What’s on the menu?

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Monument Draw, between our camp and one of our leks. Sagebrush is definitely the dominant plant out here!

Our focus in our Sage-Grouse research has been fairly limited to the lek– this is still keeping us busy even after many years of study! However, it’s always nice to get a more comprehensive view of the ecology of whatever organism you are studying, and towards that end, we have initiated a collaboration with Dr. Jennifer Forbey from Boise State University. For the Sage-Grouse, their life revolves around the sage plants (genus Artemesia) that form most of their diet, especially in the fall and winter. Jen spent a few days with us a the end of March to see our site, tell us about her research on the interaction between sage and the animals that depend on it, and plan out the first steps in our research together.

What at first seems like a uniform world of “sage” out here turns out to be a variable landscape of food quality for the grouse. First of all there are different species of Artemesia. In our site we have at least two, the basin big sage and Wyoming big sage. These are usually pretty distinguishable, although sometimes smaller Basin plants can look like larger Wyoming plants. The leaves are usually pretty different though, as Jen demonstrated. Jen gave us a handy rule of thumb for this: you can remember the Wyoming sage is like a Wyoming native giving the middle finger to the Californians! We got a laugh out of that.

Sage-Grouse usually cut all but the base of the leaf.

Jen showed us how to distinguish foraging by different herbivores in the area. The grouse tend to pick just the leaves, so if you have a sharp eye you can find the remaining leaf base. Old foraging will show a brown scar in the middle of the leaf, but if you happen to find a place where they have been foraging during the past day or two it will be bright green. Rabbits, on the other hand, tend to cut the entire stem off in a neat angled cut. They harvest the leafy parts before the sage can mount an defense (see below).

Neat diagonal cut = rabbit

Sage stems harvested by rabbits.

The sage are full of all sorts of secondary chemicals such as phenols and terpenes, making them pretty unpalatable to most animals. Jen had us taste a leaf and those little things pack a punch, leaving a persistent bitter taste in our mouths.

The Sage-Grouse obviously have a way around this since they eat almost nothing but sage for months out of the year. One adaptation is a specialized gut with two large caeca (blind pouches coming off the intestine). These are places where bacteria can work their magic and help detoxify and digest the sage. On the lek you’ll often find a dark, gooey tar-like caecal casts left by the grouse, which look very different from their normal (goose-like) poop. I can’t believe I don’t have a photo at hand to show this!

It gets more interesting when you look at variation among plants of a species. While the Sage-Grouse can eat the sage, Jen’s work has shown they prefer to feed off of plants that have less of these secondary chemical compounds. Eating bad quality sage with too high a concentration of these means the grouse have to work harder at digesting for fewer nutrient rewards.

The sage plants themselves are not passive players in this. When something starts to damage the leaves of a sage plant, it will begin to produce more of these defensive chemicals. Even more impressive- as the volatile compounds reach the air, they can spread to nearby plants, causing neighboring bushes to ramp up their production of chemicals as well. What this means is that the longer Sage-Grouse spend foraging in a given patch of sage, the lower quality the food becomes.

Male sage-grouse leaves the lek

Male sage-grouse flying.

This chemical response by the sage may solve a mystery stemming from a 1980’s study of sage-grouse behavior from the Mono Basin in California. Sandy Vehrencamp and colleagues followed radio-tagged males and found that the “good” males (with high energy reserves) were actually traveling farther from the lek, while the males with poor reserves foraged close to the lek. It could be that the plants near the lek tend to build up more of these secondary compounds, so males that can travel farther may actually encounter better areas in which to feed. We hope to follow up on this possibility as we learn more about the way that off-lek foraging behavior interacts with on-lek courtship and performance.

Mid-season Update

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It’s March 31st, and as we trundle towards April, I realize how tardy I have been with general updates this year. Every season is a little different, and this one is throwing us some curves.

Nine Mile Hill shrouded in snow.

We saw our first copulation on our biggest lek, Cottontail Lek ten days ago (March 21st). This date is pretty normal. We’ve found one earlier (March 19th) in a couple of years, and later some other years. Usually once we see the first one, within a few days every lek is showing multiple copulations. Not this year! We got hit with a blast of really cold weather (lows around 10℉) as well as a few inches of snow.  The females seemed rethink their interest in the males, and it was several days later before we saw the next mating on any of the leks. So while the breeding season opened at a fairly average time, I think the season as a whole is going to be on the late side. On balance, I’m not sure if this will be good or bad for our work this year. The longer we have big groups of real females on the lek, the harder it will be to give our robotic females a private audience. On the other hand, the males may stay interested in courtship a little bit longer so we may not have the problem of the males just giving up at the end of the season the way they sometimes do. We’ll have to see what happens!

