pangolin is, you obviously haven’t been looking at enough Snapshot images! Shoo, get back out there and ID some more.

Just kidding, we never really see these guys. This is what they look like:

The one and only awesome pangolin picture our camera traps have ever taken

I have friends living on reserves in South Africa who have only seen on of these guys in there entire life, so it’s neat that we do get to see these guys through out cameras. The pangolin (or “scaly anteater”) is a small insectivorous mammal coated in thick keratinous armored plates. Why would you want to be coated in armor made of finger-nail material? Well, every once in a while it appears to come in handy..

(This video is extremely silly and dramatic. But dang, that is a lot of lions)

Anyhow, I was a little slow on the draw for this one, so we’re going to have wait an entire year for this epic holiday to roll around again. To keep you busy in the meantime, here are some neat pangolin videos for your enjoyment: 

 

 

 

Snapshot Serengeti: Not *just* for procrastinating anymore…

That’s right. Even though many of us probably ID photos on Snapshot Serengeti because we really don’t feel like writing up that expense report or answering emails or formatting our bibliographies, Snapshot is also a fantastic tool for *deliberate* learning.

Check out how post-doctoral researcher Annika Moe has incorporated Snapshot Serengeti into college classrooms.  It’s a pretty compelling argument for engaging students with authentic research — I’m just glad that Snapshot Serengeti got to be part of such a cool new approach to learning.

 

 

Just ask nicely

I don’t think this will work…

A cute article came out a few weeks ago in a one of the big methodological journals in my field. (Methods in Ecology and Evolution, published through the British Ecological Society.)

The article pointed out that researchers often have to leave equipment out in the field to collect data (sound familiar?), and that this equipment sometimes gets damaged or stolen. So they did a little experiment where they labeled the equipment with a note. The note was in one of three “tones”: personal, neutral, or threatening.

The equipment and labels used by Clarin et al. 2013.

The equipment and labels used by Clarin et al. 2013.

 The personal note read: ‘Part of my thesis – Please do not touch – Please call me if you have any questions and would like to know more:’ and a photograph of a juvenile squirrel. 

The neutral note read: ‘Part of an  experiment – Please do not touch’ and a warning sign. 

And the threatening note: ‘Part of an experiment – Every theft will be reported to the police! GPS monitored!’

Lo and behold, cameras with the personal note and a picture of a cute baby squirrel had the fewest instances of vandalism and theft! (Also note in the chart below that the equipment with the “threatening” note had the most encounters!)

Figure 3 from Clarin et al, showing the # of incidents experienced by cameras with different note types.

Figure 3 from Clarin et al, showing the # of incidents experienced by cameras with different note types.

I thought this experiment was fun and the results heartening. Unfortunately, though, I’m not so sure nice notes will work so well on the Serengeti wildlife…

The last picture *this* camera ever took…

Reference: Clarin, B.-M., Bitzilekis, E., Siemers, B.M. & Goerlitz, H.R. (2013) Personal messages reduce vandalism and theft of unattended scientific equipment. Methods in Ecology and Evolution, doi: 10.1111/2041-210X.12132.

Have you watched your television lately?

As I happen to be an impressionable first year student, many of my introductory courses are focused on molding us younglings not only into insightful and profound scientific geniuses, but also on instilling within us a sense of scientific responsibility, particularly when it comes to sharing our work with others. It’s important to be able to convey how freakin’ awesome the research that we do is to people outside of science, which can be really hard when our most exciting result happens to be a string of numbers that popped out of an evil-looking matrix swimming in a sea incomprehensible code.

Most of what we cover in these types of classes is science writing – and there are true gems out there, people with a real talent for sitting down with a biologist who only talks in “ontology” and “heteroscedasticity” and translate all that jargon into an informative, enjoyable piece of literature. You can pick up these pieces in a variety of places – newspapers like The New York Times can have very comprehensive science news articles. Peruse the magazine rack of any book store and, although you may have to dig behind the “Cosmo”, there are popular science magazines covering every disciple under the sun (and beyond!). You’ve already entered the blogosphere, where very passionate people are writing about the discoveries they and others make and the questions, queries, and quandaries still to be explored. Shout out to two of my favorites bloggers – after all of us here at Snapshot Serengeti, of course – Carl Zimmer and Ed Yong, who discourse on all sorts of topics over at National Geographic. And I won’t even start on the wealth of science literature, because I actually do have some stats to run and if I get sucked into this, we’ll be here all night.