Two male sage-grouse battle in the fresh snow on Chugwater Lek.

Other challenges we’ve had to contend with are the incredible shrinking leks. Our initial impression from the first couple of weeks of the season seems to be correct– male attendance is down considerably from last year in our area. This may be due to the drought the Lander area is experiencing, at least there’s not an obvious other candidate for the decline. Our sage-grouse manager contacts have mentioned that the rough demographic analysis from hunting data suggested low recruitment (not many yearling birds taken compared to the number of adults).

To give you a sense of the change in abundance since we started the project here: Monument Lek, our main focal lek since 2006 when it had over 100 males, has dropped to under 10 birds and males are not staying as reliably on their territories. Anna has still gotten some playback experiments done, but Monument is right on the edge of being useful or not as one of our experimental leks.  We just showed the PBS Nature episode featuring our research (“What Females Want…”) as part of another outreach event down at the Lander Public Library. The footage was shot in 2007 when the male counts were an order of magnitude higher. The difference definitely makes us a little sad, and we are hoping this lek rebounds quickly as it has done in the past. Sue at the BLM told us that in the 80’s it was down to 4 birds, and later climbed back to over 100, so we hope this is another one of those cycles.

Shallow trenches prepared for laying microphone cables at Monument Lek. This lets us put microphones all over the lek, while keeping the cables underground. The speakers are for the playback experiment.

Otherwise we are in pretty good shape with most of our “normal” tasks. We have microphone arrays deployed on all three focal leks now, and have gotten several days of sound recording in.  We’ve also gotten at least one round of counts at our non-focal leks, to help the local sage-grouse managers monitor the grouse population in the district. The only things we are missing are the new robots (Gail is working on taxidermy aspects now, so those should be ready soon), and the encounternet telemetry tags. I say “only”, although those are definitely two very important pieces for our research goals this year and in the next couple of years!

Kiwi Commentary

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It looks like the commentary that I wrote with Lauryn Benedict write is now online (it may require journal access- feel free to email me if you aren’t able to get it through your university’s network and would like a copy). Lauryn and I share a lot of the same pedigree: we were undergrads at Cornell, then jointly advised by Walt Koenig and Eileen Lacey at UC Berkeley for our PhDs . We even did our field research in the same place- the Hastings Natural History Reservation in Carmel Valley. Lauryn studied another one of those common but not terribly well known birds, the California Towhee.

It’s fun to get to write something up with a friend and colleague like this. Our manuscript puts some context around a paper on vocal behavior and duetting in a species of kiwi.

 

Playback Experiment, 2013 Edition

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In my last post, I talked about the usefulness of our robotic grouse for studying complex social interactions on the lek. This week we tried another method for modifying a male’s social experience– audio playback.

Male Sage-Grouse listening to our rock speakers.

We have a long history of playing back sounds to the Sage-Grouse. For the first several years our basic behavior studies were running along side the ‘Noise Project’, an extensive research program into the effects of noise associated with energy development on the grouse. The centerpiece of the Noise Project was playing back the sounds of two common noise sources (drilling sounds and road noise) from the Pinedale Anticline/Upper Green River area.  We used fake rock speakers, possibly the same kinds you might have seen in a SkyMall catalog, to play these sounds at leks, and compare how many birds showed up and their behavior between the noisy leks and control leks that had. I’ll talk more about the results from this project in a future post.

We also used the speakers in 2011, this time as part of the basic behavioral research program. We’ve been interested in the importance of “courtship skills” in the males, and part of that is how attuned males are to changes in their social environment. Does a male change his courtship behavior a lot when a female gets closer, or not very much? Our first experiment with the fembot showed this was related to the success a male has in courting females.

One species used in our 2011 playback study: Pronghorn

Our experiment in 2011 was designed to look at another dimension of responsiveness- how attuned are males to the threat of potential predators? Here we chose alarm calls o f three different species that live with the sage-grouse: ravens, killdeer, and pronghorn antelope. We played these from the rock speakers and measured the strength of the grouses’ reaction, as well as how long it took them to resume their original behavior. Analysis is ongoing, so we don’t yet know how this sort of “ecological” responsiveness relates to their social responsiveness or their success on the lek.

Fast forward to 2013, and we’ve set up the speakers once again, this time to measure how males respond to other males. It would be great to have a robotic male, but as you can imagine, making a mechanical male that is realistic enough to give a convincing display would be a steep technical challenge (never mind making one sturdy enough to withstand an attacking male). Instead, we are playing back the sounds of male struts from the rock speakers to see how males respond to a simulated male at the edge of the lek.  Anna has been putting together recordings with different call rates, so we can see if they are attuned to differences in the signals that males may be sending out. We’ve only just begun, but this will hopefully allow us to collect some interesting data on how males respond to other males while Gail puts together the new fleet of robots.

We also played a control vocalization– Horned Lark.

In other news, we observed the first copulation of the season yesterday! The breeding season has officially begun. Our earliest observation ever was on March 19th (in two different years), so we are on the early end of things.

Why a Robot?

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Photo Gail Patricelli.

Yesterday we got to take off our researcher hats and put on our outreach hats (we also traded our field clothes for some clean pants). Gail and I brought “Snooki”, the latest version of our robotic female grouse, down to Lander to participate in Teen Tech Week at the public library. Word had spread among the library staff; they were quite excited to get to meet the robot in person. Some of the kids were apprehensive, but most jumped right in to give the test drive. I had loaded some videos of the fembot and the grouse on my iPad so they could see how she looked in action.

 

With the exception of the wheels, the robot makes a pretty convincing sage-grouse. This version has the mechanics tucked inside a fiberglass shell that was poured over a grouse-specific taxidermy mold. Gail artfully arranged real grouse skins over this to complete the disguise. “Snooki” can turn in place using the wheels, the body can pivot down, the neck bend up and down, and the head can swivel back and forth. You can see a video of the fembot in action at the bottom of this post.

Fembot (left) and "undressed" fembot, right.

One of the common questions we get at this sort of event is “Is the robot just for fun? What do you do with it?” Let me take a moment to answer that.

Our robotic sage-grouse

In my recent post, I talked about how we use leks as a way to study sexual selection and mate choice. Most studies of lekking animals have looked at male traits that don’t vary much over the course of the breeding season. For example, in peafowl, biologists can look at which males have the longest tails or most tail eye-spots, and see if that might relate to patterns of mate choice. You could picture this as each male holding up a sign with his “score”, and females look around until they find the male with the highest score.

Anyone who’s watched animal courtship knows that males and females aren’t always politely assessing each other from a distance. Real courtship often involves complex decisions and interactions: deciding whom to approach, how quickly, reading signals or cues and responding accordingly. For a male to succeed in the mating game, the skills required to navigate the complex world of courtship can be as important as the physical traits he carries. Some of you may even have personal experience with this situation– meeting someone who is very attractive but who comes on a little too strong, for example.

Unfortunately we don’t know much about the importance of these “social skills” in non-humans because they can be hard to measure, especially in the wild. This is where the robot comes in.  With a robotic female, we can control one side of the conversation. The fembot gives us two important tools for comparing males on the lek.

Male courting fembot.

First, it presents all males with a standardized stimulus. In live courtships, females may approach the top guys much more closely and provide signals of interest, while other males are consistently given the cold shoulder. The robot lets us measure all the males on an even playing field.

Second, it allows us to experimentally control the conditions of courtship. In a previous experiment, we could look at how male sage-grouse responded to a very basic aspect of female behavior– how close or far away she is from a male. With the more advanced version of the robot that we debuted last year, we could send either “coy” or “interested” signals to the males. I’ll describe the plan for this year’s experiments when we get a little closer to conducting them.

The older version of the robot ran on train tracks. Here we are moving her closer to two admirers.

The robot also serves an important function as a target of courtship- one of the skills we are interested in is the male’s ability to aim his best signal at the female, and in a past iteration, the robot could record what a female would hear, rather than what a biologist can record from some arbitrary position on the lek.

There are several ways that biologists can manipulate an animal’s social environment (video playbacks in the lab, audio playbacks of bird song, etc), but the robot gives us a unique way to interact with animals in wild.