I think, however, that one of the most easily accessible types of science dissemination, and the kind likely to reach the further-ranging audience (I know I’m always the only B&N browser with my face in the latest issue of “Scientific American”), is television. Now sure, there is a LOT of bad television out there, I think it goes without saying. Even some purported “educational” channels are going a bit off the deep end (case in point: Animal Planet and their mermaid “documentaries”). But when you’ve just dragged yourself home from a long day in the office and can’t bring yourself to pick up your latest science tome, flip on the tube, find a documentary, and learn a little something.

Particularly for kids and young people, science television is an important inspirational medium. As corny as it sounds, Bill Nye the Science Guy was HIGHLY instrumental in my own scientific development (I still watch an episode every now and again to remind myself that “science rules!”). This type of television shares not only information, but conveys enthusiasm about science, humanizing and breaking down topics which people may have considered beyond their understanding. Speaking of Bill Nye and his science outreach, did people watch his debate with Creationist Ken Ham the other week? It was streamed live by 520,000 people and subsequently downloaded by over a million. Talk about far-reaching, and being picked up by an audience that wasn’t necessarily science-inclined.

Another aspect of science television (and I’m starting to sound a bit like a TV junkie at this point, aren’t I?) that was important to me at least was exposure to fantastic places and creatures. I’m probably not making it to Madagascar anytime soon – are you? But we can learn all about the bizarre and beautiful endemic wildlife, courtesy of everyone’s favorite Sir David Attenborough. I feel like I can practically use ‘Attenborough’ as a synonym for ‘nature documentary’. And remember the sensation when BBC came out with ‘Planet Earth’? Or ‘Life’? Or ‘Human Planet’? You can find them on the channels, you can find them on the internet. Always a winner are the PBS NOVA specials  — be sure to scroll down and check out “Poop-Eating Sloth Moths,” because you know you want to. Also, it’s a neat new discovery about a highly entwined natural system. Would have known otherwise? And when you exhaust all those links, here’s another 300 “mind-expanding” documentaries for your enjoyment: http://www.diygenius.com/mind-expanding-documentaries/

So veg out and watch some science!

The surprisingly powerful role of fear

Fear. 

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.

How spiders affect grasshoppers affect plants. Excerpted from Schmitz et al. 1997.

How spiders affect grasshoppers affect plants. Excerpted from Schmitz et al. 1997.

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.

The Bug-Hunters

As you can see, our primary research involves the big stuff: large carnivores, giant antelope, ungulates that could run you down. The camera trap grid is set up to record the movement patterns of these organisms… Which isn’t to say that other types of creatures which traverse the Serengeti don’t get captured in the net as well. I’m sure that many of you who actively identify have spotted the occasional bird, sighted a wildcat, or perhaps even happened upon a basking reptile. Spatial and temporal data is being gathered on these guys too, and for a small side project, I decided to delve into some of the less well-explored information.

I’m tackling a particular guild of small mammals. The questions I’m asking involve occupancy patterns and coexistence among organisms that compete for a common resource — sort of like that Ali does with large carnivores, but applied to other groups. Right now, I’m looking at data on spatial partitioning among myrmecophagous (there’s your buzzword for the day) animals: animals that eat ants and termites. The Serengeti landscape is littered with termite mounds – giant mud constructions held together by termite spit and seething with social insects. Termites are highly important to serengeti ecosystem functioning, breaking down dead plant matter and churning soil. Furthermore, they form over 80% of the diets of three mammals, the aardwolf (Proteles cristata), the bat-eared fox (Otocyon megalotis), and the aardvark (Orycteropus afer). Let’s meet them, shall we?

 

The Aardwolf:

Sometimes I still can’t manage to convince even other scientists in our department that I’m not making the aardwolf up. Not an wolf (not an “aard” either), looking suspiciously like some sort of pygmy hyena, and eating primarily insects. I’m sure you can see my problem. Well, at least it is in the hyena family – one of the smallest, coming in at a very slender 7-10 kg. These guys produce saliva that is particularly sticky for licking up ants and termites off of the soil surface. While they can’t break into the giant termite mounds, they are the only African ant-eater to be able to tolerate the chemical defense secretions of the Trinervitermes termite soldier cast.

Best true fact about aardwolves: Aardwolves apparently “roar” when chasing off intruders. Kind of adorable right? Don’t melt too much: if that doesn’t work, they proceed to emit foul-smelling liquid from their anal glands. Delightful.

 

The Bat-eared fox:

These guys are the only canid to have given up almost entirely on mammals to prey on insects. Although small (only 2-5 kg), a bat-eared fox can scarf up over one million termites per year. In fact, they don’t even need to drink because they fulfill the majority of their water intake needs from all of the insects they consume.

Best true fact about bat-eared foxed: Their ears are sensitive enough toe detect the sound of termites chewing on grass, or, better yet, hear beetle larvae chewing their way out of an underground ball of dung.

 

The Aardvark:

Definitely the heftiest member of the bunch, at twice the weight of a labrador retriever even though they only stand about 2 feet tall. These guys are solitary and nocturnal, shuffling around at night in search of termite mounds which they tear open with their powerful digging claws. The fox and the aardwolf are unable to break through the thick crust of dirt, and there are intriguing reports of these other guild members trailing aardvarks during seasons when termites are most scarce – perhaps hoping to snatch up some of the termite-crumbs? Having breached a nest, the aardvark slobbers up hundreds and hundreds of insects with its 12 inch tongue. Rather than masticating this mouthful with its teeth, grinds up the ants using the powerful muscles of its gizzard. They’re the sole surviving representative of an obscure mammalian order called the “Tubulidentata” — everyone else in the order kicked the bucket before the end of the Pleistocene.

Best true fact about aardvarks: Although their diet contains mostly ants and termites, they are known to consume a fruit charming called an “aardvark cucumber”.

The diets of all these creatures is composed of exactly the same resource, which can become limiting during particular times of year. No information yet on what kind of partitioning we may find – do the bigger guild members exclude the smaller ones? Is there commensalism (a relationship where one member benefits without affecting the other) between aardvarks and the other mammals? Are some members forced to forage during times when predators are most active?

It’s all connected

A few weeks ago, I wrote about how losing top predators from ecosystems can produce effects that radiate throughout the ecosystem, and talked a bit about how sea otters provide one of the better known of these examples. Today I want to talk a bit more about these reverberating consequences and how they come about.

These patterns are known as “tropic cascades.” Derived from the Greek word for “food”, trophic refers to the position that a species occupies in a food web. Plants consume sunlight. Herbivores consume plants. Carnivores consume herbivores (and sometimes other carnivores). Some carnivores, like bears, are really omnivores — eating both other animals as well as plants. So, things in one trophic level typically consume things from a lower trophic level. And critters within a trophic level compete with other critters in that trophic level for resources — sunlight, water, food, whatever. Trophic cascades are when changes in one trophic level (say, the top carnivores) have effects that cascade down to affect herbivores and plants.

The ways in which these cascades can happen are many and complex. The classic example describes how sea otters protect kelp forests by keeping sea urchin populations low. Without otters, the sea urchin populations explode and eat all of the kelp. But this is just one story of just one pathway.

For example, research on the Aleutian Islands reveals that foxes can change island grasslands into tundra. The islands provide a fantastic natural experiment, because 19th century fur traders brought foxes to some islands but not others, creating a whole pile of very similar islands, some with, and some without, foxes. On islands without foxes, seabirds eat fish from the sea and and…deposit…the nutrients from those fish on land (yes, in the form of droppings). All of the nitrogen and phosphorous in seabird droppings provide the nutrients to support long, lush grasses. But foxes reduce seabird populations, which in turn reduces the influx of nutrients to the islands, an results in a very different tundra-like plant community.

One of my favorite recent papers is a 2011 Science review by Dr. Jim Estes and colleagues that documents the many and complex changes that apex predators trigger in natural systems.  This figure from the Estes et al. publication gives us a tiny hint of just how complex these pathways are.

A figure from Estes et al. 2011 documenting the various pathways in which the loss of a top consumer affects many other things.

A figure from Estes et al. 2011 documenting the various pathways in which the loss of a top consumer affects many other things. For example, in this last row, coyotes suppress mesopredators (smaller predators). Mesopredators suppress small vertebrates. So losing coyotes means more mesopredators and thus fewer small vertebrates. The blue bar shows high levels of biodiversity in systems with coyotes. The brown bar, which is so low it’s invisible, indicates that in systems without coyotes, biodiversity is really, really low.

You can see from this figure that it’s not only predators that have reverberating consequences for the larger ecosystem.  In the late 1800s, a disease called rinderpest decimated wildebeest populations. This led to increased woody vegetation and increased incidence of savanna wildfires, When wildebeest populations recovered, their grazing patterns transformed the Serengeti back into a grassland and reduced the fuel available for wildfires. Fires since then are far fewer and far less intense.

So there are many, many ways in which one species can have cascading effects on the larger system. You can hear Jim talk more about the paper here.

Ultimately, we’re left with two profound and lingering realizations. The first is that everything inside an ecosystem is connected to everything else in a complex web of interactions. Sometimes shaking this web doesn’t do much, but sometimes losing a species from this web can have dramatic and unexpected effects. Everything is connected to everything else. The second realization is that people are inexorably changing the shape of these webs as they exist in the natural world. Because of their large body size, need for large spaces and lots of food, and tendency to come into conflict with people, large predators are one of the first things to go in human dominated landscapes. With everything connected to everything else, we don’t yet know what the extent of these losses will be.